# Natural Bass



## Patrick Bateman

In a car it's very easy to generate deep bass, and lots of bass. But it's exceptionally difficult to generate natural bass.

In this thread I want to explorer why this is. After that I'll explore potential solutions, and simulate the bass configuration of a few cars.


----------



## Patrick Bateman

The small dimensions of a car radically alters the output of a speaker. That's why low bass is cheap and plentiful in a car.








Andy from JBL posted this pic a few years back. It demonstrates the "cabin gain" of various cars. We see a few things here:


In a typical sedan, there's about 20db of "free" output at 20hz.
Even at 40hz, there's a lot of gain. About 12db on average.
All is not roses - things go to hell above 40hz.

That last part is critical, and understanding whats going on in the three octave from 40hz to 320hz is critical to achieving natural bass.


----------



## Patrick Bateman

This post is going to be fairly technical. If you want to skip over this one and get to the graphs, feel free. Re-reading this post may help explain what's going on in the illustrations.

Here goes...

At low frequencies, there are two mechanisms going on in our cars. The most famous one is "cabin" gain. Quoting from Rod Elliott*, "When room dimensions become small compared to wavelength, soundwave propagation will not work, and bass can only be reproduced by pressurising (and de-pressurising) the listening space ... pressure mode."

Take a look at the graph above, you can see what Rod is referring to. For instance, the dimensions of my Accord's cabin are four feet wide and eight feet long. That corresponds to a frequency of 280hz and 140hz respectively.

What do you see in the graph?

A slow increase in SPL, which starts around 280hz.

Now this is a bit contrary to what most people consider "cabin gain." For instance, I've typically heard a figure of 12db/octave, beginning at 80hz. (IE, +24db at 20hz, +12db at 40hz.)

The answer is *reflections.*

Whenever a soundwave hits a surface and reflects back to the original source, a series of reflections will occur. A dip in the frequency response will appear at one quarter wavelength. A peak in the frequency response will occur at one half wavelength.

Let's crunch the numbers on this one:

The cabin of my Accord is eight feet long. This means there will be a dip at 35hz, along with a peak at 70hz.

_Here's the math : (speed of sound / wavelength / 4) = (13500 inches per second / 96 inches / 4) = 35hz_

Note that this has nothing to do with the speaker parameters - it's due solely to the length of the cabin.

But wait! The cabin is four feet wide. That's going to create a dip at 70hz. So we end up with a dip to the cabin LENGTH, and a peak due to the WIDTH.

If you really want to make your head explode, consider the fact that the LOCATION of the speaker changes everything. (That's one of the reasons sound sub different if they're faced forwards or backwards.)

Obviously, this problem is way too complex to solve manually. So it's time to crank out a computer simulation of the problem.

* The Subwoofer Conundrum


----------



## Patrick Bateman

Have you ever replaced the woofers in your car, and found that one set sounded *different*, but not necessarily *better*? For instance, you replaced your door woofers, and at first you noticed that the new woofers played noticeably lower. Not night and day, but definitely deeper. So you were stoked for a few weeks there, but then you started to notice that you were still suffering from the same integration issues. The midbass didn't blend with the sub, or perhaps the new woofer played low, but couldn't get as loud as the woofer it replaced.

In other words, you traded one set of problems for another.

This situation is one of the things that makes car audio so frustrating. I think it's one of the reasons that so many people just throw in the towel, or simply spend years replacing component after component.

I used a computer program to simulate the interior of my car, to demonstrate how the dimensions wreak havoc with our loudspeakers.
























Here's a comparison of two woofers, mounted in the doors of a Honda Accord coupe. One is a Hertz midbass, the other is a Dayton RS180.

First thing you'll notice is that this is ANYTHING but flat. It's a mess really - there's a massive suckout at 400hz, and an entire octave from 80 to 160hz.

In other words, both woofers suffer from the same problems, but to varying degrees. The Hertz (blue) plays lower. The Dayton (orange) is more efficient and smoother.

I think this is fairly consistent with what people have reported here - the Hertz woofers are famous for playing very low, but needing a lot of power.


----------



## Patrick Bateman

After looking at the simulation above, someone is bound to say "it can't POSSIBLY be that bad."

I mean, we'd have to be DEAF to tolerate frequency response that's THAT bad! There are dips and peaks over SIX db!!!










Sorry to say, it's really THAT bad. Here's the in-car response of a two-way speaker, measured in my car. The on axis (green) graph shows that the speaker fits in a window of +/- 3db from 350hz to 10khz.

This is really great performance, right 

But look below 400hz, and it goes to hell 

That's reflections for ya. You can also see cabin gain kicking in at the very bottom.

The red line is the off-axis performance, and you can see that it's an abysmal mess. But I've already documented the solution to that* 

Before we explore potential solutions to the bass problem, let's discuss briefly why we can tolerate performance that's this bad. At low frequencies our hearing acuity is quite poor. Our acuity is also level dependent. Have you ever noticed that it's difficult to appreciate bassy music at low volumes? Have you ever wondered why nobody listens to techno at polite volumes? That's because we're literally insensitive to low frequencies, and it's worse at low volumes.

In addition to all that, the way we perceive sounds actually changes at high frequencies. For instance, if your left and right tweeters aren't carefully matched, your soundstage goes to hell. But at low frequencies we can barely even *perceive* the difference in level between two sources. If you don't believe me, have a friend reduce the gain on one of your subs by half, without telling you which one. You'll be able to tell that there's less bass, but you won't be able to tell which one is lower because the wavelengths are so long.

Anyways, to make a long story short, we can tolerate extraordinarily poor frequency response at low frequencies. But that doesn't mean that we SHOULD. By improving the power response of our midbass and our subs, we can improve the entire stereo.

* Creating a Soundstage with Waveguides and Psychoacoustics - diyAudio


----------



## Patrick Bateman

As I alluded to in the previous post, I have a few ideas of how we can improve the bass and midbass response in a car.

Before we get into that, I wanted to examine the performance of a few cars.

To achieve excellent bass and midbass performance, we need a few things:


The midbass location has a big impact on the size and depth of our soundstage. So the further and wider we can locate it, the better. It doesn't necessarily have to be in front of us; Speaker Works built a series of winning cars where the midbass was far and wide, but BEHIND the driver. This is because it's difficult to localize low frequencies from front to back. This "trick" requires a low distortion midbass, since distortion occurs at high frequencies.
To achieve good dynamics with a midbass, we need an ability to generate serious output. Because of cabin gain, it's easy to generate high SPLs below 80hz. But generating a lot of output in the two octaves from 80 to 320hz requires a serious midbass.
As noted in the previous posts, the hostile acoustic environment of an automobile wreaks havoc with the frequency response from 80 to 320hz.

In order to compare a few midbasses, I simulated the in-car response of the following:


Hertz 165L, an excellent and popular midbass which is typically mounted in a car door
The Speaker Works Buick Grand National, which is basically the best known car stereo of all time
The best midbass that I've personally used, a B&C 8NDL51

Before I could simulate the in-car response of the Grand National's midbass, I had to figure out what it was. I did some digging through old speaker catalogs, and I'm fairly certain it's using a JBL 2204H.







Here's a pic showing the JBL woofer, and the midbass in the GN. Looks like a match to me.







Here's a simulation of the in-car response of the Hertz midbass in a car door, versus the JBL 2204H located in the rear quarter panel of the same car.

Here's some observations:


Note that the last graph of the Hertz included a sub, and this one is just the in-car response of the woofer alone. That's why it looks different.
The graphs shows the MAXIMUM output before the woofer runs out of xmax. It's downright mind boggling how badly the JBL trounces the Hertz. At 150hz the JBL has more than TWENTY db more output!!!
All the peaks and dips in the graph are a bit distracting - keep in mind that "in the real world" these would be smoothed out to a great degree. What you want to look for are broad dips or peaks, like the suckout in the Hertz at 350hz. While the response of the JBL is ragged, it fits in a tighter window than the Hertz. The performance of the JBL is very VERY good. It's kind of amazing that this woofer is almost thirty years old :O
Both woofers suffer from a "trough" around 80hz. The Grand National was crossed over at 90hz; it's possible that the subwoofers in the GN helped fill in that trough.
The Hertz is severely limited by xmax; it runs out of steam at just 15 watts at 2.9 ohms, or 6.6 volts. Due to the JBLs massive cone and generous xmax, can take gobs and gobs of power. It appears to be in a twenty liter sealed box, and it can swallow SIX HUNDRED watts before running out of xmax. That's 61 volts.















In my old car I had a B&C 8NDL51 in a very small sealed box. It's probably the best midbass I've ever used. Here's the response of the B&C, located against the firewall of the vehicle.







Here's the maximum output of the woofer that I think was in the Grand National, the B&C 8NDL51 I used in my last vehicle, and the Hertz 165L. The JBL is maxed out at 61v ([email protected]), the B&C at 46v ([email protected]) and the Hertz at 6.6v ([email protected]).

We can see that the B&C gives the JBL a run for it's money, but the JBL has a 5db advantage below 200hz. While the Hertz has a lot of bass for such a small driver, it can't compete with the sheer output of the B&C or the JBL.


----------



## nirschl

Very interesting read. Thanks and keep'um coming!

Cheers!


----------



## andy335touring

Thanks a lot for another informative post 

It's just a shame that big drivers are a PITA to find a place for in cars


----------



## Oliver

I have seen where an artificial reinforcement of the driver mounted in the doors is mistaken for great midbass


----------



## matdotcom2000

WOW is all I can say


----------



## otis857

Im in. Very interesting reading


----------



## ehkewley

I'm unsure that I can fully appreciate this thread without gratuitous amounts of folded horn pics... but subscribing anyway. Great read so far!

a$$hole, can you clarify your statement?


----------



## mitchyz250f

OK, no one laugh. Just a little brainstorming folks. If the dimensions of the car or nearest obstruction is what is causing the dips and peaks, could a second midbass in an area where the dimension are vastly different balance this out, to some degree? Such as a rear mounted and front door mount mb's? Or is it the OA dimension of the car that are critical?


----------



## caver50

Great tutorial and timely concidering I'am starting a new install. It appears to me that the larger midbass would be the way to go, but a speaker that size may not be possible in some vehicles. One of the things I've had to consider is what type of sound I perfer. (differant speakers sound differant) vs what will actually fit. My standard cab truck seems to be one of the most difficult to work with in order to achieve the high stage I'am seeking.

I have installed several systems in this truck and they all seem to be lacking.

I learned a lot from you Patrick, now I just hope that I can apply some of this information.


----------



## ben_lesmana

Hi Patrick,

What problem can we foresee with midbasses duty 80-250hz, with driver in a box placed under the 2 front seas? Apart from the PLD.

Would having 4 midbasses, 2 on stock door location and other 2 under the seats, can help with FR dips and peaks if setup like Geddes multiple subs idea?

Would it ruin the imaging/staging by doing that?

As always, excellent thread  Thanks for taking the time to write them.

Regards,
Ben


----------



## charcoal grey

*box sizing?*

Patrick

What size enclosure are you modeling the B&C 8NDL51 in?

What would the optimum system Q be when deciding what size box to build for car use? I was told for midbass use something around .8-.9 is good. I recently modeled the JBL driver and to get the Q down to below 1.0 it needed to be in a box around 28 liters or larger.


----------



## ehkewley

mitchyz250f said:


> OK, no one laugh. Just a little brainstorming folks. If the dimensions of the car or nearest obstruction is what is causing the dips and peaks, could a second midbass in an area where the dimension are vastly different balance this out, to some degree? Such as a rear mounted and front door mount mb's? Or is it the OA dimension of the car that are critical?


Not exactly apples to apples, but I did read in a home audio forum about people having a flatter frequency response with multiple subs in different areas of the room.

What about a sub and midwoofer playing some of the same frequencies in phase?


----------



## Patrick Bateman

mitchyz250f said:


> OK, no one laugh. Just a little brainstorming folks. If the dimensions of the car or nearest obstruction is what is causing the dips and peaks, could a second midbass in an area where the dimension are vastly different balance this out, to some degree? Such as a rear mounted and front door mount mb's? Or is it the OA dimension of the car that are critical?


At home I was running eight subwoofers for about six months. As usual, I stole the idea from someone else.* It was a *revelation.* Absolutely the most natural bass I've ever heard. I've never heard a commercial loudspeaker, a night club, or a car that sounded as good. All of the "bloat" and "sloppiness" that you hear in a lot of subs just vanished. Back in the 90s I used to listen to a lot of old school techno, and I started digging up all those tracks again. It's just amazing how certain music types are unlistenable without a good subwoofer.

As I understand it, the reason that it works so well is just what you described. When you have one or two strong reflections, you get a few strong peaks and dips. But as you *increase* the number of reflections, and *randomize* the frequency, the response begins to smooth out.

So, yeah, that's exactly where this whole project is headed.

* Multiple Small Subs - Geddes Approach - diyAudio









Here's a pic of an AudioKinesis Swarm. My sub array was built into the floor.


----------



## Patrick Bateman

_“Hokey simulations and ancient software are no match for a good microphone at your side kid - Han Solo”_

It's kind of ironic that I tell everyone that measurements are critical, and then I spent a day and a half creating a software simulation of my car.

It looks like I missed something in the model, or the car environment is simply too complex to simulate properly.

Here's what I mean:







This is the Akabak simulation of a B&C 8NDL51 located in the quarter panel of my car. Simulations will exaggerate the peaks and dips. What you want to look for are big suckouts and broad peaks. In this sim, we see a 15db suckout that's about an octave wide, centered around 100hz.






Here's an actual measurement of a B&C 8NDL51 located in the quarter panel of my car. This is a polar measurement, taken at 10 degree increments from one side of the car to the other. The big fat line is an avereage of all nine measurements.

Instead of a suckout at 100hz, we see it's at 320hz. Instead of being 15db deep, it's 5db deep. On the upside, we *do* see something going on at 100hz - if you look at the polar response it's completely ragged. Note that it swings as much as 10db depending on how far off-axis you are 

Anyways, I'm going to have to put the Akabak sim on the shelf, and rely on my microphone instead. I'll publish the sim in the next day or so, in case someone else wants to take a crack at it.


----------



## jbholsters

Patrick, the mid bass drivers in the Buick were JBL. The subs were rebranded (USD) EV 15's


----------



## Patrick Bateman

In the event that some people out there are considering the quarter panels for their midbass, like the Grand National and Harry Kimura's Acura, here are some measurements of a prosound midbass located there. It's a B&C 8NDL51 in literally the smallest enclosure I could build. Total air volume is three liters or so, give or take a liter.







Location looks like this. Picture an eight in a sealed box here.







Here are gated measurements of the polar response. I used a dual gate, to increase the accuracy. Each measurement is at a ten degree increment. The response varies like crazy - we can see that the in-car response of a speaker is NOTHING like what you'd get on a flat baffle. The aberrations at 90hz and 240hz are particularly troublesome. 15db suckouts that disappear when you move two inches aren't A Good Thing.







Exact same measurement, but with an average of all the polars. It's funny that the response swings by 15db if you move your head two inches, but the average is quite good. That's why polar measurements are so important.







In this measurement I've taken the same speaker and relocated it to the kick panels. Again, this is a polar measurement taken at 10 degree increments from one side of the car to the other.







Same location, but I've included an average of all the polars. If you compare these polars to the last set, you can see the quarter panel is better behaved than the kick panel. I'm guessing this is because there are fewer obstructions near the quarter panel. It's not a flat baffle, but it's a lot closer to flat than the kick panel.







Here's a head-to-head comparison of the averages. The voltage for both measurements is identical, the SPL level isn't calibrated tho.

The upside to the kick panels is that we're getting a LOT more bass. I believe the corner of the car is horn loading the woofer at low frequencies - we're picking up an extra 5db in the kick panel, versus the quarter panel. This woofer has an FS of 66hz, and we're getting it down to 70hz in a three liter box! Whoah. Did I mention that a pair of these can take EIGHT HUNDRED watts before they run out of excursion? The Hertz runs out of excursion at 15watts, mostly because the volume of a car door is so large. (A small sealed box reduces excursion.)

Now I remember why I like this midbass so much


----------



## Luke352

This has me interested as I currently use floor mounted midbass, as seen here http://www.diymobileaudio.com/forum/diyma-build-logs/6387-fiesta-install-2.html#post811316 you can only see the passenger side but the drivers side I finished over the weekend and the results are great! But I can't drive with shoes now because my feet sit quite high on the pedals, and although it doesn't seem that odd driving I am concerned about my ability if I need to stop in an emergency how accurately and smoothly I can break in a hurry (it's incredible how having kids changes your perspective). 

My rear quarter panels actually have a nice armrest area that would make the perfect spot to mold an enclosure into. My only concern is how low I would need to cross my midbass to prevent them dragging the stage back, the lowest I can go is 200hz 24db slope. Now as it is the in the floor there is no dragging of the stage downwards if I lift my feet of the floor, but with my feet on the floor I am getting bone conduction which is dragging the stage down to my feet in the lower freqs, I was going to address this with some custom floormats made with a combination of foam and MLV but this will raise my feet more and I don't think I could safely have my feet higher. 

All of this leads me to think it would be fine in the rear quarters and actually be better as I won't get any bone conduction issues. The beauty of my floor enclosures is that they lift out easily enough and I could try them on the back seat lent against the rear quarters. Guess this is my test for the weekend!


----------



## ben_lesmana

Luke,

When you installed both side, can you give your findings?

I want to put an 8" midbass under the seat, in a sealed enclosure. 

I tried placing them behind my seat, in the rear passenger foot area with a test box. Compared to my front mounted midbass (stock area), the image is still solid in front. XO are 18db 200hz. But the soundstage is wider to my left and to my right side. Where the midbass in stock location image is always in front of me. So there is a side-pull, but not dragging the image to the rear.

So I was wandering if I run both midbass, under seat and at stock location, I can have flatter(?) response, the more output should be a bonus.

I guess by experimenting I can found out the result, just want to know whats people opinion first.

Regards,
Ben


----------



## Oliver

ehkewley said:


> I'm unsure that I can fully appreciate this thread without gratuitous amounts of folded horn pics... but subscribing anyway. Great read so far!
> 
> a$$hole, can you clarify your statement?


The extra added bass sounds as if it is not in time with what the driver is producing , sometimes it will actually muddy up the sound as opposed to clear liquid smooth sounds that blend with the rest of the music.


----------



## lucas569

i remember reading RC had rewound the voice coils in all the speakers.


----------



## ehkewley

a$$hole said:


> The extra added bass sounds as if it is not in time with what the driver is producing , sometimes it will actually muddy up the sound as opposed to clear liquid smooth sounds that blend with the rest of the music.


Can proper TA help fix this issue?


----------



## michaelsil1

a$$hole said:


> The extra added bass sounds as if it is not in time with what the driver is producing , sometimes it will actually muddy up the sound as opposed to clear liquid smooth sounds that blend with the rest of the music.





ehkewley said:


> Can proper TA help fix this issue?


This is most likely an integration issue. Natural sounding Bass is very difficult.


----------



## chad

lucas569 said:


> i remember reading RC had rewound the voice coils in all the speakers.


I also heard he did it on the moon, by hand.


----------



## Oliver

There is plenty of it and the guy thinks he has the best midbasses in the world

MrMarv has heard the same thing , we've discussed it at length


----------



## Patrick Bateman

a$$hole said:


> There is plenty of it and the guy thinks he has the best midbasses in the world
> 
> MrMarv has heard the same thing , we've discussed it at length


If you'd like to suggest some alternatives, I'd be happy to explore them. Keep in mind that I am an engineer and I have a very specific set of criteria to satisfy. So I'm not particularly interested in opinions on the *sound* of a speaker. What I'm trying to accomplish here is finding a midbass solution that can keep up with a good car audio subwoofer.

For instance, let's say you have a sub that can put out 130db. That's fairly common these days.









If you paired this midbass with your sub, you'd need TWENTY THOUSAND WATTS to match the sub.

It's a fundamental problem we have in the car. Due to cabin gain, generating 130db from a sub is trivial. Hell, there are people who've pulled that off with a single sub.

*But how do you keep up with that?*

In the two octaves from 160 to 640hz, there's virtually no cabin gain. Look at my measurements, or JBLs. They demonstrate this as clear as day. So it takes gobs of power, gobs of efficiency, or BOTH to generate SPL in those octaves.

If there is a midbass solution that can do that, by all means, let me know. At the moment I am targeting the Grand National because it appears to have a well-engineered midbass solution. I am certain there are others.


----------



## Oliver

Patrick,

Other than *larger drivers* [ twelves in the GN ] or *doubling up on the drivers *like some do, I can't think of anything that can keep up with the output from a decent subwoofer.


----------



## Patrick Bateman

When I first discussed the use of a woofer array with Geddes on diyaudio, I was a skeptic. In my car, I can hear a difference when I move a woofer even six inches. For instance, the difference in stage depth between the kick panel and the door is HUGE. We're not talking about a subtle difference here.

So the idea of using three or even EIGHT woofers just seemed completely bizarre. The locations were outlandish too - for instance he recommends varying their height.

So I tried it, and lo and behold, it's the most natural bass I've ever heard.

From listening to it, I could tell that it worked. There was no doubt. But the engineer in me really wanted to figure out WHY it worked.

Here's some things I learned from the woofer array, and how I think they can help us create natural bass in the car.


Multiple woofers smooths out the response via randomization of the peaks and dips that occur in a car or room, particularly at low frequencies. Check out my measurements of a single midbass - you can see the response swings by as much as 10db when you move your head TWO INCHES. That's completely unacceptable for good soundstaging, or even natural tonality.
A side benefit of woofer arrays is a reduction in distortion, an increase in efficiency, and an increase in power handling. This is more important in a car than in the home, because our subwoofers are so efficient. (At home? Not so much.)
When you start looking for places to hide eight woofers, you end up using locations that are anything but ideal
The thing that saves us is a psychoacoustic trick called "intensity trading."

In the next post I'll demonstrate intensity trading.


----------



## Patrick Bateman

In this post we'll talk about *intensity trading.*

Even an untrained listener can tell when a midbass is relocated. That's why a lot of us build elaborate kick panels - it stages better than the door.

According to psychoacoustic research, _"an interaural time delay can be compensated for by an appropriate interaural intensity difference."*_

It's the same reason that turning the balance knob to the right moves the image that way. The left speaker is still too close, but reducing the intensity of the left speaker relative to the right moves the image.






Here's a diagram of my car, which has dimensions that are fairly typical for a coupe. The "nodes" are various speaker mounting locations, from the kick panel to the doors to the quarter panel to the rear deck. The path lengths are calculated in three dimensions. For instance, we can see that the distance from the kick panel is nearly a foot further than the distance from the rear deck. (30cm.)

_* Acoustics and Psychoacoustics, page 104_


----------



## briansz

I wonder if that's what was happening in the Buick. I've read of a generic psychoacoustic trick that RC used to prevent the midbass from being pulled backwards, but nobody has ever identified it specifically in the articles I've read. 

Some people say that there were the two USD 15's aperiodic, the two 12" midbasses, and two beryllium compression drivers horn loaded under the dash. Others say there were small full ranges under the dash as well. Lots of conflicting info on a car that hasn't been in the lanes for 15 or 20 years.


----------



## Patrick Bateman

Based on the diagram from the previous post, let's talk about three hypothetical speaker mounting locations.







This graph shows us how much intensity we need to "trade" for delay. For instance, if two speakers are playing the same sound, and one is 2.7" closer, you should reduce it's output *at that frequency* by 2db. (sound travels 13.5" in one millisecond.)


The first example is a typical three way stage. There's a midbass in the door, a midrange in the kick panel, and a tweeter in the kick panel or the A Pillar. The crossover is 2nd order. The midbass transitions to the midrange at 640hz, and it plays down to 80hz. At 640hz the output of the midrange and the midbass is equal, _but the image is dragged towards the door by the time difference._ Even worse, the image is dragged towards the door even half an octave or _a full octave above the midbass_, because it takes ELEVEN decibels to overcome the difference in distance. (That's why electronic crossovers with steep slopes work so well in the car.)
In the second example, let's do something bizarre. Let's put a midbass in the kick panel, the door, and THE REAR DECK. Crazy right? All three are covering the same frequency. Each one has an efficiency of 90db, and they're being fed with 100 watts. When all three are playing, we're getting about 119.4db with 300 watts total... Now we're in the ballpark of where we want to be. The *problem* is that the door speaker and the rear deck speaker are 11" closer than the kick panel, and now our soundstage is gone.
Here's how we fix the mistake we made in the second example. In order to compensate for the location of the door speaker and the deck speaker, we need to increase the volume of the kick panel by TEN db. (It takes eight tenths of a millisecond for sound to cover eleven inches.) That's an enormous increase in the SPL of the kick panel, and it "drags" the location back to where we want it. That's basically a preview of what I am going to do in this project. Use a single midbass that can take some abuse (like a prosound eight) along with an array of smaller midbasses. The presentation is dominated by the main midbass, but the midbass array increases power handling and efficiency. Most important of all, it should smooth the response via randomization and diffusion of the reflected energy.


----------



## 94VG30DE

Luke352 said:


> My rear quarter panels actually have a nice armrest area that would make the perfect spot to mold an enclosure into. My only concern is how low I would need to cross my midbass to prevent them dragging the stage back, the lowest I can go is 200hz 24db slope. Now as it is the in the floor there is no dragging of the stage downwards if I lift my feet of the floor, but with my feet on the floor I am getting bone conduction which is dragging the stage down to my feet in the lower freqs, I was going to address this with some custom floormats made with a combination of foam and MLV but this will raise my feet more and I don't think I could safely have my feet higher.
> 
> All of this leads me to think it would be fine in the rear quarters and actually be better as I won't get any bone conduction issues. The beauty of my floor enclosures is that they lift out easily enough and I could try them on the back seat lent against the rear quarters. Guess this is my test for the weekend!


This rear quarters for the midbass is actually what they did from the factory in my 94 Toyota Celica. It was a 6.5" speaker with a deep cone (for a OEM speaker) set into the area above the rear passengers' arm rest. The back seats were small enough that only people you didn't like were allowed to sit back there, and it was a short hatchback. IIRC it sounded pretty good for what it was. I still have one of those drivers laying around I think, I might be able to take a pic. But it didn't seem to draw attention too far back. It certainly wasn't like having stock 6x9s in the rear deck of a sedan.


----------



## Patrick Bateman

briansz said:


> I wonder if that's what was happening in the Buick. I've read of a generic psychoacoustic trick that RC used to prevent the midbass from being pulled backwards, but nobody has ever identified it specifically in the articles I've read.
> 
> Some people say that there were the two USD 15's aperiodic, the two 12" midbasses, and two beryllium compression drivers horn loaded under the dash. Others say there were small full ranges under the dash as well. Lots of conflicting info on a car that hasn't been in the lanes for 15 or 20 years.


Yeah, it's surreal to consider the quality, considering it was in the eighties! At the time I was using Dynaudio, Audax and Seas. And I thought I was pretty smart, since the performance I was getting was comparable to the very best brands around, but at half the price.

But load up the spec sheets on those old JBL speakers, it's downright depressing how far ahead of their time they were. For instance, I didn't see a shorting ring in a speaker until the mid nineties, and neodymium motors didn't become commonplace for another five years after that.

To put this in perspective, I have JBL drivers with distortion reducing alnico motors and silver (not copper) shorting rings that are about THIRTY years old.























Pics are worth a thousand words... Here's an old JBL midrange. (not my JBLs; I've posted pics of mine in other threads.) If the Grand National had hidden midranges, they were probably like this. Look at the MOTOR on these beasts... Amazing that these are nearly three decades old!


----------



## lucas569

chad said:


> I also heard he did it on the moon, by hand.


wrong it was on mars


----------



## thehatedguy

Clark said they were Bose 4" mids under the dash.

The Speaker Works guys he is full of crap.

The USD subs were Emilar. Emilar had the same model number with the same specs...

The midbasses in the GN could have been either 2202 or 2204s. But 2202s were suited for horn installation with a rising FR. The 2204s were suited for direct radiator use. I concluded they were 2204s...so I bought a set, and they have been sitting unused since then.

Harry's old car had 2123s on the rear deck.


----------



## sqshoestring

Nobody seemed to think much of my idea of using shallow 10s for midbass, though still a pain to install.

And people still say I'm nuts for running rear speakers to create a 'midbass array' mostly. They are full range, but I never hear the highs if they are working right.


----------



## otis857

How does mounting the mid bass speakers in the floor under the seats pointed up towards the dash play into this discussion? A few years back, I did some bodywork on a home audio guy's 66 LeMans with that config. He had a custom installer do an active 3 way front stage with the mid basses (6.5's I think) mounted there in pods glassed into the floor, mids in the door and tweets in the A pillars. It staged excellent and sounded very well balanced. 

I was a total greenhorn to car audio back then, but the location intrigued me and the results were impressive.


----------



## thehatedguy

Depends on how high they are playing. Through the midbass frequencies it is interaural delay which gives us the illusion of width. If you have no delay, then the stage width will collapse towards the side with no delay. How do you get IUD? Place the speakers wide, you have to have some delay from each ear and with the midbasses in the middle of the car (and middle of the head) there is no delay for a given side. If you are not overly concerned with such things then don't worry about it as much.


----------



## Oliver

Patrick Bateman said:


> The first example is a *typical three way stage*. There's a midbass in the door, a midrange in the kick panel, and a tweeter in the kick panel or the A Pillar. The crossover is 2nd order. *The midbass transitions to the midrange at 640hz*, and it plays down to 80hz. At 640hz the output of the midrange and the midbass is equal,







thehatedguy said:


> *Depends on how high they are playing*. If you are not overly concerned with such things then don't worry about it as much.


Just how high is too high ?


----------



## Luke352

ben_lesmana said:


> Luke,
> 
> When you installed both side, can you give your findings?
> 
> I want to put an 8" midbass under the seat, in a sealed enclosure.
> 
> I tried placing them behind my seat, in the rear passenger foot area with a test box. Compared to my front mounted midbass (stock area), the image is still solid in front. XO are 18db 200hz. But the soundstage is wider to my left and to my right side. Where the midbass in stock location image is always in front of me. So there is a side-pull, but not dragging the image to the rear.
> 
> So I was wandering if I run both midbass, under seat and at stock location, I can have flatter(?) response, the more output should be a bonus.
> 
> I guess by experimenting I can found out the result, just want to know whats people opinion first.
> 
> Regards,
> Ben


Thay are both installed.

I haven't done any extensive listening at this stage, but initial impressions are good. Image and focus seems quite good and they seem to be transparent in there location if you don't have your feet on the enclosure which is kind of a problem, because you do all the time, and when you do it drags the stage down and muddy's everything up. So I need to figure out how to deaden the enclosure's more, the top panel is 16mm MDF.


----------



## ben_lesmana

Luke,

For best result, this shouldnt be a midrange unit, strictly midbass only, whats the xover freq?

Ben


----------



## Luke352

It is a midbass, it's a Morel 8" crossed over @ 200hz 24db slope on the top end, and then I have 6.5" midrange in the upper door area playing from 200-450, and then another dome mid playing from 500hz-5500hz, and tweeter 6k up. I was worried about the 6.5" mid in the door being localizable but it is actually the most transparent driver in the whole setup, I forget they are even there half the time.


----------



## jbholsters

lucas569 said:


> i remember reading RC had rewound the voice coils in all the speakers.


Don't believe everything RC says that he did to the car. A lot of it is BS.


----------



## chad

jbholsters said:


> Don't believe everything RC says that he did to the car. A lot of it is BS.


I heard he broadcast said propaganda personally from Jupiter.


----------



## benny

chad said:


> I heard he broadcast said propaganda personally from Jupiter.


quoted for troof


----------



## lucas569

chad said:


> I heard he broadcast said propaganda personally from Jupiter.


blasphemous!


----------



## 14642

jbholsters said:


> Don't believe everything RC says that he did to the car. A lot of it is BS.


WHAT? NO WAY! Snake oil comes in many flavors.


----------



## chad

Andy Wehmeyer said:


> WHAT? NO WAY! Snake oil comes in many flavors.


Especially when harvested from snakes indigenous to South-Eastern Uranus.


----------



## ehkewley

chad said:


> Especially when harvested from snakes indigenous to South-Eastern Uranus.


Perhaps a backstory for those of us who are uninitiated?


----------



## thehatedguy

I resemble that remark...lol.



chad said:


> Especially when harvested from snakes indigenous to South-Eastern Uranus.


----------



## andy335touring

*[Edit]Sorry, i re-read the the thread and most of my questions are covered[/edit]*

Sorry for the dumb questions......

1. So are you best off useing the *same make/model* speaker if you want to make a mid base aray and have the fronts playing louder ?

*better or easier to get a unified sound thats less likely to drag the sound rearwards ?*

2. Or use a louder mid base up front like the B+C pro driver with a normal midbase to the rear ?

3. Will T/A still be needed to sync' the midbases if you have the fronts playing louder ?


----------



## andy335touring

Ideally you'd have mid bases playing up to 600hz ish ?

At the moment my *set up* it oriented to have the cross over point in the 200-300hz range to keep the cross over point away from the vocal range ?

*SLS 8" and Trinity WB*



Patrick Bateman said:


> In the two octaves from 160 to 640hz, there's virtually no cabin gain. Look at my measurements, or JBLs. They demonstrate this as clear as day. So it takes gobs of power, gobs of efficiency, or BOTH to generate SPL in those octaves.


----------



## Patrick Bateman

ehkewley said:


> Perhaps a backstory for those of us who are uninitiated?


Here's my take on it. Keep in mind I'm an "outsider." I've never met Richard Clark.

Anyways...

Richard Clark bought the Grand National from Speaker Works, which is owned by the Holdaways. The Holdaways are genuinely great guys. For instance, I once visited their store, and discussed horns with Eric Holdaway. Rather than sell me a pair of horns, I think Eric realized I had the know-how to build my own, and he actually encouraged me to do it!

That really impressed me, that Eric was more interested in encouraging someone to become "invested" in the hobby, rather than making a quick sale. (I actually bought a set eventually, after building my own. Wanted to compare their horns to my own creations.)

While the Holdaways openly discussed their cars, Richard Clark was *incredibly* oblique about the Grand National. It's not that he wouldn't discuss it. But his discussion always seemed to include statements that were questionable, and he would never directly confirm or deny The Secrets of The Grand National. His amp challenge pissed off people in a huge way too.

In Clark's defense, he was involved in a sport. In auto racing it isn't uncommon for teams to pull the same stunts. For instance, the drivers that Clark used gave him a competitive edge, and that's one of the reasons he never came out and stated what they were. He was particularly secretive about the midrange configuration, and I think the midbass and the midrange were the number one reason that his soundstage was so famous.

Kimura, Matsubara, and Eldridge all used horns. IIRC, Eldridge actually bought his Altecs from Clark. What gave Clark the competitive edge?

I think the answer lies in his midrange and midbass solution - and that's why he never admitted what it was. Ever.


----------



## chad

**** man, I gots some Altec drivers for sale! Name the right price and I'll throw in some 511B horns!


----------



## briansz

If I am remembering my articles correctly, RC is on the record as saying the Buick brought in over $50K in prize money (whether or not that broke him even on his investment is subject to debate). When that sort of coin is on the line, you'd better believe people are going to spin propaganda if not make up outright lies about the golden goose.

Even if that was a factor back in the day, I'm not sure what the upside to keeping a lid on it fifteen years later could be. It's not as if RC is out there selling the 'magic midrange maker' using his Grand National technology. Maybe there is just no good incentive to reveal the truth either.


----------



## Patrick Bateman

chad said:


> **** man, I gots some Altec drivers for sale! Name the right price and I'll throw in some 511B horns!


Well I can't fit Altecs on my dash 

Eldridge had to tear his four runner apart to fit them in.

Hence, my use of Unity horns.


----------



## Patrick Bateman

briansz said:


> If I am remembering my articles correctly, RC is on the record as saying the Buick brought in over $50K in prize money (whether or not that broke him even on his investment is subject to debate). When that sort of coin is on the line, you'd better believe people are going to spin propaganda if not make up outright lies about the golden goose.
> 
> Even if that was a factor back in the day, I'm not sure what the upside to keeping a lid on it fifteen years later could be. It's not as if RC is out there selling the 'magic midrange maker' using his Grand National technology. Maybe there is just no good incentive to reveal the truth either.


Think about it this way. Imagine that you're a race car driver, and you won a series of races with your Bugatti Veyron.

After winning the races, you told everybody that the secret to your success was the paint job.

Then everyone spent the next twenty years copying your paint job and applying it to their Honda Civics.

This would be good for lulz, no?

And I don't think this is an exaggeration. I've modeled the performance of Clark's solution. The output and lack of distortion from those JBL and Altec drivers is mind boggling.

Even the most unobtanium car audio woofers get crushed in this comparison, just as a Honda Civic will never outrun a Bugatti.


----------



## 94VG30DE

briansz said:


> Even if that was a factor back in the day, I'm not sure what the upside to keeping a lid on it fifteen years later could be. It's not as if RC is out there selling the 'magic midrange maker' using his Grand National technology. *Maybe there is just no good incentive to reveal the truth either.*


I'm not sure there is much of an upside to letting it out of the bag either. It would be going against his previous tendencies, and would require a big expenditure of effort to document what he did. There might be a little benefit to learning all the tricks he tried to create the effects he did, and what worked and what didn't. In the grand scheme of things, few people (compared to the greater car audio "industry" population) would likely be able to understand and/or utilize the concepts used to make that car what it was. For most it would simply be a completion of a piece of history, and if that is it's only merit I'm not sure it is worth releasing. It's possible that RC is thinking the same thing. 

Then you have guys like P Bateman (and a LOT of other guys on this forum) that seem to simply enjoy putting the information out there and let the masses do with it what they will. But that is not everyone's style. Annoying, possibly, but not necessarily wrong for someone to withhold their own research and findings.


----------



## jbholsters

If you do a search over at carsound forums some of the stuff might still be up. I really long thread about the Buick vanished a few years ago. Basically RC said in an article (with pix of the drivers in his hand) that he replaced the compression drivers with some huge Altecs and that he had diamond crystals grown on the diaphrams. The problem is that those drives would have stuck up through the dash by about 4-5 inches. The horns curved up toward the underside of the top of the dash. He also said that he installed a pair of 4" mids under the dash. He also fained ignorance about the installation of 9v batteries in the amps (kept amps from having noise). blaa blaa blaa on and on...... I judged the GN when the Holdaway's owned it and again at a Regional in Philly a while after RC had it. Also listened to it a few years later in the Monster Cable booth at a trade show in Baltimore. The car didn't sound any better after RC "changed things". In fact, Eric Holdaway usually went to events and tuned the car after it was sold. If my memory is correct, Eric was demoing the car in Baltimore. At one point RC took out the Alpine amps and replaced them with Kenwoods (it was not the same car with the Kenwood amps). He also said that the mid bass drivers pulled the stage to the rear, but I never noticed it when listening. But to be fair I heard it 4 times for about 5-10 minutes each sitting, so it could depend on the music that was being played. He always used to demo a Linda Ronstadt song, which sounded phenomenal in that car. Hands down the most dynamic car I ever heard. Also the best sounding car, by far with horns. That car got so loud you couldn't stand it. In Philly he hit 130dB in the lanes like 4-5 seconds into Lil Daddy, which is impressive. That song is not bass heavy. (4-5 seconds is still on the drum stick hits)


----------



## jbholsters

Oh, I think he also said that he replaced the D/A converter in the 7909. He added 3 1 fared stiffening caps (under the hood). By all accounts it was the most winning car in history. That car (thanks to Holdaways) started the use of horns in cars, AP mats. RC made the use of stiffening caps all the rage, and helped launched his venture with David Navone (AutoSound 2000). RC was also responsible for putting together several of the IASCA Cd's as well. If I remember correctly he was instrumental in the development of pressing Cd's and owns/owned one of the companies that does so.


----------



## Patrick Bateman

jbholsters said:


> <snip>He always used to demo a Linda Ronstadt song, which sounded phenomenal in that car. Hands down the most dynamic car I ever heard. Also the best sounding car, by far with horns. That car got so loud you couldn't stand it. In Philly he hit 130dB in the lanes like 4-5 seconds into Lil Daddy, which is impressive. That song is not bass heavy. (4-5 seconds is still on the drum stick hits)


Thanks for taking the time to write that. I've never heard the car. But I've "reverse engineered" it, and the sims are jaw dropping.

For instance, let's say you put a couple of seven inch woofers in your door. Cost is no object, so you use a pair of Scan Speak midbasses with an efficiency of 87 db and feed them 250 watts each. Even with zero power compression, that gets you to 117db.

Now look at the Grand National. My sims demonstrate that the woofer can take 500 watts without running out of excursion, and with an efficiency of 95db that gets you to 122db... With ONE woofer.

And as you can imagine, a pair of Scan Speaks are on the verge of detonation at 500 watts, while a prosound twelve is built for abuse. 

Of course Clark isn't the only person who ever used a prosound midbass, or the only person who ever used large woofers for midbass. The difference is that no one ever took it to this extreme, back then or now. Kimura used a JBL model that had 6db less output because it was excursion limited. Zausmer used a B&W model with over ten DB less output, because B&W optimized it for sub bass, not midbass.

I'm crunching the numbers on an enclosure which *should* be able to match it. It's very difficult to exceed the midbass performance of the Grand National, but I have a few tricks up my sleeve...

I'll post the simulations once they're finished, and then I intend to build it.


----------



## chad

There is certainly a lot to be said for pure un-adulterated efficiency and low power compression. My stance is quite firm in that too many people look at X-Max figures.


----------



## michaelsil1

chad said:


> **** man, I gots some Altec drivers for sale! Name the right price and I'll throw in some 511B horns!


I had a home system in the 60's with Altec Lansing 15's and Horns. 

At the time it was the Sh*t.


----------



## 14642

I think it's also important to consider one's motivations. RC's motivation may have been to sell books, stuff, seminar tickets and to help the industry out of the dark ages of witchery and into the enlightened era of science. I'm thankful that he was partly successful. However, some of his postulates are as useful as the snake oil pitched by the likes of wire companies. 

There's no practical difference between suggesting something is true when it isn't and disproving a myth without offering a reliable alternative solution. It isn't sufficient to say, "this doesn't work" without saying "but this does and here's why". 

As a hobbiest, one's motivation may be to learn and share. As a product developer, one's motivation may be to learn and sell. As a competitor, one's motivation may be to learn, conceal and win. 

I believe that If we make the right products, telling the truth about the way thay work and why they work the way they do ought to be the right sales pitch.


----------



## Izay123

Right now I'm working on a system design for my girlfriend's 1998 Cadillac Seville. I am getting held up about what to do for midbass. I'm planning to go with Boston stuff all around (PRO60SE's in front, multiple G512's IB) but Im still unsure that I will get enough midbass juice. A few years ago, I built my Buick Regal with 2 15's for lows and 1 10" for midbass/high subbass shooting through the ski pass and it worked pretty well. I'm wondering how well using lets say 2 8" or 2 10" boston subs bandpassed from ~80 to ~200/300 hz would do if mounted sealed in the rear deck and individually time aligned. Would there be noticeable beaming if I used 12's instead? what about mono midbass time delayed?


----------



## chad

michaelsil1 said:


> I had a home system in the 60's with Altec Lansing 15's and Horns.
> 
> At the time it was the Sh*t.


I even got the N500 networks for them... you want them, I have them, and don't really want to have them.


----------



## briansz

Patrick Bateman said:


> I'm crunching the numbers on an enclosure which *should* be able to match it. It's very difficult to exceed the midbass performance of the Grand National, but I have a few tricks up my sleeve...
> 
> I'll post the simulations once they're finished, and then I intend to build it.


I think I speak for a lot of people when I say that I really appreciate the time and effort you put into your threads and the forum in general. I'll be waiting for more info and updates on this. Neutrality in a system impresses me, but at the end of the day dynamics gets it done for realism IMHO.

I've just been gifted with a '73 F100 pickup that has a nice big simple interior. I have some USD Horns, a lot of power (1770 watts RMS on three old school Zed amps) and two JBL 1200GTi's on tap, and will be looking around for midbasses that can come close to keeping up for a build in the spring.


----------



## mikey7182

Andy Wehmeyer said:


> I think it's also important to consider one's motivations. RC's motivation may have been to sell books, stuff, seminar tickets and to help the industry out of the dark ages of witchery and into the enlightened era of science. I'm thankful that he was partly successful. However, some of his postulates are as useful as the snake oil pitched by the likes of wire companies.
> 
> There's no practical difference between suggesting something is true when it isn't and disproving a myth without offering a reliable alternative solution. It isn't sufficient to say, "this doesn't work" without saying "but this does and here's why".
> 
> As a hobbiest, one's motivation may be to learn and share. As a product developer, one's motivation may be to learn and sell. As a competitor, one's motivation may be to learn, conceal and win.
> 
> I believe that If we make the right products, telling the truth about the way thay work and why they work the way they do ought to be the right sales pitch.


Ironically (or maybe not so), the core of his setup came from you guys.  Which is to say, JBL has been making badass, ahead-of-its-time products since long before I was born. It would be nice to figure out exactly what made his car so successful, but as has been mentioned, it's a "secret of the pros." See you on the 9th green at 9.


----------



## ehkewley

Andy Wehmeyer said:


> I think it's also important to consider one's motivations. RC's motivation may have been to sell books, stuff, seminar tickets and to help the industry out of the dark ages of witchery and into the enlightened era of science. I'm thankful that he was partly successful. However, some of his postulates are as useful as the snake oil pitched by the likes of wire companies.
> 
> There's no practical difference between suggesting something is true when it isn't and disproving a myth without offering a reliable alternative solution. It isn't sufficient to say, "this doesn't work" without saying "but this does and here's why".
> 
> As a hobbiest, one's motivation may be to learn and share. As a product developer, one's motivation may be to learn and sell. As a competitor, one's motivation may be to learn, conceal and win.
> 
> I believe that If we make the right products, telling the truth about the way thay work and why they work the way they do ought to be the right sales pitch.


I agree completely. Works well for Software as well *cough* Microsoft *cough*. I much appreciate it when people, and corporations take the time to explain things.. be it technology or a product.


----------



## jbholsters

Back in the day everyone BS'd about what was in their cars.

Remember too that 4 of the 3545's were bridged (one on each sub and one on each mid) @ 700watts, while the 5th one was playing stereo @ 250 x 2 to each horn. 

Patrick, the mid bass were JBL 2204's.

Call Eric and he should have the specs for the 15's. They marketed them in there USD line of speakers.

Clark also added servo drives, which were located in the sub box.


----------



## thehatedguy

He also said his Caddy sounded better than the GN.

Those 15s were Emilar or Radian...Emilar had the exact same part number and specs. The new owner of the Acura said he got some new 15s from USD for it and they had Radian stickers on them.

RC said the GN had Altec 288Gs in it...but the install/build log showed some Emilar or Radian drivers on the horns. I saw the magazine article where he had the horns with the Altec drivers attached, and I don't have a clue as to how they would physically fit into the car.


----------



## chad

Emilar and radian were one in the same for a while, Emilar died off and was absorbed into radian, then radian began concentrating on compression drivers and OEM replacement diaphragms.


----------



## hal2000

The efficiency and tonality of those old JBL's keep me dipping into my vintage lockup. : )


----------



## Patrick Bateman

Izay123 said:


> Right now I'm working on a system design for my girlfriend's 1998 Cadillac Seville. I am getting held up about what to do for midbass. I'm planning to go with Boston stuff all around (PRO60SE's in front, multiple G512's IB) but Im still unsure that I will get enough midbass juice. A few years ago, I built my Buick Regal with 2 15's for lows and 1 10" for midbass/high subbass shooting through the ski pass and it worked pretty well. I'm wondering how well using lets say 2 8" or 2 10" boston subs bandpassed from ~80 to ~200/300 hz would do if mounted sealed in the rear deck and individually time aligned. Would there be noticeable beaming if I used 12's instead? what about mono midbass time delayed?


It's difficult for me to match the perfromance of the GN's 2204s because they have more displacement than my eights. One of the ideas that I'm considering is putting them in bandpass enclosures under the dash. This gets you a few things:


The bandpass enclosure reduces the excursion of the midbass to almost nothing at the low end.
The B&C midbass has higher power handling than the JBL 2204
Bandpass loading increases the efficiency, depending on the bandwidth
Combine those three things, and you end up with a midbass solution that can exceed the 2204. (I hope!)
Another neat thing about the bandpass is that you can put the bass where you want it, by locating the vent as far and wide as possible.

To make this scheme work, you need a midbass with a very specific set of parameters. Bandpass boxes and horns aren't like conventional enclosures - you can't just use any driver.

To determine what range you can cover, insert your Thiele Small parameters* into this equation:

_2 * FS / QES_
For my 8NDL51s, this gives me:
_2 * 66 / .41 = 324HZ_

In other words, the 8NDL51s work ideally in a bandpass enclosure with a tuning frequency centered at 324hz. You can squeeze a couple of octaves out of a bandpass, depending on the QTS value and how "peaky" it is. But it's safe to assume the 8NDL51 will cover 162 to 648hz.

In a car we can get that down to 81hz, thanks to cabin gain.

But you can see from the equation that you'll run into problems if the T/S isn't right. If it resonates too high there's a hole between the subs and the midbass. If the bandpass resonates too low, there's a peak in the midbass due to cabin gain. Of course the second one can be dealt with via EQ, but it *does* make integration with the midrange or waveguides tricky.

HTH

* B&C 8NDL51 is a lightweight 8" woofer that woofer - B&C Speakers - B&C 8NDL51 neodymium 8" mid-bass speaker for 2 or 3-way systems. B&C 8NDL51 neodymium bass speakers available now.


----------



## jbholsters

thehatedguy said:


> I don't have a clue as to how they would physically fit into the car.


they wouldn't have

Not sure why but I thought the 15" were EV


----------



## jbholsters

good luck. I never thought bandpass mid-bass worked (SQ) as well as plain old sealed. Too bad you can't fit a pair of 12's under there. I've seen lots of 2204's for sale and you can get them re-coned easily.


----------



## ClinesSelect

jbholsters said:


> Back in the day everyone BS'd about what was in their cars.
> 
> Remember too that 4 of the 3545's were bridged (one on each sub and one on each mid) @ 700watts, while the 5th one was playing stereo @ 250 x 2 to each horn.
> 
> Patrick, the mid bass were JBL 2204's.
> 
> Call Eric and he should have the specs for the 15's. They marketed them in there USD line of speakers.
> 
> Clark also added servo drives, which were located in the sub box.


I might have a spec sheet for the 15s. I still have three of them in the original boxes.


----------



## jbholsters

cool, I'd be interested to see it. As I said before, the original box they were in was huge and took up most of the trunk, hence the switch to the AP enclosure. The Holdaway's were way ahead of the curve. 


There you go Patrick, maybe ClinesSelect will sell them to ya. Then you can start shopping for a mid 80's GM T-Type


----------



## Patrick Bateman

jbholsters said:


> good luck. I never thought bandpass mid-bass worked (SQ) as well as plain old sealed. Too bad you can't fit a pair of 12's under there. I've seen lots of 2204's for sale and you can get them re-coned easily.


Yeah horns are exceptionally difficult to work with... You really need a lot of time and dedication to geth them right. A lot of measurements helps too 

Also, horns and bandpass boxes are two points on a spectrum. A bandpass box is basically a horn with a mouth that's tuned to one frequency instead of many.


----------



## Patrick Bateman

thehatedguy said:


> He also said his Caddy sounded better than the GN.
> 
> Those 15s were Emilar or Radian...Emilar had the exact same part number and specs. The new owner of the Acura said he got some new 15s from USD for it and they had Radian stickers on them.
> 
> RC said the GN had Altec 288Gs in it...but the install/build log showed some Emilar or Radian drivers on the horns. I saw the magazine article where he had the horns with the Altec drivers attached, and I don't have a clue as to how they would physically fit into the car.


IIRC, Clark and Eldridge were running Altecs, and nearly everyone else was running Radian 475PB.

In my 2001 Accord I started with Selenium, moved up to USD, and then replaced the USD (Radian 450PB) with a JBL.

Here's a pic of the JBL, with a freaken' PAINT CAN for comparison. The Altec is basically the same size.









I fit these under the dash of an Accord. You can see from the horn that it was chopped up and re-assembled. That's the easiest way to make a big driver fit. Instead of chopping up the car, chop up the horn.


----------



## thehatedguy

I know RC said they were Altecs...he also said he had Bose 4s gated to the 12s. From the pictures I saw, there was no way what he was pictured holding would have fit in his car.


----------



## chad

My Altec 806A's are about the size of the JBL's PB picd


----------



## danssoslow

The memory runs on me at times; but I remember an article in CA&E where he said the speaker in the horns had been built with some NASA technology. Anyone recall this?


----------



## Patrick Bateman

danssoslow said:


> The memory runs on me at times; but I remember an article in CA&E where he said the speaker in the horns had been built with some NASA technology. Anyone recall this?


If memory serves me, Clark claimed in the CA&E article that he had the diaphragms of the Altecs replaced with a diamond composition.

Then again, I haven't read the article in fifteen years or so. Wish I'd held on to a copy of that.

The Accuton diamond tweeters are $5800/pair, and are much less complex than the Altec compression drivers.










Personally, I take this claim with a grain of salt. A diamond diaphragm offers few benefits. If you don't need power handling, aluminum is tough to beat. I replaced the titanium diaphgragms in my JBLs with aluminum. It lowered the power handling but increased high frequency extension. (Titanium is more durable than aluminum, but heavier.)


----------



## Nitin

danssoslow said:


> The memory runs on me at times; but I remember an article in CA&E where he said the speaker in the horns had been built with some NASA technology. Anyone recall this?


i remember reading that article - i lent my copy of the mag to a buddy a long time ago and never got it back - does anyone have that article - if so could they scan it and let us all download it so as to remember what Richard said in the article 

if i recall correctly they had a pic of him holding the speaker drivers and it stated that they cost something like $15000 at the time and used a diaphragm made of some form of diamond (as was stated above) i cant remember any mention of NASA but i could be wrong since it was a really long time ago

someone above also questioned whether he had replaced the DAC on the 7909 - according to that article he was using an Apogee studio DAC


----------



## danssoslow

I don't quite remember exactly what I read; but believe it was something to the effect of diamonds crystallizing on a membrane. Something reminiscent of rock candy forming on a piece of string; and that it was a NASA developed technology?

I was in my teens, but not yet smoking weed heavily. Please forgive me. I do, however, remember the picture of him holding that horn up like a proud fisherman.


----------



## 60ndown

Patrick Bateman said:


>


hmmm my favorite,




*DEEP BASS.*


----------



## thehatedguy

I built some 1/3rd sized 250 hertz exponential horns for the old Accord...I know how large they can get. Mine were for a 2" throat driver, and the 1.4" Altecs would have been even longer.

Found some pictures for size comparison sakes...roughly about the same size that were in the GN.


----------



## Patrick Bateman

danssoslow said:


> I don't quite remember exactly what I read; but believe it was something to the effect of diamonds crystallizing on a membrane. Something reminiscent of rock candy forming on a piece of string; and that it was a NASA developed technology?
> 
> I was in my teens, but not yet smoking weed heavily. Please forgive me. I do, however, remember the picture of him holding that horn up like a proud fisherman.


In the last post I said that there was no advantage to doing it, which made me doubt that he did. But one thing I hadn't considered is that it would allow the Altecs to play lower, at the cost of efficiency. It *might* improve the breakup behavior too. So who knows, maybe he DID do it?

Here's some info on Beryllium versus diamond from NASA's Lewis Research Center.

http://www.springerlink.com/content/w23764812n7l3k47/


----------



## Oliver

I give RC credit for seeing that he didn't need to do much to make it the best it could be after some tinkering


----------



## danssoslow

Patrick Bateman said:


> In the last post I said that there was no advantage to doing it, which made me doubt that he did.





Whether it was actually done or not is not so much my concern; but rather the claims themselves. A change to lighter cones for the midbass was also mentioned.


----------



## chad

Patrick Bateman said:


> If memory serves me, Clark claimed in the CA&E article that he had the diaphragms of the Altecs replaced with a diamond composition.


He personally flew his bottle rocket to Neptune to do it by hand.


----------



## mitchyz250f

Patric - You wrote; 'But it's safe to assume the 8NDL51 will cover 162 to 648hz. In a car we can get that down to 81hz, thanks to cabin gain.

With the the JBL 12" and 500 watts, RC has 122 db with one speaker, but he was still at 116 db at 80 Hz without cabin gain. If as some people have said, the MB's were later ported (assuming 35L, tuned to 53 Hz) that one 12" would have been able to reach 120 db at 80 Hz without cabin gain. At 55Hz ported, the cone would have been moving less than 2.5 mm. Simply amazing

It is very hard to beat the performance of a 12" ProAudio MB and great amps.


----------



## chad

mitchyz250f said:


> If as some people have said, the MB's were later ported (assuming 35L, tuned to 53 Hz) that one 12" would have been able to reach 120 db at 80 Hz without cabin gain.


Sure deal, if you had the microphone element 6" from the cone... I cry ********, I use the things. 80 cycles, 120dB and that thing would be confetti even at 1M.


----------



## mitchyz250f

Let me try to dig myself out of this hole.

The mistake I made with the simulation is the while the 2206 is rated at 600 watts pink noise, the 2204 is only rated at 350 watts pink noise. Is that what you meant Chad?

Regarding the simulation, according to UniBox the JBL 2404 with 350 watts, in a 35L box, tuned to 51 Hz, would be at 119 db at 80 Hz. At 40 Hz you would exceed the max excursion. 

Chad -Would it be possible to run the speakers at this level with at steep crossover at 80 Hz or so?

My point was that it is hard to beat a 12" Proaudio MB with a 8" ProAudio that's all.


----------



## Patrick Bateman

mitchyz250f said:


> Patric - You wrote; 'But it's safe to assume the 8NDL51 will cover 162 to 648hz. In a car we can get that down to 81hz, thanks to cabin gain.
> 
> With the the JBL 12" and 500 watts, RC has 122 db with one speaker, but he was still at 116 db at 80 Hz without cabin gain. If as some people have said, the MB's were later ported (assuming 35L, tuned to 53 Hz) that one 12" would have been able to reach 120 db at 80 Hz without cabin gain. At 55Hz ported, the cone would have been moving less than 2.5 mm. Simply amazing
> 
> It is very hard to beat the performance of a 12" ProAudio MB and great amps.


My sims are consistent with your sims. 115db at 80hz in a small sealed box, with no cabin gain. What REALLY impresses me is the output at 200hz - 122db!

That's about ten DB better than even the best car audio woofers.







Here's a comparison of two woofers and four enclosures. The most impressive is certainly the JBL 2204. It has wide bandwidth, high efficiency, and incomparable output. The blue line is a B&C 8NDL51. It's response is comparable, but it has less output due to a lack of displacement. (It's xmax is the same, but the cone is smaller, hence less output.)

The orange line is a bandpass box with the B&C. By limiting it's output, we can get the most output of all four... But only over an octave and a half.

Check out the green curve - it's smaller than the bandpass box, but has a lower F3. It also plays higher. It's a horn for the 8NDL51 with a dramatically undersized mouth.

In summary, the JBL in the Grand National is a "no brainer." But there's no way for me to fit it in the front of my car. The 8NDL51 is a tight squeeze, but it will fit. It can't match the JBL in a conventional enclosure, but in an unconventional box we can trade bandwidth for output.


----------



## western47

How does the all effect the transition frequency of a car cabin?

I am assuming that the transition frequency is much higher in a car than it is in the usual home listening environment. How might that effect both the bass and mid bass region? Getting 'natural' or even bass in multiple listening positions in a home environment requires the use of multiple sources.


----------



## chad

mitchyz250f said:


> Chad -Would it be possible to run the speakers at this level with at steep crossover at 80 Hz or so?


you can, but they don't last very long. Even the 2206 crossed at 80 will experience cone failure (usually right at the first rib) at an accelerated rate.

For pro use, there's just not enough surface area there. there were not intended to play that low at high levels, not even designed to for the most part.


----------



## Patrick Bateman

western47 said:


> How does the all effect the transition frequency of a car cabin?
> 
> I am assuming that the transition frequency is much higher in a car than it is in the usual home listening environment. How might that effect both the bass and mid bass region? Getting 'natural' or even bass in multiple listening positions in a home environment requires the use of multiple sources.


Here's my understanding of the situation -

In the home, the use of an array of subwoofers can smooth the frequency response. Geddes suggests this for his loudspeaker customers, and Keele has written about this in a number of papers that are available online.

I have personally used this technique at home, and it's solved a lot of integration issues. (Basically the subs "blend" better, and sound more natural.)

There is a frequency where the room transitions to "pressure" mode. For example, in my listening room that frequency is 75hz. Based on my studies of the bass problem, it appears that *the benefits of multiple subs are greater above this frequency, and less below.*

I believe that this is a very important distinction, particularly for car audio. If my hypothesis is correct, it means that there are a lot of good reasons to use a woofer array *above* the pressure mode.

Also, the reason why the woofer array is less useful below the pressure mode is the sheer wave length. I could write a couple of pages on why this happens, and bore everyone to tears.







Rather than put everyone to sleep, here's a picture. My car transitions to pressure mode at 281hz. I believe this graph illustrates nicely what I am talking about. This graph is the *polar* response of an eight inch midbass in my car, along with the *average* of those polars.

In the midbass, there are ENORMOUS swings in the frequency response, with peaks and dips on the order of FIFTEEN DB. Fifteen DB is huuuuuugely audible. *Yet the AVERAGE of the responses is smooth.*

The response is particularly bad in the two octaves from 200 to 800hz.

Keep in mind, this isn't a driver issue - this is the car itself screwing up our response. *At these low frequencies we can't control the directivty easily.* Waveguides that big won't fit in the car, and "conventional" arrays are too big too.

What I am proposing in this thread is the use of an array of midbasses, not subwoofers, to smooth the midbass. I have a hunch that it can yield the same benefits that are heard at home - more natural bass. It is also my belief that many of the subwoofer integration issues that make car audio so difficult aren't subwoofer problems at all - they're midbass problems.

Just look at the graph, and realize that your midbasses are probably doing the same thing. And imagine how difficult it is to have "natural bass" when the response is changing ten decibels when you move your head an inch or two.

If we can solve THAT problem, I believe it will overcome the majority of the bass integration issues we face in car audio.


----------



## Patrick Bateman

Mean to mention something about the graph -

_In the measurement you'll notice the response is terrible at 280hz, is quite good at 200hz, then goes to hell again at 140hz. Not coincidentally, these frequencies correspond to the dimensions of my cabin - about 48" wide by 96" deep. An array of loudspeakers would smooth this out, by randomizing the reflections. Below 140hz you'll notice that the polar response is consistent. The reason that it's consistent is that reflections cease to exist below that frequency - the wavelength of the sound exceeds the dimensions of the cabin._

It isn't physically possible to make the speaker sound exactly the same everywhere in the cabin. But we CAN make it consistent. What we want to avoid is the violent frequency response swings, with violent peaks and dips that come out of nowhere. Below 280hz you can see that the response still varies, but the variations are relatively smooth and well behaved.


----------



## mitchyz250f

Patrick - Can we define terms? We use 'woofer' to describe anything from 3" to 12" drivers. Are we really saying any driver that s operating from 80 to 500 Hz plus? 

Also, I could never consider having eight woofers. But, I would consider 4 woofers. Since the overall dimension of the car are constant, how can we calculate the best place to put the second set off smaller woofers that might operate only from let’s say 140 to 280 Hz only. Does that make any sense?

You discuss the transition from pressure mode, is this best accomplished with a steep crossover over or less steep, that is, if your woofer (MB) can handle it.


----------



## 240sxguy

Very interesting, since RC had his midbasses right where my subwoofers are. It would be pretty easy to stick a pair of those in there if I were wiling to give up trunk space for a subwoofer setup.

Evan


----------



## Patrick Bateman

mitchyz250f said:


> Patrick - Can we define terms? We use 'woofer' to describe anything from 3" to 12" drivers. Are we really saying any driver that s operating from 80 to 500 Hz plus?


That's a good point. Last night I measured the response of an eight inch B&C woofer, along with a 3" Peerless computer speaker. The Peerless had a lower F3!

So, yeah, we're talking about any driver that can cover the midbass octaves. To me that's the three octaves from 80 to 640hz.



mitchyz250f said:


> Also, I could never consider having eight woofers. But, I would consider 4 woofers.


That's why I have a tendency to use computer speakers. They can play low in extremely small enclosures. For instance, it's easier for me to hide eight small enclosures than two big boxes for a set of eights. And when I mean small, I mean SMALL. We're talking 4" cubes. This week I finally figured out how to measure distortion, and the results were surprising to say the least. (Here's a hint - some of these computer speakers measure as good as they sound.)



mitchyz250f said:


> Since the overall dimension of the car are constant, how can we calculate the best place to put the second set off smaller woofers that might operate only from let’s say 140 to 280 Hz only. Does that make any sense?


I wish I knew! I spent nearly two days on a computer model of my cars interior, and it didn't work at all. I could post it if you want to mess with it.

Because the model doesn't work, I believe the only thing we can rely on are measurements in an actual car.

Random locations will smooth the response, but the soundstage will be dominated by the first arrival (Haas effect.)

Due to that, I intend to "taper" the volume of the midbasses that are closer than optimal. For instance, the midbasses under the dash will get 4x as much power as the ones that are located in the quarter panels. The extra power to the primary midbasses prevents the quarter panels from dominating the sound field.



mitchyz250f said:


> You discuss the transition from pressure mode, is this best accomplished with a steep crossover over or less steep, that is, if your woofer (MB) can handle it.


For the past few weeks I've been trying both. Personally I prefer the shallower slopes. When multiple woofers are overlapping, the gentler slopes sound more natural and the soundfield is more "diffuse."

As Andy Wehmeyer warned in a previous post, there *are* drawbacks however. I've noticed that intelligibility suffers. At the moment I am using no power tapering whatsoever, and I'm confident that including this will overcome the drawbacks.


----------



## SSSnake

> Very interesting, since RC had his midbasses right where my subwoofers are. It would be pretty easy to stick a pair of those in there if I were wiling to give up trunk space for a subwoofer setup.
> 
> Evan


Rather than replacing them with midbasses see if they can handle a higher xover freq without localization. There is NO reason not to in your case (if I remember your install pics correctly... - the first thing I thought about was swapping the subs out to pro audio woofers and creeping up the xover freq). The only issue is distance to the listener and this should be addressed with time alignment.


----------



## western47

This of course becomes a more complex problem:surprised:

You mentioned locating the main mid in the front of the car. Knowing your car type pretty well, can I ask where you are proposing for location and port location on the BP box?

Multiple small drivers makes a lot of sense as you can place them in different areas. The problem I ran into before when considering a solution mildly similar to this scenario is the fact that you would ideally have control over each driver output using a single amp channel with phase control. Any thoughts on this?


----------



## jbholsters

Patrick, or anyone else. A friend of mine still has the CA&E article on the Buick. When I get a chance I can go get it, scan in, and make it available if anyone wants to take a look.

I was trying to remember what purpose the servos served, but I'm not sure if that article goes into it. Haven't read it for 10? years or so.

Patrick, I take it you are planning to run (4) 4" per side up front? I would think you could easily fit them in the box and location against the firewall where you have/had the B&C's. Do you have any pics of those locations anymore? The pix on carsound forums are gone.


----------



## Fast1one

This is getting very interesting. I have considered multiple subwoofers in a car for quiet some time. Patrick, once again your dedication to science is paving the way for new techniques. 

I do have some questions though. I don't have very much processing available to me other than your basic 3-way active network and time alignment. With the traditional multi-sub alignments, it is beneficial to have adjustable crossover networks for EACH woofer. Obviously, level compensation can easily be achieved using L-pads. But what about crossover points? Would it be ok to just have a set bandpass for the "extra" woofers and just randomize their positions?


----------



## 94VG30DE

Fast1one said:


> This is getting very interesting. I have considered multiple subwoofers in a car for quiet some time. Patrick, once again your dedication to science is paving the way for new techniques.
> 
> I do have some questions though. I don't have very much processing available to me other than your basic 3-way active network and time alignment. With the traditional multi-sub alignments, it is beneficial to have adjustable crossover networks for EACH woofer. Obviously, level compensation can easily be achieved using L-pads. But what about crossover points? Would it be ok to just have a set bandpass for the "extra" woofers and just randomize their positions?


This is what I was worried about as well. A lot of us are going to be short on processing power to run multiple drivers at multiple levels and crossover points, if that is the idea you have in mind.


----------



## Nitin

jbholsters said:


> Patrick, or anyone else. A friend of mine still has the CA&E article on the Buick. When I get a chance I can go get it, scan in, and make it available if anyone wants to take a look.
> 
> I was trying to remember what purpose the servos served, but I'm not sure if that article goes into it. Haven't read it for 10? years or so.
> 
> Patrick, I take it you are planning to run (4) 4" per side up front? I would think you could easily fit them in the box and location against the firewall where you have/had the B&C's. Do you have any pics of those locations anymore? The pix on carsound forums are gone.


that would be much appreciated thank you - ive been asking around if anyone has that article - im dying to read it again


----------



## mitchyz250f

Without TA, the easiest way, if possible, would be to find a place within the 'Circle of Confusion' in which the 'woofer' is producing diffent nodes.


----------



## SSSnake

Not really "within" but on the same radius (unless you use TA to adjust arrival times).


----------



## 240sxguy

SSSnake said:


> Rather than replacing them with midbasses see if they can handle a higher xover freq without localization. There is NO reason not to in your case (if I remember your install pics correctly... - the first thing I thought about was swapping the subs out to pro audio woofers and creeping up the xover freq). The only issue is distance to the listener and this should be addressed with time alignment.


Interesting thought here, I can T/A out the woofers seperately from my 8053. I don't have any gear installed at all right now except for woofers. Amps are on the shelfs, deck is at united radio getting a transport. I have phass tweeters and usher woofers ready for the front stage. Since it is going to be such a drastic gear change I might as well try it. 

Evan


----------



## 94VG30DE

I guess with only using 4 woofers, you could probably place the "auxiliary" pair of midbasses somewhere close to the same distances, and then start adjusting your T/A from that point instead of the main set right? That way you wouldn't explicitly have control over those speakers, but you would have active control over your other 4 speakers (plus sub). With speaker level adjustment, T/A and phase, you might be able to get everything close.


----------



## mitchyz250f

SS-That is what I meant, but not what I wrote. Thanks.


----------



## npdang

This whole thread is pretty much summed up in my sig 

I find that one of the most difficult things to do in a car is to improve the sense of depth and space, while at the same time improving imaging and tonal balance. While the former requires taking advantage of the listening environment's acoustics, the latter generally requires minimizing room interactions. I'm a believer that dsp is going to be the way of the future in this respect... especially with respect to the ability to be able to "imprint" the sonic and spatial characteristics of a much larger room onto a smaller one.


----------



## 14642

OK. Time to weigh in here.

Patrick, I'm amazed by your dedication to this and the calm and cool way you handle all of this. I also appreciate your willingness to make and post real measurements. 

Some time ago, some of our research guys developed a modeling program that would take measurements made of up to 8 woofers (or maybe 6) in a room at several microphone positions and would caluclate the level, delay and a couple of EQ bands required to smooth the response over all the measurement positions. THe reason for this research was to compliment (or maybe make obsolete) the procedure by which subs are placed in modes and anti-modes. Partners often object to the aesthetics of bunches of subs located in those locations because they aren't often the nicest looking or most convenient locations. For subs in rooms, it worked great and provides smooth and consistent bass over the entire coverage area. This was implemented in a product called the BassQ. Here's a link ot the owner's manual: http://manuals.harman.com/JBL/HOM/Owner's%20Manual/BassQ_OM_LR.pdf

At some point during the development of this algorithm, I caught wind of this and wondered if it would work in a car--but not at super low frequencies (below 50Hz) because this kind of optimization simply isn't needed down there. My suggestion was that we should try it in the midbass--precisely in the range that you're looking at. The size of the speaker and the excursion requirements of the speaker are directly related to the output level requirements--our requirements didn't include an SPL target that required lots of power--consequently, we didn't install big woofers, we just used six six-inch woofers mounted in front and rear doors and the rear package tray. 

We took a bunch of measurements in each seat--I think there were 6 mic positions in each of 4 seats--of the response of each of the 6" woofers. These were loaded into the program and it crunched numbers overnight to determine the delay, level and EQ required to optimize the response over all the locations. For optimizing the frequency response, it worked well. However, there was no image in any seat. Constraining the level adjustment so that the front woofers always played at least 6dB louder than any other woofer and ensuring that the front woofers "led" the arrival time optimization helped to locate the bass in front, but the rest of the optimization fell apart. At that point, I was done and concluded that there must be a better way to use all of that DSP power.

I then began to question the long-held MYTH that gentle slopes and lots of overlap between subs and all of the midbass drivers would help to locate the bass in the front of the car and provide a better blend (the spread-the-chaos-around theory). Trying to make that work well always sounded unnatural to me and resulted in really stupid crossover and EQ settings.

What I discovered is that MINIMIZING overlap and multiple locations worked best. In fact, we retuned one of the most famous competition cars on the JBL Team one year at USACi. The system originally included a bunch of drivers playing the same midbass scheme--big woofers in back with a relatively high crossover, big midbasses in front playing all the way down to 20Hz and big midrange speakers that played down to about 40Hz. Once we limited each set to a specific band of frequencies and minimized the overlap, things got better fast. I'm not telling you which car, because this guy has never divulged this improvement.

Anyway and in my experience, the very best way to do this easily is to minimize the interaction of the sources with crossovers and signal steering. Bass below 50Hz in cars can be equalized almost as if it's a minimum-phase system. That's simple and EQ will fix anything that's linear in that region. Above that, in the problem areas you're working on, it's helpful to have several midbass drivers (I find that 3 is best) located in the front of the car in the conventional left right and center positions to which the left, right and only common information are steered. With a center channel that includes a midbass driver, even door locations are fine. I find that limiting sides and rear speakers to no lower than 80Hz is a requirement. 

Then, I suggest that each location be tuned for identical response (or as close as you can get) to the target function I've posted on this forum at least a hundred times, including the blend with the subwoofer. Once that's done, there's no more need for tuning and the level of the subwoofer (gain control) should be left alone. Adding bass to make up for bass-shy recordings is best done using a shelf that boosts below 60Hz, but never above 160Hz. That filter should be applied to ALL channels that include midbass speakers. That filter isn't a simple shelf. Rather, it's one in which the slope of the shelf changes according to the amount of boost or cut (steeper for more boost). 

This works because the image and placement of the bass and the frequency response over the coverage area aren't determined by the combination of the output of speakers playing the same frequencies (well--they are for left-of-center and right-of-center), but the improvement over standard stereo and standard installation practice is huge. These features are built into the someday-released MS-8.

Sorry I don't have graphs to post.


----------



## thehatedguy

There was only a couple Team JBL cars that used a setup like that...and only one that I know who does USACi. That vehicle is probably in Spain now though.


----------



## 14642

I should add that we retuned the car the day before the show and after a several-day tuning session at a certain car-audio compound located south of the Mason-Dixon line. Now that I think about Patrick's hypothesis and about the crossover, EQ and delay settings that I remember suggesting that we save in case my suggestion didn't work, I believe they may have been chosen based on what Patrick is suggesting. That was a long time ago, though, and I've been caught walking around the park next to my house in my bathrobe with no idea where I was several times since then. In any case, if that was the objective, it didn't work in that specific instance.

Now I'm super curious to see what Patrick turns up, not only for selfish reasons...


----------



## Patrick Bateman

jbholsters said:


> good luck. I never thought bandpass mid-bass worked (SQ) as well as plain old sealed. Too bad you can't fit a pair of 12's under there. I've seen lots of 2204's for sale and you can get them re-coned easily.


Back in the day I made some really atrocious sounding bandpass boxes. I basically gave up on them for a decade, and then I discovered that they were hideously mis-tuned. I'd built mine based on published specs and computer sims, without measuring the woofers or the vent tuning.

If either one is off, the response goes to hell, and I mean by A LOT.









Here's an example of this. This is a computer sim of a bandpass box for a pair of AuraSound NS4 woofers. The top box was simulated with the published specs. The bottom box is THE SAME BOX, but I plugged in the actual specs of my woofers, after measuring the T/S parameters.

Also, see all that high frequency noise? That's for real - there's a LOT of output above the passband. WinISD won't tell you that - it's not as sophisticated as other free tools. (I use HornResp and Akabak.)

Crazy huh? We go from an octave and a half of smooth output to three octaves worth of peaky garbage.

The really scary thing is that the vent tuning varies by a LOT more than the drivers itself. Even with a bunch of measurement tools, it usually takes me an hour to fiddle with the port length and get it right. And the SMALLEST leak will screw up the entire thing. I've seen the response get screwed up by a single leak that's the size of pin head.


----------



## Melodic Acoustic

Andy Wehmeyer said:


> OK.
> 
> 
> What I discovered is that MINIMIZING overlap and multiple locations worked best. In fact, we retuned one of the most famous competition cars on the JBL Team one year at USACi. The system originally included a bunch of drivers playing the same midbass scheme--big woofers in back with a relatively high crossover, big midbasses in front playing all the way down to 20Hz and big midrange speakers that played down to about 40Hz. Once we limited each set to a specific band of frequencies and minimized the overlap, things got better fast. I'm not telling you which car, because this guy has never divulged this improvement.
> 
> Anyway and in my experience, the very best way to do this easily is to minimize the interaction of the sources with crossovers and signal steering. Bass below 50Hz in cars can be equalized almost as if it's a minimum-phase system. That's simple and EQ will fix anything that's linear in that region. Above that, in the problem areas you're working on, it's helpful to have several midbass drivers (I find that 3 is best) located in the front of the car in the conventional left right and center positions to which the left, right and only common information are steered. With a center channel that includes a midbass driver, even door locations are fine. I find that limiting sides and rear speakers to no lower than 80Hz is a requirement.
> 
> Then, I suggest that each location be tuned for identical response (or as close as you can get) to the target function I've posted on this forum at least a hundred times, including the blend with the subwoofer. Once that's done, there's no more need for tuning and the level of the subwoofer (gain control) should be left alone. Adding bass to make up for bass-shy recordings is best done using a shelf that boosts below 60Hz, but never above 160Hz. That filter should be applied to ALL channels that include midbass speakers. That filter isn't a simple shelf. Rather, it's one in which the slope of the shelf changes according to the amount of boost or cut (steeper for more boost).
> 
> This works because the image and placement of the bass and the frequency response over the coverage area aren't determined by the combination of the output of speakers playing the same frequencies (well--they are for left-of-center and right-of-center), but the improvement over standard stereo and standard installation practice is huge. These features are built into the someday-released MS-8.
> 
> Sorry I don't have graphs to post.


This is great guys. Now time for me to learn a little something more.

Now I have a question or two Andy.

Now with what your saying above about 3 mid-basses Right-Center-Left. 

1. Would the same thing hold true if the center was only a mid-bass not a true full-range single?

I guess I can use the system I working on now to get a better under standing of this.

My system has a 12" in each kick panel, seal enclosures to is built in the fender area. They will more the likely be playing up to 70-80hz. Not that it matters PLD from side to side is about 4"

Now the midranges are 5.75" wide-band drivers that will be playing from about 150-200hz or so and up. They will be located in the corners of the SUV mounted between the bottom of the A-Pillars and the windshield. PLD from each seat is about 5" maybe a little less. They are about 5" below eye level.

Then 6.5" mid-bass directly under the mid-ranges playing from 70-80hz up to 150-200hz or so and avoiding overlapping as I total agree with you, I never have liked the sound of to much overlapping. PLD is about the same as the midranges 5" maybe a little less. Putting them about 6-7" below eye level

Processor in question is the BitOne. With the current system setup I would have pair of channels open that could be used for another set of mid-bass. Would adding just a center mid-bass of the same size or smaller having any benefits/or same benefits as you described above without and true center processing; just summed L/R. And if so what range would you recommend as a starting point of the center unit (same, lower, higher then the left and right)

SUV is question is a 95 Jeep Cherokee, total rebuild of the interior as you can tell.

Thanks for a great topic guys. As the mid-bass to sub-bass transition is one of my major concerns.

:snacks:


----------



## Patrick Bateman

If you've been following this thread, you know that I'm working on a solution to generate natural bass in the car, the kind that blends seamlessly with the rest of the system.

To achieve this, I think we need to satisfy a specific set of criteria.

Everyone looks at frequency response, but our hearing mechanism is relatively insensitive at low frequencies. HOWEVER, if you look at the polar response of a midbass in a car, you can see that the response jumps by as much as FIFTEEN DB if you move your head an inch or two. THAT'S the key. We can live with a response blip here and there, but we can't live with 15DB dips that appear and disappear when you adjust your seat. _The proposed solution to this is the use of multiple midbasses to smooth the response, via randomization of the reflections._ This is very important in the two octaves from 160 to 640hz, less so from 160hz and down. (The reasons are explained in previous posts.)
Once we solve the response problem, we need to solve the location problem. Due to the way our hearing mechanism works, we're extraordinarily sensitive to the LOCATION of low frequency sounds. This is why competition cars use kick panels to equalize the pathlengths. It improves the soundstaging. Based on my study of The Haas Effect, it may be possible to use additional woofers in locations that are less than ideal IF their amplitude is reduced. Ideally we would use DSP to time align the additional woofers. I do not intend to do this, because the additional woofers will be masked by the primary woofers, due to the tremendous difference in volume.
The last part of the criteria is something that I've avoided so far. We need to reduce distortion. The reason that I've avoided it is that I didn't have a good grasp on how much distortion their is in the car. I have seen distortion measurements on a flat baffle, like the ones that Brandon and John Krutke* have published. But I've never seen a single distortion measurement inside a car.

Without further ado, let's see the measurements.









B&C 8NDL51 in a very small sealed box. This is the box I used for the polar measurements in the kick panel and the quarter panel of the car. It used to live under the brake pedal of my 2001 Accord. I ripped off all the upholstery because the woofer was "buzzing" against it.








IIRC, it's less than four inches deep.








In our passband, the three octaves from 80 to 640hz, third harmonic distortion is buried about 35db below the primary. There IS a rise below 150hz; I believe this is due to excursion. I have a hunch you could reduce it with a port, a smaller box, or a shallow high pass filter. Note that the 2nd harmonic is lower than the third. I believe this is an indicator of shorting rings, and underhung motor, or both.









My original plan for the Accord was to fill in the midbass region with a tapped horn that would sit on the rear deck of the car. This is my first try at it. The sides are sloped so that it would tuck under the rear window, and the rear window would extend the horns mouth. Those are AuraSound NS4 woofers.








Duct tape is the greatest thing if you're building vented boxes or horns. If you use screws the box leaks air.








The tapped horn was quite a shock. I've never seen a single distortion measurement published for a TH. This is very good performance. The B&C has lower distortion overall, but the puny AuraSound is "in the ball park." Most shocking of all, the TH has lower 2nd harmonic distortion between 40 and 160hz than the B&C. My hunch is that this is due to the excursion reduction of the tapped horn. If you're curious about how a TH reduces excursion and power compression, check out my tapped horn thread.*

Is the B&C better? Yes. But you can purchase twenty of the NS4 for the cost of a pair of B&Cs. OTOH, a pair of B&Cs will probably take more power than twenty NS4s 









In my Accord there are two sets of drivers covering the midrange. There's a waveguide above the dash, and a horn below. The horn below the dash is a lot like the ones sold by USD and Image Dynamics. Except mine are loaded with a prosound mid, instead of a compression driver.








I think this measurement is an awesome example of how easy it is to "chase your tail" in audio. I spent the better part of a month working on the horns for my car. From day one, I wasn't particularly happy with the sound of the horns. I tried a billion things to improve the sound, and documented it online.** I tried different drivers, damping the horn, modifying the mouth and the throat, etc... We're talking a MONTH of work, easy.

Now look at that distortion measurement. See what the problem is? The overall distortion performance of the B&C and the NS4 is in a whole 'nother league. And what the hell is going on from 250 to 500hz?

This measurement REALLY threw me for a loop. These horns are doing what they're supposed to - I am using them to cover two octaves, about 250 to 1khz. They're +/- 3db in their passband, except for a blip at 1200hz which is easily EQ'd.

But the distortion performance is ATROCIOUS.

Again, a HUGE eye opener. Because we can fix frequency response, but we can't fix directivity, and there's a very limited range of things we can do to reduce distortion.

Garbage in, garbage out.​
* http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/65945-small-tapped-horn-car.html
** Creating a Soundstage with Waveguides and Psychoacoustics - Page 3 - diyAudio


----------



## Hernan

I have no measurements at hand. In the last year I have experimented with two insteresting things, a delayed rear fill playing from 400 to 900, two NS3s wired in parallel to the center channel of a 701 (at the rear headrest looking backwards) and playing the sub at 70hz LP first order.
The bass is still up front in both cases, ambience is better and front stage is wider, not deeper but more stable.


----------



## mitchyz250f

chad said:


> you can, but they don't last very long. Even the 2206 crossed at 80 will experience cone failure (usually right at the first rib) at an accelerated rate.
> 
> For pro use, there's just not enough surface area there. there were not intended to play that low at high levels, not even designed to for the most part.


So if 119 db at 80 Hz couldn't be reached by the 2204, let's say for the sake of argument that the speaker could be run at 115 db at 80 Hz. So how did RC reach 130 db's? The crossover of 80 Hz, I think is agreed upon my most. It doesn't seem possible that even with cabin gain that he would be able to reach 130 dbs. So how did he do it? 

Is this the smoking gun of the 'other' mystery midbass that is often talked about? Is this proof that RC had another set of midbasses? He always said that it 'if you want bass up front you have to have bass up front'.


----------



## mitchyz250f

double post.


----------



## thehatedguy

130 in the small confines of a car is a bit different that 130 in free space.


----------



## Oliver

mitchyz250f said:


> So if 119 db at 80 Hz couldn't be reached by the 2204, let's say for the sake of argument that the speaker could be run at 115 db at 80 Hz. So how did RC reach 130 db's? The crossover of 80 Hz, I think is agreed upon my most. It doesn't seem possible that even with cabin gain that he would be able to reach 130 dbs. So how did he do it?
> 
> Is this the smoking gun of the 'other' mystery midbass that is often talked about? Is this proof that RC had another set of midbasses? He always said that it 'if you want bass up front you have to have bass up front'.


perhaps he had an inticate knowledge of sound reproduction type stuff that helped him modify an extremely nice car, [ The Holdaways were the forefront of sound installs back then], to a level of unbeaten for the money car 

He seems to know a thing or 2 that weren't commonly known. [in his bag of tricks]


----------



## Patrick Bateman

mitchyz250f said:


> So if 119 db at 80 Hz couldn't be reached by the 2204, let's say for the sake of argument that the speaker could be run at 115 db at 80 Hz. So how did RC reach 130 db's? The crossover of 80 Hz, I think is agreed upon my most. It doesn't seem possible that even with cabin gain that he would be able to reach 130 dbs. So how did he do it?
> 
> Is this the smoking gun of the 'other' mystery midbass that is often talked about? Is this proof that RC had another set of midbasses? He always said that it 'if you want bass up front you have to have bass up front'.


I've never seen or heard the Grand National. So what I'm about to say is simply based on my reverse-engineering of the system.


According to my sims, a single 2204 is good for about 123db.* Factor in cabin gain, and add another woofer, and you're well over 130db. In fact the limiting factor is *the amplifier*, not the woofer. The trick is to use an extraordinarily small enclosure. This reduces excursion in a huge way. Check out the picks of my 8NDL51 enclosure. It's barely big enough to contain the basket. If you've seen my projects, you'll notice that I use extraordinarily small enclosures. Programs like WinISD don't factor in cabin gain. Once you add that in, you see that a small box with a high F3 offers enormous power handling and smooth response in the car. Controlling excursion is critical.
I *do* believe there were midbasses up front. I do *not* believe they were on a relay. I believe they were playing simultaneously. Clark alluded to this in a few posts on audiogroupforum. I believe that his claim that they were on a relay was pure smoke and mirrors. I believe Clark was using The Haas Effect to "steer" the image away from the rear midbasses.
The front midbasses would have virtually no effect on the car's SPL, because of comb filtering. But they *would* pull the image off the rear deck. A number of people who listened to Kimura's Legend and Clark's GN commented that the Legend's image would wander to the back on occasion. As Clark noted, if you want the midbass to sound like it's coming from the front, you need a midbass in the front. (note he never said it has to be the only one. And it wasn't.)

* http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/69060-natural-bass-4.html#post879749
(note that the 2204 WILL blow up if you use a box that's too big, or a highpass that's too low. Again, you have to keep the excursion under control or else the cone will destroy itself due to over-excursion. It's fragile.)


----------



## mitchyz250f

Wasn't Harry K. car using 2123's. And wasn't he running the 2123's up to 800 Hz at least through some part of the cars career?

Patrick, do your sims include cabin gain? So what Qts do you use?


----------



## Patrick Bateman

mitchyz250f said:


> Wasn't Harry K. car using 2123's. And wasn't he running the 2123's up to 800 Hz at least through some part of the cars career?
> 
> Patrick, do your sims include cabin gain? So what Qts do you use?


Yes, I've heard that Kimura used a 2123. The 2123 has a Vd of 4.87 cubic inches. The 2204 has a Vd of 22.69 cubic inches.

_So even though Harry's midbasses have an efficiency advantage, Clark's midbasses win because they have a *displacement* advantage._

As my sim shows, the 2204 is limited by the amplifier alone.

My home speakers use a completely state of the art (and monstrous) midbass. and they have a Vd of 46.2 cubic inches.

So even if you stepped up to a MONSTER of a fifteen, instead of a twelve, you're only gaining about 3db.










Parts-Express.com:B&C 15TBX100 15" Woofer | 15tbx100 b&c woofer high xmax pa woofer high power woofer

As for cabin gain, no, it's not included. You'd have to measure the car since it varies on where the woofer is placed. It's a safe bet that you're picking up a few db at 80hz, but it really starts to "kick in" around 40hz.


----------



## T3mpest

While we are talking about crazy midbasses we should probably mention the Acoustic Elegance td line. Those are 90db/1w/1m+ effecient depending on the size and they can all take 1000 watts if you get the upgraded version the regular ones are still good for 500 watts. I'm thinking about using a td10m in my kicks once I get some extra cash if John can get me some 2ohm versions. Power compression is claimed to be very good as well.


----------



## Electrodynamic

Patrick Bateman said:


> I've never seen or heard the Grand National. So what I'm about to say is simply based on my reverse-engineering of the system.
> 
> 
> According to my sims, a single 2204 is good for about 123db.* Factor in cabin gain, and add another woofer, and you're well over 130db. In fact the limiting factor is *the amplifier*, not the woofer. The trick is to use an extraordinarily small enclosure. This reduces excursion in a huge way. Check out the picks of my 8NDL51 enclosure. It's barely big enough to contain the basket. If you've seen my projects, you'll notice that I use extraordinarily small enclosures. Programs like WinISD don't factor in cabin gain. Once you add that in, you see that a small box with a high F3 offers enormous power handling and smooth response in the car. Controlling excursion is critical.





WinISD doesn't account for cabin gain because it's extremely difficult to account for the differences among various car acoustical volumes/environments which can highly affect cabin gain. If you were listening to your subwoofer system in an anechoic chamber, WinISD is a pretty accurate program for predicting the F3 of your system but not the overall frequency response. 

And by your simulations (of which you have admitted to smoothing the responses) you also claimed that it would take a pair of 13W7's with a pair of 1000 watt amps to do over 140 dB in a vehicle based off of the sensitivity of the drivers alone. Anyone who has been around a 12W7, let alone a 13W7 knows that a pair of them are capable of 144+ dB even on the new TL mics. I asked you in that particular thread how much power you were using on the tapped horn and you couldn't supply a clear figure. Not even 1 watt or 1000 watts. You just said you were unsure. Not only that, but you gained less than 2 dB by taking a tapped horn and placing it in a car where your reasoning for the huge 'gain' of a typical bass reflex's advantage in SPL inside of a vehicle vs. the minimal gain by your tapped horn was the "small bandwidth" of a bass reflex, when in reality it was because when you take a horn (high pressure at the throat, low pressure at the mouth) and put it in a car (which is a high pressure environment) it doesn't yield the same acoustical gain that it does with a non-horn loaded enclosure. In car audio subwoofers, customers are largely concerned with being able to play linear from their crossover point all the way down to 20 hz and below. Most of the time they don't care about having a mini-fridge-sized enclosure just to play loud from 65 Hz to 100 Hz.


----------



## jbholsters

The GN's SQ was about the same when the Holdaway's owned it, as when I heard the car right before RC installed the Kenwood amps. I'm not convinced that there were any 4" drivers under the dash, or that they were gated to turn off at a certain level. This conclusion is based on the fact that Eric went to several shows after RC bought the car, including the Regionals in Philly (after most of the mods) to tune the car for RC, so I'm thinking he would have known if these 4" drivers were installed. In my opinion the Holdaway's are responsible for that cars SQ. RC just added some neat stuff that got him more creativity points. 

The amplifier power went past the limit of those drivers (700 watts per driver), and even running an 8 ohm load, I'm sure they were squeezing everything out of the JBL's, and don't forget the horns had 250 watts going to each one. Lil Daddy is not bass heavy but it is dynamic. Most of that songs energy is above sub bass frequencies, so setup such as the GN might have higher sound pressure levels than a vehicle with lots of subs.


----------



## mitchyz250f

My point is that Chad says (and Chad would know) that these speakers will not produce sound levels of even 119 db without the cones self distructing. Sims will not show that.


----------



## chad

mitchyz250f said:


> My point is that Chad says (and Chad would know) that these speakers will not produce sound levels of even 119 db without the cones self distructing. Sims will not show that.


BUT as stated earlier, in the confines of a vehicle, loaded by the interior they stand a great chance of doing much better. One also needs to understand my background, these suckers get run HARD for long periods of time. the duty cycle of said driver is much lower in a car. BUT i still would not run them lower than 80 cycles.


----------



## Patrick Bateman

Electrodynamic said:


> WinISD doesn't account for cabin gain because it's extremely difficult to account for the differences among various car acoustical volumes/environments which can highly affect cabin gain. If you were listening to your subwoofer system in an anechoic chamber, WinISD is a pretty accurate program for predicting the F3 of your system but not the overall frequency response.
> 
> And by your simulations (of which you have admitted to smoothing the responses) you also claimed that it would take a pair of 13W7's with a pair of 1000 watt amps to do over 140 dB in a vehicle based off of the sensitivity of the drivers alone. Anyone who has been around a 12W7, let alone a 13W7 knows that a pair of them are capable of 144+ dB even on the new TL mics. I asked you in that particular thread how much power you were using on the tapped horn and you couldn't supply a clear figure. Not even 1 watt or 1000 watts. You just said you were unsure. Not only that, but you gained less than 2 dB by taking a tapped horn and placing it in a car where your reasoning for the huge 'gain' of a typical bass reflex's advantage in SPL inside of a vehicle vs. the minimal gain by your tapped horn was the "small bandwidth" of a bass reflex, when in reality it was because when you take a horn (high pressure at the throat, low pressure at the mouth) and put it in a car (which is a high pressure environment) it doesn't yield the same acoustical gain that it does with a non-horn loaded enclosure. In car audio subwoofers, customers are largely concerned with being able to play linear from their crossover point all the way down to 20 hz and below. Most of the time they don't care about having a mini-fridge-sized enclosure just to play loud from 65 Hz to 100 Hz.


In a few months, when I get tired of publishing my measurements, it will be because of people like you.

If you don't like tapped horns, *don't build one.*

But making statements about my measurements that are false and misleading does a disservice to the people that appreciate them.

(For those that don't know the back story, this person is a subwoofer vendor. I write software for supercomputing linux clusters for a living - I have no vested interest in selling horns, or loudspeakers. By measuring loudspeakers in an automotive environment, I've learned a lot about the behavior of loudspeakers in cars, and done my best to share the information online. Because, obviously, I have nothing to gain by keeping the information private.)


----------



## mitchyz250f

Thanks for clarifying.


----------



## 94VG30DE

Electrodynamic said:


> In car audio subwoofers, customers are largely concerned with being able to play linear from their crossover point all the way down to 20 hz and below. Most of the time they don't care about having a mini-fridge-sized enclosure just to play loud from 65 Hz to 100 Hz.


Keep up the good work PB. Some of us like tinkering and knowledge, regardless of whether we intend to employ the information directly as it was presented. Just because I am not currently working on plans for a TH or something in my car does not mean I haven't learned a TON from this thread and others. 

The difference between what I feel is the intention of this thread, and the above quote, is the POV from which each post is written. As a manufacturer/company, your focus is consumers/customers and the market. You are forced to focus on what is palatable. However, this is a DIY forum, so we are at liberty to go off on any tangent we want if that tangent is so much as borderline interesting or curious. I think PB alludes to this in the post above.


----------



## Electrodynamic

Patrick Bateman said:


> In a few months, when I get tired of publishing my measurements, it will be because of people like you.
> 
> If you don't like tapped horns, *don't build one.*
> 
> But making statements about my measurements that are false and misleading does a disservice to the people that appreciate them.
> 
> (For those that don't know the back story, this person is a subwoofer vendor. I write software for supercomputing linux clusters for a living - I have no vested interest in selling horns, or loudspeakers. By measuring loudspeakers in an automotive environment, I've learned a lot about the behavior of loudspeakers in cars, and done my best to share the information online. Because, obviously, I have nothing to gain by keeping the information private.)


Patrick, your simulations and data are valid when they are within context. What I don't agree with is watching you post about how high-sensitivity drivers are vastly superior to less sensitive drivers based on sensitivity alone (which, IIRC, was the premise behind the thread comparing the 13W7's vs. a tapped horn). In a car audio environment, a larger bandwidth can be achieved while keeping SPL the same with smaller boxes (usually half the volume that a tapped horn occupies if not smaller) than a tapped horn. It's not un-common to have a 2 to 2.5 ft^3 enclosure doing 137 to 140 dB from 25 Hz all the way up to 100 Hz. The latter is a much larger bandwidth than 55 Hz to 100 Hz. 

I have no problem with people preferring bass reflex, TL, tapped horn, BP, etc enclosures. I use some of those alignments frequently when I design subwoofer systems for them. It does rub me the wrong way when I see you turning your cheek as to why other enclosures / alignments might be preferable and/or be able to achieve the same results as a tapped horn _in a vehicle_. For instance, in your first tapped horn thread with the W7 comparison, I was asking how much power you were using because I was curious - not because I wanted to prove something. It would have been really surprising to me if you were achieving the same SPL numbers with half the power or so because horns don't benefit the way that other alignments do in a vehicle. If you were achieving the above you would have seen a plethora of PM's from me asking for even more data for my own knowledge. 

As to you falsifying information, I only stated what you already admitted to doing; and that's smoothing out some of the responses that you publish.

You are correct - I design subwoofers for car audio. I also design midbass, full range, and other drivers, along with complete speaker systems, for other clients. Some are OEM, some are not. 

Everything has its place. Are you familiar with the Matterhorn? It's a tapped horn that was designed for the military. A bunch of small sealed box, bass reflex, etc, subwoofers could never achieve what that subwoofer does (SPL, bandwidth, and directionality).


----------



## Electrodynamic

94VG30DE said:


> The difference between what I feel is the intention of this thread, and the above quote, is the POV from which each post is written. As a manufacturer/company, your focus is consumers/customers and the market. You are forced to focus on what is palatable. However, this is a DIY forum, so we are at liberty to go off on any tangent we want if that tangent is so much as borderline interesting or curious. I think PB alludes to this in the post above.


Very true. Maybe I was taking the intention of this thread (and others) the wrong way.


----------



## cubdenno

My question on using multiple midbass drivers is this.

I currently am using a Dayton RS225 8 inch in my door. it runs 80-1100 hertz. there is no angling of the driver

Would running a second Dayton in an enclosure in the kickpanel or behind the brake/accelerator pedals on the drivers side and passenger footwell on passenger side, on axis, increase the "natural bass effect" ? I understand there is no way of knowing without trying but is this what your own results have found?

Also would running one set of the 8's 80hertz-320 hertz or higher rather than the same frequency as the other set?

I took out my BG Neo 8 planars and have been running the Neo 3's with the RS225's in a two way set up, no rear fill processed by the Alpine H701. So I have an extra set of outputs from the processor that can be used to do the extra midbass.


----------



## Patrick Bateman

94VG30DE said:


> Keep up the good work PB. Some of us like tinkering and knowledge, regardless of whether we intend to employ the information directly as it was presented. Just because I am not currently working on plans for a TH or something in my car does not mean I haven't learned a TON from this thread and others.
> 
> The difference between what I feel is the intention of this thread, and the above quote, is the POV from which each post is written. As a manufacturer/company, your focus is consumers/customers and the market. You are forced to focus on what is palatable. However, this is a DIY forum, so we are at liberty to go off on any tangent we want if that tangent is so much as borderline interesting or curious. I think PB alludes to this in the post above.



For me, the most rewarding part of doing measurements is making the connection between what I'm hearing and what the box is doing. Measurements help me understand what I am hearing.

Here's an example of this:


















This is the frequency response of an eight inch woofer in a sealed box and in a horn. The horn SOUNDS louder, and it takes a LOT more power, with more finesse.

Yet look at the measurement - from 30 to 100hz, the response is virtually identical.

If I relied on my ears alone, I might proclaim that Electrodynamic is wrong, and that the horn is OBVIOUSLY louder. I mean, my ears SAY it's louder.

But the graph disproves what the ears are hearing. The reason that the horn SOUNDS louder is that the horn has more output from 100 to 200hz, and that's where our sensitivity is very high. Below 50hz, the small sealed sub is actually more efficient.

Now the horn still has a couple of advantages in the car. It raises the impedance, which is why the power handling goes through the roof. The red curve in the graph above is the horn. The orange is the sealed box. The minimum impedance of the woofer has gone from 3.6ohms to 7.2ohms. The horn basically turned a 4ohm driver into an 8ohm driver. And the distortion is likely lower because the horn reduces excursion.

Anyways, *yes*, I prefer to make weird enclosures, because those are the fun ones. Figuring out how it all works is the fun part.


----------



## jbholsters

Here are the scans from the Aug 92' CA&E I promised to scan. Appears he changed out the 12's and the box is ported in the pics, whereas it is not in the SW install book.


----------



## Patrick Bateman

Thanks for posting this! I haven't read this article in 15 yrs or so. I knew Clark swapped the USD compression drivers for Altec, but didn't realize he swapped the JBL midbass for something else. Based on the pics on the Speaker Works site, the car originally had a Radian 475PB or something comparable. Clark mentioned on Audiogroupforum that he sold a set of Altec 288C compression drivers to Mark Eldridge, so chances are good that he was using the same.

If anyone has some money to burn, you can get these on Ebay. The price that Clark quotes is accurate - they're over two thousand a pair. Here's a pair for $2680.

Altec Lansing 288 - A284WVL pair NEW - eBay (item 260483841085 end time Nov-27-09 22:37:15 PST)

I will post some information on how to mod the USD horns with a compression driver thats similar to Clark's Altec 288s, but costs under $400 a pair.

As for the midbass, if I had to hazard a guess, SpeakerWorks installed a JBL 2204 and Clark replaced it with a JBL 2206.









Here's a pic of the 2206. Appears to be an "improved" version of the 2204, but with some improvements. Remember how Chad noted that cone failure was a problem with the 2204? Well guess what the 2206 fixes...

_"With increased power handling, special attention was paid to increased mechanical integrity. A new cone design which greatly improves cone strength allows for increased reliability and longer life. Greater linear excursion for matched power and displacement levels was achieved via a new surround topology and edge damping treatment._

If anyone is interested in the 2206, they seem to be ubiquitous. There are eight on ebay right now, and a handful on Craigslist.

Here's a discussion of the 2204 vs the 2206 and the 2202:

Searching for best Midbass - Lansing Heritage Forums


----------



## thehatedguy

That car never had 1" compression drivers in it.


----------



## Nitin

thanks jbholsters that article is much appreciated - ive been searching high and low for a copy of it and could never ever find it - we can now have a look at this properly even if what he said was inaccurate


----------



## TREETOP

thehatedguy said:


> That car never had 1" compression drivers in it.


I agree, minimum 2". There's no way 1" drivers will play down to 400 cycles. The Altec drivers that PB linked to look right, the voice coil (and diaphragm) of those Altecs could very well be 4" in diameter.

I heard the Grand National, I was able to get a couple minutes of seat time in it a looong time ago. I was a noob at the time with Pyramid subs running off a Majestic amp in my own car so it must've been 1989ish. :blush: Unfortunately I don't think I was able to securely grasp the extent of what it was I was listening to in the GN. I can say that it sounded like EVERYTHING was coming from up front, not just the vocals and not just the midbass. There was a lot of talk at the time of hidden speakers in the floor, of subs in the dash, and all kinds of conspiracy theories regarding the way it sounded. Nobody at the time had any logical reason to believe that only 6 speakers, 4 of them behind you, could/would sound that way.


----------



## Patrick Bateman

thehatedguy said:


> That car never had 1" compression drivers in it.


I know that you have first hand experience with the car - my entire knowledge of it is based on reverse engineering. I *have* heard other cars at Speaker Works, I own a set of USD waveguides, and I've "cloned" Clark's waveguides to some extent. (I'll document that in the next few weeks.)

I am aaaaaaaaalmost starting to believe that Clark wasn't lying about the diamond diaphragms. Here's why:

A conventional compression driver has a very large diaphragm. Due to the diaphragm size, you can't get them to play cleanly beyond 10khz or so. All of the output above 10khz is generated by diaphragm resonances and manipulation of the phase plug. *And a bigger compression driver is even worse - getting a 1.4" or 1.5" to play above 10khz is a struggle.**

















The throat is just one inch, but the diaphragm is over three inches in diameter. That's an aluminum aftermarket diaphragm. My JBL 2470s are using aluminum Radian diaphragms. This one is from Great Plains Audio - that's their logo. This set is $2468 on ebay.








Side view. Note the similarity to Clark's pic








Here's an RTA measurement of the 288. Note the top octave is almost completely AWOL. And then there's a peak above 20khz.








Here's a gated measurement of a different 288. It illustrates nicely why I like gated measurements more than RTA measurements  Anyways, the high frequency peak is still there, but this is much better behavior. Probably a better horn with excellent mouth treatment.

As usual, a picture is worth a thousand words. Here are pics of the Altec 288. Notice that the compression driver is identical to what Clark is holding in the article. Clark also recommended the 288 a number of times on audiogroupforum. Now look at the frequency response. See that big peak up top? That's the diaphragm resonance. Just like the one you see in a metal dome tweeter, but lower in frequency.

If Clark really and truly modified the diaphragms, it would raise the resonance to a higher frequency and reduce it's amplitude.

Not saying he did it... But it's possible. There are good reasons to do it.

* IMHO, the BMS ring radiators have basically made a diamond diaphragm obsolete. All of their one inch models play past 15khz, some past 20khz.


----------



## ehkewley

Those magazine pages seem to be touting things we take for granted today in car audio. Were these pretty novel concepts in '92?


----------



## TREETOP

ehkewley said:


> Those magazine pages seem to be touting things we take for granted today in car audio. Were these pretty novel concepts in '92?


Yes, extremely. Most of it was practically unheard of unless you were in the inner circles.


----------



## jbholsters

ehkewley said:


> Those magazine pages seem to be touting things we take for granted today in car audio. Were these pretty novel concepts in '92?


Yeah, this car was cutting edge. No one ran computers in cars, think back to what computers were like back then and try to imagine implementing that into the audio system. Same thing with noise gates. The only people that knew about or used them were sound engineers. The cap bank was also cutting edge. 

If that car was still together today I believe it would still kick butt in the lanes.


----------



## mitchyz250f

Does the ported box appear larger than the sealed box he had before? Seemed that the first box was even with the sheet metal, this one appears to stick out 3 inches or so. Also, the interior panel appeared to be stock like before, now it is flat and custom.


----------



## jbholsters

No, the box looks the same. Same brackets attach the box to the side panels. Originally the grills over the 12's were covered in grey grill cloth. RC had them redone to look more factory.


----------



## Fast1one

Looks like this thread has morphed into a discussion on the GN 

I think I want to try the multiple midbass solution on my own. What I was thinking was finding the distance of my left midbass to the listening position and finding multiple positions with the same delay and do the same for the right. Then use the Haas effect to my advantage with level control (L-pads). As far as crossovers go, with limed processing power and a two-way active front stage I wanted to use the same highpass as the front stage, and make a simple 6th or 12th order lowpass for the satellite woofers. Not sure what would be ideal. Based on your measurements, looks like somewhere around 400-500hz is about right. 

Patrick, do you have any suggestions as to which drivers to use? I want to use something small so that I can stuff it nearly anywhere. I don't have a large budget either. And keep in mind that I'm not looking for ultra high dynamics, just "natural"

Partsexpress has those neo mini woofers that resemble the Auras in varying sizes: http://www.parts-express.com/wizard...11-10-2009&utm_campaign=Home+Page+Flash+Panel


----------



## Patrick Bateman

Fast1one said:


> Looks like this thread has morphed into a discussion on the GN
> 
> I think I want to try the multiple midbass solution on my own. What I was thinking was finding the distance of my left midbass to the listening position and finding multiple positions with the same delay and do the same for the right. Then use the Haas effect to my advantage with level control (L-pads). As far as crossovers go, with limed processing power and a two-way active front stage I wanted to use the same highpass as the front stage, and make a simple 6th or 12th order lowpass for the satellite woofers. Not sure what would be ideal. Based on your measurements, looks like somewhere around 400-500hz is about right.
> 
> Patrick, do you have any suggestions as to which drivers to use? I want to use something small so that I can stuff it nearly anywhere. I don't have a large budget either. And keep in mind that I'm not looking for ultra high dynamics, just "natural"
> 
> Partsexpress has those neo mini woofers that resemble the Auras in varying sizes: Parts Express: Featured Categories


There's a reason that I've been a bit quiet about the midbasses. When I started out, my goal was to emulate the performance of a winning system - the Grand National. And in my simulations, I demonstrated that the GN could hit about 130db in the midbass. Most cars are lucky to hit 120 at that range, because there's no real cabin gain in the three octaves from 80 to 640hz.

For instance, a pair of Seas Excels will hit about 110-115db before they run out of excursion.

But there's a problem with this line of thought.

*If a combination of sheer SPL and clever use of the Haas Effect is the secret of the Grand National's midbass, then why do some midbasses sound good at moderate levels?*

I mean, it's not like ALL midbasses sound like garbage, just 90% of them do.

So that led me to believe that it's more than just sheer SPL.

My current line of thought is that it's distortion. Manufacturers rarely publish distortion specs, but my measurements indicate that it's a lot worse than I realized.









Black horn at the right uses a conventional woofer.






Here's the measured distortion of a conventional loudspeaker mounted in a horn under my dash. See how there are huge spikes at 350hz and 1.2khz?

This particular driver has perplexed me for some time, because no amount of EQ can make it sound good. I have other drivers that don't mind a a bit of frequency shaping, but this one just doesn't behave. But this distortion measurement shows the real story - there's a lot of it.









The shallow grey enclosure at the left has a B&C 8NDL51.






Compare the last measurement to this one. This is a B&C 8NDL51 in a small sealed box. From 500hz to 2khz, all distortion is buried a minimum of 35db below the fundamental.









This is what push pull loading looks like. It's supposed to cancel 2nd harmonic distortion. This is a Danley Sound Labs TH-Spud.








Here's a half finished front loaded horn for an AuraSound NS4. Dayton sells a clone of it under their "neo-sym" line. The other woofer fits inside this horn, on the other side of the enclosure.






Here's the measured distortion of the AuraSound NS4 in a push-pull front loaded horn. Check out the 2nd harmonic distortion - it's as low as the B&C now.

Interesting results, aren't they? Who would've know than a conventional speaker performs so poorly? More startling is that a $20 computer speaker can compete with a $150 prosound midbass _if it's selected very carefully._ The NS4 has an underhung motor to reduce distortion, and push-pull loading helps too. My distortion measurements indicate that a large xmax helps reduce distortion at low frequencies too.

This is way more than you wanted to read, I'm certain 

All you asked is if the neo-sym woofers are good. If they're similar to the NS4, and they appear to be, then they are quite good.

But this little journey isn't over yet. You might notice that this set of distortion measurements is different than the ones I posted for the B&C last week. The reason is that I measured every single woofer at the same volume, to level the playing field. And I did about 20 measurements, of nearly every enclosure I have.

What I found is that the push-pull AuraSound enclosure can keep up with the B&C when it comes to distortion performance. But the B&C has a big efficiency advantage. However the funky looking tapped horn in that pic *is almost as efficient as the B&C.* Tapped horn loading gives the AuraSounds a HUGE bump in efficiency - over TWELVE db at some frequencies!!!








So here's what I'm building now.

This enclosure uses the same distortion-killing mechanisms as the one that's in the photographs above. It has woofers with underhung motor in a push-pull configuration. But it's a tapped horn, which raises efficiency.

*Now obviously, this is a ridiculous amount of work.* While I don't talk a lot about how speakers "sound", I'll happily admit that the B&C sounds spectacular. And the measurements correlate well with the sound. The main reason that I'm jumping through all these hoops with the AuraSound woofers is that the B&C brings my soundstage forward. Even with the woofer in the kick panel, I'd say it brings the whole stage forward by about a foot.

The horns under the dash, when properly treated, make the soundstage sound like it's back by the firewall. So that's why I'm going through all this rigamarole with the NS4 - it has the longest pathlengths of all.


----------



## Fast1one

It wasn't too much to read at all Patrick 

I really like the idea of midbass horns under the dash, but I am not sure what you are getting at. Do you want to use the horns in conjunction with other midbass speakers, or do you want to use them IN PLACE OF your midbass? I would think the former is the case, but I could be wrong. 

Reason I ask is because my midbass is also my midrange. I don't have very much processing power anymore so I am going back to active two-way so the woofer will play up to about 2khz in the kickpanels. The woofer I want to use is the CSS SDX7, in small sealed enclosures.


----------



## Patrick Bateman

Fast1one said:


> It wasn't too much to read at all Patrick
> 
> I really like the idea of midbass horns under the dash, but I am not sure what you are getting at. Do you want to use the horns in conjunction with other midbass speakers, or do you want to use them IN PLACE OF your midbass? I would think the former is the case, but I could be wrong.


The pathlength of sound below 1khz has a big impact on the dimensions of the soundstage. The B&C 8NDL51 has low distortion and excellent dynamics, but due to the sheer size of the woofer, it's difficult to place it far and wide. So every configuration that I've used it for has had a negative impact on the dimensions of the soundstage. When place in the quarter panels it delivers a deep and wide soundstage, but the soundstage collapses when you turn your head. When placed under the brake pedal it delivers a deep but narrow stage. When placed in the kick panels, it delivers a wide shallow stage.

The midbass horns are the only solution that deliver a wide AND deep stage.

Note that the mouth of the horns isn't in the front - it's in THE BACK. So the mouth of the horn begins at the firewall, NOT the dash.

I have a hunch that reticulated foam would soak up enough reflections that it might even convince you that the midbasses are *beyond* the firewall, which is a neat trick!









Here's a measurement of the polar and power response of my first attempt at this. Basically a "proof of concept."

It looks terrible, but the basic idea is to cover from 80 to 640hz, and that's it. This version plays too high, and not low enough. The dip and the peak in the midrange is due to a panel that's vibrating, I didn't glue the thing together.

My second stab at it will play lower, I'll secure the panel to get rid of that buzzing, and hopefully it will play flat in the passband. (crosses fingers.)



Fast1one said:


> Reason I ask is because my midbass is also my midrange. I don't have very much processing power anymore so I am going back to active two-way so the woofer will play up to about 2khz in the kickpanels. The woofer I want to use is the CSS SDX7, in small sealed enclosures.


I *was* a bit surprised that a horn that's pointed BACKWARDS and firing into a carpeted firewall played up to 2khz. The sim said it wouldn't go past 500hz. I think it's because the dimensions are so small.

You can take a soundwave and basically bend it any which way you feel like, as long as the soundwave does not exceed the dimensions of what it's traveling through. So this thing is completely facing the wrong way, but because the largest dimensions is 3.5", we get output to 2khz. (a 2khz soundwave is 3.5 inches long.)

Once I have the primary set of midbasses sorted out, I intend to add another three or so. Probably one in the kick panel, one in the quarter panel, and one behind the seats. Enclosures will be very small, no more than 4" cubes.


----------



## Fast1one

Every time I read your threads it makes me want to rip everything out and start over, lol. 

I don't know if I like the idea of using the "Double four" as a midrange as well. I suppose that's not what its intended for though. If I could find something to cover down to 1khz or lower that would likely be more doable. Stack a set of mini bodies below the midbass horns? Hehe...

Edit: I keep forgetting your name is NOT Patrick. John right? lol...

It is now 11:50 my time and I have reread this thread, your "GNIB" thread and your HOMster thread about three times each. Getting pretty exited now and its all coming together, 

I think for my next setup I want to try midbass horns AND "HOMsters" with treatment. I am inquiring someone about a set of mini-bodies, which have output down to 1khz. Hopefully that works out because it will be within my budget.

Now, you said that the bandwidth you care about is 80-640hz. For my particular application, do you think the midbass horns will have enough output to blend them into the main horns? ( with some EQ work).

I suppose I will have to wait until you actually build them. The dayton drivers are a bit different than the Auras. Plus the NS4s are not in stock at Madisound


----------



## jbholsters

Fast1one, if I'm reading PB's post correctly, the 4" will not be mounted to the under dash as a horn body would be , it will be as far forward as possible under there, then the horn could be mounted normally. (you won't see the 4 inch cubes)

If it ends up working well, it could open a lot of possibilities. I would think depending on where the mid bass horn opening is positioned you could not only make it sound as if the stage is beyond the firewall, but add width as well.


----------



## chad

Patrick Bateman said:


> The throat is just one inch, but the diaphragm is over three inches in diameter. That's an aluminum aftermarket diaphragm. My JBL 2470s are using aluminum Radian diaphragms. This one is from Great Plains Audio - that's their logo. This set is $2468 on ebay.
> 
> 
> 
> 
> 
> 
> 
> 
> Side view. Note the similarity to Clark's pic
> 
> 
> 
> 
> 
> 
> 
> 
> Here's an RTA measurement of the 288. Note the top octave is almost completely AWOL. And then there's a peak above 20khz.
> 
> 
> 
> 
> 
> 
> 
> 
> Here's a gated measurement of a different 288. It illustrates nicely why I like gated measurements more than RTA measurements  Anyways, the high frequency peak is still there, but this is much better behavior. Probably a better horn with excellent mouth treatment.
> 
> As usual, a picture is worth a thousand words. Here are pics of the Altec 288. Notice that the compression driver is identical to what Clark is holding in the article. Clark also recommended the 288 a number of times on audiogroupforum. Now look at the frequency response. See that big peak up top? That's the diaphragm resonance. Just like the one you see in a metal dome tweeter, but lower in frequency.
> 
> If Clark really and truly modified the diaphragms, it would raise the resonance to a higher frequency and reduce it's amplitude.
> 
> Not saying he did it... But it's possible. There are good reasons to do it.
> 
> * IMHO, the BMS ring radiators have basically made a diamond diaphragm obsolete. All of their one inch models play past 15khz, some past 20khz.


I'm investigating this diamond thing, but methinks they may have has diamond shapes on them, and quite possibly a diaphragm out of a newer (at the time) JBL... cough 2450, cough. which don't do too shabby at HF, not spectacular but not too shabby. Lots of JBL **** fits in altec ****. (wonder why  :laugh

The altec pic, WTF is that connector stuck to the magnet assembly? Or is that a field coil HF driver (never see one of those.)

As for the 2206 special space carbon bulletproof recone, ******** that appears to be a flippin bone stock 2206, possibly the back was reinforced to add some stiffness with special neptune carbon but from a front view.. that is a JBL cone.


----------



## sundownz

I've wanted to try those 8" B&C in-car for some time myself...


----------



## thehatedguy

Back then there wasn't a lot of large format drivers that could play past 10k, but there are a few today that can do it no problem. And if diaphragm tricks are needed, you can get (or in the near future can get) beryllium diaphragms for pretty much any major manufacture's compression driver.


----------



## Patrick Bateman

jbholsters said:


> Fast1one, if I'm reading PB's post correctly, the 4" will not be mounted to the under dash as a horn body would be , it will be as far forward as possible under there, then the horn could be mounted normally. (you won't see the 4 inch cubes)
> 
> If it ends up working well, it could open a lot of possibilities. I would think depending on where the mid bass horn opening is positioned you could not only make it sound as if the stage is beyond the firewall, but add width as well.


Right now I'm evaluating two horns. Both of them use dual Aurasound woofers in a push-pull arrangement to cancel distortion.

I've built a few horns and waveguides that use the foam treatment that Geddes has invented, and I noticed that it changes the apparent location and size of the horn or waveguide.







Here's a pic to illustrate the theory.

Basically, in a conventional horn, the sound appears to emanate from the mouth of the horn. It's also very "big." The dimensions of the sound source appear to be the size of the horn mouth.

In a foam lined horn or waveguide, the sound appears to emanate from somewhere a few inches back from the mouth, and the apparent size is much smaller. The difference is particularly noticeable in the Summa, where the mouth has been treated to reduce diffraction, and the depth of the foam plug is over a foot long.

Here's my hypothesis. Firs we know about the Haas Effect. "When two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first. To the listener, this creates the impression that the sound comes from that location alone due to a phenomenon that might be described as "involuntary sensory inhibition" in that one's perception of later arrivals is suppressed."

In a horn, the reflections generated inside the horn can exceed the energy generated by the device itself. You can see this in a frequency response plot, where the amplitude of the device will increase by as much as 10db.

In a nutshell, by "soaking up" reflections with the foam, and diffusing reflections at the mouth with a roundover, the Summa "shrinks" the apparent size of the sound, and "pushes" back the soundstage.

Hopefully the picture helps. The photo at the right are my Summas - you can see the roundover and the foam in the profile. The photo at the left is a set of Geddes speakers being built, and you can see the dimensions of the waveguide. In the illustration, you can see that reflected energy is attenuated by going through the foam. At the mouth reflections are further diffused by the roundover. One analogy that I like to use is the idea of looking at a cars headlights in the fog. The fog makes it impossible to perceive the depth of the headlights, and their size is distorted. But if you remove the fog, you can perceive the depth and distance of the headlights. The inventions that Geddes has provided remove the fog.

I believe this may help to explain why listeners have reported that the Summas don't "sound" as big as they look. A lot of horns have a very "large" presentation. If you didn't see the Summas before your eyes, and you only listened to them, you would think they were a much smaller speaker. They image like a mini-monitor.

Anyways, the reason that I am currently evaluating three different midbass options is that the Geddes diffraction treatments have the potential of "tricking" the listener into thinking the sound source is further away than it really is.

With the B&C woofers in the kick panels, the soundstage is basically defined by the cars boundaries. When I turn off the B&Cs, the soundstage falls back about half a foot.

When I read about the Grand National back in the 90s, one of the things that was exciting about it was the concept that the waveguides had a pathlength of something like six or eight feet. But in all the horns I've built the sound appears to emanate from the mouth. And this makes sense, right? There are a ton of reflections at the mouth, and those reflections are closer to you than the driver itself. So the Haas effect dictates that the sound will appear to be located at the mouth. _The reflected energy will take precedence over the original signal._ When you listen to horns in a nightclub, this isn't a big deal, because they're all the way across the room. But in the car we have a lot of reasons to soak up those reflections, and relocate the apparent source of the sound back to the speaker itself, not the mouth.

If I had some time to kill, it would be interesting to see if you could really take this to the extreme. Put a couple of full range drivers in a veeeeeery long horn, go crazy with the stuffing, and see if you can create the impression that the sound is coming from well outside the car. The key would be to absolutely obliterate any reflections off the mouth, so you'd have to use a roundover from hell. 

With the midbass horns, the soundstage *appears* to be around the firewall. I'd like to see if I can get it back further than that, by "soaking" up some of those reflections that are illustrated in the diagrams above.

Basically trade some efficiency for a bigger soundstage.


----------



## chad

there were plenty that could play past 10K, they were not cheap, they were "new" but even a 2445 could get over 10K no problem. This was not the stone ages, it was the early 90's, it's not like he was tossing western electrics on those horns


----------



## Patrick Bateman

chad said:


> I'm investigating this diamond thing, but methinks they may have has diamond shapes on them, and quite possibly a diaphragm out of a newer (at the time) JBL... cough 2450, cough. which don't do too shabby at HF, not spectacular but not too shabby. Lots of JBL **** fits in altec ****. (wonder why  :laugh
> 
> The altec pic, WTF is that connector stuck to the magnet assembly? Or is that a field coil HF driver (never see one of those.)
> 
> As for the 2206 special space carbon bulletproof recone, ******** that appears to be a flippin bone stock 2206, possibly the back was reinforced to add some stiffness with special neptune carbon but from a front view.. that is a JBL cone.


The problem with compression drivers isn't getting them to play low, it's getting them to play *high.* The phase plug will improve high frequency response, but there's a limit to how high a three inch diaphragm is going to play. That's why I swapped the diaphragms in my 2470s from titanium to aluminum - aluminum is lighter. (The 2470 was sold with FIBERGLASS diaphragms, ugh).

Beryllium is even better, and then there's diamond.







Here's the polar and power response of a JBL 2470 with an aluminum diaphragm on a treated USD horn, along with the "stock" radian compression driver. I personally believe the "stock" driver is fairly close to what the GN was sold with originally - Speaker Works has a tendency to use Radian. (Radian is less than a mile from their shop!) See how the response falls off in the top octave? We can EQ the hell out of both because their distortion is very low and efficiency is very high, but we're never going to get the large format JBL 2470 to play past 16khz.


The process that Clark describes makes a lot of sense. Now whether he did it or not, or whether the compression drivers even made it into the car is another questions.

A quick google search reveals a number of places that will diamond coat your tools:

http://www.calicocoatings.com/pvd/

I have no idea what it costs. Boeing surplus in Seattle routinely sold diamond coated router bits for under $20.

To do this to a loudspeaker diaphragm, you'd have to eliminate part of the diaphragm. Otherwise the coating would make the diaphragm HEAVIER, which is the last thing we need.

What Clark described in the CA&E article was elminating part of the diapragm with chemicals, then growing a diamond substrate on what remains.

Sounds good to me.

All of this is academic though. As Winslow noted, we have better technology these days. I really can't think of a good reason to go to all this trouble with the diaphragms when you can buy a set of BMS drivers that hit 20khz without breaking a sweat, for under $500 a pair.


----------



## chad

Patrick Bateman said:


> The problem with compression drivers isn't getting them to play low, it's getting them to play *high.* The phase plug will improve high frequency response, but there's a limit to how high a three inch diaphragm is going to play. That's why I swapped the diaphragms in my 2470s from titanium to aluminum - aluminum is lighter. (The 2470 was sold with FIBERGLASS diaphragms, ugh).




The 2470 was sold with Phenolic diaphragms and generally suffixed FH for foghorn. 

As you said, phase plug geometry can help and the geometry in the 2470, well, ain't all that. Swapping to a lighter diaphragm was a good call but that still does not help the fact that the phase plug is of vintage design. they ARE getting respectable HF out of 2" throat horns, the 2450/51 works damn well, the 2445 does better than the 2470 and has a 4" diaphragm.

You are not gonna pull media off of a horn diaphragm and replace it with ANYTHING chemical and retain it's strength, there's a LOT of pressure in front of that sucker even though it's not moving a ton. I have seen diaphragms just fall apart in high SPL situations. Saying someone took media away THEN played it down to 400 (incidentally well below the loading point of that horn pictured) is just insane.

Sometimes it's easier to just rely on common sense than to read something then try to figure you why and how it was done all the time attempting to convince yourself as to why and how it could work... only to realize that you were wasting your time because it's impossible to fly a bottle rocket to Neptune.


----------



## thehatedguy

Yeah, the JBL 2441s would get to 10k and down to 500 on a 6 db slope in the house. That is one of Dr. Edgar's favorite midrange compression drivers to use. And you could get a set of 375s/2440s and put the 2441 diaphragm in them and get to 10k on them. Hell, the 2445s are ferrite versions of the 2440/2441 alinco drivers.

TAD could get you down low and all the way out, Radian PB950s could too. The Beymas I have (CP755 Nd) could play 500-20k. Several others out on the market too.


----------



## Fast1one

jbholsters said:


> Fast1one, if I'm reading PB's post correctly, the 4" will not be mounted to the under dash as a horn body would be , it will be as far forward as possible under there, then the horn could be mounted normally. (you won't see the 4 inch cubes)
> 
> If it ends up working well, it could open a lot of possibilities. I would think depending on where the mid bass horn opening is positioned you could not only make it sound as if the stage is beyond the firewall, but add width as well.


Yeah I got the mounting scheme. But the horns are not 4 inch cubes. Those are satellite woofers to help smooth the response which will be located throughout the cabin. There are two ingredients to this midbass solution. The main double horns are what define the width and depth of the soundstage. The satellite woofers (4 inch cubes) merely smooth out the response. 

I am biting on the ID CD-1es as an initial test with horns. I will be treating them with a round-over (PVC or otherwise) and foam. Which brings me to a question. I thought I saw the answer before but I can't find it. 

John, what type of foam is used to soak up the internal reflections of the horn? Thank you again for all of your work.

Edit: NVM I got the answer. Reticulated foam


----------



## Patrick Bateman

Fast1one said:


> Yeah I got the mounting scheme. But the horns are not 4 inch cubes. Those are satellite woofers to help smooth the response which will be located throughout the cabin. There are two ingredients to this midbass solution. The main double horns are what define the width and depth of the soundstage. The satellite woofers (4 inch cubes) merely smooth out the response.


There's still a decent chance I'll go with the B&C for midbass, and not the midbass horns. Physics says that a 100hz horn should be about the size of the entire front of the the car. I'm reducing the size of this thing to an absurd degree. The only reason it works at all is that I'm stealing some tricks from Tom Danley to flatten out the response. (Offsetting the drivers and using an array smooths out the response. This design would never work at all if the drivers were mounted conventionally.)







To illustrate how absurd this midbass horn is, here's a comparison of the midbass horn and the same woofer in a sealed box, but outside of the car. Check out the efficiency - the horn is actually LOWER than the sealed box. I've never seen that happen.

But if you look at the distortion, the horn is working to reduce distortion. (green is 2nd harmonic, purple is 3rd.) It's reducing distortion to virtually unmeasurable levels. Above 500hz the horn's distortion is over 10-20db lower than the sealed box.

Even stranger, the horn is smoother than the sealed box. The response measures +/- 3db for a three octave bandwidth from 200hz to 1800hz. And the rolloff on either side is damn near perfect, which makes it a lot easier to cross over.

So this is quite a strange box.







Here's a pic of the baffle for the new box, a tapped horn. You can see the baffle is as small as I can possibly make it.







In my distortion measurements I've noticed that even a tiny bit of vibration manifests itself as a peak in the distortion curve. To fight this, I'm putting the woofers in a sandwich of baltic birch plywood. Rather than screw the drivers in, I'm bolting them in.







Even the smallest leak will ruin bass output, and the frame on the Aura woofers is terrible. Rope caulk helps seal it.







Another pic of the plans.







The new tapped horn will be the same width as the third box in this pic, but a bit shallower.



Fast1one said:


> I am biting on the ID CD-1es as an initial test with horns. I will be treating them with a round-over (PVC or otherwise) and foam. Which brings me to a question. I thought I saw the answer before but I can't find it.
> 
> John, what type of foam is used to soak up the internal reflections of the horn? Thank you again for all of your work.
> 
> Edit: NVM I got the answer. Reticulated foam


Here's the URL:

http://www.mcmaster.com/nav/enter.asp?partnum=2195K52&pagenum=605

I use the 1/2" roll


----------



## Fast1one

Patrick Bateman said:


> Here's the URL:
> 
> http://www.mcmaster.com/nav/enter.asp?partnum=2195K52&pagenum=605
> 
> I use the 1/2" roll


Wow that stuff is NOT cheap. lol. 98 per roll? Unless I'm looking at the wrong one.


----------



## 94VG30DE

Fast1one said:


> Wow that stuff is NOT cheap. lol. 98 per roll? Unless I'm looking at the wrong one.


It is 4' wide by 10' long though...


----------



## Fast1one

94VG30DE said:


> It is 4' wide by 10' long though...


Yeah I don't need nearly that much. Unless I start treating the rest of the car with it  For now I just want some for the horns (which are on their way now). 

Might have to buy some from you John if that's ok 

Regarding the midbass, the B&C 8 inch midbass look very nice but are a bit out of my budget (x2). I was looking into increasing the size to 10 inch since I can't seem to find anything that looks too good for a budget of $150 or less. 

Maybe the Eminence Beta? 
Parts-Express.com:Eminence Beta-10A 10" Guitar/PA Driver 8 Ohm | beta-10a bass guitar driver keyboard speaker pa woofer pa driver

Might not work as well in a tiny sealed enclosure, but the efficiency is nice and throw isn't horrid.

Or even the Delta:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-412


----------



## ClinesSelect

Patrick Bateman said:


> In a foam lined horn or waveguide, the sound appears to emanate from somewhere a few inches back from the mouth, and the apparent size is much smaller. The difference is particularly noticeable in the Summa, where the mouth has been treated to reduce diffraction, and the depth of the foam plug is over a foot long.



To the ear (not a mic) the roundover makes an audible improvement, to me. I can't say the same for the foam however. But then I noticed that you used a foam plug in the Summa which fills the entire mouth. Now I am wondering if more foam is the key. Instead of just lining the horn, use more of a foam plug?















Fast1one said:


> Wow that stuff is NOT cheap. lol. 98 per roll? Unless I'm looking at the wrong one.


30 ppi foam can be purchased at pet stores in much smaller quantities for less than $10. FilStar Foam 30.


----------



## western47

Yes, the foam should be used more like a plug than just lining the walls. The concept is to attenuate the reflections inside the horn while allowing the direct sound to have the least amount of foam to travel through. If done properly, the direct sound should just have a slight reduction in overall output without a change in frequency.


----------



## ClinesSelect

western47 said:


> Yes, the foam should be used more like a plug than just lining the walls. The concept is to attenuate the reflections inside the horn while allowing the direct sound to have the least amount of foam to travel through. If done properly, the direct sound should just have a slight reduction in overall output without a change in frequency.


The HOMster does not appear to be stuffed in the photos and this was the result:



> There's a dramatic reduction in the output level. It's down 3db at 1khz, but almost EIGHT db at eight khz. I think this is enlightening, because it illustrates that a significant percentage of the horn's output is being damped by the foam. I have stuffed an OS waveguide with foam, and measured it, and the reduction in SPL wasn't as dramatic as this. I believe this proves that the HOMster has more HOMs than an OS waveguide.


----------



## Patrick Bateman

ClinesSelect said:


> The HOMster does not appear to be stuffed in the photos and this was the result:


It's stuffed right up to the bug screen in my USD horns.









In my BMS 4540 I actually CUT OUT the bugscreen, just so I could get closer to the diaphragm. You can see the conical phase plug pointing out here.

You really want to go crazy with the foam, the best results are when you use A LOT of it.









Here's the plug that's in my current car. About 9 inches deep iirc.

One thing that sucks about tuning the foam "by ear" is that the treble will sound a bit odd at first, but this is the absence of reflections. It takes a little getting used to. Untreated horns sound unlistenable to me now, which is part of the reason I take the time to post threads  Gotta spread the word!


----------



## Patrick Bateman

ClinesSelect said:


> To the ear (not a mic) the roundover makes an audible improvement, to me. I can't say the same for the foam however. But then I noticed that you used a foam plug in the Summa which fills the entire mouth. Now I am wondering if more foam is the key. Instead of just lining the horn, use more of a foam plug?


I posted some thoughts on why the improvement may be elusive here:

The HOMster! (or How I Learned How to Fix a Horn) - Page 8 - diyAudio


----------



## ClinesSelect

Patrick Bateman said:


> I posted some thoughts on why the improvement may be elusive here:
> 
> The HOMster! (or How I Learned How to Fix a Horn) - Page 8 - diyAudio


Well done. One thing however, to the ear, the roundover underneath the mouth was not nearly as effective as the roundover which protrudes into the mouth. In my opinion of course and just as a FYI for anyone experimenting with the horns. 

As a side note, the roundover is not really that noticeable especially painted to blend with the rest of the interior.


----------



## mosconiac

So if I understand your comments properly, you are not mounting the PVC flush with the mouth of the horn (as in #1 below), but a little high to reach into the mouth of the horn (as in #2 below). Is that right?

My limited knowledge of horns would lead me to believe the latter would effect the cross-sectional area of the mouth and negatively impact it's low-freq response.

Also, I would assume method#1 is best because it represents the smoothest transition where #2 presents a small "hump" in the mouth which should create odd reflections at the mouth.


----------



## jbholsters

I kind of wish I wouldn't have pulled the horns out of my car now, so I could try this.


----------



## beerdrnkr

Great thread and thanks for all the time you're putting into this. I'm currently using a 9887, 4 2" fullrange drivers in the a-pillars, 8's in the doors, and 3 12's ported that will be changing to 1 12" sealed. I'm changing everything up and will be trying out a pointsource set of comps in my kickpanels w/ passive xovers (300wrms to each set), I'm keeping the dayton 8's in the doors (300wrms to each), and shortly I will also install dayton 7's in the rear doors with about 150wrms to each. So like you were saying, I want to give the front midbass a lot more power so I'm not bringing the midbass to the back. I'm not sure how much more processing I'll need to really keep the midbass up front but I'm planning on looping the rca's from one midbass amp to the other and using the t/a to get it as up front as possible although it will be affecting each set of midbass differently. I have my front doors deadened pretty solid and my rear doors will also be very deadened. I'm just curious if anyone in this thread has tried anything similar and what the results were. Am I just wasting money?


----------



## rawdawg

To me, it appears that the Round Over is centered on the lip of the Wave Guide, like so...











Really interested in this thread since I have BC-300's in my ride.


----------



## beerdrnkr

beerdrnkr said:


> Great thread and thanks for all the time you're putting into this. I'm currently using a 9887, 4 2" fullrange drivers in the a-pillars, 8's in the doors, and 3 12's ported that will be changing to 1 12" sealed. I'm changing everything up and will be trying out a pointsource set of comps in my kickpanels w/ passive xovers (300wrms to each set), I'm keeping the dayton 8's in the doors (300wrms to each), and shortly I will also install dayton 7's in the rear doors with about 150wrms to each. So like you were saying, I want to give the front midbass a lot more power so I'm not bringing the midbass to the back. I'm not sure how much more processing I'll need to really keep the midbass up front but I'm planning on looping the rca's from one midbass amp to the other and using the t/a to get it as up front as possible although it will be affecting each set of midbass differently. I have my front doors deadened pretty solid and my rear doors will also be very deadened. I'm just curious if anyone in this thread has tried anything similar and what the results were. Am I just wasting money?


Anyone ever try anything like this before?


----------



## ClinesSelect

Patrick Bateman said:


> It's stuffed right up to the bug screen in my USD horns.
> 
> You really want to go crazy with the foam, the best results are when you use A LOT of it.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's the plug that's in my current car. About 9 inches deep iirc.



I re-stuffed the horns in layers from the screen to the edge of the mouth. Now there is a difference. 




rawdawg said:


> To me, it appears that the Round Over is centered on the lip of the Wave Guide, like so...
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Really interested in this thread since I have BC-300's in my ride.



I tried methods #1 and #2 above but they are currently exactly like your drawing.


----------



## Patrick Bateman

ClinesSelect said:


> I re-stuffed the horns in layers from the screen to the edge of the mouth. Now there is a difference.


I think I "stumbled upon" the reason that stuffing the throat, and even the compression driver itself makes a difference.

Here's my theory:

In the Image Dynamics and the USD horns, the compression driver is mounted at a ninety degree angle.















Here's a couple of pics that illustrate what I'm talking about. There's the compression driver, on a USD horn.

If you've followed my "improve your soundstage for two bucks" thread, I've talked about how reflections are created by reflection and diffraction. We can calculate where they'll occur. A dip is created when there's a reflection at one quarter wavelength, and a peak is created at one half wavelength. *The dips are worse than the peaks, because it creates a perfect null.* The peak will be 6db at the most, a dip can be infinite.

Now in the pic above, see how the distance from the middle of the compression driver to that bend is two inches? And two inches is one quarter wavelength of 1688z. _(speed of sound / wavelength / 4) = (13500 inches per second / 1688hz / 4)._







Now here's the response of a Celestion compression driver, on a USD horn. This is treated and untreated. *I didn't stuff the throat.* Now look what's happening at 1688hz. 

Pretty neat huh?









You can see the poly fill spilling out of the throat here. (I used poly fill instead of foam, they both do the same thing, foam is better because it's more consistent.)






For comparisons's sake, here's a Radian compression driver, and a JBL. The JBL was stuffed all the way to the diaphragm. See how the JBL suffers from the same problems as the Radian and the Celestion, *but to a much lesser extent?*

Now obviously, the best solution is to eliminate this "kink" entirely. But if you can't, it looks like the foam does an impressive job of smothing out the response, as illustrated in the JBL's power response. (All graphs above were with the same horn.)


----------



## thehatedguy

Does the USD horn use a reflector in the bend? The Image horns do, and this will allow for proper wavefront summing. And you are right, the further the bend the lower you will have nulling problems. The drivers on the ID horns are about an inch away from the midline of the deflector, which would put your nulls up around 19k. And is one reason why I said the horns in the GN were a bad design.

Looking at the pictures, the USD seems to bend in to the throat of the horn. This is a very bad idea and a bad design flaw.


----------



## ClinesSelect

Patrick Bateman said:


> Now obviously, the best solution is to eliminate this "kink" entirely.


Probably one of the biggest criticisms I have read about horns designed for a vehicle application is the bend and the resulting problems it causes, as you have illustrated. 

I have yet to install the horns on the right. No bend.


----------



## thehatedguy

Huygen's wavefront reconstruction...

http://volvotreter.de/downloads/Edgar-Monolith-Horn-02.jpg


----------



## thehatedguy

My horns-

One when I first got them and had 1" exit drivers, and a couple with the large format Beymas on them. They were custom made for me back in 2002 by Image Dynamics.


----------



## rawdawg

It looks like Patrick puts his round over on the very edge of the lip. I wonder which is best?


----------



## Brian Steele

Here's an interesting 12" midbass driver that I heard about on another forum: the APX-1206 (APX1206)

It's interesting because not only because it's quite cheap at $80, but also because the specs suggest good midbass response and it that can also be used in a fairly small (~4.5 cu.f.t. net) TH that can down to 30 Hz easily in-car. And low mounting depth requirements too.


----------



## Patrick Bateman

Brian Steele said:


> Here's an interesting 12" midbass driver that I heard about on another forum: the APX-1206 (APX1206)
> 
> It's interesting because not only because it's quite cheap at $80, but also because the specs suggest good midbass response and it that can also be used in a fairly small (~4.5 cu.f.t. net) TH that can down to 30 Hz easily in-car. And low mounting depth requirements too.


I wonder if this is one of those "if it's too good to be true" moments?

Here's the APX:









It appears to be a manufactured by the same factory as this:









(That's a Goldwood, note the same basket, surround, terminals, magnet, etc... The APX has a rubber boot on the magnet.)

Anyways, the reason that I bring up "The Goldwood Connection" is that it reminds me of a series of speakers that were sold a few years back. A number of people got excited about them because they were very VERY inexpensive. Here's a couple threads:

high sensitivity open baffle bass driver recommendations

PSW Sound Reinforcement Forums: Product Reviews: Sound Reinforcement => eBay listing... interesting.

But then the horror stories started:

madison executioner vs omega pro 12 ?????? - TalkBass Forums
"The Madisons are available through Music Supply Center. They are however, Goldwood's, which you can also buy through Parts Express. Same speaker, different label."

"One of my members recently bought a pair of the Goldwood Monterey series 'pro' woofers to see if they were any good, They weren't. Absolute junk."

DO NOT BUY FROM musicsupplycenter.com OR shredmuzic.com - ClubCivic.com - Honda Civic Forum
"Well, about a month ago, 2 15" speakers in one cabinet blew..."

Music Supply Center-Madison-Legion stuff - TalkBass Forums
"I'd try out some of their Knight ten inch speakers that they have in the Madison 810 and 410 cabs. I put them in a 210 cab I had, and wouldn't you know it, I had a 50 50 chance, and one of the drivers is junk..."


----------



## Brian Steele

Patrick Bateman said:


> I wonder if this is one of those "if it's too good to be true" moments?
> 
> Here's the APX:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> It appears to be a manufactured by the same factory as this:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> (That's a Goldwood, note the same basket, surround, terminals, magnet, etc... The APX has a rubber boot on the magnet.)




Nope - that Goldwood appears to have a different basket and possibly a smaller spider. The spider and surround also seem to be very different. Take a closer look . 

The APX basket is a lot closer to the JBL 2206H basket (the supports for the 2206 terminate at the bottom of the standoff for the spider instead of at the top, but that's about the only major difference I can see).

A review of the APX driver can be seen here: R.i.p 55-1740 - Page 2 - diyAudio

There is of course the possibility that this driver is just too good to be true, but for only $80, it might be worth a test.


----------



## thehatedguy

I was thinking it looked a lot like a JBL knock off.


----------



## jbholsters

Yeah, those baskets are definitely not the same. The surround actually looks different as well


----------



## Hernan

Back to topic, from Werewolf:

by werewolf on Mon Jul 31, 2006 10:34 am
I posted a long response over on the carsound thread recently ... but it was curiously deleted. I'll re-post here 

A few principles of sound localization relative to the discussion :

- The dimensions of the outer ear are simply too small to affect the acoustic transfer function to our eardrums below about ~1kHz, certainly below ~500Hz. Therefore, for midbass frequencies (not necessarily midrange, mind you) we can think of our heads as the classic "sphere with a hole in each side".

- An acoustic source playing midbass freqs is ABSOLUTELY localizable ... but the ear/brain relies on inter-aural time differences, rather than inter-aural intensity differences, in the midbass. The wavelengths are simply too long for even "head shadowing" to play a role.

- The real situation has two sources (drivers) and two receivers (ears) of course, but it's instructive to decompose the problem and consider a single midbass driver, plus two ears, to understand how that single midbass driver is localized.

Conclusions :

- In the midbass region, there's a "circle of confusion" ... any point on this circle is indistinguishable from any other point. The circle is in a plane perpendicular to a line drawn between the ears, with it's center on that line. A driver at any point on this circle will generate the same inter-aural time difference to our "spherical heads" as any other point on the circle. It's very important to understand the simple geometry that makes this a FACT ... not open to interpretation.

- For a wide soundstage, you still want this "circle" to be as far left (and right) as possible.

How it pertains to midbass driver placement :

- There's nothing fundamental that prevents rear-mounted midbass drivers from "linking" to higher frequency drivers which the ear can localize to the front. Front localization involves outer ear dimensions, head shadowing, etc ... none of which pertains to midbass freqs below maybe ~500Hz.

- It's a MUCH better idea to put rear midbass drivers in the rear quarter panels, rather than in the rear deck. Drivers in the rear deck will be located directly BEHIND your head, no better ... from a stage width perspective ... than midbass drivers located directly in FRONT of your head. You still want the "circle" as far left/right as possible, or else the stage will be collapsed.

- Time alignment, both parallel and delta, helps of course.

- The key to making this illusion work is to make sure that the drivers aren't playing frequencies they're not supposed to. Shallow slope xovers, driver or amplifier distortion, panels ratlling/vibrating ... these will all allow driver localization. I strongly recommend playing pink noise through the midbass driver ALONE ... with the appropriate crossover, of course ... and look or listen for signs of higher frequencies. Solve the problems found. You MUST take this step before you can judge the success of the illusion.

Guess that's all for now


----------



## Patrick Bateman

thehatedguy said:


> I was thinking it looked a lot like a JBL knock off.


If anyone in the Seattle / Portland area is interested in having me build them some tapped horns, I think I'd be willing to give it a go with those woofers.

Basically, I am curious to try out a new tapped horn folding scheme, but I need another subwoofer like I need a hole in my head. I actually have a tapped horn sitting in my bedroom, not even hooked up, I'm running out of places to store my subwoofers 

There are two caveats to this offer:


I'll be trying out a new layout, there's no guarantees it will work as predicted. Worst case scenario, you wasted $40 on plywood
It's going to be big - about six to eight cubic feet
I hate finishing boxes. So I'll build and measure the sub, but you gotta carpet or veneer it 

Anyways, if anyone's interested, hit me up in email. I'm excited to try this woofer out, but I literally have no room for subs at the moment.


----------



## michaelsil1

I miss werewolf!


----------



## chad

Brian Steele said:


> The APX basket is a lot closer to the JBL 2206H basket (the supports for the 2206 terminate at the bottom of the standoff for the spider instead of at the top, but that's about the only major difference I can see).


The proof in the puddin is when the cone is out... does the gap resemble/mimick the JBL VGC design or is it just a plane-ol gap?


----------



## beerdrnkr

Hernan said:


> Back to topic, from Werewolf:
> 
> by werewolf on Mon Jul 31, 2006 10:34 am
> I posted a long response over on the carsound thread recently ... but it was curiously deleted. I'll re-post here
> 
> A few principles of sound localization relative to the discussion :
> 
> - The dimensions of the outer ear are simply too small to affect the acoustic transfer function to our eardrums below about ~1kHz, certainly below ~500Hz. Therefore, for midbass frequencies (not necessarily midrange, mind you) we can think of our heads as the classic "sphere with a hole in each side".
> 
> - An acoustic source playing midbass freqs is ABSOLUTELY localizable ... but the ear/brain relies on inter-aural time differences, rather than inter-aural intensity differences, in the midbass. The wavelengths are simply too long for even "head shadowing" to play a role.
> 
> - The real situation has two sources (drivers) and two receivers (ears) of course, but it's instructive to decompose the problem and consider a single midbass driver, plus two ears, to understand how that single midbass driver is localized.
> 
> Conclusions :
> 
> - In the midbass region, there's a "circle of confusion" ... any point on this circle is indistinguishable from any other point. The circle is in a plane perpendicular to a line drawn between the ears, with it's center on that line. A driver at any point on this circle will generate the same inter-aural time difference to our "spherical heads" as any other point on the circle. It's very important to understand the simple geometry that makes this a FACT ... not open to interpretation.
> 
> - For a wide soundstage, you still want this "circle" to be as far left (and right) as possible.
> 
> How it pertains to midbass driver placement :
> 
> - There's nothing fundamental that prevents rear-mounted midbass drivers from "linking" to higher frequency drivers which the ear can localize to the front. Front localization involves outer ear dimensions, head shadowing, etc ... none of which pertains to midbass freqs below maybe ~500Hz.
> 
> - It's a MUCH better idea to put rear midbass drivers in the rear quarter panels, rather than in the rear deck. Drivers in the rear deck will be located directly BEHIND your head, no better ... from a stage width perspective ... than midbass drivers located directly in FRONT of your head. You still want the "circle" as far left/right as possible, or else the stage will be collapsed.
> 
> - Time alignment, both parallel and delta, helps of course.
> 
> - The key to making this illusion work is to make sure that the drivers aren't playing frequencies they're not supposed to. Shallow slope xovers, driver or amplifier distortion, panels ratlling/vibrating ... these will all allow driver localization. I strongly recommend playing pink noise through the midbass driver ALONE ... with the appropriate crossover, of course ... and look or listen for signs of higher frequencies. Solve the problems found. You MUST take this step before you can judge the success of the illusion.
> 
> Guess that's all for now


Thanks for this, it helps a little in answering my previous question. Somehow this thread ended up towards talking about horns..lol


----------



## michaelsil1

beerdrnkr said:


> Thanks for this, it helps a little in answering my previous question. Somehow this thread ended up towards talking about horns..lol


He was talking about having Horns playing Mid Bass then it went South for the Winter.


----------



## Patrick Bateman

If anyone is wondering why the thread has been a bit quiet lately, it's because I'm really trying to figure out the best solution to this midbass problem.

If I simply reverse-engineer the midbasses in the Grand National, I'll have awesome dynamics and low distortion.

The thing that's perplexing is why some cheap midbasses *sound* good.

This is something I really obsess over, why some speakers (seem) to measure poorly, but sound good.

For example, to my ears, the cheap AuraSound and Peerless full range drivers are nearly the equal of the B&C. They sound a LOT better than run-of-the-mill Focal and Seas woofers. So do the Dayton Reference woofers.

My hypothesis is that the answer lies in the power response and the distortion. For the past few weeks I've been obsessively doing measurements of the power response of various drivers both outside of the car, AND in the car.

I've had some people ask about the use of inexpensive woofers in lieu of the B&C, and I'm cautiously optimistic about these small inexpensive woofers. The catch is that I would recommend using an array to increase efficiency and power handling, and run them push-pull to lower 2nd harmonic distortion.

Due to comb filtering, you have to get them very VERY close together too.

I'll be posting some results on this in the next few days. I've done the measurements, but need to collect and comment on them.


----------



## bayvanman

Patrick I've hit a wall with regards to Peerless speakers.
In the GNIB thread you suggested the Parts-Express.comeerless 830987 3" Full Range Woofer | Peerless 830987 3" Full Range Driver bass mid midbass mtm 2-way vline logic line array lat tymphany09 Peerless 830987.
Ordering these from the USA for me is a bit of a no no at the moment.
However, I've found them in Europe, but they don't seem the same...
830987 - Peerless 3" full range inverted - EUROPE AUDIO
There is also the 830986...
830986 - Peerless 3" full range - EUROPE AUDIO
Which looks like the 830987.
Argh
Which look the most appropriate to your suggestions???

Cheers


----------



## POLKAT

The 830987 has the inverted surround. I am using them in my A-pillars. The documentation for them at Madisound, Parts Express and other retailers is wrong. 

830987 | Tymphany

The 830987 and 830986 are very similar. The main difference is a slightly higher fs of the 830987.


----------



## bayvanman

Thank you Polkat!
Sorry to take this OT.


----------



## western47

Patrick Bateman said:


> This is something I really obsess over, why some speakers (seem) to measure poorly, but sound good.
> 
> My hypothesis is that the answer lies in the power response and the distortion. For the past few weeks I've been obsessively doing measurements of the power response of various drivers both outside of the car, AND in the car.


I am in the camp of data showing that there is very little information connecting certain distortion measurements and audible perception. The linear distortions along with power response should give you a much better picture of what is actually happening.

Either way, keep up the great work. I, for one, am possibly going to copy some of your efforts.


----------



## ben_lesmana

Hi, 

I still failed to see how 4 or 6 pcs of 3" woofer in a really small enclosure can match a pair B&C 8" in terms of output in the midbass area (100hz-300hz?). Can someone elaborate further?

Regards,
Ben


----------



## thehatedguy

You are picking up a lot of efficiency with the tapped horn. The B&Cs are only using the front side of the speaker for output. The tapped horn lets you use both sides of the cone for output.


----------



## Fast1one

thehatedguy said:


> You are picking up a lot of efficiency with the tapped horn. The B&Cs are only using the front side of the speaker for output. The tapped horn lets you use both sides of the cone for output.


Pretty sure he was referring to the suggestion to use three 3 inch woofers per side in extremely small sealed enclosures. Two under the dash near the firewall per side and two randomly placed in the cabin.


----------



## Patrick Bateman

ben_lesmana said:


> Hi,
> 
> I still failed to see how 4 or 6 pcs of 3" woofer in a really small enclosure can match a pair B&C 8" in terms of output in the midbass area (100hz-300hz?). Can someone elaborate further?
> 
> Regards,
> Ben


A B&C 8NDL51 in a small sealed box will play louder and cleaner than an AuraSound NS4. Absolutely.

Here's where things get tricky though.

The goal of this thread is to figure out why some midbasses sound "natural", and most do not.

For instance, I briefly used a pair of paper coned Focal woofers in my 2001 Accord, and they *never* sounded natural or coherent.

*Why is that?*

With careful placement, I was able to exceed the performance of the Focal woofers using a cheap pair of computer speakers. (AuraSound NS3s.)

*Why is that?*

Keep in mind, I'm a total audio nerd, and simply swapping gear out for the rest of my life won't work for me. The whole idea of this thread, and these projects, is to find out why some midbass solutions sound natural, and some do not.

If anyone's interested, my current thoughts are along these lines:


Everyone fixates on the frequency response of a loudspeaker as measured on a flat baffle. But in a car the response goes to hell. I believe Geddes was one of the first to really attack the problem, 25 years ago when he did car sound for Ford.* Geddes is no longer active in the auto sound arena, unfortunately. (My home speakers are hand built by Geddes, and are my reference for all these projects.)
At JBL, Keele has documented that reflections aren't a bad thing, in fact they can even improve intelligibility and the perception of a soundstage.**
The audio treatments that some use are short sighted, because they only treat a single frequency. To effectively treat a room (or a car) you need to absorb or diffuse sound across a broad range of frequencies.**

There's another "twist" though, which I've been exploring. While the results are still preliminary, it *appears* that certain enclosure types work better than others in this scheme.

It's too bad that Geddes isn't involved in this thread, because I'm certain he's explored this one too. All of the simulations I've seen from Harman are based on monopoles (ie, simple sealed boxes.)

I'll post some data once it's "ready for prime time."

* AES E-Library: The Localized Sound Power Method
** http://www.harman.com/EN-US/OurComp...p/Documents/Scientific Publications/13686.pdf


----------



## Patrick Bateman

Fast1one said:


> Pretty sure he was referring to the suggestion to use three 3 inch woofers per side in extremely small sealed enclosures. Two under the dash near the firewall per side and two randomly placed in the cabin.


The GNIB thread and this one have some overlap. This thread is basically "how do we create natural midbass in a car?"

The GNIB thread is basically a post-mortem on my previous system, which was inspired by the Grand National. In the process I threw out a recommendation for a $500 system that shares some of the GN's magic.

I'll post some info clarifying what the midbass options are in that thread.


----------



## Patrick Bateman

thehatedguy said:


> You are picking up a lot of efficiency with the tapped horn. The B&Cs are only using the front side of the speaker for output. The tapped horn lets you use both sides of the cone for output.


I stumbled on a solution this morning that is pure lulz

I am actually kicking myself that I'd never considered this one before.

I've tried the AuraSounds in a sealed box, in a front loaded horn, and in a tapped horn. They all have their advantages and disadvantages. The sealed box is easy to build, but has limited output. The front loaded horn has lower distortion and higher output than the sealed box, but it's tricky to build. The tapped horn has the most output of all, but the response has a notch in it, and it's also a challenge to build.

So here's the one I never considered:

An open baffle. Literally a stupid sheet of plywood, with the woofers bolted in.

Because we're getting output from both sides of the cone, we get six dB more output at certain frequencies. The *really* cool part about open baffle is that you can go crazy and buy lots of woofers, raising your power handling dramatically. For instance, a box for eight NS4s would take up the whole firewall, but with an open baffle, you're basically limited by your budget and the physical size of the drivers themselves.

Another bonus is cancellation of 2nd harmonic distortion, like in a tapped horn.

Why didn't I think of this before??!!







Here's a sim with four NS4s. We're picking up a ton of gain around 650hz, with a gentle rolloff on both sides. The F3 is 200hz. Admittedly, that's very high, but cabin gain starts to "kick in" at 280hz. So I wouldn't be surprised if we can get down to 100hz in the car, and hand off to a subwoofer.

The sheet of plywood would tuck *under* the dash, out of the way of the pedals. Similar to what USD and Image Dynamics do with their horns, but much shallower. I included a 1" "lip" to improve cosmetics.

Because we're getting output from both sides of the cone, this is virtually like having dual eights up front in sealed boxes. (The eights will have more output below 300hz.)

I tried modeling it with a CSS Trio8 also, but the NS4 worked better. An array of small woofers is smoother than one big woofer.

It's cheap too - under $100 per side.


----------



## 12vTools

Stereophile: Carver Amazing Loudspeaker (Platinum Edition)


like Bob did it?


----------



## SSSnake

> (The eights will have more output below 300hz.)


Not trying to nitpick but this thread started as a thread about "natural bass". We should be striving for more and better output below 300hz. I agree that cabin gain can help, but it has been my experience that you have some nulls in this area as well. If you do have these nulls, this solution would run out of steam pretty quickly.

I love the novel ideas but I'm not sure all of them will get the average reader where they want to be.


----------



## western47

Average reader?! Heck, we should be striving for ultimate type levels with achievable installation methods. 

One question that I have is one regarding mulitple bass drivers for the sub region as well. Why would we not have the same mode issues down low in a car environment as we do in the home? 

I would think that the statistical region of a car would be lower in frequency than in the home.


----------



## cubdenno

western47 said:


> Average reader?! Heck, we should be striving for ultimate type levels with achievable installation methods.
> 
> One question that I have is one regarding mulitple bass drivers for the sub region as well. Why would we not have the same mode issues down low in a car environment as we do in the home?
> 
> I would think that the statistical region of a car would be lower in frequency than in the home.


I would think it would have to do with the difference in volume between a room and a vehicle. Even an SUV is way smaller.


----------



## Blake Rateliff

Wouldn't an open baffle have to be quite large to prevent cancellation at lower frequencies? Maybe I'm completely misunderstanding the principles behind open baffles.


----------



## western47

cubdenno said:


> I would think it would have to do with the difference in volume between a room and a vehicle. Even an SUV is way smaller.


I totally agree. I would think that having multiple low bass sources would be just as important as the midbass. The cabin gain will help with output but not with evenness across a space.


----------



## SSSnake

I think that you guys are missing my point. Bass is below 300hz by most peoples definition. If you are not increasing the output level and/or uniformity of repsonse in this area then you are not addressing the problem.

BTW - It is a very difficult problem and I am very interested in effective methods to address this issue but more response around 650hz does not help.


----------



## SSSnake

Why don't we do a quick summary...

We have three high efficiency solutions/variations:

Grand National - 12" midbasses 
Advantages: LOTS of output (can cut out any response anomolies with EQ)
Fewer reflections due to rear quarter panel mounting (no console reflections)
Low distortion

Disadvantages: BIG
Localization toward the rear with any rattle or buzz

B&C sealed 
Advantages: Lots of output in the upper midbass (110db in free space above 160hz)
Low distortion
Disadvantages: weak lower midbass output (F3 at 125Hz w .4 cube box)

Tapped Horn
Advantages: Lots of output 
Low distortion

Disadvantages: Large enclosure (comparatively)
Hard to get into forward and wide location

Then we have a couple of multiple location solutions

Geddes multiple driver w random placement (adpated to midbass in a car)
Advantages: Even response
Lots of output

Disadvantages: To avoid directivity clues secondary locations must be -6db below primary locations (this prevents correction of variations above 6db wo location concerns) 

Andy W LCR Approach
Advantages: Uses multiple drivers to smooth response
Can provide very strong center and side location clues
Lots of output (from increased number of drivers)

Disadvantages: Finding a center channel that can handle midbass
Processing requirements

Finally we have multiple source open baffle
Advantages: Increased directivity in horizontal plane

Disadvantages: Baffle size for low midbass response


PB - This is my interpretation but this is your baby. Could you add/subtract where appropriate?


----------



## Patrick Bateman

SSSnake said:


> I think that you guys are missing my point. Bass is below 300hz by most peoples definition. If you are not increasing the output level and/or uniformity of repsonse in this area then you are not addressing the problem.
> 
> BTW - It is a very difficult problem and I am very interested in effective methods to address this issue but more response around 650hz does not help.









The efficiency of the dipole at low frequencies is terrible. But the dipole has a few upsides:

At frequencies where the front and back wave are separated, efficiency is nearly 6dB higher than a monopole (sealed box.)
The big advantage is that you can cram as many woofers as you can fit. The Jamo dipole above is a good example of what I mean. The baffle is barely big enough for the woofer. So the woofers rolls off very early, but you have tons of excursion available, which gives you the liberty of EQ'ing it flat.
Here's an example of what I mean:
Let's say you have a four inch woofer in a sealed box, with an F3 of 100Hz. It has an efficiency of 84dB. At 100Hz, it will be putting out 81dB.
Now replace that four inch woofer with FOUR of them, in an "open baffle." The F3 is 200Hz. With four times the power, and four times the cone area, the array is putting out 96dB with the same excursion. At 200hz response has drooped to 93dB, and at 100Hz it's down to 81dB* - the exact same efficiency as the sealed box.
I'll post some measurements shortly that will help illustrate this.
In a nutshell, I'm trading one sealed woofer for four in a dipole.
I could also do what Jamo did, and use a very large woofer. But then depth becomes a problem. I want to keep the depth under three inches. The Dayton ND105s are 2.8" deep.
By trading one sealed box for four woofers in an array, we reduce distortion dramatically from 300hz and up, because theres simply less excursion.
This one is totally subjective, but dipoles just sound, uh, "open." There's something about dipole radiation which sounds excellent.

* In free air, dipoles roll off at 24dB/octave, but in a room or in a car the rolloff isn't as steep. Measurements will be coming soon...


----------



## jbholsters

The beauty of the GN was...simplicity. Never mind all the crap RC added to the install. The heart of that car was 6 high efficiency drivers and big beefy amps (Alpine 3545's: [email protected] and [email protected])


----------



## mitchyz250f

What about plain old fashioned porting?


----------



## SSSnake

In the case of the 8NDL51, .4 cubes tuned to 70Hz us very nice. Getting .4 cubes in the right location is tough.


----------



## mitchyz250f

I wasn't thinking about the BC when I mentioned porting, but that speaker does very well ported.


----------



## Patrick Bateman

mitchyz250f said:


> What about plain old fashioned porting?


I never considered a ported box because the box size gets out of control in a hurry. Here's what I mean:

I want this box to fit under the dash. I'd like to use at least four woofers, for displacement reasons. A single woofer has too much distortion, and simply can't move enough air.

To give you an idea of how much space it will take up, my tapped horn with two woofers is four inches tall. A ported box with four of the same woofer would be TWENTY TWO INCHES tall :O

So, obviously, that won't fit under the dash 







This is the predicted response of various options. This is for a single woofer - multiply the volume by four.







Here's a crazy idea though. Bear with me, this is a weird one.

Here's a vented box, which fits under the dash. The woofers are mounted push-pull, which reduces distortion. It's a vented box. The weird part about this box is that it's tuned very high. If you try and model this in WinISD, it will look terrible. But WinISD doesn't factor in the time delay from the pathlength, and it doesn't factor in the distance from the woofer to the port.

I believe that you can move up the tuning frequency, and reduce the box size, as long as you keep the port as far from the woofers as possible. This is because the distance from port to woofer introduces a delay, which allows you to move up the tuning frequency. This delay reduces the cancellation problems inherent in a vented design. (IE, if you tuned the vent to 200hz, it would create a huge null in the speaker because it's out-of-phase with the woofer. Hence, moving the port away from the woofer is essential.)

Does that make sense?

Keep in mind that a vented box is a dipole; there are very few simulations that factor in the dipole radiation. (Quarter-Wave can do it.)


----------



## Patrick Bateman

I've come to the conclusion that imaging is more important to me than maximum SPL. I've decided to abandon the idea of using an array of midbasses, or one big midbass, under the dash.

Instead I am building a new Unity waveguide. This one will be a three-way, and should go down to 100hz.

The entire stage will be up on the dash.

Here's the link:

http://www.diymobileaudio.com/forum...forum/71993-unity-v-midbass-strikes-back.html


----------



## cubdenno

Quitter!!!!


----------



## jbholsters

Patrick Bateman said:


> The entire stage will be up on the dash.


 so a 2 seater is out the window. Why not try this under the dash?


----------



## Patrick Bateman

jbholsters said:


> so a 2 seater is out the window. Why not try this under the dash?


Don't tempt me 

If it wasn't for Western47, I wouldn't have tried the QSC waveguide in the car.

Based on the discussion that Eric Stevens had on this forum, I'm starting to change my mind about the under-dash horns. I think that you *may* be able to trick the brain into believing the soundstage is at eye level. I started thinking about the Image Dynamic horns, and realizing that the extremely broad vertical directivity is masking the fact that they're located at waist level.







I tried an under-dash Unity last week. Here's a pic of the horn, loaded with a large-format JBL compression driver and a 3" Peerless midbass. The problem with this combination is that you need a supertweeter. That's not the end of the world, but I'd really like to get the entire range on one waveguide. The reason that you can't add a tweeter to this horn is that you can't get the drivers close enough. They need to be about 1/4 wavelength apart at the crossover frequency. So if you added a supertweeter, it would have to be 0.35" away with a 10khz crossover. Obviously, that's impractical.







Here's the frequency response. Red is the tweeter, orange is the midbass, purple is both. The midbass is raising efficiency at 300hz by 12dB, right where we need it. Three more would bring that up *another* 12dB.

The dash still has one big advantage, and that is sheer size. If you terminate a dash mounted waveguide properly, it "sees" the entire dash as an extension to the mouth. This makes a big difference for the midbass, and really smooths out the response. Check out some of the measurements I did of the under-dash horns over in the "waveguides and psychoacoustics" thread at diyaudio. The response was quite poor, particularly on-axis. The response of the OS waveguide was much better.


----------



## thehatedguy

Use the BMS or B&C coax compression drivers. The BMS has output from 300 hertz to 20k.


----------



## lycan

michaelsil1 said:


> I miss werewolf!


excellent threads like this one might just bring him back from the dead 

The midbass problem in vehicles is over-constrained : arraying drivers to generate a smoothed magnitude response, while at the same time maintaining the "circle of confusion" to preserve inter-aural time delay (or, if you like, differential phase response), is no small task. Kinda like Andy said earlier ... a well-diversified array might make the magnitude response look pretty good for a variety of listening positions, but the stage will collapse if ITD's aren't maintained.

A very good read though ... thanks guys


----------



## thehatedguy

Your phone not work these days?


----------



## chad

thehatedguy said:


> Use the BMS or B&C coax compression drivers. The BMS has output from 300 hertz to 20k.


I have yet to hear those things but they sure look cool!


----------



## thehatedguy

I hear mixed stories about the BMS units. Most complain about the tweeter integration being not so good. But I think given our nature of liking a lot of active processing in the car, we could probably do more with that problem than the home guys trying to deal with it passively. But then again, the Euros like BD Design love them.

Haven't heard anyone use the B&C coaxes yet.


----------



## chad

They are gonna require a HUGE horn man


----------



## thehatedguy

Thank good our dashes act as extensions of the horn. My ID horns are actually shortened and modded for 2" drivers...I use a 2-1.5" adapter for the Beymas. I had a set of BMS 4591s- the BIG ferrite midrange part of the coax I was going to use. Those are some NICE sounding midranges. BMS recommends a 300 hertz XO point for pro use, driver has response down to 200. Max SPL is 136 dB at 150 watts, which it is rated to do above 400 hertz. 136 dB of midrange is, uh, loud lol.


----------



## Fast1one

lycan said:


> excellent threads like this one might just bring him back from the dead
> 
> The midbass problem in vehicles is over-constrained : arraying drivers to generate a smoothed magnitude response, while at the same time maintaining the "circle of confusion" to preserve inter-aural time delay (or, if you like, differential phase response), is no small task. Kinda like Andy said earlier ... a well-diversified array might make the magnitude response look pretty good for a variety of listening positions, *but the stage will collapse if ITD's aren't maintained.*
> 
> A very good read though ... thanks guys


I don't think it will. I'm pretty close to trying this for myself. Each of the satellite woofers needs to be 6db down in amplitude compared to their respective channels to take advantage of the Haas effect. Hence using 6 woofers is the easiest to do without the aid of additional external processing. Use two per channel in the front as the main midbass drivers, and use one per channel for the smoothing woofers if you will.


----------



## chad

thehatedguy said:


> Max SPL is 136 dB at 150 watts, which it is rated to do above 400 hertz. 136 dB of midrange is, uh, loud lol.


No doubt about that!


----------



## SSSnake

Listen to the Lycan!

Without equal ITDs your midbass will turn to mud. This is NOT the freq band where you want arrival times skewed.


----------



## lycan

stay tuned for a (moderately) lengthy post, that's still under moderation cuz me=noobie


----------



## thehatedguy

Uh huh right.:vanish:



lycan said:


> cuz me=noobie


----------



## SSSnake

Return of the wolf? 

If true, things are looking up around here.


----------



## manslayer

super interesting thread, nice discussion going on guys, i've learned alot


----------



## bboyvek

lycan said:


> stay tuned for a (moderately) lengthy post, that's still under moderation cuz me=noobie


of course!! you only have 4 posts, no one will listen to you


----------



## lycan

i certainly wouldn't listen to me, or that crazy alter ego ... he was mad as a hatter. methinx i gotta get my post count over 5, to post freely and with reckless abandon.


----------



## Bmxnick101

great read guys. i need to start over again and reread all of it. so much to learn BRAIN OVERLOAD.


----------



## lycan

Thanks to Patrick again for a great thread!


----------



## lycan

Well i thought i'd take some time to _quantify_ an item of discussion ... namely, how "much" would an additional midbass driver "collapse" the stage, assuming it was added in a non-ideal location? We'll study a simple case of a _first_ driver, placed somewhere to the left of the listener on the "circle-of-confusion", augmented by a _second_ midbass driver located directly _behind_ the listener. The first midbass driver may be in a kickpanel or door, and the second may be on the rear package tray.

First, we must recognize that the ear/mind localizes midbass by ITD (inter-aural time differences). It's been known for a century or two (Lord Rayleigh, i think?) that the ear most definitely CAN localize midbass in the L/R direction (but not in the vertical plane). But the wavelengths are simply too long for the localization cues to be intensity-based (IID) ... head-shadowing, for example, plays no role in the midbass ... so the cues but be arrival-time based. However, if we imagine our heads as spheres with holes in the sides (valid model in the midbass, where the outer ear has no effect), we'll immediately recognize that there's many points where a midbass source can be located and still yield the same ITD. Hence, the so-called "circle-of-confusion" 

So, we'll start with a simple model of a _first_ driver operating at a single midbass frequency *w* to describe the two signals at each ear :

left : *A1*sin(*w*t)
right : *A1*sin(*w*(t-*Td1*))

where *A1* represents the midbass _amplitude_ at each ear, and *Td1* represents the _arrival time_ difference between the ears.

Now we add a _second_ midbass driver directly behind our heads. We're adding this driver to help "randomize" midbass source locations in the listening space, in order to "smooth" the amplitude response. But this new driver adds no ITD, because it's located directly behind us. Without loss of generality, we'll assume that this second midbass is time-aligned to the first. The new, combined signals at our ears will be :

left : *A1*sin(*w*t) + *A2*sin(*w*t)
right : *A1*sin(*w*(t-*Td1*)) + *A2*sin(*w*t)

where *A2* represents the midbass amplitude of the _second_ driver, at each ear. Make sense? I'm going to continue in a second post, to make sure these posts are working


----------



## lycan

The new signal at the left ear is easy to determine (or simplify) :

left : (*A1*+*A2*)sin(*w*t)

The more interesting case is what's happening at the right ear  I've chosen to use sinewave algebra, but the exact same analysis can be performed with vector algebra. The "vectors" would have amplitudes that correspond to *A1* and *A2*, with phases corresponding to the time delays under consideration (actually, frequency*(time delay) ... time delay being nothing more than a phase shift that's linear wrt frequency). The interesting point to be made, ultimately, is this :

*If you add two vectors of different amplitude and phase, you end up with a single resultant vector of new amplitude and phase  But ... and here's the rub ... you can't "significantly" impact the resultant amplitude without also "significantly" impacting the resultant phase.*

What this means for us is that the expression for the right ear can be "simplified" into a _single_ sinewave, with a DIFFERENT amplitude and ... most importantly ... a DIFFERENT time delay. YES, adding a second midbass driver will still result in a "pair" of time delayed signals at our ears, but the delay ... and consequently, the apparent "location", of the "combined" midbass source will be MODIFIED by the presence of the second source.

Here's the resulting expression for the right ear signal :

right : *Ar*sin(*w*(t-*Tdr*))

where *Ar* is the new combined amplitude at the right ear, and *Tdr* is the new combined time delay at the right ear, given by :

tan(*w*Tdr*) = sin(*w*Td1*)/[cos(*w*Td1*)+*A2/A1*]

I'll conclude with a numerical example next  But for now, in general terms, we've got an expression that will tell us how much a second source will "collapse" the apparent location of a midbass driver. We can even specify the location of the first driver, and amplitude ratio of the two drivers


----------



## lycan

well before we do a numeric example, let's check our expression that defines the _new_, combined inter-aural time delay resulting from the addition of a second midbass placed directly behind our heads :

tan(*w*Tdr*) = sin(*w*Td1*)/[cos(*w*Td1*)+*A2/A1*]

It's always a good idea to _verify_ a newly developed expression with a few _extreme_ cases, to make sure it's right 

1. *A2* = *0*. This is the case where the second midbass (behind our heads) has zero amplitude. In this case,

tan(*w*Tdr*) = sin(*w*Td1*)/cos(*w*Td1*) = tan(*w*Td1*)

or

*Tdr* = *Td1*

this makes infinite sense ... if the second midbass has zero amplitude, the resulting ITD will be identical to that from the first midbass alone 

2. *A2* --> huge, much bigger than *A1*. In this case,

tan(*w*Tdr*) = *0*,

or

*Tdr* = *0*

this also makes infinite sense ... if the amplitude from the second midbass completely _swamps_ the first midbass, the signals at our ears will be completely dominated by the second midbass, which has zero ITD (because of where we placed it) 

OK ... now that we have confidence in our analysis, time for a more meaningful example


----------



## thehatedguy

I've missed you my old friend.


----------



## dbiegel

Wow great stuff! So if I understand you correctly:

- The farther you can get a midbass to the left/right of the car, the wider the stage. Front/back doesn't matter at these frequencies, and neither does up/down, because our head is just a sphere with two holes.

- The louder a second midbass (mounted further toward the center of the car, laterally) plays relative to the first (mounted further outward), the more the stage will "narrow" toward the second midbass location. 

I'm confused as to what does "t" represent? Is it the time it takes for the sound to get from the driver to the ear?


----------



## thehatedguy

Yes and yes


----------



## Mic10is

lycan said:


> well before we do a numeric example, let's check our expression that defines the _new_, combined inter-aural time delay resulting from the addition of a second midbass placed directly behind our heads :
> 
> tan(*w*Tdr*) = sin(*w*Td1*)/[cos(*w*Td1*)+*A2/A1*]
> 
> It's always a good idea to _verify_ a newly developed expression with a few _extreme_ cases, to make sure it's right
> 
> 1. *A2* = *0*. This is the case where the second midbass (behind our heads) has zero amplitude. In this case,
> 
> tan(*w*Tdr*) = sin(*w*Td1*)/cos(*w*Td1*) = tan(*w*Td1*)
> 
> or
> 
> *Tdr* = *Td1*
> 
> this makes infinite sense ... if the second midbass has zero amplitude, the resulting ITD will be identical to that from the first midbass alone
> 
> 2. *A2* --> huge, much bigger than *A1*. In this case,
> 
> tan(*w*Tdr*) = *0*,
> 
> or
> 
> *Tdr* = *0*
> 
> this also makes infinite sense ... if the amplitude from the second midbass completely _swamps_ the first midbass, the signals at our ears will be completely dominated by the second midbass, which has zero ITD (because of where we placed it)
> 
> OK ... now that we have confidence in our analysis, time for a more meaningful example


glad to have you back as well..youve been missed


----------



## michaelsil1

Welcome back! epper:


I looked up the definition of lycan a few days ago.


----------



## lycan

thanks for the kind words guys ... glad to see a few old friends (enemies as well, i'm sure!) in these parts.

But the real kudos go to Patrick of course  He's been doing some GREAT work in theory AND practise, and ... perhaps most importantly ... merging the two. And, not surprisingly, the ideas that DON'T quite pan-out are often as inspirational, and certainly as educational, as those that DO  Inspirational enough to bring a dusty old man out of retirement (i'm referring to Michael Schumacher of course).

To summarize the point of my last couple posts : an additional midbass, added directly behind our heads (zero ITD), will "change" the ITD of left-mounted midbass. The analysis of this simple case is pretty straightforward, and will be a good indicator of how much "stage collapse" we can expect, even with a reduced amplitude in the second midbass.

Numeric example to follow.


----------



## bassfromspace

Nice to see you back Wolf.

For the sake of clarity, would you mind giving us a frequency-based definition of midbass?


----------



## jp88

So what happens if the 2 midbasses on both sides are in the front and rear doors?


----------



## lycan

midbass = higher than subbass, lower than midrange 

Let's define midbass as STRONGLY in the ITD frequency range. Wavelengths approximately longer than the distance between our ears, but approximately less than interior dimensions of a vehicle. How does between 80 Hz and 320 Hz strike you? I wouldn't argue with extending the upper limit by another octave. I like to think in octaves 

Midbass in front door, augmented by midbass in back door is not a terrible idea. This placement (much like a rear quarter panel midbass) at least "tends" to preserve ITD's for the additional midbass. In my view, it's better than putting an extra midbass directly in front of you, directly behind you, or directly under you (where the additional midbass can't possibly be preserving ITD's). Now, whether or not the additional midbass in the rear door ... or, rear quarter panel ... is "random" enough to help smooth _amplitude_ variations, i don't know


----------



## sqnut

I wish I could understand the language of numbers. I believe the OP had an issue with too much cabin gain in the 20-50hz range and a loss of mid bass response. This normally happens with the mids are mounted near the bottom of the door. The cabin gain from the floorwell is the main culprit. Mounting the mids higher up on the door, would lessen this effect and give a better mid bass response. Thats one option. 

By default my mid location is high up on the door. I have great pace and clarity in the 60-200hz range. The time delay between your far mid and the sub is also one way to get better mid bass. Play your far mid and your sub together. If you increase the delay between your sub and mid (by moving the sub back one notch at time, 0.5" for the pio premier units or 0.05ms for other decks) you'll notice an improvement in your mid bass response. The idea is to delay to the point where you have the sub bass flowing out the far mid while still hearing the mid bass *clearly*. 

When you time align your mids start by only playing the 60-200 range. You will also have to correct for l/r level in this range. For most of this range the far side is stronger than your near side. A frequency like 160 is 6db louder from the far side. All cars are built to emit ambient noise in the 60-200 range. Slap bang where you mid bass is. Think of all the cancellations. Add road and engine noise to this mix. 

Reflections are relevant for 800hz upwards, not so much for the mid bass. A lower sub/mid xover point would also help. I xover at 50hz and put the sub on a 36db slope. Anything more than 70hz and sub gets located. I'd be happy to xover at 40hz but the stage height gets too low. Install issues I guess. 

What I'm saying is, try tweaking on the tuning / install to see if you can get to where you want. Sorry if this seems like a basic response in this highly technical thread. But does it get the problem solved? I hope this post doesn't come out sounding pretentious. Cause its not meant to be.


----------



## BigAl205

The OP obviously doesn't have a clue...


----------



## TREETOP

Welcome back, Lycan. You and I have never communicated directly but you're one of the few old-schoolers whose posts I actually search out when wanting to learn more. Whatever the reason for your absense (a very long full moon maybe?), I'm very glad you've chosen to return. Thank you.


----------



## Patrick Bateman

First off, I have to mention that I can't stand woofers in doors. The pathlengths are all wrong.

Second, as crazy as this sounds, I can usually get better deep bass from a small woofer in an absolutely airtight box than I can from a larger woofer in a door. The problem is that a door is inherently leaky; even if you pour a thousand dollars worth of Dynamat and Deflex into a door, it's still going to leak. And in the measurements I've done it seems that even a small leak will sap all the low bass out of a woofer.

This isn't to say you can't make a door woofer sound good; I'm sure you can. I've just found that a small sealed box works better. YMMV

Having said that, someone asked me how I would mount an eight under the dash. Here's how I would do it.








Basically it's a box with the same footprint as an underdash horn, but it's for a midbass. I would personally use a single reflex bandpass box. Here's why:


With a bandpass you can put the bass where you want it. I'd direct the port into the firewall. This fools your brain into thinking the bass is coming from the firewall, since the auditory cues occur where the port is located, not the woofer itself. _Be sure to leave some space near the port, or it will screw up the tuning frequency._
You can trade bandwidth for efficiency in a bandpass
A bandpass box lowers distortion








In my 2001 Accord I used a sealed box for the same purpose. I went with a sealed because I needed to squeeze about four octaves out of the woofer, which is tough to do with a bandpass. On the upside, it sounded really natural, the tonality of the box is very good. Power handling was outrageous, because a small sealed box raises your power handling and lowers distortion by reducing excursion. (Compared to a car door, that is.)

On the down side, the small sealed box narrowed the soundstage because it's basically in front of the driver. Hence, I'd used a bandpass if I did it again.


----------



## Patrick Bateman

Oh, forgot to mention:
In my mind a sealed box and a single reflex bandpass are the same thing. The only difference is that one has an acoustical lowpass filter lumped in front of it.

So when I say that "a sealed box delivers better low bass than a car door", I'm also including single-reflex bandpass in the definition of "sealed box."


----------



## dcm220

Patrick, I'm having trouble picturing this scenario. Would you recommend using the small 3" Peerless or Aura full-range drivers for this application? What would this look like?



Patrick Bateman said:


> First off, I have to mention that I can't stand woofers in doors. The pathlengths are all wrong.
> 
> Second, as crazy as this sounds, I can usually get better deep bass from a small woofer in an absolutely airtight box than I can from a larger woofer in a door. The problem is that a door is inherently leaky; even if you pour a thousand dollars worth of Dynamat and Deflex into a door, it's still going to leak. And in the measurements I've done it seems that even a small leak will sap all the low bass out of a woofer.
> 
> This isn't to say you can't make a door woofer sound good; I'm sure you can. I've just found that a small sealed box works better. YMMV
> 
> Having said that, someone asked me how I would mount an eight under the dash. Here's how I would do it.
> 
> 
> 
> 
> 
> 
> 
> 
> Basically it's a box with the same footprint as an underdash horn, but it's for a midbass. I would personally use a single reflex bandpass box. Here's why:
> 
> 
> With a bandpass you can put the bass where you want it. I'd direct the port into the firewall. This fools your brain into thinking the bass is coming from the firewall, since the auditory cues occur where the port is located, not the woofer itself. _Be sure to leave some space near the port, or it will screw up the tuning frequency._
> You can trade bandwidth for efficiency in a bandpass
> A bandpass box lowers distortion
> 
> 
> 
> 
> 
> 
> 
> 
> In my 2001 Accord I used a sealed box for the same purpose. I went with a sealed because I needed to squeeze about four octaves out of the woofer, which is tough to do with a bandpass. On the upside, it sounded really natural, the tonality of the box is very good. Power handling was outrageous, because a small sealed box raises your power handling and lowers distortion by reducing excursion. (Compared to a car door, that is.)
> 
> On the down side, the small sealed box narrowed the soundstage because it's basically in front of the driver. Hence, I'd used a bandpass if I did it again.


----------



## lycan

Patrick, couple points i'd take (minor) issue with ...

First, pathlengths aren't _that_ bad in a door ... at least, for a large category of vehicles where the door midbass is directly adjacent to the kickpanel area. It's instructive, i think, to differentiate pathlengths from a _single_ driver to _each ear_ of a single listener, versus pathlengths from _two_ drivers to _each_ of two listeners:

a. Pathlengths from a single driver to each ear of a single listener. Clearly, midbass drivers directly behind, directly in front of, or directly under a listener fail miserably here. There's just no ITD, and no electronic manipulation for this midbass source can add any ITD where there's none to begin with. The stage width must necessarliy suffer, at least in the midbass.

b. Pathlengths from each of two drivers to each of two listeners. Kickpanels are still the winner here, but doors are a close second in many vehicles. And it seems to me that doors would still be preferable to a midbass driver directly under, in front, or behind the two listeners. Measure the pathlength differences from a listener's nose to those locations with zero ITD, i'd say, and see how bad the door scores in comparison  It just hard to imagine that even in this second category, kicks would would be first, and a door midbass ... directly _adjacent_ to the kicks, while still being far left & right ... would be last.

Second, i totally agree that it's _impossible_ to completely seal a door. A door, without serious work, makes a rather terrible enclosure. BUT ... small leaks won't impact bass performance that much. It's easy to model small leaks in Thiele/Small models by adding a large resistance in parallel with the capacitance that models the energy storage of the enclosure air-spring. Large resistors = small leaks, will not materially impact the bass response ... especially in the midbass. 

I've heard good midbass from doors, and i've heard good midbass from kicks. Neither is a clear, slam-dunk winner in my experience. I've never heard midbass directly in front, directly under, or directly behind a listener in a vehicle, but it's hard for me to imagine any stage width (at least, in the midbass) with this arrangement. Yes ... it may allow the best enclosure, but in the balance i don't see it as a winner, if stage width is very important.


----------



## dbiegel

Given the cone of confusion effect, wouldn't midbass in the doors actually give better stage width -- for both the driver and passengers -- than in the kicks, due to being mounted further out (laterally)?


----------



## lycan

man you gotta see what some of these crazy dudes can accomplish in their kick panels ... yank off that plastic cover, don't be shy about cutting metal, that damn kickpanel midbass can be mounted W-EYE-DDD  Not unusual to see kickpanel midbass drivers _at least_ as wide as the door mount, often vented to the outside (almost IB, or maybe aperiodic).


----------



## 12vTools

lycan said:


> man you gotta see what some of these crazy dudes can accomplish in their kick panels ... .


Ahem, winslow...


----------



## 12vTools

you were missed btw Lycanthropic one.


----------



## Patrick Bateman

lycan said:


> Patrick, couple points i'd take (minor) issue with ...
> 
> First, pathlengths aren't _that_ bad in a door ... at least, for a large category of vehicles where the door midbass is directly adjacent to the kickpanel area. It's instructive, i think, to differentiate pathlengths from a _single_ driver to _each ear_ of a single listener, versus pathlengths from _two_ drivers to _each_ of two listeners:


True. In my 2001 Accord (a four door) I found that the sealed midbass enclosures could only be mounted against the firewall. So you gain a little bit of depth, but you lose some width. This was due to the diameter of the enclosure - almost sixteen inches.

My 2005 Accord coupe (among others) has a space where you can extend your leg allllll the way to the firewall. The space is only big enough for an enclosure that's about 2-4 liters, but it allows you to put the midbasses waaaaaay back. In my car, it's about sixteen inches further than the door speakers, so this makes a huge difference in ITDs. Of course to squeeze an enclosure in that small space it would have to be a small woofer. And then the car would be less comfortable.

Of course, this all depends on your car. My GF has a Mazda 3, and the pathlenghts are completely different.

At this point I'm inclined to sacrifice some soundstage width and depth to get the midbasses up on the dash, where they're better integrated with the midranges and the tweeters.

Of course I may change my mind completely in 3 months


----------



## lycan

lycan said:


> well before we do a numeric example, let's check our expression that defines the _new_, combined inter-aural time delay resulting from the addition of a second midbass placed directly behind our heads :
> 
> tan(*w*Tdr*) = sin(*w*Td1*)/[cos(*w*Td1*)+*A2/A1*]
> 
> It's always a good idea to _verify_ a newly developed expression with a few _extreme_ cases, to make sure it's right
> 
> 1. *A2* = *0*. This is the case where the second midbass (behind our heads) has zero amplitude. In this case,
> 
> tan(*w*Tdr*) = sin(*w*Td1*)/cos(*w*Td1*) = tan(*w*Td1*)
> 
> or
> 
> *Tdr* = *Td1*
> 
> this makes infinite sense ... if the second midbass has zero amplitude, the resulting ITD will be identical to that from the first midbass alone
> 
> 2. *A2* --> huge, much bigger than *A1*. In this case,
> 
> tan(*w*Tdr*) = *0*,
> 
> or
> 
> *Tdr* = *0*
> 
> this also makes infinite sense ... if the amplitude from the second midbass completely _swamps_ the first midbass, the signals at our ears will be completely dominated by the second midbass, which has zero ITD (because of where we placed it)
> 
> OK ... now that we have confidence in our analysis, time for a more meaningful example


Let's do a numerical example or two 

What we've got is an expression that will determine the apparent location of a "resultant" midbass driver (location defined by *Tdr*), given a first "real" midbass driver location (defined by *Td1*) of amplitude *A1* and a second "real" midbass driver (amplitude *A2*) located directly behind, under, or in front of the listener.

For these examples, we're gonna pick the midbass frequency to be smack in the middle of the midbass range : 160Hz. Not only is this frequency well within the midbass bass, but it makes the math easier, as the radian frequency *w* will be about equal to 1000 rads/sec 

EXAMPLE 1 :

Let's "place" our first midbass driver directly to the left of our ears. In other words, the first midbass driver will be exactly on a line that runs between our ears ... or, on a circle of confusion that has a radius shrunk down to zero  Although this is unrealistic for a car application, it gives us an instructive "baseline" to analyze a case where a first midbass driver is directly to our left, augmented by a second midbass driver directly behind us, with an amplitude ratio that we can adjust.

In this case, *Td1* will simply be the exact time delay for a soundwave to travel between our ears (had we placed the first midbass at some angle in front of us, the ITD would be some fraction of this number). Well, ears are about 7 inches apart and sound travels at about 1100 feet per second, so :

*Td1* = 0.530 milliseconds

and since we're picking our radian freq *w* to be 1000 rads/sec,

*w*Td1* = 0.530 rads

Now we have to pick the amplitude ratio of our two midbass drivers. Let's start by setting the amplitude (or volume) of our second midbass EQUAL to the amplitude of the first midbass, so that *A2/A1* = 1. Doing a little number crunching in our expression yields :

*w*Tdr* = 0.2650 rads

and finally

*Tdr* = 0.265 milliseconds

An interesting, but not surprising result  This tells us that the addition of a midbass driver directly behind our heads will cut the "apparent" ITD in half, if the amplitude of the second midbass is equal to the first. The resultant "apparent" midbass has essentially "moved" from far left, to an angle of probably about 45 degrees in front of (or behind) us. We can use the ratio of *Tdr*/*Td1* as an indicator of "stage width reduction", and in this case the indicator is 0.5 

Next up, we'll reduce the volume of our second midbass (compared to the first) and see what happens. If anyone wants to join in the fun, please feel free


----------



## bboyvek

As always enjoying your replies, i remember i joined diyma after seeing some of your threads 

Quick questions tho, I understand that your focusing on stage width and apparent position of the midbass but how does this relate to the the problem patrick is trying to tackle? (the poor frequency response of the midbass in a car)

And for patrick, in one thread you said how incredible ib is and in this you said that you havent been able to achieve good result from your midbass mounted in your doors, doesnt a door install is pretty similar to a IB setup?

Thx


----------



## BigAl205

What is ITD?


----------



## bboyvek

lycan said:


> First, we must recognize that the ear/mind localizes midbass by *ITD (inter-aural time differences)*. It's been known for a century or two (Lord Rayleigh, i think?) that the ear most definitely CAN localize midbass in the L/R direction (but not in the vertical plane). But the wavelengths are simply too long for the localization cues to be intensity-based (IID) ... head-shadowing, for example, plays no role in the midbass ... so the cues but be arrival-time based. However, if we imagine our heads as spheres with holes in the sides (valid model in the midbass, where the outer ear has no effect), we'll immediately recognize that there's many points where a midbass source can be located and still yield the same ITD. Hence, the so-called "circle-of-confusion"


He has already explained


----------



## BigAl205

Sorry..I missed it. :blush:


----------



## lycan

bboyvek said:


> As always enjoying your replies, i remember i joined diyma after seeing some of your threads
> 
> Quick questions tho, I understand that your focusing on stage width and apparent position of the midbass but how does this relate to the the problem patrick is trying to tackle? (the poor frequency response of the midbass in a car)


Irregular amplitude response in the midbass in cars leads to a possible solution of using an "array" of midbass drivers placed at various points inside the vehicle. You may indeed "smooth" the amplitude response of the midbass with this "randomizing" technique, but you will pay the piper in soundstage reduction. In "vector-parlance", we would say that you can't materially impact the _amplitude_ without also materially impacting the _phase_ 

My analysis is a simple base-case study, to demonstrate how the addition of a second midbass will reduce stage width. I think Patrick has already come to this conclusion, as has Andy (and perhaps others in this thread as well). We might still choose to sacrifice some stage width for improved midbass amplitude response, but we must all recognize that there's a trade-off involved ... there's no free lunch! So i'm just supplying some simple math to support this trade-off.

It's my hope that there's also a broader, more subtle message behind my analysis as well : vector math is pretty comprehensive at describing midbass soundstage cues, where ITD's reign supreme. Also, a "combination" of midbass sources can be "combined" into a single, apparent midbass source


----------



## Dryseals

BigAl205 said:


> What is ITD?


Interaural time difference. Basics, the time a sound reaches both ears. It give you a sense of dirrectivity. The hunted and the hunter. A hunted animal such as a rabbit can move just his ears to locate a sound. What do we do to pinpoint a sound, we turn our head.

Mr. Lycan is offering the use of ITD to help place stage location in your car. While I may agree on some points, my mind shifts back and forth to a phase relation and amplitude.

I like many, want to produce the effect of the sound emerging from in front of us, a rather tough task in a vehicle when in most vehicles we have a limited front space and normally far more rear space. So our speakers often end up behind us. Not too many of us go to a concert and have our backs face the stage.

So is there a way we can manipulate the ITD enough so to bring the stage forward. I lean more towards a phase shift accomplishing the goal. I'm just not aware of any equipment on the market that can accomplish it.


----------



## lycan

lycan said:


> Let's do a numerical example or two
> 
> What we've got is an expression that will determine the apparent location of a "resultant" midbass driver (location defined by *Tdr*), given a first "real" midbass driver location (defined by *Td1*) of amplitude *A1* and a second "real" midbass driver (amplitude *A2*) located directly behind, under, or in front of the listener.
> 
> For these examples, we're gonna pick the midbass frequency to be smack in the middle of the midbass range : 160Hz. Not only is this frequency well within the midbass bass, but it makes the math easier, as the radian frequency *w* will be about equal to 1000 rads/sec
> 
> EXAMPLE 1 :
> 
> Let's "place" our first midbass driver directly to the left of our ears. In other words, the first midbass driver will be exactly on a line that runs between our ears ... or, on a circle of confusion that has a radius shrunk down to zero  Although this is unrealistic for a car application, it gives us an instructive "baseline" to analyze a case where a first midbass driver is directly to our left, augmented by a second midbass driver directly behind us, with an amplitude ratio that we can adjust.
> 
> In this case, *Td1* will simply be the exact time delay for a soundwave to travel between our ears (had we placed the first midbass at some angle in front of us, the ITD would be some fraction of this number). Well, ears are about 7 inches apart and sound travels at about 1100 feet per second, so :
> 
> *Td1* = 0.530 milliseconds
> 
> and since we're picking our radian freq *w* to be 1000 rads/sec,
> 
> *w*Td1* = 0.530 rads
> 
> Now we have to pick the amplitude ratio of our two midbass drivers. Let's start by setting the amplitude (or volume) of our second midbass EQUAL to the amplitude of the first midbass, so that *A2/A1* = 1. Doing a little number crunching in our expression yields :
> 
> *w*Tdr* = 0.2650 rads
> 
> and finally
> 
> *Tdr* = 0.265 milliseconds
> 
> An interesting, but not surprising result  This tells us that the addition of a midbass driver directly behind our heads will cut the "apparent" ITD in half, if the amplitude of the second midbass is equal to the first. The resultant "apparent" midbass has essentially "moved" from far left, to an angle of probably about 45 degrees in front of (or behind) us. We can use the ratio of *Tdr*/*Td1* as an indicator of "stage width reduction", and in this case the indicator is 0.5
> 
> Next up, we'll reduce the volume of our second midbass (compared to the first) and see what happens. If anyone wants to join in the fun, please feel free


EXAMPLE 2 :

Same as EXAMPLE 1 above, but with the amplitude (or volume) of our second midbass (driectly behind us) reduced by 6dB. So our new amplitude ratio *A2/A1* = 0.5. Our expression now yields :

*w*Tdr* = 0.354 rads

for *Tdr* = 0.354 milliseconds.

So we see that, even with our second midbass reduced in amplitude by 6dB, we still get a reduction in stage width. Our "stage width indicator" is :

*Tdr/Td1* = .667

*CONCLUSION: Loosely speaking, we've lost 1/3 of our stage width in the midbass by adding a second driver directly behind our heads ... even though that second driver is reduced in amplitude by 6dB.*

My advice is this : If you're really interested in midbass arrays, try your best to preserve ITD's in the placement of the array. In other words, aim for placement along the circle-of-confusion ... keep those midbass drivers as far left, and as far right, as you can! Other locations can "work", especially in terms of providing better enclosures, or smoothing the combined amplitude response. But mother nature will not be fooled ... there will always be some stage width reduction (at least, in the midbass) with these less-than optimal locations


----------



## Patrick Bateman

bboyvek said:


> As always enjoying your replies, i remember i joined diyma after seeing some of your threads
> 
> Quick questions tho, I understand that your focusing on stage width and apparent position of the midbass but how does this relate to the the problem patrick is trying to tackle? (the poor frequency response of the midbass in a car)
> 
> And for patrick, in one thread you said how incredible ib is and in this you said that you havent been able to achieve good result from your midbass mounted in your doors, doesnt a door install is pretty similar to a IB setup?
> 
> Thx


The problem that I run into with midbass woofers in my doors is that it brings the stage forward. In my particular car (a 2005 Honda Accord coupe), the furthest pathlength is a spot under the dash, against the firewall, which is "hollowed out" by Honda. It's basically a place to set your foot, and it stretches a good sixteen inches beyond the door locations.

Due to that additional sixteen inches, I can get a much deeper stage with woofers mounted there.

IMHO people worry way too much about aiming midbasses. A 135hz soundwave is longer than the entire cabin of my car - it's 100 inches long. Due to that length, you can safely cram a woofer *behind* the dash, without screwing up the frequency response much.

OTOH, 2700hz is just five inches long, and due to how *small* that is, even the slightest obstruction will screw up your frequency response (and your soundstage with it.)

For instance, if you're pant leg rests next to your kick panels, it's going to mess up the imaging of your tweeters if they're mounted in the kicks.

To make a long story short, that's why infinite baffle works great for subs, but I am not a fan of door-mounted woofers. The path lengths to the trunk are better than the path lengths to the door, and at very low frequencies, small obstructions do not cause reflections.*

* keep in mind there are still reflections at low frequencies - but they're caused by the cabin itself, not by the small stuff. Always be cognizant of the wavelength.


----------



## lycan

Dryseals said:


> Interaural time difference. Basics, the time a sound reaches both ears. It give you a sense of dirrectivity. The hunted and the hunter. A hunted animal such as a rabbit can move just his ears to locate a sound. What do we do to pinpoint a sound, we turn our head.
> 
> Mr. Lycan is offering the use of ITD to help place stage location in your car. While I may agree on some points, my mind shifts back and forth to a phase relation and amplitude.
> 
> I like many, want to produce the effect of the sound emerging from in front of us, a rather tough task in a vehicle when in most vehicles we have a limited front space and normally far more rear space. So our speakers often end up behind us. Not too many of us go to a concert and have our backs face the stage.
> 
> So is there a way we can manipulate the ITD enough so to bring the stage forward. I lean more towards a phase shift accomplishing the goal. I'm just not aware of any equipment on the market that can accomplish it.


midbass doesn't know front versus back, only left and right. If the band at the concert venue were playing ONLY midbass frequencies, and your eyes were closed, you could absolutely not tell if you were facing the stage, or facing the back of the concert hall.

Location cues in the midbass are _only_ ITD's. That's why the ear is absolutely fooled by a big midbass in the rear quarter panel ... as demonstrated by a couple (in)famous old-school cars described in this thread  Any and all drivers on the circle of confusion are indistinguishable in location.

But you REALLY need to understand this point, otherwise nothing but confusion will emerge from "midbass behind you" threads. All locations behind you are NOT identical, anymore than all locations in front are identical. Midbass in a rear quarter panel might be EXCELLENT, whereas midbass in the rear shelf might be LOUSY. There's a WORLD of difference between ITD's in those two locations.


----------



## Patrick Bateman

lycan said:


> EXAMPLE 2 :
> 
> Same as EXAMPLE 1 above, but with the amplitude (or volume) of our second midbass (driectly behind us) reduced by 6dB. So our new amplitude ratio *A2/A1* = 0.5. Our expression now yields :
> 
> *w*Tdr* = 0.354 rads
> 
> for *Tdr* = 0.354 milliseconds.
> 
> So we see that, even with our second midbass reduced in amplitude by 6dB, we still get a reduction in stage width. Our "stage width indicator" is :
> 
> *Tdr/Td1* = .667
> 
> *CONCLUSION: Loosely speaking, we've lost 1/3 of our stage width in the midbass by adding a second driver directly behind our heads ... even though that second driver is reduced in amplitude by 6dB.*
> 
> My advice is this : If you're really interested in midbass arrays, try your best to preserve ITD's in the placement of the array. In other words, aim for placement along the circle-of-confusion ... keep those midbass drivers as far left, and as far right, as you can! Other locations can "work", especially in terms of providing better enclosures, or smoothing the combined amplitude response. But mother nature will not be fooled ... there will always be some stage width reduction (at least, in the midbass) with these less-than optimal locations


In the Grand National I understand that Richard used a primitive car PC to control the gains to the various amplifiers. In AutoSound tech brief #2447 he drops some huge hints about the "secret midbasses" that were under the dash of the GN.

I'm guessing that one of the reasons the PC was in play was to adjust the gains on the midbasses.

Basically as the volume is cranked, the rear midbasses come into play. So you trade soundstage depth and width for dynamics.

This is a clever solution, basically best of both worlds. You get high SPL dynamics when you need them, and moderate-SPL soundstaging the rest of the time.

I still can't think of a way to do this *without* mechanically adjusting the gains, unfortunately. Foobar 2000 *might* be able to do it, but then you need a carputer.

Another idea that I had was to build a custom volume knob, basically a stepped attenuator instead of an analog potentiometer.

With a stepped attenuator you could "rig up" a circuit to mimic this behavior. At low volumes the rear midbasses wouldn't be playing at all. At moderate volumes the rear midbasses would start to kick in, but at a very reduced level. At full-tilt the front midbasses would be attenuated, to keep them from blowing up, and the rear midbasses would be doing 80% of the work.


----------



## Dryseals

lycan said:


> midbass doesn't know front versus back, only left and right. If the band at the concert venue were playing ONLY midbass frequencies, and your eyes were closed, you could absolutely not tell if you were facing the stage, or facing the back of the concert hall.
> 
> Location cues in the midbass are _only_ ITD's. That's why the ear is absolutely fooled by a big midbass in the rear quarter panel ... as demonstrated by a couple (in)famous old-school cars described in this thread  Any and all drivers on the circle of confusion are indistinguishable in location.
> 
> But you REALLY need to understand this point, otherwise nothing but confusion will emerge from "midbass behind you" threads. All locations behind you are NOT identical, anymore than all locations in front are identical. Midbass in a rear quarter panel might be EXCELLENT, whereas midbass in the rear shelf might be LOUSY. There's a WORLD of difference between ITD's in those two locations.


I beleive the it has more to do with the ability of the signal to be produced in it's entirety. Cars don't offer that very well.

Take for instance my shop, it's about 60 x 26 brick structure. I put an 8' pool table at one end and built some speakers. My goal was to not present a fixed stage, but instead have the music surround you equally at all angles. Seemed simple enough, put a speaker in each corner around the table equal distance apart. Not so because as you near a corner, you'll be able to pin point the source. How do I compensate for each corner? Well on the longest wall, I added two more speakers up high near the ceiling very near each other. Now no matter were you stand, it all sounds equal. With one exception, the sub woofer, it's crossed low enough but you can still pin point the source, Why? because the signal has ample time to be produced before it reaches your ears. If I look at an 80 cycle signal, it takes 12.5 ms for each cycle or will take 168 inches to complete a full cycle, about fourteen feet. When I move within this 14 foot barrier, the directivity decreases, theres not enough distance to create the full signal before I can hear the reflections.

Now if we assume that the average distance to your ears from the source in a car is 3 feet, what would be the lowest freq you could produce before it had time to create a full cycle. Sound travels 13500 inches per second divided by 36 comes out to 375 hz. Hmmm. So in a sense, if I can hear the reflections before I hear the full wave, then I have a hard time pin pointing the source.

I'm enjoying this, some thing tells me I may not get things accomplished today that I have set out to do, mainly install a system in my little 350z. I'm adding two 8" speakers in the rear hatch back. The distance from there to my ears is 4.5 ft, or 250hz before reflections. Plus with the slope of the glass, it'll be a subtle horn effect.


----------



## bboyvek

Patrick Bateman said:


> At low frequencies, there are two mechanisms going on in our cars. The most famous one is "cabin" gain. Quoting from Rod Elliott*, "When room dimensions become small compared to wavelength, *soundwave propagation will not work*, and bass can only be reproduced by pressurising (and de-pressurising) the listening space ... pressure mode."


see the mechanism how frequencies bigger than the length of your cabin is different than those that are smaller (hint in your shop subbass frequencies are smaller than your shop therefore they can be localize)


----------



## loddie

Lycan, welcome back. Perfect timing as I was going to try and track you down to ask you several midbass questions.

I am more of a visual learner, so I quickly drafted the attached image.

Green=kick panel midbasses
Red=door mounted midbasses
Blue=rear mounted midbasses
Two heads=designed for two passenger optimization
Orange line=distance from listener to left kick panel and left rear midbasses
Turquoise line=distance from listener to left door mounted midbass
Magenta line=distance from listener to right kick panel and right rear midbasses
Black line=reference line for angles of orange, turquoise, and magenta lines

Questions:

1. When referring to wide is better, what is the definition of "wide"?

For example, consider the left door panel and left kick panel locations. They are both located at the same "width" location in the vehicle. However, notice the orange line (26 degrees from reference black line) vs. the turquoise line (49 degrees from the reference black line). I realize from Lycan previous tutorials the sound is localized in each ear and each midbass is really many tiny speakers. However, the illustration was simplified for ease of understanding. Is the left Red midbass "wider" than the left Green midbass?

2. Between the green and red midbass, which is better and why? 

3. The orange line/circle illustrate the distance from the listener to the left kick panel midbass is equal to the distance to the left rear midbass. If both green and blue left midbasses are mounted, would this allow for multiple midbasses without collapsing the stage width?

I think the answers are obvious, but I want to confirm Lycan's math corresponds with what I am visualizing.:santa:


----------



## jbholsters

Patrick Bateman said:


> In the Grand National I understand that Richard used a primitive car PC to control the gains to the various amplifiers. In AutoSound tech brief #2447 he drops some huge hints about the "secret midbasses" that were under the dash of the GN.
> 
> I'm guessing that one of the reasons the PC was in play was to adjust the gains on the midbasses.
> 
> Basically as the volume is cranked, the rear midbasses come into play. So you trade sound stage depth and width for dynamics.
> 
> This is a clever solution, basically best of both worlds. You get high SPL dynamics when you need them, and moderate-SPL soundstaging the rest of the time.
> 
> I still can't think of a way to do this *without* mechanically adjusting the gains, unfortunately. Foobar 2000 *might* be able to do it, but then you need a carputer.
> 
> Another idea that I had was to build a custom volume knob, basically a stepped attenuator instead of an analog potentiometer.
> 
> With a stepped attenuator you could "rig up" a circuit to mimic this behavior. At low volumes the rear midbasses wouldn't be playing at all. At moderate volumes the rear midbasses would start to kick in, but at a very reduced level. At full-tilt the front midbasses would be attenuated, to keep them from blowing up, and the rear midbasses would be doing 80% of the work.


The Intel board monitored the output voltage from the head unit in the GN. My understanding is that the gains (on the amps and processors) were turned up in a non linear fashion to account for the ears inability to hear certain frequencies at different amplitudes. So with the volume low, the subs and mid-bass actually had more output compared to the horns and as the volume increased the horns amplitude would increase at a higher rate than the low frequency drivers in the car. Think of it as a smart loudness control. I don't think it gated in a pair of "magical" 4 inch drivers.

You should easily be able to write a simple program that you can dictate output voltage to an amp/processor gain at a given input voltage from the volume control. I'm surprised that there aren't any good DSP's that do this. Maybe the bit 1 will.


----------



## 94VG30DE

jbholsters said:


> The Intel board monitored the output voltage from the head unit in the GN. My understanding is that the gains (on the amps and processors) were turned up in a non linear fashion to account for the ears inability to hear certain frequencies at different amplitudes. So with the volume low, the subs and mid-bass actually had more output compared to the horns and as the volume increased the horns amplitude would increase at a higher rate than the low frequency drivers in the car. Think of it as a smart loudness control. I don't think it gated in a pair of "magical" 4 inch drivers.
> 
> You should easily be able to write a simple program that you can dictate output voltage to an amp/processor gain at a given input voltage from the volume control. I'm surprised that there aren't any good DSP's that do this. Maybe the bit 1 will.


+1 for that being easy to do. I would think the hardest part would be deciding what rate to increase the different speakers at, relative to each other. It would basically be a digitally-variable line driver that can vary voltage to each line. Expensive, and would require code, but it's easy code as long as you have a shell to run it in.


----------



## jbholsters

loddie said:


> Questions:
> 
> 1. When referring to wide is better, what is the definition of "wide"?
> 
> For example, consider the left door panel and left kick panel locations. They are both located at the same "width" location in the vehicle. However, notice the orange line (26 degrees from reference black line) vs. the turquoise line (49 degrees from the reference black line). I realize from Lycan previous tutorials the sound is localized in each ear and each midbass is really many tiny speakers. However, the illustration was simplified for ease of understanding. Is the left Red midbass "wider" than the left Green midbass?
> 
> 2. Between the green and red midbass, which is better and why?
> 
> 3. The orange line/circle illustrate the distance from the listener to the left kick panel midbass is equal to the distance to the left rear midbass. If both green and blue left midbasses are mounted, would this allow for multiple midbasses without collapsing the stage width?
> 
> I think the answers are obvious, but I want to confirm Lycan's math corresponds with what I am visualizing.:santa:


A car audio system is a series of compromises. If you left kick location sticks out into the cars interior more than the door location you will probably have a narrower sound stage, even if the kick is farther away. The further away the driver gets, the more the stage width is compressed and with speakers closer it is wider but not suitable for 2 seat listening. The mid bass in the rear side panels (having close PDL's with the kicks) will appear wider since they are mounted in the cavity of the car panel, and are further away from the cars center. You can also fit a much larger driver in that area. This is why it is better to put mid bass in the side panels. Same goes for rear deck mounted mid bass. They are mounted closer to the cars center than if mounting them in the rear side panels.


----------



## jbholsters

94VG30DE said:


> +1 for that being easy to do. I would think the hardest part would be deciding what rate to increase the different speakers at, relative to each other. It would basically be a digitally-variable line driver that can vary voltage to each line. Expensive, and would require code, but it's easy code as long as you have a shell to run it in.


It would just be a matter of programing the voltage steps while A/B-ing frequencies. The most ideal solution would be to do this via a EQ, but would take some time to set up correctly. You could start with models of ISO 226 and tweek from there. While you're at it you could write a program that allowes for 360 degress single step phase adjustments for each frequency


----------



## ErinH

The bit one does actually do this via it's dynamic EQ. 
Problem is that you have to use the bitone DRC to control volume to get these feature. It will not work with any other form of volume control.


----------



## jbholsters

Ah, cool that is does it, and not so much that you can't use the hu's volume control. I'm an idiot though. I meant to say I wonder if the MS-8 will do something like this.


----------



## ErinH

I've wondered if there's a way to tap into the DRC's volume control somehow and tie it to the steering wheel controls. No idea, though. Might not even be worth it.


----------



## jbholsters

I would think you could tie in to the head unit somehow. Someone, somewhere could figure it out. Does the DRC have a remote. If so, couldn't you program the PAC mod to it?


----------



## 94VG30DE

Depends on how the DRC does it's volume control. If both DRC and head unit have analog (meaning a physical pot) volume control, it might be straightforward. If one of them is digital, it might be a mess. If both are digital, it might be impossible haha. 

EDIT: if someone is willing to send me both units, I am more than willing to tear into them


----------



## ErinH

the DRC has a pot (I guess, since it's a turn knob). 
My headunit has digital control. Push button on the faceplate.

I wonder if you could use the SWI to control the DRC volume control, and then the rest would be aftermarket headunit control.


----------



## kvndoom

Most of this is way over my head (and beyond my budget), but it has been hella fun to read. I need to explore this site more.


----------



## jp88

bikinpunk said:


> the DRC has a pot (I guess, since it's a turn knob).
> My headunit has digital control. Push button on the faceplate.
> 
> I wonder if you could use the SWI to control the DRC volume control, and then the rest would be aftermarket headunit control.


Just because it has a knob does not mean its a potentiometer. It could be a rotary encoder (If it is very modern it most likely is) which is digital.


----------



## Knobby Digital

The knob in the DRC is digital.


----------



## thehatedguy

You can do something like that with some pro audio pieces. You can create presets for each click of the knob...that way you can change XO, EQ, and levels at every volume level. I know it has been done before. Now I need to find out if my Rane can do that or if it mutes outputs with each change in preset...I don't remember if it does.

But I really urge you guys not to put too much into what the GN did. Competitors and industry people from back in the day have a really really good feeling that whatever CD you listened to in the car was mastered for that car. You never heard the car with your own CD, only whatever RC was playing. 

Remember where RC made his money? It was making CDs.


----------



## ErinH

^ the last bit of conversation, at least from my POV, was simply trying to tap the audison DRC's volume pot for another volume knob. Without the DRC volume control, you can't take advantage of the bitone's dynamic EQ, which is why I'm curious if there's some way to mimic or reroute the DRC's volume control at all so that you can use your headunit's or even steering wheel's volume control. Thus eliminating the need for having to use two sources for different things (drc for volume and headunit for everything else). 
I don't have any knowledge in this area at all and wouldn't even know where to begin.


----------



## danssoslow

Patrick Bateman said:


> With a bandpass you can put the bass where you want it. I'd direct the port into the firewall. This fools your brain into thinking the bass is coming from the firewall, since the auditory cues occur where the port is located, not the woofer itself. _Be sure to leave some space near the port, or it will screw up the tuning frequency._
> You can trade bandwidth for efficiency in a bandpass
> A bandpass box lowers distortion



So this gets me thinking. With a 4" speaker, on a mounting ring inserted into a piece of 6" pvc mounted up into the dash, sealing off one end, and using a 2-3-4" external port (whatever the size is that is needed) heated and bent to exit at the furthest corner of the firewall and kickpanel.

I wouldn't mind trying this with one of the 4's I have; or possibly use the two sets of peerless 3's I have in an isobaric 4th order so that maybe a 4" pvc enclosure could be used for simpler packaging in the dash.

You have a program to come up with some bandpass plans?


----------



## TREETOP

danssoslow said:


> So this gets me thinking. With a 4" speaker, on a mounting ring inserted into a piece of 6" pvc mounted up into the dash, sealing off one end, and using a 2-3-4" external port (whatever the size is that is needed) heated and bent to exit at the furthest corner of the firewall and kickpanel.
> 
> I wouldn't mind trying this with one of the 4's I have; or possibly use the two sets of peerless 3's I have in an isobaric 4th order so that maybe a 4" pvc enclosure could be used for simpler packaging in the dash.
> 
> You have a program to come up with some bandpass plans?


Reminds me of an install I did a long time ago with 5" Bazooka tubes under the dash of an El Camino.


----------



## danssoslow

TREETOP said:


> Reminds me of an install I did a long time ago with 5" Bazooka tubes under the dash of an El Camino.


G body? I used to drive an 80's El Camino as a parts truck; and remember the dash being alot more shallow than a typical G body dash for some reason. Was it easy to fit them under the dash? How did that sound?


----------



## jbholsters

thehatedguy said:


> Competitors and industry people from back in the day have a really really good feeling that whatever CD you listened to in the car was mastered for that car. You never heard the car with your own CD, only whatever RC was playing.
> 
> Remember where RC made his money? It was making CDs.


I heard the car when the Holdaway's owned it and it sounded really nice at that time. I also judged the car when they were still using the white labeled IASCA CD (2nd IASCA CD?) and the car sounded excellent (RC had nothing to do with that IASCA disc). He may have engineered a CD for auditions, I surely don't know. Regardless, the simplicity of the basic system (crap loads of power on minimal amount of high efficiency drivers) is what I have always taken away from that install. Most guys around that time were trying to get as many speakers in their car as they could. 

There were servos that controlled the gain structure, so it's not without merit that they ramped the gains in a non linear manner. I'm not sure how you would master a CD to mimic more low end and highs at low volumes and then flatten out as the volume increased. 



bikinpunk said:


> I'm curious if there's some way to mimic or reroute the DRC's volume control at all so that you can use your headunit's or even steering wheel's volume control.


The simplest way I can think of would be mechanical. Have a servo control the volume knob on the DRC's knob (attached to the actual control). Or do like Biggs did and use (if I remember correctly) a vacuum system.


----------



## 94VG30DE

danssoslow said:


> So this gets me thinking. With a 4" speaker, on a mounting ring inserted into a piece of 6" pvc mounted up into the dash, sealing off one end, and using a 2-3-4" external port (whatever the size is that is needed) heated and bent to exit at the furthest corner of the firewall and kickpanel.
> 
> I wouldn't mind trying this with one of the 4's I have; or possibly use the two sets of peerless 3's I have in an isobaric 4th order so that maybe a 4" pvc enclosure could be used for simpler packaging in the dash.
> 
> You have a program to come up with some bandpass plans?


This reminds me: what about smaller high-excursion speakers with a passive radiator? I was at the junkyard a while back and found a small enclosure with what looked like long-throw 3" full range speakers on one end, and a ~4" PR on the other end. The enclosure was curved a little and mounted directly up under the dash about where the driver and passenger knees would sit. It was a early 90s Toyota I think. I found them in a few different Toyotas of that MY range. No idea how they sound, but almost bought a pair just to see.


----------



## DaleCarter

Electrodynamic said:


> In car audio subwoofers, customers are largely concerned with being able to play linear from their crossover point all the way down to 20 hz and below. Most of the time they don't care about having a mini-fridge-sized enclosure just to play loud from 65 Hz to 100 Hz.



We are not customers, we are DIY enthusiasts. If we were typical "customers", we would be happy with how hard our subs "hit at mad debeez". 

We wouldn't be here.


----------



## Patrick Bateman

danssoslow said:


> So this gets me thinking. With a 4" speaker, on a mounting ring inserted into a piece of 6" pvc mounted up into the dash, sealing off one end, and using a 2-3-4" external port (whatever the size is that is needed) heated and bent to exit at the furthest corner of the firewall and kickpanel.
> 
> I wouldn't mind trying this with one of the 4's I have; or possibly use the two sets of peerless 3's I have in an isobaric 4th order so that maybe a 4" pvc enclosure could be used for simpler packaging in the dash.
> 
> You have a program to come up with some bandpass plans?


Werewolf and Andy from JBL have kinda messed me up on this one. Because for ages I'd put my midbasses as far and wide as I possibly could. By putting speakers *behind* the dash, instead of in the kick or in the doors, I've been able to get pathlengths that are about 12-24" further than what most cars have.

The problem is that I run tweeters on the dash, and the pathlength to the tweeters is quite a bit shorter.

So I can't really answer this question at the moment. I know that it's absolutely possible to use waveguides and horns to get extraordinarily long pathlengths to the midbass, but I'm not certain if it's a good idea at this point.

Tentatively, I still thinks it's good to have them as far away as possible. A waveguide on the tweeter can control reflections for the first millisecond, eliminating a great deal of the phantom imaging cues common in car stereo.

Huge pathlengths contribute to the perception that the soundstage exceeds the boundaries of the car itself, which is a neat trick.


----------



## Patrick Bateman

loddie said:


> Lycan, welcome back. Perfect timing as I was going to try and track you down to ask you several midbass questions.
> 
> I am more of a visual learner, so I quickly drafted the attached image.
> 
> Green=kick panel midbasses
> Red=door mounted midbasses
> Blue=rear mounted midbasses
> Two heads=designed for two passenger optimization
> Orange line=distance from listener to left kick panel and left rear midbasses
> Turquoise line=distance from listener to left door mounted midbass
> Magenta line=distance from listener to right kick panel and right rear midbasses
> Black line=reference line for angles of orange, turquoise, and magenta lines
> 
> Questions:
> 
> 1. When referring to wide is better, what is the definition of "wide"?
> 
> For example, consider the left door panel and left kick panel locations. They are both located at the same "width" location in the vehicle. However, notice the orange line (26 degrees from reference black line) vs. the turquoise line (49 degrees from the reference black line). I realize from Lycan previous tutorials the sound is localized in each ear and each midbass is really many tiny speakers. However, the illustration was simplified for ease of understanding. Is the left Red midbass "wider" than the left Green midbass?
> 
> 2. Between the green and red midbass, which is better and why?
> 
> 3. The orange line/circle illustrate the distance from the listener to the left kick panel midbass is equal to the distance to the left rear midbass. If both green and blue left midbasses are mounted, would this allow for multiple midbasses without collapsing the stage width?
> 
> I think the answers are obvious, but I want to confirm Lycan's math corresponds with what I am visualizing.:santa:



Due to an avalanche of commitments at work, I haven't been doing a lot with the car. For the past few weeks I've been running an array, and some people might be interested in messing around with the idea.

Here's how it works:







When most people here the term "array" they picture something like the speaker above.















But something like this works a lot better in a car, because the footprint is smaller.

Even though the second speaker doesn't look like a conventional array, it definitely IS an array. And it gives us the benefits of an array - higher power handling and lower distortion.

Because of comb filtering, the high frequency response of any array is limited by the center to center distance. For instance, if you have an array of 5" woofers like the first pic, you're going to see your response fall off around 1350hz. (center-to-center distance / speed of sound.)

So one of the "neat" side benefits of the second array is that it plays higher than a conventional array, because the woofers are so tightly spaced.

I know all of this is counter intuitive; it would seem that turning the woofer on it's side would ruin the high frequency response. But sometimes things aren't what they seem... The biggest problem with the second array is that there are parallel surfaces and wells which generate peaks and nulls at certain frequencies. But this isn't a huge issue for midbasses or woofers, since the peaks and nulls occur outside of the passband (if you choose your dimensions carefully.)

To make a long story short, the second array allows you to get the output of a larger driver in a small footprint, and in car audio, that's A Very Good Thing. A side benefit is extended high frequency response, and if you're building an array of midbasses, that's ALSO a very good thing!

For instance, you can get the output of a six inch driver using a couple four inch drivers in an array that can fit in the palm of your hand. Very handy if you're trying to hide the drivers under the dash.

Also, I should clarify, I am not suggesting that you use dipole subwoofers in a car. I am suggesting that you use ARRAYS in the car, and the packaging scheme that Linkwitz uses is VERY space efficient. Just because Linkwitz uses a dipole doesn't mean that you can't make it sealed. Either way it's a VERY efficient use of space. And if you're trying to cram woofers under the dash, that's important.

And don't be afraid to pack those drivers tightly; you can make the gap just big enough so that the cone of one woofer touches the basket of the other. (Factor in excursion of course.)

The tight spacing saves space, and increases high frequency extension. A win-win.


----------



## eficalibrator

If I may digress to the original theme of this thread for a moment, I have another idea that I'd like to float.

Given that:

1) reflections can actually be helpful in smoothing the response in the frequency range in question, since they cancel out some of the inherent off-axis resonances
2) door locations next to the kick panel aren't really all that bad for ITD's
3) my car ( a C6 corvette) has HUGE speaker openings in the door that easily accommodate a Dayton Reference 8" mid (which seems to be well received here) and has enough power to get "loud enough" for me at max effort

Why wouldn't we consider intentionally creating reflections from a portion of the existing single mid per side? This could be done with some form of rigid barrier in front of the cone, directing a portion of the output toward the dash or footwell, but still hidden behind the stock grille.

Pros
Single point location
good ITDs in midbass range
widest stage possible within reason for the simple install
relfections would help smooth response in the midbass
loudest signal is still the original location with reflections attenuated by carpet, legs, etc...

Cons
may require more power/excursion to deliver same dynamic response
possible contamination of upper frequencies played by the speaker (currently plays to ~1.8kHz where it blends with a pair of NEO3 PDRs)

I guess the last point is my biggest concern. The Dayton 8" naturally rolls off around 2kHz anyway, but would intentional reflections really hurt the 800-2kHz range? There's already a ton of these from the glass, dash, etc in the car that can't be addressed.


----------



## Patrick Bateman

eficalibrator said:


> If I may digress to the original theme of this thread for a moment, I have another idea that I'd like to float.
> 
> Given that:
> 
> 1) reflections can actually be helpful in smoothing the response in the frequency range in question, since they cancel out some of the inherent off-axis resonances
> 2) door locations next to the kick panel aren't really all that bad for ITD's
> 3) my car ( a C6 corvette) has HUGE speaker openings in the door that easily accommodate a Dayton Reference 8" mid (which seems to be well received here) and has enough power to get "loud enough" for me at max effort
> 
> Why wouldn't we consider intentionally creating reflections from a portion of the existing single mid per side? This could be done with some form of rigid barrier in front of the cone, directing a portion of the output toward the dash or footwell, but still hidden behind the stock grille.
> 
> Pros
> Single point location
> good ITDs in midbass range
> widest stage possible within reason for the simple install
> relfections would help smooth response in the midbass
> loudest signal is still the original location with reflections attenuated by carpet, legs, etc...
> 
> Cons
> may require more power/excursion to deliver same dynamic response
> possible contamination of upper frequencies played by the speaker (currently plays to ~1.8kHz where it blends with a pair of NEO3 PDRs)
> 
> I guess the last point is my biggest concern. The Dayton 8" naturally rolls off around 2kHz anyway, but would intentional reflections really hurt the 800-2kHz range? There's already a ton of these from the glass, dash, etc in the car that can't be addressed.




It's a bit tricky due to the wavelengths we're dealing with here.








For instance, picture a laser beam. It has a narrow beam, and if it hits something that's larger than the beam, it reflects. (As you can see in the picture.)

Sound behaves in a similar way. If it hits something that's bigger than it, it will reflect. The problem is that low frequency sounds are verrrrrrrrry long. For instance, a 160hz sound wave is over seven feet long!








So the use of multiple midbasses makes sense for the same reason you might use multiple lights in your living room.

Having said that, there's a lot of good reasons to put a physical barrier in front of a woofer to control it's wavefront. It's better known as a phase plug:

Phase Plugs


----------



## eficalibrator

Patrick Bateman said:


> So the use of multiple midbasses makes sense for the same reason you might use multiple lights in your living room.


I've also seen rooms lit very evenly by a single light source that gets reflected/diffused widely.








Think of the Pantheon with its single hole in the center of the roof, but fewer harsh shadows inside of it. Sure there's no trouble locating the single dominant source, but there's also light almost everywhere.



> Having said that, there's a lot of good reasons to put a physical barrier in front of a woofer to control it's wavefront. It's better known as a phase plug.


Now we're on to something. The woofer I'm using already has a stationary phase plug in the center. Perhaps adding either an outer ring as you picture or some sort of plate that runs as a chord across the speaker's O.D. would create enough constructive reflections without compromising output.


----------



## Juanhanded

Patrick Bateman said:


> I've come to the conclusion that imaging is more important to me than maximum SPL. I've decided to abandon the idea of using an array of midbasses, or one big midbass, under the dash.
> 
> Instead I am building a new Unity waveguide. This one will be a three-way, and should go down to 100hz.
> 
> The entire stage will be up on the dash.
> 
> Here's the link:
> 
> http://www.diymobileaudio.com/forum...forum/71993-unity-v-midbass-strikes-back.html


This thread seemed to be heading in the direction of an under the dash installation or something similar.Then...bam.

Is the conclusion that imaging will only be adequate up on the dash for bass?

Was the decision for a dash installation made purely because of physical constraints,or was it a philosophical decision?

In the GN that is mentioned above,was the imaging considered good?The bass was not considered natural?

My apologies,for I have just begun to dig through these threads.


----------



## Patrick Bateman

Juanhanded said:


> This thread seemed to be heading in the direction of an under the dash installation or something similar.Then...bam.


Yes, you *should* be able to smooth the midbass response by using multiple midbasses. The reason why this works at low frequencies, but not at high frequencies, is that the wavelengths are so long, and the dimensions of the car are relatively small. If you tried the same trick at high frequency, it would simply screw up your imaging.

I would also recommend inverting one midbass and running it in reverse phase, to reduce 2nd harmonic distortion. If you do this trick, you should have the midbasses located close together for maximum effect.

Something like this:










Note that it doesn't have to look _exactly_ like that. That's just one example of this technique. There are more details earlier in the thread.



Juanhanded said:


> Is the conclusion that imaging will only be adequate up on the dash for bass?


That depends on who you ask. I've been working on car stereos for nearly two decades. In my experience, if you want an image that's at eye level, you need your high frequencies at high level.

The reason that the Unity horns are up on the dash is that the entire frequency range is emitted from a single waveguide.



Juanhanded said:


> Was the decision for a dash installation made purely because of physical constraints,or was it a philosophical decision?
> 
> In the GN that is mentioned above,was the imaging considered good?The bass was not considered natural?
> 
> My apologies,for I have just begun to dig through these threads.


Couldn't comment on that - I've never heard the GN. I *have* heard other cars from SpeakerWorks, and the "impact" of these systems literally changed my life. I wouldn't be a raving fan of horns if it wasn't for Speakerworks. Mad props to the Holdaways.


----------



## Juanhanded

Patrick Bateman said:


> I would also recommend inverting one midbass and running it in reverse phase, to reduce 2nd harmonic distortion. If you do this trick, you should have the midbasses located close together for maximum effect.
> 
> 
> 
> The reason that the Unity horns are up on the dash is that the entire frequency range is emitted from a single waveguide.


Did you constuct an array similar to the one you began to propose earlier on this page?It would seem that the array would adhere to many of the ideas that you propose herein.

Or...do you see the Beolab clone as possibly holding the ultimate answer to natural base?


----------



## wiseman454

....


----------



## Patrick Bateman

Juanhanded said:


> Did you constuct an array similar to the one you began to propose earlier on this page?It would seem that the array would adhere to many of the ideas that you propose herein.
> 
> Or...do you see the Beolab clone as possibly holding the ultimate answer to natural base?


While working on the Beolab clones, I cut 90% of the way through my thumb on my right hand. Another quarter of an inch and I would have cut it in half.

So I think I'm going to avoid working on these "miniature" speakers as much as possible.

It's about 90% better now, but that was a close one.


----------



## Joehs

incredible read. Trying to keep up, but I keep getting lost


----------



## Hernan

I'm at the "world" of confusion! 
What is what really matters at midbass frecuencies, PLD or ITD?
PLDs could be improved by DSP. 
ITD doesn't

Sorry for the TOO late question.


----------



## 94VG30DE

Patrick Bateman said:


> While working on the Beolab clones, I cut 90% of the way through my thumb on my right hand. Another quarter of an inch and I would have cut it in half.
> 
> So I think I'm going to avoid working on these "miniature" speakers as much as possible.
> 
> It's about 90% better now, but that was a close one.


Don't do that. On behalf of the forum (and presumably the folks at the _other_ occupation that uses your typing hands) I say be careful, and get well soon  



Hernan said:


> I'm at the "world" of confusion!
> What is what really matters at midbass frecuencies, PLD or ITD?
> PLDs could be improved by DSP.
> ITD doesn't
> 
> Sorry for the TOO late question.


http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/69060-natural-bass-12.html#post917499 

I would look around that area of the thread. Before and after is the mathematical analysis and commentary on that issue. To understand, read and repeat


----------



## Hernan

94VG30DE said:


> I would look around that area of the thread. Before and after is the mathematical analysis and commentary on that issue. To understand, read and repeat


My maths are a bit forgiven... I really like them but I they are not cake now.
I post this because I feel that I'm not alone at this "confusion".
(I have another bump at the road, english is not my lenguage...)

As far as I can understand, the "cone of confusion" depends on ITDs. and amplitude. PLDs helps but are only part of the problem, and so part of the solution.


----------



## Patrick Bateman

A forum member sent me an email asking how I listen at bone-crushing levels.

I was going to post a reply, then realized most of the info has already been posted. As far as I'm concerned, this is one of those things that's fairly easy to fix. While creating a believable soundstage is an art, I think that good bass is fairly straightforward.

First, you need displacement. A LOT of displacement. I do not understand people who buy a 12" sub, stick it in a sealed box, and call it a day. I'd consider using a 12" woofer in a sealed box on one condition: *there's four to eight of them.*

I tend to use a lot of exotic enclosures, but that's mostly because they're fun and cheap and I don't like blowing a lot of money. If price is no object, get a bunch of decent twelves or fifteens and a big amp. Problem solved.

I think there's a lot of "exotic" things that you can do to improve bass.

First, decouple the enclosure from the car. The bass in Jon's Magic Bus is better than anything I've heard, and that sub box is floating on neoprene. I think that suspending the box would also work, but I've never seen anyone do it.

Second, I really like the sound of cardoids and dipoles. I personally don't think it matters if you do it passively or actively, but active cardioids are a heck of a lot smaller than passive cardioids.

I intend to do a end-fire array in my Mazda, but I'm working on the front stage right now.

In summary:

1) A small sealed box is great if you don't intend to get loud, if you DO, you better get more displacement
2) Cardioids sound awesome
3) Isolation the sub box from the room/car it's makes a huge difference


----------



## MetricMuscle

Patrick Bateman said:


> A forum member sent me an email asking how I listen at bone-crushing levels.
> 
> I was going to post a reply, then realized most of the info has already been posted. As far as I'm concerned, this is one of those things that's fairly easy to fix. While creating a believable soundstage is an art, I think that good bass is fairly straightforward.
> 
> First, you need displacement. A LOT of displacement. I do not understand people who buy a 12" sub, stick it in a sealed box, and call it a day. I'd consider using a 12" woofer in a sealed box on one condition: *there's four to eight of them.*
> 
> I tend to use a lot of exotic enclosures, but that's mostly because they're fun and cheap and I don't like blowing a lot of money. If price is no object, get a bunch of decent twelves or fifteens and a big amp. Problem solved.
> 
> I think there's a lot of "exotic" things that you can do to improve bass.
> 
> First, decouple the enclosure from the car. The bass in Jon's Magic Bus is better than anything I've heard, and that sub box is floating on neoprene. I think that suspending the box would also work, but I've never seen anyone do it.
> 
> Second, I really like the sound of cardoids and dipoles. I personally don't think it matters if you do it passively or actively, but active cardioids are a heck of a lot smaller than passive cardioids.
> 
> I intend to do a end-fire array in my Mazda, but I'm working on the front stage right now.
> 
> In summary:
> 
> 1) A small sealed box is great if you don't intend to get loud, if you DO, you better get more displacement
> 2) Cardioids sound awesome
> 3) Isolation the sub box from the room/car it's makes a huge difference


So, if I'm using subs mounted IB on my rear deck, would isolating the baffle from the rear deck make a difference?
Would using neoprene or some other such isolating material be sufficient?


----------



## sqshoestring

I don't think you can really isolate IB baffles like he is saying because the sub is mounted to the car...not to an enclosure. You can isolate a box by placing it on something or suspending it, etc. However I used truck topper foam to mount my baffle and it works really well to dampen and seal the baffle to the car. Best of all it comes right off should I ever remove it. But I think the baffle needs to be 'as one' with the car as much as possible. I don't know it all, but have run IB for decades and that is the way it worked best for me. I typically try to make the car stronger with my baffles.


----------



## Stookie

Big thanks on answering the Q i had - yep given that huge bass will give you that effect but I find that then drowns out the front stage. Currently my JL pro wedge completely overpowers my front and i have to turn it down to hear the 'music' Make no mistake i love big bass but am missing that front volume - was hoping for much more with the setup i have so whats the next step in the eviluion of big power and SQ ?


for those who will see this first time im 
Alpine H800 active/ TA into 
Focal fps4160
into Focal krx2's
rear alpine pdx-m12 
jl pro wedge 12


----------



## sqnut

Stookie said:


> i love big bass but am missing that front volume - was hoping for much more with the setup i have so whats the next step in the eviluion of big power and SQ ?


Your issues are 100% down to tuning and how you've set things on the h-800 and perhaps the gains on your amps. Too many things that could be an issue from the xover point & slopes to the gains on each channel to the timing, response etc. Start a tuning thread.


----------



## MetricMuscle

sqshoestring said:


> I don't think you can really isolate IB baffles like he is saying because the sub is mounted to the car...not to an enclosure. You can isolate a box by placing it on something or suspending it, etc. However I used truck topper foam to mount my baffle and it works really well to dampen and seal the baffle to the car. Best of all it comes right off should I ever remove it. But I think the baffle needs to be 'as one' with the car as much as possible. I don't know it all, but have run IB for decades and that is the way it worked best for me. I typically try to make the car stronger with my baffles.


Good info.

If I absorbed what Patrick was explaining in this thread, isolating the subwoofer enclosure is to keep it from exciting the body of the car and vice versa. 
I'm using a 2-piece baffle for my sub. To help with sealing these to the cutout area on my rear deck I was planning to use some sort of material like sound deadening material or neoprene and then a caulk sealant. The baffle rigidity will remain but there should be some isolation/decoupling from the sealing material.


----------



## Patrick Bateman

sqshoestring said:


> I don't think you can really isolate IB baffles like he is saying because the sub is mounted to the car...not to an enclosure. You can isolate a box by placing it on something or suspending it, etc. However I used truck topper foam to mount my baffle and it works really well to dampen and seal the baffle to the car. Best of all it comes right off should I ever remove it. But I think the baffle needs to be 'as one' with the car as much as possible. I don't know it all, but have run IB for decades and that is the way it worked best for me. I typically try to make the car stronger with my baffles.


If you check out the posts by Earl Geddes, he's posted a lot of very elegant solutions to problems we deal with in loudspeakers.

Here's three that apply to the problem at hand. I'm reciting these off the top of my head, so I'd strongly suggest reading his posts at diyaudio to fact-check all of this.

1) My Summas were probably the deadest loudspeaker I ever owned. I owned them for years, and I'd long assumed that they were MDF covered in carbon fiber. *I was wrong.* When I opened them up last year, I found that they were made of something completely unexpected. I won't say what it is - I'm not sure if Geddes himself has revealed it. (If he has, by all means, post it.) But here's a hint:
According to Geddes, stiffnes is the square of thickness. IE, the stiffness of a panel rises dramatically as it gets thicker. The effect isn't linear; a 1" panel isn't twice as stiff as a 1/2" panel, *it's four times as stiff.*

This sounds like a small thing, but it's not. In my measurements, over the years, I've consistently found that the subs that I've built didn't match the predictions in the bottom octave. In fact, I've trashed three subs because of this.

For YEARS I'd thought that this effect was due to my habit of building very small subs; but it wasn't that at all. It wasn't that the SUBS were too small, it's that the WALLS were too small.









Here's an example of this. I spent a week building this sub, and it didn't function as designed. I ended up throwing it away.

TLDR: You really might consider using ultra-thick walls for a sub. The walls of my Summa were something like 2". No, that's not a typo, TWO INCHES. And they weren't wood...

2) You want to isolate the sub from the car, not the woofer from the car. This one has been hotly debated at diyaudio, with some real heavyweights chiming in, including Earl Geddes, David Smith from Kef/JBL/Bose/Snell, and Siegfried Linkwitz.

Best example of this that I am aware of is the Magic Bus, and the way that Jon did it is documented on his site. He'll be demoing the Bus in Orange County later this month at T.H.E. Show.

Geddes has an incredibly simple solution to the same problem - simply suspend the sub with bungee cords. It's pretty hard to beat that, the sub isn't going to shake the car if it's suspended by a cord.









3) The last trick is also used in the Kef LS50. The trick is to *use cross braces with a damper.*
Here's how this works:

Let's say that you have a panel that's vibrating. There are two ways to address the vibration. The first is to make the panel denser. The increase in density will lower the resonance of the vibration, and the amplitude also.
The second way to reduce the vibration is to damp the panel. For instance, with Dynamat.
Or do both.
In the real world, we've seen that a little bit of Dynamat will dampen a resonance very well. (We've all seen the Dynamat demos in stores, with a paint can lid.)
The same idea is used by Kef in their cross braces. The braces aren't glued to the enclosure with a glue that's hard, like wood glue. *The braces are glued with a glue that remains pliable.* So the brace reduces the vibration of the panel, and the damper does also.









BTW, if Kef does something, it's probably worth doing. If you look at their engineering over the years they've consistently come up with elegant solutions to these problems, such as running a metal rod between woofers to physically "bind" the two structures together. A $1 tweak that works.


----------



## sqshoestring

I think Patrick knows way more about it than I do, lol, I don't go that far because its a daily driver and about 1000 other things would need to be damped/fixed before I would notice any difference from isolating the sub. And in this car these subs make enough air pressure to vibrate the roof and other panels.

Thickness certainly is a factor of stiffness with a composite. A surfboard is made of foam with a thin layer of glass and resin on it, so thin you can bang a heel print into some so it fits you better. The boards don't bend. That is how some race boat hulls are made that take incredible beatings at high speeds on the water, yeah they are more HD than a surfboard but similar construction.

One can make a composite out of foam and resin that is very light and stiff, or make a baffle out of reenforced concrete that would dampen much more and possibly be heavy depending on what fillers were used. Maybe some of us still remember the stories of high end home speakers long ago with hollow walls filled with sand. But I have to say its really nice to have IB and not have the rear of my car dragging from the weight of a giant box that can reach 25hz...and fills up my trunk space so I can't use it.

Incidentally one of the hot setups for a sub in a speed boat where weight slows you down, is a sonotube. You can resin the tube to waterproof it, its light, the tube shape is strong due to its shape. Nobody wants to put a heavy MDF box in a speedboat and also try to water/moisture proof it lol.


----------



## Orion525iT

Patrick Bateman said:


> 1) My Summas were probably the deadest loudspeaker I ever owned. I owned them for years, and I'd long assumed that they were MDF covered in carbon fiber. *I was wrong.* When I opened them up last year, I found that they were made of something completely unexpected. I won't say what it is - I'm not sure if Geddes himself has revealed it. (If he has, by all means, post it.) But here's a hint:
> According to Geddes, stiffnes is the square of thickness. IE, the stiffness of a panel rises dramatically as it gets thicker. The effect isn't linear; a 1" panel isn't twice as stiff as a 1/2" panel, *it's four times as stiff.*


It's not just Geddes that states stiffness is the square of thickness, it's a well known engineering principle. It is why core materials are used in composites. You can increase the stiffness of a composite by using core material to minimize costs and reduce weight. A solid layup of equal stiffness will be much heavier, use more of the expensive fabrics, and use more resin. 

When it it comes to core materials, there are many options. The most basic is plain styrofoam. The problem with styrofoam is that it has pretty poor mechanical properties and (of course) it doesn't play nicely with polyester or vinylester resins. But it is inexpensive and you can cut it with a hot wire. There are more exotic foams that come in a variety of densities like polyether polyurethane, which is easy to cut and shape, and pvc foams which can be thermoformed. None of these really add any real mechanical properties beyond those gained by increased laminate thickness, and the exotic foams can get expensive.

There are natural sources of core materials too, which I think are better suited for building loudspeaker boxes. Balsa works nice, and adds some to the mechanical properties. But the most interesting to me is cork. Not only is cork a good core material, which has good mechanical properties, but it also has very good damping ability. This is why it has been considered for use in interior panels and trim of modern passenger aircraft. If I ever get around to making my own boxes for a home system, I plan to build them with laminate using cork as a core. The laminate would be super stiff, relatively light, and have damping built into the mix. 

In regards to cardioid, my build has that as a possibility. Basically, the front and back waves are separated in a way that the back wave must travel an extra 6' or so before it can interact with the front wave. It's really just an experiment to play with. I also have it set up to act as a normal IB, venting to the outside of the car. I can vary the amount of the back wave that interacts by altering the size of the holes that exit the car and enter into the cabin, or even by adding materials to act like an aperiodic membrane. The only thing I can't alter easily is the distance the back wave travels. Lots of variables to play with to see what works.


----------



## Patrick Bateman

That last post is amazing. 

I'm a software developer by trade, and my knowledge of composites is limited. Most of what I know is based on my love of bike building. My father built three boats by hand, so I may have learned a little of that along the way. 

It sounds like a foam core may not be 100% necessary? IE, maybe hollow walls would be sufficient?

The reason that I bring this up is because I've been having lots of issues with delamination. I've tried two different adhesives to bond wood to foam. The first faked completely (PL 400). Now I'm trying PL300. I haven't tested it yet; I'm giving it a looong time to cure. 

Geddes abandoned the construction technique used in the Summas and now uses some type of cast polymer iirc. 

I'm fairly decent with 3D software; it seems like it should be possible to make some type of monocoque enclosure. 

The question is, can it be done with wood?


----------



## Orion525iT

Patrick Bateman said:


> The reason that I bring this up is because I've been having lots of issues with delamination. I've tried two different adhesives to bond wood to foam. The first faked completely (PL 400). Now I'm trying PL300. I haven't tested it yet; I'm giving it a looong time to cure.
> 
> The question is, can it be done with wood?


I should have stated things more clearly. The core materials do add some to overall strength especially in compression, just some do better than others. The core material forces the two composite skins to act in tandem, not as separate thin sheets. When a load is applied, the core forces one skin to stretch and the other skin to compress. The thicker to core, the more one side is stretched and the other side is compressed, which is why the stiffness increases dramatically with thickness. 

I assume you are using styro foam of some sort? Delamination is a big issue with all core materials. You can use a perforation roller to increase surface area. The other thing is that most of those polyurethane adhesives are very thick. As a result, you have to apply a **** ton of pressure evenly to get good contact across the core; so much that you would most likely crush the core in the process. You really need complete adhesion across the entire core with no dry areas or these areas will act as weak spots where delamination can creep. You can get the poly adhesive to slide better and squeeze out more easily if you mist the surface with water, but that also makes it cure quicker. 

So my suggestion would be to use a lower viscosity adhesive, like epoxy.

Still, trying to squeeze out and get complete contact will be tricky, I think. I have laminated multiple sheets of plywood together with wood glue, and even that is a ***** and easy to f' up.

You could use wood as reinforcement over a core, but the issue above make it impractical to do by hand I think.

Why not just do fiberglass hand layup? End grain balsa as a core works well as long as the shape is not too complex. Being end grain, the balsa will soak up some of the resin, which will decrease the chance of delamination. E-glass is easy to work with, comes in varies weaves and weights. 

I almost used balsa, and considered cork in the manifolds I built for my car. But in the end, I used core mat, e-glass and vinyl ester resin. I used vinyl ester because it is stiffer than poly, stronger, and is even lower in viscosity (which makes it very easy to properly wet out the glass). But it stinks to high hell.


----------



## sqshoestring

You need to vacuum bag it, lot of guys doing hulls that way now and some little project would be easy to do that way. The vacuum will press it together and remove excess resin. My source when I was working on boats was screamandfly.com go to the section they are recoring hulls. I used wests epoxy the stuff was great, low odor, bonds well, when I put a new transom in a boat. Also did some other projects with ply and never had an issue bonding, that stuff is superglue. I've bonded plastic together but it was not for high strength, but I was surprised it worked at all. I've used the other stuff on auto repairs, such as fiberglass bodied cars. Usually with wood you paint the wood with resin until it stops absorbing it, then you start laying up glass on it. But if you are coring a hull you tend to do it all at once and there are tricks to making it work well, for bedding the core properly. You need to apply the resin before 24hours for the next time, to keep a chemical bond, when you do multiple layers/coats/etc. Otherwise you grind it a lot and only have a mechanical bond. They usually score foam to get a better grip on it, some has holes through it at intervals. I guess you can use that stuff for insulating houses as its more dense and that works better (for non boat projects). Of course if you mount to it then you need to beef up that area, for example outboard boats all have aluminum or wood solid plates in the transom where the outboard mounts to and the bottom might all be cored with stringers inside to distribute force from the motor and transom up the bottom. You can't put a bolt through a foam composite it will crush it. You would glass a bushing or wood pad (or some other solid core material) in for the hole and use that. Its like a cheap house door; it has heavy wood where the lock goes, wood around the edges, but the center is largely empty.

Ply is a little heavy for a boat, but a great thing to make a composite with. If you lay glass on both sides of thick ply it will be very strong, and since its ply you could screw brackets or whatever to it anywhere. I laid up 3/8 ply for floor panels once and was amazed at how much stiffer they were with the glass on them. I made a new ski locker door in the floor.

Another way is to lay blocks of core they do that with endgrain balsa. You lay each piece and resin goes between, that way your composite is secured around each piece to bond the skins together at each distance your block size is. A boat core might be 6" or however it comes I forget. You bed those on one skin, then lay the outside skin on when done, within 24 hours. Your skin never goes much distance between bonds this makes delamination much more difficult.


----------



## MetricMuscle

I have actually read thru this whole thread and would love if we could summarize the important aspects of overcoming the issues that make Natural Bass difficult to achieve. If I have understood correctly.....

1. The inside dimensions of a vehicle will determine cabin gain at different frequencies.

2. 80Hz and down are easy to produce, lots of cabin gain. 80Hz to 320Hz are difficult to produce, cabin dimensions work against these two octaves and cancel much of it out. Not much difference between a Civic and a Suburban in this regard.

3. More effort will be needed to produce powerful mid bass than sub bass.

Someone quoted RC a couple of times saying "To have bass up front, you need to have bass up front." Is this true today with modern DSP? Do I still have to have powerful mid bass drivers up close to the listening position or can I mount them farther back on the rear deck with my IB subwoofer?
Can I task the subwoofer(s) with covering the difficult mid bass, up thru 320Hz?
Of course the woofer would have to be capable of this but this would be much more realistic than trying to get larger drivers up front on my doors or.......?
ProAudio woofers don't typically have a low FS. Their potential performance in a car can be misleading since cabin gain works in their favor, boosting where they roll off on the low end and not helping where they really shine, in the mid bass region.


----------



## Orion525iT

MetricMuscle said:


> Someone quoted RC a couple of times saying "To have bass up front, you need to have bass up front." Is this true today with modern DSP?


Sometimes when I see RC quotes, I think they are about as useful as a political campaign add when it comes to truthfulness. There seems to be a lot of voodoo and hyperbole in what he says. You have to remember that this is the guy who had 12" JBL midbass drivers in the quarter panels behind the listening position. There is too much speculation behind what was done or _not_ done to get that to work. When I first saw that quote, I wondered if perhaps it was tacit admission to what was long speculated; there were hidden midbass drivers under the dash. But I will leave it up to you to decide whether that was true, and how it may have worked.


----------



## ErinH

MetricMuscle said:


> Someone quoted RC a couple of times saying "To have bass up front, you need to have bass up front." Is this true today with modern DSP?


I'll say this...

I have a friend with 10" woofers in his floor board of his SUV, playing stereo (initially they were midbass only and he's shifting gears and planning to use them in lieu of subs). The install is done VERY well. And his car sounds fantastic. 

When he asked me to help him out and test the usefulness of these drivers as subwoofer replacements, he simply bypassed the crossover. In that instance, there was still bass 'behind me', because it lit up certain modes in the car in different manners. 



Another example: my car. If I drop the high-pass filter on my 8's up front and run them all the way down, I have more tactile energy in my seat back than I do with them using a HPF. I've literally had people tell me they could "hear" the sub behind them, thinking I still had my subs turned on in this case. When in reality, there were no subs enabled; just the 8" woofers in the floor playing without a HPF.



So, as I've come to learn over the years, *just because you have a subwoofer physically placed up front, it doesn't guarantee you will get 'up front bass'.* The best 'up front bass' I've ever gotten is with my current setup. And I'm using 15" woofers behind me.


----------



## sqshoestring

MetricMuscle said:


> 2. *80Hz and down are easy to produce, lots of cabin gain. * 80Hz to 320Hz are difficult to produce, cabin dimensions work against these two octaves and cancel much of it out. Not much difference between a Civic and a Suburban in this regard.
> 
> .


Then why all the 1K-2KW+ amplifiers and giant throw subs?


----------



## sqshoestring

My point was if you want SQ (or really loud bass) you have to have some displacement or a super quiet car to get the low notes. Still have to tune a good FR either way, IMHO, what any natural sounding bass is all about.

What was that Patrick Bateman thread about midbass arrays, that is a good read for anyone not familiar with it. Midbass is important you cant have good bass without it, can't blend subs without it either. People laugh at me running rears when half the reason is to get more midbass, sorry I can't get to the huge project of putting big midbass in front as this car is not well equipped to do it.

I had a car with subs and 6x9 in the rear (old muscle car), for a while only dome tweets in front. I got it sounding really nice....until you turned your head and realized most of the system was behind you lol. But the bass and midbass were awesome in that car.


----------



## Patrick Bateman

MetricMuscle said:


> I have actually read thru this whole thread and would love if we could summarize the important aspects of overcoming the issues that make Natural Bass difficult to achieve. If I have understood correctly.....
> 
> 1. The inside dimensions of a vehicle will determine cabin gain at different frequencies.
> 
> 2. 80Hz and down are easy to produce, lots of cabin gain. 80Hz to 320Hz are difficult to produce, cabin dimensions work against these two octaves and cancel much of it out. Not much difference between a Civic and a Suburban in this regard.
> 
> 3. More effort will be needed to produce powerful mid bass than sub bass.
> 
> Someone quoted RC a couple of times saying "To have bass up front, you need to have bass up front." Is this true today with modern DSP? Do I still have to have powerful mid bass drivers up close to the listening position or can I mount them farther back on the rear deck with my IB subwoofer?
> Can I task the subwoofer(s) with covering the difficult mid bass, up thru 320Hz?
> Of course the woofer would have to be capable of this but this would be much more realistic than trying to get larger drivers up front on my doors or.......?
> ProAudio woofers don't typically have a low FS. Their potential performance in a car can be misleading since cabin gain works in their favor, boosting where they roll off on the low end and not helping where they really shine, in the mid bass region.


I think you summed it up well here.

In a nutshell, *getting the two octaves from 80hz to 320hz correct is really difficult.* This is due to three things:

1) There's no real cabin gain in those two octaves
2) "there's no replacement for displacement" and it's hard to find a spot for a woofer with a lot of output.
3) The door is the obvious choice for a location, but the door is a ****ty enclosure, primarily because it leaks.


One of the reasons that I qualified my statement about cabin gain is that 80hz to 160hz is in a transition area. Basically the wavelengths are transitioning to a range where they're so long, cabin gain shoots through the roof. (80hz is over four meters long; nearly the length of the car.) But that's a big part of the problem; it's a chaotic octave where the waves aren't QUITE long enough that your location doesn't matter, but not quite short enough that we can fix them with a waveguide. IE, at 2khz it's pretty easy to put the sound where you want it, a 17cm waveguide will do the job. But at 1khz it's a lot harder, and by the time you're down to 500hz or 250hz, you really need a different solution.

End fire arrays look really attractive, but the processing and number of speakers is still fairly steep. You're probably looking at about $1000 for the amps, speakers and processing for a sixteen channel end fire array. (8 drivers per array, and a stereo array.) I'm not prepared to drop $1000 on a "hunch", not quite yet.

Jon's bus sounds really nice. If I could justify having a recording studio on wheels, that solution works well. I agree with Jon that it wouldn't be possible to achieve that level of absorption in a car, there's just not enough space for all the Helmholtz absorbers.


----------



## oabeieo

Patrick Bateman said:


> Have you ever replaced the woofers in your car, and found that one set sounded *different*, but not necessarily *better*? For instance, you replaced your door woofers, and at first you noticed that the new woofers played noticeably lower. Not night and day, but definitely deeper. So you were stoked for a few weeks there, but then you started to notice that you were still suffering from the same integration issues. The midbass didn't blend with the sub, or perhaps the new woofer played low, but couldn't get as loud as the woofer it replaced.
> 
> In other words, you traded one set of problems for another.
> 
> This situation is one of the things that makes car audio so frustrating. I think it's one of the reasons that so many people just throw in the towel, or simply spend years replacing component after component.
> 
> I used a computer program to simulate the interior of my car, to demonstrate how the dimensions wreak havoc with our loudspeakers.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's a comparison of two woofers, mounted in the doors of a Honda Accord coupe. One is a Hertz midbass, the other is a Dayton RS180.
> 
> First thing you'll notice is that this is ANYTHING but flat. It's a mess really - there's a massive suckout at 400hz, and an entire octave from 80 to 160hz.
> 
> In other words, both woofers suffer from the same problems, but to varying degrees. The Hertz (blue) plays lower. The Dayton (orange) is more efficient and smoother.
> 
> I think this is fairly consistent with what people have reported here - the Hertz woofers are famous for playing very low, but needing a lot of power.


I was using a tone generator yesterday and could here the nodal responce just like that , it would be loud and than quiet than loud and over and over as I turned up the frequency, interesting , it weird how many sudden dips there are between the 1/3 oactave bands and there so extreme at some bandwidth s that I'm amazed you don't notice it as much with music


----------



## MetricMuscle

Patrick Bateman said:


> I think you summed it up well here.
> 
> In a nutshell, *getting the two octaves from 80hz to 320hz correct is really difficult.* This is due to three things:
> 
> 1) There's no real cabin gain in those two octaves
> 2) "there's no replacement for displacement" and it's hard to find a spot for a woofer with a lot of output.
> 3) The door is the obvious choice for a location, but the door is a ****ty enclosure, primarily because it leaks.
> 
> 
> One of the reasons that I qualified my statement about cabin gain is that 80hz to 160hz is in a transition area. Basically the wavelengths are transitioning to a range where they're so long, cabin gain shoots through the roof. (80hz is over four meters long; nearly the length of the car.) But that's a big part of the problem; it's a chaotic octave where the waves aren't QUITE long enough that your location doesn't matter, but not quite short enough that we can fix them with a waveguide. IE, at 2khz it's pretty easy to put the sound where you want it, a 17cm waveguide will do the job. But at 1khz it's a lot harder, and by the time you're down to 500hz or 250hz, you really need a different solution.
> 
> End fire arrays look really attractive, but the processing and number of speakers is still fairly steep. You're probably looking at about $1000 for the amps, speakers and processing for a sixteen channel end fire array. (8 drivers per array, and a stereo array.) I'm not prepared to drop $1000 on a "hunch", not quite yet.
> 
> Jon's bus sounds really nice. If I could justify having a recording studio on wheels, that solution works well. I agree with Jon that it wouldn't be possible to achieve that level of absorption in a car, there's just not enough space for all the Helmholtz absorbers.


My options and restrictions are
1. I'd want to mount the additional mid-bass drivers on the rear deck/package tray on either side of my subwoofer, all 3 IB. This is the only realistic location for me to mount an 8" or 10" or 12" woofer.

2. I'm using MS-8 so this new arrangement, where 300Hz and below will now be coming from the rear deck, can't wreak havoc on calibration etc. MS-8 won't allow for overlapping frequencies either so the mid-bass in my front doors will now be limited to 300Hz and up. I really like this since the OE 5"ers are in a vented factory enclosure and would be much happier relieved of the lower octaves. The enclosures also are too small for any replacement woofer to make any low frequency with reasonable authority.

3. I would use the subwoofer output signal from MS-8 to feed the sub and mid-bass amp and then use the crossover in the amp to cross between the two. This would allow for the same TA for all 3 woofers on the rear deck, actually MS-8 doesn't delay the subwoofer channel just all of the others to it, IIRC. In a typical set up MS-8 will provide the illusion of bass up front so hopefully raising the low pass point won't mess that up.


----------



## Orion525iT

MetricMuscle said:


> My options and restrictions are
> 1. I'd want to mount the additional mid-bass drivers on the rear deck/package tray on either side of my subwoofer, all 3 IB. This is the only realistic location for me to mount an 8" or 10" or 12" woofer.
> 
> 2. I'm using MS-8 so this new arrangement, where 300Hz and below will now be coming from the rear deck, can't wreak havoc on calibration etc. MS-8 won't allow for overlapping frequencies either so the mid-bass in my front doors will now be limited to 300Hz and up. I really like this since the OE 5"ers are in a vented factory enclosure and would be much happier relieved of the lower octaves. The enclosures also are too small for any replacement woofer to make any low frequency with reasonable authority.
> 
> 3. I would use the subwoofer output signal from MS-8 to feed the sub and mid-bass amp and then use the crossover in the amp to cross between the two. This would allow for the same TA for all 3 woofers on the rear deck, actually MS-8 doesn't delay the subwoofer channel just all of the others to it, IIRC. In a typical set up MS-8 will provide the illusion of bass up front so hopefully raising the low pass point won't mess that up.


I honestly don't think you need to limit the fronts to 300hz.

I am finally in the early testing phases of my project. I am using the minidsp 4x10 (a bit deceptive description), but I have digital and analog in and 8 analog channels out. There are various designs I considered. But I have stereo subs IB in wide as possible flanking positions in the rear quarters. The subs are 87db 1w/1m each, and I have 4 of them per side wired parallel down to 1 ohm. The midbass are 6.5", 94db 1w/1m, in tiny sealed .16L enclosures at the traditional front of door location. The enclosures are designed for an f3 of ~150, though in testing, I found they have good output below that. Midbass has only 4.5mm of xmax to use. 

Subs are low q, so they roll off right were cabin gain really starts to bump things up. Where cabin gain starts to diminish, I have tons of cone area to work with (856cm2 per side; a little more than your average 15" woofer). I set 24 db/oct xover at 130hz for the subs, and 12db/oct xover at 150hz for the midbass.

In initial testing it gets loud. Louder than I would ever want to listen to. The midbass are not even getting close to xmax. I can't tell the subs are behind me. What I am thinking is that those ported enclosures you have might be perfect for a larger driver sealed, or another more capable 5" ported and you can probably get to 150hz without issue.


----------



## MetricMuscle

Orion525iT said:


> I honestly don't think you need to limit the fronts to 300hz.
> 
> I am finally in the early testing phases of my project. I am using the minidsp 4x10 (a bit deceptive description), but I have digital and analog in and 8 analog channels out. There are various designs I considered. But I have stereo subs IB in wide as possible flanking positions in the rear quarters. The subs are 87db 1w/1m each, and I have 4 of them per side wired parallel down to 1 ohm. The midbass are 6.5", 94db 1w/1m, in tiny sealed .16L enclosures at the traditional front of door location. The enclosures are designed for an f3 of ~150, though in testing, I found they have good output below that. Midbass only has 4.5mm of xmax to use.
> 
> Subs are low q, so they roll off right were cabin gain really starts to bump things up. Where cabin gain starts to diminish, I have tons of cone area to work with (856cm2 per side; a little more than your average 15" woofer). I set 24 db/oct xover at 130hz for the subs, and 12db/oct xover at 150hz for the midbass.
> 
> In initial testing it gets loud. Louder than I would ever want to listen to. The midbass are not even getting close to xmax. I can't tell the subs are behind me. What I am thinking is that those ported enclosures you have might be perfect for a larger driver sealed, or another more capable 5" ported and you can probably get to 150hz without issue.


I think my OE enclosures are right around ~0.1 cuft ish. I actually have some 6.5" CDT CL-6MB mid bass woofers which would work well in a small sealed enclosure from 80Hz and up. Just doesn't sound like a pair of 6.5" mid bass woofers will be up to the task in an automotive environment.

300Hz wasn't a hard and fast crossover point, I'm sure I would experiment.


----------



## Orion525iT

MetricMuscle said:


> I think my OE enclosures are right around ~0.1 cuft ish. I actually have some 6.5" CDT CL-6MB mid bass woofers which would work well in a small sealed enclosure from 80Hz and up. Just doesn't sound like a pair of 6.5" mid bass woofers will be up to the task in an automotive environment.
> 
> 300Hz wasn't a hard and fast crossover point, I'm sure I would experiment.


I'm a dork, I meant .16 cu ft, not .16L in my previous post. .16L would be super, super tiny.


----------



## jpeezy

Patrick Bateman said:


> That last post is amazing.
> 
> I'm a software developer by trade, and my knowledge of composites is limited. Most of what I know is based on my love of bike building. My father built three boats by hand, so I may have learned a little of that along the way.
> 
> It sounds like a foam core may not be 100% necessary? IE, maybe hollow walls would be sufficient?
> 
> The reason that I bring this up is because I've been having lots of issues with delamination. I've tried two different adhesives to bond wood to foam. The first faked completely (PL 400). Now I'm trying PL300. I haven't tested it yet; I'm giving it a looong time to cure.
> 
> Geddes abandoned the construction technique used in the Summas and now uses some type of cast polymer iirc.
> 
> I'm fairly decent with 3D software; it seems like it should be possible to make some type of monocoque enclosure.
> 
> The question is, can it be done with wood?


3M Panel Bonding Adhesive 08115.
I've used this to bond wood/plastic, wood/foam,plastic/metal,just about anything.if applied correctly you will have to destroy one of the paired materials before this stuff will fail.


----------



## MetricMuscle

Orion525iT said:


> I'm a dork, I meant .16 cu ft, not .16L in my previous post. .16L would be super, super tiny.


LOL! Yep, that would be pretty hard to work with.


----------



## High Resolution Audio

Subbed for future reference.


----------



## claydo

Well gerald, you bumped an old thread here didn't ya, lol. I'm gonna have to put my 2 cents on this matter after reading a bit on the thread. "Natural" or smooth low bass is not as hard as everyone makes it out to be.......I feel it's much more about as solid of an instal as you can get for your subs, and from there 100% tuning. I don't think it takes near the cone area, efficiency, and special decoupling methods as are discussed here. Now I'm discussing the very bottom end here, midbass is an entirely different story. Low bass in a car is fairly easy simply because of the small space we have to pressurize, that's the one advantage we have over the home audio game. My own car gets constant raves about its low bass performance, and has more output down low, and plays louder, than 95% of the sq cars I have demoed.......from two sealed 8s.....lol. As a matter of a fact, to make it blend and sound nice, smooth, and tight, I must throttle them back a bit. Now I'm not saying my car is the "be all, end all", not by any means, I'm just saying that folks get way too caught up in the output ability, when in a car, tuned properly, it doesent take that much along the lines of power and cone area, with proper tuning, and use of the "help" our interiors provide in this area of sound reproduction. My subs do load of of the back glass (its a sedan), and they bass quality improved dramatically when I bolstered the subs with enough ability in the midbass area to let the subs do what they were designed for, simply pressurize the space. My midbass drivers are larger than my subs........


----------



## High Resolution Audio

claydo said:


> Well gerald, you bumped an old thread here didn't ya, lol. I'm gonna have to put my 2 cents on this matter after reading a bit on the thread. "Natural" or smooth low bass is not as hard as everyone makes it out to be.......I feel it's much more about as solid of an instal as you can get for your subs, and from there 100% tuning. I don't think it takes near the cone area, efficiency, and special decoupling methods as are discussed here. Now I'm discussing the very bottom end here, midbass is an entirely different story. Low bass in a car is fairly easy simply because of the small space we have to pressurize, that's the one advantage we have over the home audio game. My own car gets constant raves about its low bass performance, and has more output down low, and plays louder, than 95% of the sq cars I have demoed.......from two sealed 8s.....lol. As a matter of a fact, to make it blend and sound nice, smooth, and tight, I must throttle them back a bit. Now I'm not saying my car is the "be all, end all", not by any means, I'm just saying that folks get way too caught up in the output ability, when in a car, tuned properly, it doesent take that much along the lines of power and cone area, with proper tuning, and use of the "help" our interiors provide in this area of sound reproduction. My subs do load of of the back glass (its a sedan), and they bass quality improved dramatically when I bolstered the subs with enough ability in the midbass area to let the subs do what they were designed for, simply pressurize the space. My midbass drivers are larger than my subs........


Hello Clay, My guess is that you are running with the Pioneer P-99 for a head unit? In all my life, I haven't ever been able to achieve what you proclaim to be so easy to achieve. I seem to but together systems that have good mids and highs, but bass and mid bass is where I've always fallen short. I'm trying to read as many threads as possible on the topic. 

The closest I ever got to having great bass was the same exact set up but using the P-99 for a head unit. Installing that made me seem like a low end genius.

Maybe because in my quest for tight clean bass, I always make my sealed enclosures as small as possible as per the recommend range per manufacturer?


----------



## claydo

Yes, I'm using a p99. As far as the recommended box specs, it depends on the manufacturer, I'm running jl subs and have had better luck out of these using slightly larger than recommended. Experimentation is the key with location, loading boundaries or lack there of, and tuning......enclosures can help shape the sound as well, but recommended or modeling yourself should usually get you close.

My biggest recommendation tho is a stout well tuned midbass driver, I enjoy a sub doing its below 50 job without mudding up the midbass due to the serious excursion needed to produce these frequencies. I know this flies in the face of the process of most using their subs to reinforce the midbass, but for me, it's just my preferred method.....you can then use smaller drivers that can produce adequate sub bass without being so huge to stay clean at the 60-150 pass band while they are trying to pump out a satisfying low end rumble. The folks who use very large subs, I believe are doing so to have enough cone area for sub bass output with less excursion to keep the sub clean up to the lower midbass. Kind of like two way vs three for keeping midbass excursions out of the way of the pristine production of midrange......


----------



## claydo

And........ I'm also a big fan of sealed, not only because of the construction simplicity, but the sound of a sealed sub, when pushed hard, is better in my mind than ported, or the highly sought after ib. Ported and ib can sound great, mind you.......but a sub in a sealed enclosure pushed up near it's limits is a beautiful thing.......if I were to go with a ported or ib setup I'd have to far surpass my current driver size simply because these two arrangements sound best when barely working the cone, so they require much more cone area.......


----------



## claydo

Oh....and gerald, the p99 really doesent seem all that different than other sources for bass reproduction for me.......it's clean, don't get me wrong, but I don't believe it has any advantages. The vehicle most commented as having the best bass in an automotive environment has to be the magic bus, and he's using the same source as you! So rest assured you can get there.......keep on tuning and experimenting!

Oh, and I will add.....midbass tuning is a royal *****.


----------



## High Resolution Audio

claydo said:


> Oh....and gerald, the p99 really doesent seem all that different than other sources for bass reproduction for me.......it's clean, don't get me wrong, but I don't believe it has any advantages. The vehicle most commented as having the best bass in an automotive environment has to be the magic bus, and he's using the same source as you! So rest assured you can get there.......keep on tuning and experimenting!
> 
> Oh, and I will add.....midbass tuning is a royal *****.


 Really good information here. But I can guarantee you that the P-99 has the ability to produce low frequencies lower, tighter, and cleaner, and more robust than any Alpine Unit that I have ever used ( and that totals 8 different Alpine head units). I have had both the P-99 and Alpine F#1 head units (as well as 5 other Alpine head units ) in the same vehicle with the same amps and same, drivers in the same positions, and the difference in the bass with the P-99 is night and day.

As far as having the best bass in any automotive environment, I have sat in the magic bus and did not find the bass overly impressive. I've sat in other vehicles that scored very high in the competitions, and they share one thing in common that bothers me. I get very distracted by having the low frequencies originate from behind me, or at least stage behind me. For me that is something that just does not sound right. The first thing I noticed when sitting in the magic bus was that the bass came from behind me. That was the very first comment I made to Jon after hearing the system for 15-20 seconds. 
My first words were,
"It makes a big difference having the sub-woofers behind rather than in front."
He said,
"Yes it does."

I understand that in a vehicle it is not always possible to get bass drivers in front due to space restrictions, but that's where the mid-basses come into play. Some people say that bass frequencies are non-directional, however, In my experience, they are very directional down to a certain frequency. Which specific frequency that is, I do not know.


----------



## High Resolution Audio

claydo said:


> Yes, I'm using a p99. As far as the recommended box specs, it depends on the manufacturer, I'm running jl subs and have had better luck out of these using slightly larger than recommended. Experimentation is the key with location, loading boundaries or lack there of, and tuning......enclosures can help shape the sound as well, but recommended or modeling yourself should usually get you close.
> 
> My biggest recommendation tho is a stout well tuned midbass driver, I enjoy a sub doing its below 50 job without mudding up the midbass due to the serious excursion needed to produce these frequencies. I know this flies in the face of the process of most using their subs to reinforce the midbass, but for me, it's just my preferred method.....you can then use smaller drivers that can produce adequate sub bass without being so huge to stay clean at the 60-150 pass band while they are trying to pump out a satisfying low end rumble. The folks who use very large subs, I believe are doing so to have enough cone area for sub bass output with less excursion to keep the sub clean up to the lower midbass. Kind of like two way vs three for keeping midbass excursions out of the way of the pristine production of midrange......



I agree with that philosophy. The two 15" subs I have right now are playing 40 and below. I don't think subs should be used to reinforce mid bass just as you stated that it was important to not have the mid-ranges playing down too low or they will get muddied up trying to play mid-bass. One question I do have is what is the perfect size mid-bass?


----------



## claydo

Hmmm, I have not demoed the magic bus, just going on comments from folks who had. The one thing most agreed on is the bass being spectacular. Location in relation to the listener of a sub does not matter with a properly tuned vehicle.....but modal issues within that same space can influence your opinion of the origionations of the bass. In my car the lowest of lows can sound like they are coming from the back.....and this is with the subs muted and midbass running with no high pass, or with the subs playing.....the midbass drivers are certainly placed upfront physically, but when the frequencies they play get really low, you would swear I had un-muted the subs om some notes.....lol. I don't know how to explain that phenomenon, but would be glad to demonstrate to anyone demoing my car......kick drum sounds like it going to bust through the winshield, bass guitar the same, but super low frequency info seems to engulf you from all around eminating from no specific direction, and fooling you at time to sound like it's from the back.....

Hope I get to hear your creation one of these days gerald, as well as give you a good ol loud demo in mine!


----------



## seafish

High Resolution Audio said:


> I agree with that philosophy. ... One question I do have is what is the perfect size mid-bass?


Well that is pretty much the same thing as asking -- " What is the perfect size peter ?

The answer pretty much depends on its use within the "overall system." LOL 

That being said, when it comes to bass and horsepower, there is still no replacement for displacement …the larger the better.


----------



## claydo

The perfect size midbass is the driver that will cleanly play the frequencies you need it to, at the levels the rest of your system plays.......so if your a relatively low level listener, you can probably get by on a 6.5, louder probably needs an 8.....I myself use a 10.....that should clue you in to my desired listening levels, lol.


----------



## claydo

seafish said:


> Well that is pretty much the same thing as asking -- " What is the perfect size peter ?
> 
> The answer pretty much depends on its use within the "overall system." LOL
> 
> That being said, when it comes to bass and horsepower, there is still no replacement for displacement …the larger the better.


Whoa!

Perfect peters.......and bigger is better.....

Are you trying to say yer a fan of big peters? Lmao......


----------



## High Resolution Audio

claydo said:


> The perfect size midbass is the driver that will cleanly play the frequencies you need it to, at the levels the rest of your system plays.......so if your a relatively low level listener, you can probably get by on a 6.5, louder probably needs an 8.....I myself use a 10.....that should clue you in to my desired listening levels, lol.


I'm using a 10" Boston Acoustics driver as a mid-bass that was designed to be used as a sub-woofer. I'm playing 60-125 hz through it. To me it sounds, muddy, loose, not precise. 

After researching, I found that drivers designed to be used as a sub-woofer are not designed to play well above 100 hz or so....due to high induction? Whatever that means. 


My dilemma is do I replace the 10" Boston "subwoofer" with a 10" woofer ( the driver I was considering was a 10" Scanspeak revelator.) Or do I go with two 6 1/2" mid bases per side? I could keep adding more 6 1/2s to gain output if need be . Mid-range will be 7"

I read that two 6 1/2" drivers are equivalent to one 10".

My goal is to have clean distortion free sound.


----------



## claydo

My midbass drivers are subwoofers as well......but they play nice up to about 250 or 300.......I cross them at 200 and they do a helluva job. I'm thinking the tuning is giving you fits, although some woofers do play higher than others.......like I mentioned above, midbass tuning is a *****.....


----------



## High Resolution Audio

claydo said:


> My midbass drivers are subwoofers as well......but they play nice up to about 250 or 300.......I cross them at 200 and they do a helluva job. I'm thinking the tuning is giving you fits, although some woofers do play higher than others.......like I mentioned above, midbass tuning is a *****.....


I had mine crossed at 300. But the female voice sounded congested. Kept lowering until the congestion went away. ended up at 125.


----------



## claydo

My midrange enclosure dictate the higher crossover. They are 5.5" drivers, but crammed up on the dash in smallish enclosures the response gets all funkified bellow bout 160hz.......luckily the midbass in the doors play nice higher than I have to go to match up......


----------



## High Resolution Audio

claydo said:


> My midrange enclosure dictate the higher crossover. They are 5.5" drivers, but crammed up on the dash in smallish enclosures the response gets all funkified bellow bout 160hz.......luckily the midbass in the doors play nice higher than I have to go to match up......


I would like to sit in your car and take a listen. 95DB is perfect level for me with peaks over 100.


----------



## claydo

I tend to demo mine pretty loud, but I've never actually measured to see how loud....lol. Volume has never been stated as lacking....


----------



## sqshoestring

Have to agree with you guys on large midbass drivers. One thing that shows if you model them most midbass puke by the time they get under 100 or so. That leaves a hole 50-100. If you play your subs up to 70-80 you might be able to blend them but over 80 they will localize badly, 50 is better. Either way you still have a hole under 100 where 6.5 are dying, or most common ones are. Modelling it takes a great 8 or a 10 to fill that hole without dropping out. I want to put shallow 10 subs in my doors for midbass, its all I can fit in thickness. Huge project though so not sure I will ever get to it. Anyway, the 10s model fairly flat down to 70-80 range, but I have a PEQ for them if they need it since the door enclosure could affect them one way or another.

Once had a winter beater car long ago and a set of good 6x9 with blown tweets, got the idea it would be louder with those for mids in front (and all I had on hand at the time lol) and sawed them into the bottom of the doors. I think it had 3.5 in the dash iirc. Wow did they pump the midbass, it was a revelation of what a larger cone could do. This was a 70s car with huge doors, made it easy.

I run 125rmsx4 and 500 on IB 15s, its plenty for me but does all get used at times.


----------



## Black Rain

I personally enjoy sealed enclosures or ported. I feel that give you a smoother and tighter bass. Now does the size and type of vehicle affect the overall performance of the sub and if so... by how much (generally speaking)?


----------



## I800C0LLECT

claydo said:


> Whoa!
> 
> Perfect peters.......and bigger is better.....
> 
> Are you trying to say yer a fan of big peters? Lmao......



I think what he's saying is that if "they" don't want the volume you can achieve impact with lower excursion and surface area/smaller displacement :laugh:

Not everybody wants to leave their vehicle a hot mess


----------



## claydo

I800C0LLECT said:


> I think what he's saying is that if "they" don't want the volume you can achieve impact with lower excursion and surface area/smaller displacement :laugh:
> 
> Not everybody wants to leave their vehicle a hot mess


Oh I understood what he was saying......but I couldn't let the Peter references go......lmao.


----------



## ErinH

claydo said:


> My midrange enclosure dictate the higher crossover. They are 5.5" drivers, but crammed up on the dash in smallish enclosures the response gets all funkified bellow bout 160hz.......luckily the midbass in the doors play nice higher than I have to go to match up......


may not be the best place to bring this up but ..

when I demo'd your car and you told me basically the same thing, I wondered: why not just use a smaller driver? you're obviously not reaping the benefit of a large 5.25" driver sitting in your face on the dash and using a smaller driver would permit more flexibility with a tweeter (crossover/size). I was where you are as well and the notion of a large driver was awesome to me. But we know you don't _need _a 5" midrange to get loud when you're 3 feet away, especially when you're not using it anywhere near Fs. That's why I punted my old setup. Even something like the 12m would be a good option for you if you don't want to go too small: smaller, less volume required, plays a bit higher. 

I probably wouldn't have ever mentioned this to you but since you said the above, I think it's worth thinking about. 

Just my $.02.


----------



## claydo

ErinH said:


> may not be the best place to bring this up but ..
> 
> when I demo'd your car and you told me basically the same thing, I wondered: why not just use a smaller driver? you're obviously not reaping the benefit of a large 5.25" driver sitting in your face on the dash and using a smaller driver would permit more flexibility with a tweeter (crossover/size). I was where you are as well and the notion of a large driver was awesome to me. But we know you don't _need _a 5" midrange to get loud when you're 3 feet away, especially when you're not using it anywhere near Fs. That's why I punted my old setup. Even something like the 12m would be a good option for you if you don't want to go too small: smaller, less volume required, plays a bit higher.
> 
> I probably wouldn't have ever mentioned this to you but since you said the above, I think it's worth thinking about.
> 
> Just my $.02.


Oh yes, this was very clear to me while I was creeping the high pass up on the mids and getting better sound.....my thoughts were more like...... "dammit, all that work to get these nice big mids up high, and a damn 3.5 or 4 would probably be adequate". To be honest tho, I still enjoy the setup, it doesent bother me when driving, and I probably won't redo this car anymore, as I swore to myself this was it until the next ride.....lol. It's still cool, volume wise, having a 5.5" driver with 90db sensitivity, playing the mids in your face, I finally found a setup that I actually have to turn down occasionally instead of wishing for more when it just isn't there.........


----------



## seafish

I800C0LLECT said:


> I think what he's saying is that if "they" don't want the volume you can achieve impact with lower excursion and surface area/smaller displacement :laugh:
> 
> Not everybody wants to leave their vehicle a hot mess


ROTFLMAO…something like that!!


----------

