# Small Tapped Horn For a Car



## Patrick Bateman

A few months ago I published some plans for a pair of tapped horns. Thought I'd start this thread to document the second of the pair.

First, a little background. A tapped horn is an invention of Tom Danley, who also invented the Unity horn, which is also in my car. The tapped horn is something like a bandpass box, but with some enhancements:


Like a bandpass box, a tapped horn has a limited bandwidth
Like a bandpass box, a tapped horn is one of three enclosure types which physically filter 2nd and 3rd harmonic distortion
Like a vented or a bandpass box, a tapped horn has much lower excursion than a sealed box
Because it has lower excursion, a tapped horn generally has less distortion, higher power handling, and higher maximum SPL than a sealed box

Long story short, a tapped horn is complex, but worth the trouble if you're a fan of low distortion.

Here's a pic of the first of the pair of tapped horns; it's the second I've built. It's the one at the bottom.








Here are the plans.








One cool thing about tapped horns is that they're tolerant of a lot of different drivers. You can literally pop the woofer out, put another one in, and if the params are in the ballpark, it's going to work pretty darn well. The sound of the sub is dominated by the dimensions of the horn, not the woofer.

Not to say you can throw any ol' woofer in here, but as long as the parameters are *fairly* similar you'll be fine.

Bandpass boxes are *very* particular about woofers, if someone wants to know why I'll explain. Suffice it to say that one of the reasons that bandpass boxes often sound like **** is that they're not forgiving of errors.

Anyways, here are the plans for the SECOND tapped horn, which uses a pair of MCM 55-2421s instead of the P-Audio SN-12MB. The second tapped horn is 9.5" tall, instead of 12.5" tall. In other words, it's 25% smaller.








But don't build the second one, because I have a better one in store. Stay tuned.


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## thehatedguy

How low in the car are these capable of playing?

I haven't decided on what to do for subs in my car, and I loved the TH I had in the house.


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## fish

What are the "ballpark" parameters for a tapped horn?


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## Patrick Bateman

thehatedguy said:


> How low in the car are these capable of playing?
> 
> I haven't decided on what to do for subs in my car, and I loved the TH I had in the house.


The simple answer to that question is that I have built a tapped horn that plays down to 30hz in the car, using three eight inch subwoofers in a box that's less than three cubic feet.

Horns are almost the ideal enclosure. They have lower distortion than sealed or vented boxes, lower excursion, and power handling which is downright ridiculous. I have personally built a clone of Bill Fitzmaurice's Autotuba, loaded it with a woofer that's rated for 120 watts, and fed it EIGHT HUNDRED. It took it without breaking a sweat.

Here's a pic of the guts of a similar horn:



Everyone on the board has seen "woofer porn" where the cone is practically jumping out of the basket. Last night I powered up the new tapped horn, set it to a ridiculous volume, and the cone of the woofers was barely moving. Hell, the trunk lid was moving almost as much as the woofers were. (Gotta fix that!)

But here's the problem with horns, they're too big. You can reduce their size, but the frequency response goes to hell. To demonstrate how awful the response of a small horn is, here's a simulation of a one cubic foot horn using an MCM 55-2421 and powered with one watt.










Here's the response of the exact same woofer, in a tapped horn which is a similar size.









So what do these simulations show us?


The frequency response of both are atrocious
The box size for both is rather large. A cubic foot for an eight is a lot.
The boxes aren't easy to build. Take a look at that pic of the autotuba, it's way easier to build a sealed box
For all their problems, the excursion on the two boxes is very low, and the efficiency is very high. The efficiency of the tapped horn isn't as high as some people think it is, but the *excursion* of the tapped horn is a lot lower. Which is very important for car audio.

So all in all, a horn in a car just seems like an incredibly bad idea.

But here's the key - I believe the sims exaggerate the frequency response problems. In this thread I am going to demonstrate that horns measure better than the sims would have you believe.

In particular, *tapped* horns can be made to measure very flat, with a few tricks. In this thread I'll reveal what those tricks are.

Once you deal with the frequency response problem, you're left with a sub box which has astonishingly low excursion, and high efficiency. And those two things translate to higher power handling than anything else you can build, and lower distortion.


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## 60ndown

a subwoofer imo, only needs to work from 25-60hz (maybe even 30-50 only) if the fronts are strong.

post up plans 'paddie' of a small taped horn that can generate 120db @ 30 hz in a van, and ill build it


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## 12vTools

How does a TH allow a woofer that handles 120 watts to handle 800 ?
Are you talking about the physical excursion limits and not the eletrical limits the coil can handle?


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## 60ndown

g0a said:


> How does a TH allow a woofer that handles 120 watts to handle 800 ?
> Are you talking about the physical excursion limits and not the eletrical limits the coil can handle?


for a short time


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## thehatedguy

With dynamic music, the speaker would only see bursts of that much power for short short times.

Tapped horns are very cool. But you need the right speaker to go in them or the response goes all to hell.

The jump from 30 hertz to 20 is a pretty large one considering the additional lengths of the waves we are talking about.

I think looking at horns in 1/8th space would give you a rough idea on how they'll function in a car. But even in a car, you aren't really in 1/8th space since the car for purposes of bass is considered a constant pressure environment meaning there is no wave propagation happening at those frequencies. There "may be" some modal issues in the car though. I know I dismissed a multisub setup in the past ala Dr. Geddes's home approach, but there might be something to it in the car. I suspect it would be more important for bass 50-80 hertz range rather than subbass. And we could use this to our advantage because our ears localize bass so poorly to begin with.

I need to read more on eigenmodes in small rooms first.

But I suspect that if we had a small sub say a 10 in the front or near the front of the car and another one in the rear, we could get the impact and anchoring in the front from the one in the front and feel the rumble from the one in the rear. Get them aligned via time alignment, and I think it would be very awesome...and exponentially better than just 2 subs.

I did have this happen at IASCA Finals back in 04. Had a 10 in front and it wasn't doing the rumble very well. So we brought the 3 12s in the rear in, and I had the impact from the 10 in front, bass was anchored SOLIDLY in the front and the 12s in the back provided the rumble. Was pretty cool.


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## Patrick Bateman

g0a said:


> How does a TH allow a woofer that handles 120 watts to handle 800 ?
> Are you talking about the physical excursion limits and not the eletrical limits the coil can handle?


I could probably talk about SPL all day, so I'll do my best to keep this brief.

In the 90s the primary reason I couldn't get the SPL that I wanted was that I'd run out of amplifier power. So I learned how to build bandpass boxes to maximize efficiency, and made some good ones. My studies of bandpass boxes were what led me to learn about waveguides, since Geddes is the expert on both.

In the past ten years, amplifiers have become cheap and ubiquitous. Now the main thing that limits how much SPL I can generate is the loudspeaker, the alternator, and resonances in the car itself.

So that's one of the reasons this tapped horn exists. Basically the box with the lowest amount of excursion will win any SPL comparison.

After solving the excursion problem, we have to solve the thermal problem. Basically, how can we increase the thermal power handling of a loudspeaker?

In the tapped horn, there are two innovations which increase our power handling. First, let's look at the impedance of a woofer in a sealed box.








Of course we all know that the impedance of a woofer isn't flat. So a woofer that's "4 ohm" actually has a peak at resonance, and then falls below that. You can see that in the pic.

What that means for power handling is that the woofer will increasingly draw more current from the amplifier as the frequency goes lower. So at 60hz a sealed box is barely drawing any current, because of the high impedance, but at 30 hz, it's pulling nearly all the power it can get from the amplifier.

And of course the more current you draw from the amp, the hotter the voice coil gets. Which lowers our SPL, reduces our dynamics, and kills the woofer over time.








Here's the impedance curve of a commercial tapped horn, the TH-412. Here's what I see:


In the span of three and a half octaves, there are five impedance peaks
Because of those impedance peaks, the woofers in this sub are rarely seeing anything close to what the amplifier is producing
For instance, if our amplifier puts out ten thousand watts into a two ohm load, the only time this box will see all 10,000 watts is 29hz and at 58hz
At the impedance peaks, the woofers in the sub will only see a small fraction of that 10,000 watts... and there are FIVE peaks.
I believe that the "secret sauce" in the tapped horns that have been built in the past year is that using multiple woofers smooths out the response, and broadens those impedance peaks
Tapped horns are unique in this respect. If you put three woofers into a sealed box, the impedance curve will not look any different than if they have their own chambers. But the impedance curve of a tapped horn changes because the woofers are interacting with each other inside the horn

Anyways, you probably weren't expecting me to write a book for an answer. I hope this post demonstrates why feeding a 125 watt sub with 800 watts isn't such a bad idea... And how we can generate ridiculously high SPL with a $35 subwoofer in a 3cf box.

Stay tuned for more info over the next few weeks.


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## Oliver

For subwoofer frequencies , 3 of those peaks are null and void.

If you cross it from 80Hz down.

It will have to deal with some serious amperage from about 25Hz to 39Hz though.


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## grecon144

Hello Patrick,
I actually just ordered two 55-2421 today for a car sub project and now have read with interest about your dual 8 TH. Thanks for sharing your project here. How do you think it might compare to a BFM dual8 TAT or the JBell dual T18?
Thanks


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## Brian Steele

Interesting thread so far.

Concerning THs, the two problems I've found theoretically with THs in car are 

(1) apparently a simple transfer function calculation to predict the effect of cabin gain doesn't work as well as it does for simple "direct radiator" alignments.

(2) while efficiency goes up, peak SPL is still very dependent on driver Vd. Don't expect miracles.

(3) while it might a be an efficient use of a driver, it may not be an efficient use of the volume occupied by the box. 3 cu.ft. box for a TH on an 8" driver? You can fit three 12's in that same volume. It will be easier to build and go down to single digit frequencies at significant SPL levels in-car.


As for that 66Hz ~ 79 Hz "notch" - yes, I've noticed that too. Most annoying...


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## thehatedguy

What about dual reflex ported enclosures? Group delay go all to hell? They seem to be one of the best ways to eek out the most performance for a given foot print.


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## Patrick Bateman

Brian Steele said:


> Interesting thread so far.
> 
> Concerning THs, the two problems I've found theoretically with THs in car are
> 
> (1) apparently a simple transfer function calculation to predict the effect of cabin gain doesn't work as well as it does for simple "direct radiator" alignments.
> 
> (2) while efficiency goes up, peak SPL is still very dependent on driver Vd. Don't expect miracles.
> 
> (3) while it might a be an efficient use of a driver, it may not be an efficient use of the volume occupied by the box. 3 cu.ft. box for a TH on an 8" driver? You can fit three 12's in that same volume. It will be easier to build and go down to single digit frequencies at significant SPL levels in-car.
> 
> 
> As for that 66Hz ~ 79 Hz "notch" - yes, I've noticed that too. Most annoying...


I really wanted to "hold off" on showing the results that I am getting with the new sub that I've built. I think this new tapped horn has fixed many of the problems with the tapped horn technology. The new design smooths the horns response, and increases it's bandwidth.

But I couldn't resist posting the results of my work, since you noted there are notches in the tapped horns response.

I would like to demonstrate that those notches do not exist "in the real world..."








This is the predicted response of the tapped horn that I built. I measured the actual finished horn, down to the quarter inch, so these results SHOULD match our results "in the real world."

Note that big fat 12db peak at 180hz, preceded by a six DB dip.








This is the measured response of the tapped horn above, measured outside. Pretty darn smooth huh? 

Admittedly, I used smoothing on the graph, since a lot of sub manufacturers do that too...








Here's the same response as above, without the smoothing. IMHO, this is still excellent. It's +/- three db over nearly three octaves.

The peak and the dip in the simulation is there in the real world, but it's much more benign than the simulation predicts. The 12db peak at 180hz is a 3db peak at 200hz "in the real world."

Combine that with the cabin gain of the average car, and it will cover close to four octaves...








For the sake of comparison, here's the response of the NEW tapped horn (purple line), the LAST tapped horn (dark red line), and a front-loaded horn I built in 2007 (red line).

You can read about those subs here:

The Smallest Tapped Horn - diyAudio (dark red line)

Free Horn Sub Design (sorta.) - Page 2 - CARSOUND.COM Forum (red line)

PLEASE NOTE THE LEVELS AREN'T RELATIVE.

The last two subs were measured at the same distance, but I had to measure the new sub at a closer range.

AND

The new sub isn't even finished. The response will improve once I make a few tweaks to it.

The new sub is about 90% finished - I wanted to demonstrate how flat we can make a tapped horn.

Also, big kudos to Tom Danley. It wasn't MY idea to use multiple subs. I just noticed that he's been doing that lately, and had a hunch that it would smooth the response. (and obviously, it DOES.)


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## savagebee

this looks like it has been a really good experiment, but Im still thinking more drivers in a smaller enclosure may be a better bet. I know youre not done yet, so this may not be the case, but it seems like a ton of work for no gain, what about getting a graph of the same driver in a proper qtc enclosure so we could compare the two?

or maybe I missed it and its already here

thanks you for the work youve been doing and posting everything up here, I love the experimentation


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## Brian Steele

Patrick Bateman said:


> I would like to demonstrate that those notches do not exist "in the real world..."


I was referring to the notch caused by the car's cabin dimensions, not the notches in the TH's raw response. An easy way to deal with those TH notches, well, it worked for my tapped-pipe, is to simply stuff part of the enclosure, then filter the rest with a LP filter. The stuffing is basically transparent at low frequencies, but increasingly attenuates at higher frequencies. The effective path length is also increased a bit - usually a good thing .




Patrick Bateman said:


> Also, big kudos to Tom Danley. It wasn't MY idea to use multiple subs. I just noticed that he's been doing that lately, and had a hunch that it would smooth the response. (and obviously, it DOES.)


I suspect other factors behind the multiple small drivers are to keep total Vd high without having to settle for the lower Fs of a larger driver, and to improve power handling. Using multiple drivers also provides a bit more flexibility in the TH design as far as dimensions are concerned. The down side of course is increased cost.


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## Brian Steele

thehatedguy said:


> What about dual reflex ported enclosures? Group delay go all to hell? They seem to be one of the best ways to eek out the most performance for a given foot print.


They are more complex to construct than a simple sealed or vented alignment (particularly if you want to minimize the use of available space in the car by building a molded enclosure), and they usually require more internal volume to implement as well. For the novelty factor, they're right up there with THs and other "exotic" alignments, but from the perspective of wanting maximum benefits while giving up minimum space in the process, they're worse than sealed, vented and 4th order BP alignments.


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## Electrodynamic

So you're only gaining 3 dB by placing your tapped horn in a car vs. outside a vehicle? Shouldn't your narrow-bandwidth alignment be +10 dB over a typical broad-band car audio alignment to support your efficiency / horn alignment in a car audio environment?


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## Patrick Bateman

Brian Steele said:


> They are more complex to construct than a simple sealed or vented alignment (particularly if you want to minimize the use of available space in the car by building a molded enclosure), and they usually require more internal volume to implement as well. For the novelty factor, they're right up there with THs and other "exotic" alignments, but from the perspective of wanting maximum benefits while giving up minimum space in the process, they're worse than sealed, vented and 4th order BP alignments.


I built a ton of dual reflex boxes back in the 90s, and could never get them to sound "correct." The measurements looked good, but the boxes sound wonky.

Tapped horns are the opposite - I've found that the frequency response measurements are a bit frightening, but the sound is remarkable.

Did you notice that Bose stopped selling their funky triple chamber bandpass boxes? And now they're selling transmission lines?

I have a feeling they came to the same conclusion that you did, which is that double and triple reflex bandpass boxes sound weird.


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## Patrick Bateman

grecon144 said:


> Hello Patrick,
> I actually just ordered two 55-2421 today for a car sub project and now have read with interest about your dual 8 TH. Thanks for sharing your project here. How do you think it might compare to a BFM dual8 TAT or the JBell dual T18?
> Thanks


What is a "BFM dual8 TAT"?


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## digital

Patrick Bateman said:


> What is a "BFM dual8 TAT"?


Bill Fitz Maurice's Tapped AutoTuba perhaps?


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## grecon144

Hello Patrick,
I was starting a car subwoofer project using two 55-2421.
I had intended on building a dual 8 autotuba referred to as the 
Tall Auto Tuba(TAT,20x22x17) or pehaps the jbell dual tuba18, when I ran across your dual 8 TH design. 
As your TH appears smaller, I was trying to compare other differences in these designs. 
Any thoughts on this would be appreciated.
Thanks, 
grecon144


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## Patrick Bateman

grecon144 said:


> Hello Patrick,
> I was starting a car subwoofer project using two 55-2421.
> I had intended on building a dual 8 autotuba referred to as the
> Tall Auto Tuba(TAT,20x22x17) or pehaps the jbell dual tuba18, when I ran across your dual 8 TH design.
> As your TH appears smaller, I was trying to compare other differences in these designs.
> Any thoughts on this would be appreciated.
> Thanks,
> grecon144


I have a clone of an Autotuba sitting in my garage. It's not *exactly* the same. I basically found a pic of one on google images, and figured out the dimensions, and built it.

If you can wait a day or so, I'll finish of the triple-8 tapped horn, and pit them head-to head.

That will show you the efficiency of both, frequency response, etc...

The response graphs that I've posted are of an unfinished version. I haven't glued on the side of the box. When I did that measurement I weighed the box down with 200lbs of sod on the unglued panel.

Even with 200lbs of weight, it will still leak a bit. It has to be 100% airtight to go down to 40hz.

In the car we should get 30hz.


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## Patrick Bateman

I still need to post the plans for the new sub. In the meantime, if anyone has some Image Dynamics ID8s lying around, they make an awesome match for this sub. With a pair of these you lose a little bit of efficiency over the MCM, but the simulated response is flatter and they can gobble up 600 watts without breaking a sweat, because they have double the excursion.

With a high pass filter, you could probably get away with 1000 watts at 4 ohms.

I've attached a pic.


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## thehatedguy

I have a few.


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## Patrick Bateman

If you don't want to read the whole thread, here's a summary of it:

I've built a few tapped horns, and I've noticed that the computer simulations are a lot rougher than how they measure in the real world. I built a tapped horn a few months ago which is quite similar to the Danley TH-Mini. If you're not comfortable building crazy enclosures, I'd highly recommend BUYING the TH-Mini - it's a great box.

Someone on this forum noted that my TH-Mini clone has limited bandwidth, due to the notch between 100hz and 200hz. I think the notch has some benefits - it reduces 2nd and 3rd harmonic distortion.

But if you don't want the notch, and you want a sub that has more excursion, this one's for you.

This one uses three eight inch woofers, the MCM 55-2421. Personally I used three woofers because I can run two off my stereo channels, and one off my sub amp. That maximizes my SPL while using a minimum number of channels.







If you want to build one yourself, here are the plans for the twelve.

The sub with triple eights is EXACTLY the same, with three exceptions:

The box with the twelve is 12.5" across; the box with the eights is 8.5" across
The box with the eights is designed to play a lot lower than the box with the twelve. Yes, most people think a twelve would play lower, but in this case, the eights do. The twelve is a lot more efficient.
I didn't design the second box on the computer, I just did it by eyeball. So if you want to build this, you'll have to make some guesstimates on the dimensions. The footprint is 24" x 24". The measurements in the simulation from a few days ago are 100% accurate; I measured the box dimensions after I built it.


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## Patrick Bateman

Here's some older pics of the enclosures coming together.









Wine bottles work great when you're building horns, they keep the panels vertical 









You might notice that the TH-Mini uses a humongous flare at the mouth - simulations indicate the flare flattens response at the expense of low end efficiency










I glue the side panels in strips, to make sure it's perfectly sealed. I apply two hundred pounds of weight to the enclosure to seal it. Ideally I'd use 500 or a thousand, need to buy more weights...

















I made an Akabak model of the tapped horn with multiple woofers. At the top is a sim with one woofer; at the bottom with two. You can see the dual woofer design has wider bandwidth and is smoother. Akabak is the only program which can model things like this.


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## Brian Steele

Man, that's one complicated enclosure. Ensuring that there are no gaps where the internal sections meet the side panels must be a nightmare.

BTW, Sd seems to decrease in the foldings near the bottom center section of the enclosure, but this isn't reflected in your sims.


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## Patrick Bateman

Brian Steele said:


> Man, that's one complicated enclosure. Ensuring that there are no gaps where the internal sections meet the side panels must be a nightmare.


Hmmm, you think so? You should try building a lab sub! Front-loaded horns have a sealed section INSIDE the horn, along with a coupling chamber. Now THAT'S a p.i.t.a.

Without a doubt, the stupidest mistake that I made when I built this thing was that I didn't "true up" all the internal pieces. Don't even *think* about building this thing if you don't have a table saw.

Anyways, I set the gate on the table saw to 8.5", and then started assembling it.

That was a big mistake - I should have set it to 8.75", then ran all the pieces back through the table saw a second time with it set to 8.5".

Doing it that way insures that all the pieces are the exact same height.

Because I didn't do that, I literally spent HOURS grinding down a few pieces with an angle grinder and a file. Just a MISERABLE p.i.t.a.

Anyways, if you set up your table saw properly, the whole thing can be built in three or four hours. The outer shell is a plain ol' box, and the internal pieces can be set by eyeball. A 1/4" here or there isn't a deal breaker.




Brian Steele said:


> BTW, Sd seems to decrease in the foldings near the bottom center section of the enclosure, but this isn't reflected in your sims.


That's true. No joke, I literally changed the layout by eye, just added a couple of extra folds. The original box was done in Xara, where I had the flexibility of moving pieces around. Then again, the original version took about eight hours to lay out, and these mods took less than an hour.

Check out the measured results that I'll post in the next few days. I think you'll see that the most important aspects of tapped horn design involve the design of the mouth, design of the throat, and length of the line. What happens between the throat and the mouth isn't particularly important, yet that's the part of a horn that everyone obssesses over. Mouth termination is key.


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## chithead

Subscribed to a thread of yours yet again!


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## Brian Steele

Patrick Bateman said:


> Check out the measured results that I'll post in the next few days. I think you'll see that the most important aspects of tapped horn design involve the design of the mouth, design of the throat, and length of the line. What happens between the throat and the mouth isn't particularly important, yet that's the part of a horn that everyone obssesses over. Mouth termination is key.


I'm looking forward to those results. Will you be including results that speak to the design's SPL capability? I'd be particularly interested in those, as I'm concerned that, while a TH may be an efficient alignment for a driver, it may not be the most efficient use of volume - a factor that's quite important for most car audio installations. 

Another thing - did you measure the t/s parameters of those drivers to confirm that they meet published specs?


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## Patrick Bateman

Brian Steele said:


> I'm looking forward to those results. Will you be including results that speak to the design's SPL capability? I'd be particularly interested in those, as I'm concerned that, while a TH may be an efficient alignment for a driver, it may not be the most efficient use of volume - a factor that's quite important for most car audio installations.


I don't have any way to measure sensitivity - I need an SPL meter. It's on the "to-do" list.

Having said that, I *do* have the ability to measure a bunch of subs at the same volume. That allows us to compare the efficiency of various boxes.

As promised, I have completed measurements of this tapped horn, the 12" tapped horn, and my clone of an Autotuba.

The results are interesting.

On the forums here, we see a lot of people arguing over what subwoofer is the "best." But my measurements confirm something that Dan Wiggins has been saying for years, which is that efficiency is virtually meaningless below a certain frequency. In the last couple of octaves, the only thing that really matters is displacement. Box size is irrelevant, woofer efficiency is irrelevant. The only real priority in the last octave is minimizing excursion and insuring that the voice coil doesn't burn up.

Keep in mind, that last paragraph is a good reason to run a sealed sub! So it doesn't help my case any.

But I think the measured results will demonstrate that my triple eight tapped horn has an excellent combination of high excursion, high power handling, small size, and smooth response.

If your only priority is 20-40hz, it's not the box for you. But if music is the priority, that triple-8 tapped horn is tough to beat from 40hz and up.



Brian Steele said:


> Another thing - did you measure the t/s parameters of those drivers to confirm that they meet published specs?


MCM used to sell them for $25 a pop in lots of ten. I bought ten, measured the Thiele/Small parameters of all ten, and sold a pair that were a little out-of-spec.

That's another good reason to buy a Woofer Tester - you can buy drivers in volume, and sell the out-of-spec ones on Ebay.

Keep in mind, I wasn't ripping anyone off, they all measured within 10% of each other. But there were a couple that were a bit high on the FS spec.


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## Patrick Bateman

Someone in the thread asked me about The Autotuba. Since I'll be posting my own measurements of a clone, I thought I'd link to someone elses measurements. It helps to compare and contrast.

Autotuba measurements, plus shiva [Archive] - diyAudio










The yellow line, an Adire Audio Shiva, was NOT measured at the same volume. So you can compare the F3 and the smoothness of the curves, but not the efficiency.

Read the whole post for details...


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## Brian Steele

Patrick Bateman said:


> I don't have any way to measure sensitivity - I need an SPL meter. It's on the "to-do" list.




I wasn't referring to sensitivity or efficiency, but peak SPL capability. IOW, how loud can it go before distortion becomes an issue (audible changes in tone). 

As that can be subjective, perhaps an objective measurement may be more revealing. SPL and distortion measurements @ higher input power, for example.




Patrick Bateman said:


> But my measurements confirm something that Dan Wiggins has been saying for years, which is that efficiency is virtually meaningless below a certain frequency. In the last couple of octaves, the only thing that really matters is displacement. Box size is irrelevant, woofer efficiency is irrelevant. The only real priority in the last octave is minimizing excursion and insuring that the voice coil doesn't burn up.


Well, that is almost true. If the input power is high enough, the driver's parameters shift significantly, and this is more likely to happen with systems with lower efficiency. Consider for an extreme example a 60dB/1W/1M 12" driver in a 1 cu.ft. box. Yup, you can get likely get real low with that, but you'll likely burn up the coil before you get any appreciable output .


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## Patrick Bateman

Patrick Bateman said:


> I really wanted to "hold off" on showing the results that I am getting with the new sub that I've built. I think this new tapped horn has fixed many of the problems with the tapped horn technology. The new design smooths the horns response, and increases it's bandwidth.
> 
> But I couldn't resist posting the results of my work, since you noted there are notches in the tapped horns response.
> 
> I would like to demonstrate that those notches do not exist "in the real world..."
> 
> 
> 
> 
> 
> 
> 
> 
> This is the predicted response of the tapped horn that I built. I measured the actual finished horn, down to the quarter inch, so these results SHOULD match our results "in the real world."
> 
> Note that big fat 12db peak at 180hz, preceded by a six DB dip.
> 
> 
> 
> 
> 
> 
> 
> 
> Here's the measured response of the triple-8 tapped horn. This was measured without gluing the last panel. It's being held in place with 200lbs of weights and modeling clay to seal the gaps. It will still leak a bit.
> 
> The peak and the dip in the simulation is there in the real world, but it's much more benign than the simulation predicts. The 12db peak at 180hz is a 3db peak at 200hz "in the real world."
> 
> Combine that with the cabin gain of the average car, and it will cover close to four octaves...
> 
> 
> 
> 
> 
> 
> 
> 
> For the sake of comparison, here's the response of the NEW tapped horn (purple line), the LAST tapped horn (dark red line), and a front-loaded horn I built in 2007 (red line).
> 
> You can read about those subs here:
> 
> The Smallest Tapped Horn - diyAudio (dark red line)
> 
> Free Horn Sub Design (sorta.) - Page 2 - CARSOUND.COM Forum (red line)
> 
> PLEASE NOTE THE LEVELS AREN'T RELATIVE.
> 
> The last two subs were measured at the same distance, but I had to measure the new sub at a closer range.
> 
> AND
> 
> The new sub isn't even finished. The response will improve once I make a few tweaks to it.
> 
> The new sub is about 90% finished - I wanted to demonstrate how flat we can make a tapped horn.
> 
> Also, big kudos to Tom Danley. It wasn't MY idea to use multiple subs. I just noticed that he's been doing that lately, and had a hunch that it would smooth the response. (and obviously, it DOES.)











Here's the "final" frequency response of the triple-8 tapped horn. Like the last graph, purple is the triple-8. The red line is an Autotuba clone (in this graph.)
​
Here's some thoughts on this:


As I see it, the ideal car subwoofer has response which is flat from about 40 to 80hz. When you combine that with cabin gain, you get in-car response for two octaves.
The triple-8 tapped horn is flat from 50hz to 500hz - about three and a half octave.
The triple-8 tapped horn measures +/- 5db.
If you EQ'd out the peak at 180hz, it would measure +/- 2db. That's excellent performance for a sealed box, but for a horn, it borders on the absurd.
The measurement of my Autotuba "clone" is consistent with the measurements of it's creator. I have a feeling that the measurements from diyaudio are suspect. There isn't a big dip at 55hz in mine, or Bills.
My box is waaaaaay smaller than the autotuba
The bandwidth of the autotuba is much narrower. This is normal for a front-loaded horn. The horn acts as a low pass filter, and reduces distortion.
At 60hz, where you really want a subwoofer to kick like a mule, the triple-8 tapped horn has an advantage of nearly 10db over a front-loaded horn
Here's the part where everyone is going to freak out: *The woofers in the tapped horn are wired in parallel.* Yes, this draws more current. Because the impedance peaks of the tapped horn are staggered, we can get away with a wiring scheme which isn't practical with a conventional horn, a sealed box, a vented box, or a bandpass. I'll measure the impedance in the next day or two, and you'll see what I mean. All the impedance "troughs" are staggered, due to pathlength differences for each woofer.


----------



## Brian Steele

Patrick Bateman said:


> [*]If you EQ'd out the peak at 180hz, it would measure +/- 2db. That's excellent performance for a sealed box, but for a horn, it borders on the absurd


If you stuff the first half or so of your TH, that should take care of the peaks and dips in that area of the response curve.


----------



## Brian Steele

Patrick Bateman said:


> [*]At 60hz, where you really want a subwoofer to kick like a mule, the triple-8 tapped horn has an advantage of nearly 10db over a front-loaded horn
> [*]Here's the part where everyone is going to freak out: *The woofers in the tapped horn are wired in parallel.*


Did you adjust input voltage to compensate? 

Your graphs may be showing sensitivity, rather than efficiency. You may be seeing a 10dB increase @ 60 Hz, but that might be partly due to the TH's higher sensitivty (due to its low impedance), rather than efficiency.


----------



## Patrick Bateman

Brian Steele said:


> Did you adjust input voltage to compensate?
> 
> Your graphs may be showing sensitivity, rather than efficiency. You may be seeing a 10dB increase @ 60 Hz, but that might be partly due to the TH's higher sensitivty (due to its low impedance), rather than efficiency.


No. I set the gains to get a good clean measurements of the Triple-8, measured it, then repeated the process with the AutoTuba clone. Mic and sub locations were identical, and I didn't touch a single setting anywhere.

Admittedly, the Triple-8 has a lower impedance, and will draw more current.

*If the impedance curves of the two subwoofers are identical, the AutoTuba has a 4.8db handicap, because it's a 4ohm woofer*

But that's a big "if".

The triple-8 was specifically designed to stagger the impedance troughs, and provide the efficiency of a front loaded horn with the response smoothness of a sealed box, in an enclosure comparable to a vented box...

But with better group delay, excursion, and phase response


----------



## bgavin

Excellent thread, thanks for posting the link on Bills' board.

My AT test results do not show the big dip above 40 Hz. 

I don't know if the AT measurement shown here was taken in-vehicle or not.
My were taken outdoors, groundplane.

OP, you might consider using thinner wood and more bracing for your complex builds. PL Premium Polyurethane is mandatory, to avoid leaks. I'm using 3/8" baltic birch for most of my projects, and 1/4" BB for internals that do not mount drivers. Just something to consider for weight avoidance.

I'm a pro sound guy, not mobile audio, so I am looking forward to more of this thread. Very enjoyable.


----------



## marstedt

Patrick Bateman said:


> Here's some thoughts on this:
> ...
> [*]My box is waaaaaay smaller than the autotuba


*Your *box is smaller? Which box? Smaller than what? I read this a few ways.

1. Your version of the Autotuba is waaaaaay smaller than a *stock *Autotuba.
2. Your tripple-8 TH is waaaaaay smaller than *your *Autotuba.
3. Your tripple-8 TH is waaaaaay smaller than a *stock *Autotuba.

Hmmmm ........ ?

For size reference, here's the pic from diyAudio of the Tripple-8TH, Autotuba, 12TH:


----------



## digital

BFM's Autotuba is around 4 ft^3.
PB's tripple-8 TH is around 2.8 ft^3

That tripple-8 TH looks very nice PB!


----------



## ryan s

Potentially stupid question, and I probably already know the answer...

Is there an optimal loading location for these enclosures? Where should the "mouth" face? Against a trunk wall, into the seat, into the trunk...

We both have Accords, Patrick, even though they're different years  Where do you place your box?


----------



## Patrick Bateman

ryan s said:


> Potentially stupid question, and I probably already know the answer...
> 
> Is there an optimal loading location for these enclosures? Where should the "mouth" face? Against a trunk wall, into the seat, into the trunk...
> 
> We both have Accords, Patrick, even though they're different years  Where do you place your box?


With subwoofers, direction *definitely* matters. I measured the response in the car, and it was smoother facing backwards. Facing forwards, a notch appeared around 100hz.

At the moment I'm running two of the eights full-range, and the third one is low passed at 40hz. So basically when the response starts to fall off below 40hz, the third sub "kicks in" to fill in the gap.


----------



## Patrick Bateman

marstedt said:


> *Your *box is smaller? Which box? Smaller than what? I read this a few ways.
> 
> 1. Your version of the Autotuba is waaaaaay smaller than a *stock *Autotuba.
> 2. Your tripple-8 TH is waaaaaay smaller than *your *Autotuba.
> 3. Your tripple-8 TH is waaaaaay smaller than a *stock *Autotuba.
> 
> Hmmmm ........ ?
> 
> For size reference, here's the pic from diyAudio of the Tripple-8TH, Autotuba, 12TH:


My triple-8 tapped horn is 3.17cf on the outside. My clone of the autotuba is the same size as the "real" one, I just moved the mouth to the center of the enclosure so I could use the pass-thru in the car. It's 3.89cf, or 23% bigger than the triple-8.


----------



## Patrick Bateman

bgavin said:


> Excellent thread, thanks for posting the link on Bills' board.
> 
> My AT test results do not show the big dip above 40 Hz.
> 
> I don't know if the AT measurement shown here was taken in-vehicle or not.
> My were taken outdoors, groundplane.
> 
> OP, you might consider using thinner wood and more bracing for your complex builds. PL Premium Polyurethane is mandatory, to avoid leaks. I'm using 3/8" baltic birch for most of my projects, and 1/4" BB for internals that do not mount drivers. Just something to consider for weight avoidance.
> 
> I'm a pro sound guy, not mobile audio, so I am looking forward to more of this thread. Very enjoyable.


The scale of your graph makes the rolloff look smoother, but it's quite similar. Yours is showing a rolloff of 14db/octave from 40 to 20hz. Mine is showing a rolloff of 18db/octave from 40 to 20hz.

My mic isn't calibrated - I've heard the ECM8000 loses about 3db at 20hz. If yours is calibrated, that could explain the 4db difference.

Anyways, thanks for the info! Good to see people measuring these.

You're going to freak when you see the in-car measurements, they're ridiculous. I just got back from the audio fest on Mercer Island, so I should probably get some sleep before i post those 

(it's 5:43am here.)


----------



## bgavin

The Autotuba is not intended to go below 40 Hz.
The quarter wave horn path is 210cm, which is a 41 Hz cutoff.
Since the horn is conical, it doesn't really have a "cutoff" per se, and continues to perform (poorly) below 41 Hz.

It was designed specifically to use cabin gain.

I have seen and measured a friend's AT Six Pack, which consisted of six AT with HL10c drivers, multiple amps, all drivers in parallel.
The noise was staggering, and at 20 volts.

AT is also a pretty old design.
Bill has moved on (considerably) since then.
The EXP-8 shown in the same measurement, is my own design that I use for home theater. 
It beats the AT quite handily under the same test environment. 
Mine is a 35 Hz design and a true hyperbolic flare.
Both use the MCM 55-2421 driver.


----------



## grecon144

Are the plans for your EXP-8 available for public use?
thanks


----------



## bgavin

No, they are not available.


----------



## digital

bgavin said:


> No, they are not available.


Are they available for purchase, just like AT?


----------



## TJ Mobile Audio

@ Patrick Bateman,

I have a few questions about your design. 

First, I'm wondering about all those 180° bends. Most of my designs are ported or T-line enclosures, and perhaps I'm superstitious but I've always tried to limit the number of 180° bends. Is this a concern at all with tapped horns?

Second, you mentioned this:


Patrick Bateman said:


> This one uses three eight inch woofers, the MCM 55-2421. Personally I used three woofers because I can run two off my stereo channels, and one off my sub amp. That maximizes my SPL while using a minimum number of channels.


which made me wonder if all three speakers are getting the same amount of power, the same signal, etc, and how you can control this. Perhaps I misunderstood.

Thanks in advance, and I'm looking forward to the impedance plot!


----------



## bgavin

Bends become problematic when the difference between the inner and outer arc radius is 1/2 wavelength. This introduces a severe notch into the response.

This is not a problem with subwoofers.
For example, this is 67 inches at 100 Hz.
If you had a 180 bend with a 67 inch outer arc length, you would have a notch at 100 Hz.
This is a very large bend.

This is why folded horns operating in the midrange often use a split path ("W" bin style) because the radii can be kept smaller.


----------



## Patrick Bateman

TJ Mobile Audio said:


> @ Patrick Bateman,
> 
> I have a few questions about your design.
> 
> First, I'm wondering about all those 180° bends. Most of my designs are ported or T-line enclosures, and perhaps I'm superstitious but I've always tried to limit the number of 180° bends. Is this a concern at all with tapped horns?
> 
> Second, you mentioned this:
> 
> which made me wonder if all three speakers are getting the same amount of power, the same signal, etc, and how you can control this. Perhaps I misunderstood.
> 
> Thanks in advance, and I'm looking forward to the impedance plot!


As "bgavin" noted, 180 degree bends are no big deal in a subwoofer, due to the very long wavelengths.

As for the use of varying amounts of power on the three woofers, that was one of my "tricks" with this design. When you design a horn, the smaller you make the box, the peakier the response becomes, and the F3 goes up too. So the "trick" is that you can stagger the power, so that the additional woofers come "online" as you need higher SPL.

So at low power, you have a lower F3 than at higher power, and smoother response.

Kind of neat huh? 

Note that ALL three must be connected to an amplifier channel. Otherwise the unpowered woofers will become passive radiators.


----------



## TJ Mobile Audio

bgavin said:


> Bends become problematic when the difference between the inner and outer arc radius is 1/2 wavelength. This introduces a severe notch into the response.
> 
> This is not a problem with subwoofers.
> For example, this is 67 inches at 100 Hz.
> If you had a 180 bend with a 67 inch outer arc length, you would have a notch at 100 Hz.
> This is a very large bend.
> 
> This is why folded horns operating in the midrange often use a split path ("W" bin style) because the radii can be kept smaller.


That makes sense, I probably learned that at some point and forgot.



Patrick Bateman said:


> As "bgavin" noted, 180 degree bends are no big deal in a subwoofer, due to the very long wavelengths.
> 
> As for the use of varying amounts of power on the three woofers, that was one of my "tricks" with this design. When you design a horn, the smaller you make the box, the peakier the response becomes, and the F3 goes up too. So the "trick" is that you can stagger the power, so that the additional woofers come "online" as you need higher SPL.
> 
> So at low power, you have a lower F3 than at higher power, and smoother response.
> 
> Kind of neat huh?
> 
> Note that ALL three must be connected to an amplifier channel. Otherwise the unpowered woofers will become passive radiators.


And an amplifier with good damping, I assume. What about using a design similar to this, with DVC subs, for instance. Two could be wired at 8 ohms, and one at 2 ohms; the 2 ohm one would just use a lot more power, and it could all be done on a single channel. Nominal impedance would be 1.3 ohms, but with the impedance humps the measurement would probably be much higher. Do you think that setup would introduce other problems?


----------



## thehatedguy

Wiring subs like that would be a very bad idea.


----------



## TJ Mobile Audio

thehatedguy said:


> Wiring subs like that would be a very bad idea.


Well, I know it's not general practice, and that the 2-ohm speaker would take a lot more power. However, he said he wanted one sub to use more power than the other two, so I don't see the real problem. I'm not disagreeing, but would you care to elaborate?


----------



## thehatedguy

You are a professional, something like that shouldn't have to be explained to you.


----------



## Patrick Bateman

TJ Mobile Audio said:


> That makes sense, I probably learned that at some point and forgot.
> 
> 
> 
> And an amplifier with good damping, I assume. What about using a design similar to this, with DVC subs, for instance. Two could be wired at 8 ohms, and one at 2 ohms; the 2 ohm one would just use a lot more power, and it could all be done on a single channel. Nominal impedance would be 1.3 ohms, but with the impedance humps the measurement would probably be much higher. Do you think that setup would introduce other problems?


The only real way to know is to actually build it and measure it. With three woofers in parallel, my "Triple-8" subwoofer should have an impedance of 1.2 ohms. But at it's lowest point, the impedance is over 2ohms. So the mass of air in the horn and the staggered impedance peaks are raising the impedance minimum.

You should see the impedance curve of the autotuba, it's ridiculous... Horn loading is nearly doubling the impedance minimum. It's well over 8 ohms. (the woofer has an RE of 3.6 ohms.)

I think this is something that I overlooked when building horns; even if the efficiency is no better than a sealed box, the power handling goes through the roof due to the reduction in excursion and a reduction in the current that's being drawn from the amplifier. It explains why I was able to feed the Autotuba clone with 800watts, when the woofer is rated for 125. (Due to the higher impedance, the amp was putting out 800watts; I did not know this until I saw the impedance curve.)

I'll post more measurements soon...


----------



## blamus

What an amazing thread patrick. I only just started reading into horns and began to research into Bill's tuba designs. This cleared up a lot of confusion I had about horns, however there are a few questions I have:

1. You mentioned that tapped horns are mainly dependent on the horn design itself rather than the driver chosen, and many drivers will "fit" a certain horn design. How does one choose a good driver based on its T/S for horn building? How does each T/S spec relate to the resultant horn? I have a ton of drivers lying around, how can I tell which one is suitable for your designs? What parameters are important?

2. Are Bill's tubas referred to as "front loaded horns", which have their rear chamber sealed in a very small space, and the driver is in the heart of the box, while your designs are "tapped horns" with the back of the driver close to the mouth of the horn? What are their differences fundamentally? how does one choose which design for what situation?

3. Generally speaking, how much more output will a driver put into a horn like yours have compared to just being in a sealed or ported box? Say, between 30-80Hz. 10dbs?

To be perfectly honest with you, I am not planning to put a horn in my car. One extremely important aspect of a sealed alignment is that you can use make the enclosure whatever shape you want and do stealth installs making the vehicle actually a practical tool in everyday life as opposed to a moving subwoofer! However, I'm definitely thinking about building a tapped horn for home theater use, where space is not of a real concern, while output is. I'm going to keep my eye on this thread to keep learning about horn design, and hopefully will be able to apply it to a HT horn that I want to eventually build.


----------



## mwmkravchenko

Patrick Bateman said:


> As "bgavin" noted, 180 degree bends are no big deal in a subwoofer, due to the very long wavelengths.
> 
> As for the use of varying amounts of power on the three woofers, that was one of my "tricks" with this design. When you design a horn, the smaller you make the box, the peakier the response becomes, and the F3 goes up too. So the "trick" is that you can stagger the power, so that the additional woofers come "online" as you need higher SPL.
> 
> So at low power, you have a lower F3 than at higher power, and smoother response.
> 
> Kind of neat huh?
> 
> Note that ALL three must be connected to an amplifier channel. Otherwise the unpowered woofers will become passive radiators.


This is a bit confusing!

How can you claim that you are creating power tapering? All three drivers are connected. They all see the same air mass in the horn at the same time as they are acting as a single large surface area driver that is distributed over the horn throat area. I think this is what is giving you a smooth response and is a good design concept.

And second isn't a 1.6 ohm load a bit on the dangerous side. Not all car amps like a load that low. Especially when you run the simulation where most of the bass action is you have the largest current draw as the impedance is almost 1.6 ohms. Pretty near a dead short.

I have but one other comment. The box you made that you label the Autotuba is nowhere near the volume that Fitzmaurice used. I know I built one from the Speaker builder article a way back. I listened to it for years and I understand what it does well and what it does not. But as for it's SPL capability it rocks. I used a cheap pioneer driver in it and I was getting SPL at 104 db/watt. 

Any tapped horn I have built or designed will not get you a true 10db of gain. 6 to 8 db for sure. A shorter path length for sure. But not a greater SPL capability. 

I did head to head simulations of horns with the same driver and a different layout. Front loaded against tapped horn. The front loaded wins in SPL/watt every time.

Mark


----------



## Patrick Bateman

mwmkravchenko said:


> This is a bit confusing!
> 
> How can you claim that you are creating power tapering? All three drivers are connected. They all see the same air mass in the horn at the same time as they are acting as a single large surface area driver that is distributed over the horn throat area. I think this is what is giving you a smooth response and is a good design concept.
> 
> And second isn't a 1.6 ohm load a bit on the dangerous side. Not all car amps like a load that low. Especially when you run the simulation where most of the bass action is you have the largest current draw as the impedance is almost 1.6 ohms. Pretty near a dead short.


Like all good inventions, I stumbled upon this one by accident. Here's how it happened:

Three years ago I built a clone of the autotuba. I had purchased ten of the MCM woofers to get a good deal. I have an amplifier that puts out over 800 watts when it's bridged. This is a PREPOSTEROUS amount of power for the MCM woofer; easily 500% over it's rated power. I did it anyways, because I had nine more. Lo and behold, it didn't blow up.

At the time, I thought the massive increase in power handling was due to horn-loading. Well that was part of it, but most of the story was that horn-loading the woofer had raised the impedance.









A picture tells a thousand words. Here's the actual measured impedance of the autotuba clone, the triple8 tapped horn from the article, and the exact same woofer in a sealed box. The woofer is the same in all three boxes. Orange is sealed. Red is a front loaded horn. Purple is a tapped horn. You can see the following:


The sealed box has an impedance of 8ohms at 60hz. With an amplifier that puts out 800 watts into a 4ohm load, the MCM will receive 400watts at 60hz. Definitely enough to blow it up.
At the same frequency, the front-loaded horn (Autotuba clone) has an impedance of 10ohms. So it will get about 350 watts. What is REALLY interesting about the front loaded horn is that the impedance never drops below 5ohms, and it's cruisng around 16 ohms from 25hz to 55hz. The driver has an Re of 3.6 ohms! So Bill Fitzmaurice is correct - horn loading is basically doubling the impedance of the woofer! Nice 
The trace at the bottom, with five peaks, is the Triple 8. I wired the three woofers in parallel. Normally this would be an amplifier-killing load, but it works. And the impedance curve demonstrates why. With an Re of 3.6 ohms, you'd expect a low of 1.2 ohms in parallel. But look at the curve - the low point is two ohms. Most importantly, it never dips below 3ohms from 40 to 75hz. That's where it counts, because thats where the real power demands on a subwoofer are. Crazy design huh 



mwmkravchenko said:


> I have but one other comment. The box you made that you label the Autotuba is nowhere near the volume that Fitzmaurice used. I know I built one from the Speaker builder article a way back. I listened to it for years and I understand what it does well and what it does not. But as for it's SPL capability it rocks. I used a cheap pioneer driver in it and I was getting SPL at 104 db/watt.


I copied the dimensions right off the website. Bill Fitzmaurice has published a series of horn subs for Speaker Builder - are you certain it was the same sub? Also, if you google pix of the sub online, it appears that he's changed the path length of the subwoofer. The older pathlength was shorter I believe. Based on my own experiments with horns in cars, a long pathlength works better in a car than it does in a house, because a long pathlength complements the cabin gain of a car. In the house, cabin gain isn't as significant, so a shorter pathlength along with a subsonic filter works better. 



mwmkravchenko said:


> Any tapped horn I have built or designed will not get you a true 10db of gain. 6 to 8 db for sure. A shorter path length for sure. But not a greater SPL capability.
> 
> I did head to head simulations of horns with the same driver and a different layout. Front loaded against tapped horn. The front loaded wins in SPL/watt every time.
> 
> Mark


Mark, a year ago, I built my first tapped horn. It was a disappointment. So I went on the internet, and started saying that tapped horns were no better than bandpass subs. Because I was trashing the design, it turned into quite a heated debate, and the inventor schooled me on how a REAL tapped horn works. Read it here:

Tapped Horn for Dummies - Page 6 - diyAudio

I am no Tom Danley, and I cannot school you the way that Tom schooled me. What I can tell you is this:

PLEASE STUDY YOUR IMPEDANCE PLOTS

The solution to your subwoofer problem is staring at you. You can see it in the impedance plots. A tapped horn will have a series of _well defined dips in the impedance._ The lowest dip corresponds to one-quarter wavelength, the 2nd lowest to one half wavelength, and the highest is a full wavelength.

For instance, my tapped horn has a pathlength of 129 inches. 104hz is 129 inches long. *(speed of sound / 129 inches) = (13500 inches per second / 129 ) = 104hz.* Look at my impedance plot - see that dip at 52 hz? That is where my TH is resonating at half a wavelength. Now look at 26hz - see how it's the exact same magnitude as 52hz? That's what you should see in a tapped horn. And wait! What is that at 104hz? Yep, another dip.

*A series of impedance troughs and peaks - thats what tells us that a tapped horn is working. The dips in impedance correspond to resonances, and those resonances are what flatten the response of the tapped horn.*

















This is your "tapped horn". Even without seeing the inside of your subwoofer, the impedance plot demonstrates that the tuning frequencies are too close together. See how the gap between the two peaks is just two or three hz? That tells us the front and back of the woofer are too close together. Your woofers are unloading. That's why you can't get a lot of SPL out of your sub. Your subwoofer is basically running without a baffle, inside of a box.









This is a real Danley Tapped Horn. See the well defined troughs at 30hz, 60hz and 120hz? This shows us where Danley is tuning the tapped horn, without even taking the box apart. The impedance plot tells the tale.

















This is the triple8, the subject of this thread. See the dips at 52 and 104hz? That corresponds to the length of the entire subwoofer.

Do you see what I'm getting at here? The impedance plot tells the tale. In a tapped horn, there are a series of impedance troughs, which correspond to the tuning frequencies.

Also, simulations can get you in the ballpark, but horns behave a lot different in the real world than the sims would indicate. Bill's AutoTuba proves this nicely. I need to post the in-car response of the clone I built, because it's a LOT better than what the simulations would have you think. Bill has clearly refined the design "in the real world", not on a computer.


----------



## SSSnake

> Wiring subs like that would be a very bad idea


VERY, VERY bad idea

what happens when the woofer with the most power generates a pressure wave and that wave reaches the lowest powered woofer? 




It moves in the wrong direction causing a loss in output and if any signal outside the passband gets through you can bottom the voice coil (overexcursion).


----------



## chithead

I see now why MiniVanMan made the decision that he did.


----------



## blamus

chithead said:


> I see now why MiniVanMan made the decision that he did.


what decision did he make?


----------



## cubdenno

he resigned. But not sure how that pertains to this thread.


----------



## mwmkravchenko

Patrick Bateman said:


> PLEASE STUDY YOUR IMPEDANCE PLOTS
> 
> The solution to your subwoofer problem is staring at you. You can see it in the impedance plots. A tapped horn will have a series of _well defined dips in the impedance._ The lowest dip corresponds to one-quarter wavelength, the 2nd lowest to one half wavelength, and the highest is a full wavelength.
> 
> This is your "tapped horn". Even without seeing the inside of your subwoofer, the impedance plot demonstrates that the tuning frequencies are too close together. See how the gap between the two peaks is just two or three hz? That tells us the front and back of the woofer are too close together. Your woofers are unloading. That's why you can't get a lot of SPL out of your sub. Your subwoofer is basically running without a baffle, inside of a box.


Hi Patrick

I'm not knocking your design. The measurements speak for themselves. It measures very well. It must speak with authority and give you a great big smile when you listen to it.

So as long as we are comparing measurements. The ones you posted as being "my" horn impedance plot is actually the faulty driver impedance plot taken before installed into the enclosure. Or the free air measurement. The UNHORN enclosure displays a double resonance situated at the low end near 30 hz and the upper end 60 hz. I did not post these as the resulting measurements are very bad due to the blown driver. I get a double peak as it has two resonant cavities and a small throat coupling the two. The size of throat has a great deal to do with how smooth the response becomes. The size and shape of the resonant cavities helps get the response to go lower up to a point. The desired effect is as close to a horn SPL level as I can get with the smallest enclosure that I can design. The latest gets a 10db increase. That's about as good as a horn gets as far as I have been able to design. To put that into perspective. Every 3 db is a doubling in efficiency. Or you need half as much power to get the same SPL. So a gain in 10 db efficiency is 8 times and change as efficient as the starting point. 100db is 8 times more efficient than 90 db. These horn designs both yours and mine are awesome in a car when at ear bleeding levels you are only pumping in less than 10 watts! 

Second point. A tapped horn has three impedance peaks and two troughs. Most of us that have designed them know this. My box is not a tapped horn. It is a double tuned resonator similar to a band pass box but with greater available mechanical gain. That is why I call it the unhorn. I did not want to post about it here. This is your thread.

But to clear up a couple of points. The drivers are placed in the wrong position as you point out. The box was a prototype as was stated. I posted this same statement this morning in the tapped horn for car thread in diyaudio.com. I also posted the solution to the wrong position. When I and a friend did the resulting simulation that confirms both that the new location as being the proper one and the resulting gain in SPL response. Two drivers that are 85db/watt in this enclosure will get you 96 db in a 2 pi environment. And 103 db/watt in a corner or a car. Exactly as predicted the box as it exists produces the passband it was designed for. Even with a blown driver in a non optimal location I get 30hz out of the box. We attained 112 db with 5 watts as per the simulation into 1/8th space ( car environment) done in Hornresp.

The length factor you talk about can be accounted for when you create a resonant chamber at least 1/4 the desired low frequency wavelength. As long as the horn is at least 1/4 wavelength you can get the desired low end response if the box is designed to work with this limitation. This is a well known design minimalist length when working with horns. The trade off being like a tapped horn the ultimate SPL capability will be slightly reduced. A front loaded horn will always be more efficient. 

This is the premise for the two UNHORN designs. They are shorter than a competing front loaded horn. One of the designs when properly used is nothing short of amazing. It is less then a cubic foot uses two 6 1/2" drivers and gives clean bass down to 40 hz at crazy efficiency. This was the whole point in their design. Try something different instead of copying the work of others.

Heck I've been building horns since 1994 and speakers professionally and semi-professionally since 1989. Front loaded , back loaded, vented, sealed, transmission line and bandpass. And yes I still learn things from people like you. And I appreciate it! Keep up the good work. Your posts on wave guided midrange are worth the reading. And I truly hope they sound as good as the measurements you posted. But please do not try to knock someones work without having at least built some of it. As you say the simulations are but a stepping stone to the real world. When I started building horns the calculations were the worst part. Now we can do simulations that are pretty damned close to what we get when we make saw dust. The simulations save time and allow for some out of the box thinking.

How about posting the dimensioned measurements for your three driver box. I post my build measurements. I'd love to build your design and listen to it. I've got quite a few drivers kicking around as well.

Mark


----------



## jsun_g

Hi Patrick,
I have a single ID8 (dual 4 ohm, version 2) and have an old test ported box I built...IIRC it is a little under 1 cube internal volume and tuned around 35Hz.
Powered with an old Coustic 65x2 amp at 4 ohms, this sub gets up to 118-119dB in the trunk of a sedan in the 50-55Hz range, has a small dip at 40, back up to ~114dB in the 30-35Hz range, and then really falls off under 30Hz. I have had a pair of ID8's run in another ported box, with 300W to each sub and using a 20Hz subsonic filter, with no problems, but I did not measure SPL using the dual sub box.

What is the SPL reading in the thumbnail graphed from (is that in-car response?), and at what input power? I am trying to understand what advantage(s) your enclosure design would have over a simple ported box for the ID8.




Patrick Bateman said:


> I still need to post the plans for the new sub. In the meantime, if anyone has some Image Dynamics ID8s lying around, they make an awesome match for this sub. With a pair of these you lose a little bit of efficiency over the MCM, but the simulated response is flatter and they can gobble up 600 watts without breaking a sweat, because they have double the excursion.
> 
> With a high pass filter, you could probably get away with 1000 watts at 4 ohms.
> 
> I've attached a pic.


----------



## mwmkravchenko

Here is an ID 8 :

//www.imagedynamicsusa.com/products.php?Family_Id=2&Product_Id=9

But this is the driver I'm using:

http://meniscusaudio.com/css-trio8-p-946.htmlhttp:

Their specs are pretty damn close. The TRIO 8 has an X-max of 14 and a x-mechanical of almost 20 mm. So does the ID8. The voice coil is larger on the TRIO8 and therefore can handle more power. 200 watts Actual no smoke and mirror power rating. It is a driver that is more easily paralleled to.

And it costs $80

ID8V.3-D2 - Image Dynamics ID 8" Subwoofer

These guys are selling the ID8 at $120 

Just thought I would throw in some food for thought. It's not as cool looking in some respects but the performance is equal if not better. If your on a budget the MCM drivers are hard to beat. And two MCM drivers ($34 each) beat one TRIO8 ($80) or ID8 ($119) with a big stick. 
Mark

P.S. If the thumbnail your talking about is from my post then it is the electrical impedance for the horn enclosure that I have built that is giving me some headaches. The graph demonstrates that it is a double tuned resonant enclosure because there are two peaks in the impedance where the two chambers give the moving cone the most resistance to movement. The good thing about the enclosure is that the peaks are not that high in impedance. Who ever said that speaker are 8 4 or 2 ohm loads should have his head examined. They are not at all. The numbers are the lowest points in the loudspeakers resistance curve. The higher the resistance the less power you can pump into them. Double the resistance and you halve the power input. So at the peaks where you have 20 ohms for example you have a heck of a lot less power going into the driver and a lot more heat coming off of the voice coil.


----------



## jsun_g

mwm - sorry for any confusion. I was referring to Patrick's thumbnail from post #24 -specifically, the FR plot of the ID8.

I wasn't aware of the CSS driver...nice comparison to the ID8 and even nicer price  I wonder how their 10" fares against the ID10v3's I'm currently using. 2 ID10's are getting me to 144dB in a ported box tuned to 35Hz in a trunk.


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## mwmkravchenko

I'm at work so I checked things out on my phone... So a quick survey of the differences are this. 4mm more X-max, smaller Vas, same power handling. Better price.

Need I say more?

Those fancy logos are costing you guys!
There are really good drivers that are not as well known.

Mark

P.S. Mark is fine my last name is harder.


----------



## Brian Steele

mwmkravchenko said:


> Double the resistance and you halve the power input. So at the peaks where you have 20 ohms for example you have a heck of a lot less power going into the driver and a lot more heat coming off of the voice coil.


Are you suggesting that there is more heat coming off of the voice coil when the impedance is high?


----------



## mwmkravchenko

Brian Steele said:


> Are you suggesting that there is more heat coming off of the voice coil when the impedance is high?


Hi Brian

First off I don't want ti highjack Patricks thread. 

Second Brian you of all people know the answer to that question. It depends on what you are trying to accomplish.

A steady state input of 1 watt into 4 ohms or 2 volts will look like .02 volts at 40 ohms which is a typical impedance near a drivers resonance. So if you don't change the volume knob no greater heating should happen. That ia untill you take this into consideration.

When we listen we are looking for equal pressure response. Or equal loudness. When this is thrown into the mix we will try to drive the woofer with greater power (watts) just at or around the areas where it is least efficient. So yes a driver can warm up more when working in the real world.

Another reason why Patricks design is a good idea is the much more modest peaks and lulls in the impedance of the composite driver.

Mark


----------



## chad

mwmkravchenko said:


> I'm at work so I checked things out on my phone... So a quick survey of the differences are this. 4mm more X-max, smaller Vas, same power handling. Better price.
> 
> Need I say more?
> 
> Those fancy logos are costing you guys!
> There are really good drivers that are not as well known.
> 
> Mark
> 
> P.S. Mark is fine my last name is harder.


Holy ****, you are possibly eluding to one of the founding principles of this forum!


----------



## Brian Steele

mwmkravchenko said:


> A steady state input of 1 watt into 4 ohms or 2 volts will look like .02 volts at 40 ohms which is a typical impedance near a drivers resonance. So if you don't change the volume knob no greater heating should happen. That ia untill you take this into consideration.
> 
> When we listen we are looking for equal pressure response. Or equal loudness.


Are you suggesting then that (1) an amplifier's output voltage will decrease when when a driver's impedence increases, and (2) the system's output would subsequently decrease at that increased impedance, therefore (3) you would have to turn up the volume to maintain the same output that you get at other frequencies where impedance is lower?

Just trying to understand your train of thought here.


----------



## Patrick Bateman

jsun_g said:


> Hi Patrick,
> I have a single ID8 (dual 4 ohm, version 2) and have an old test ported box I built...IIRC it is a little under 1 cube internal volume and tuned around 35Hz.
> Powered with an old Coustic 65x2 amp at 4 ohms, this sub gets up to 118-119dB in the trunk of a sedan in the 50-55Hz range, has a small dip at 40, back up to ~114dB in the 30-35Hz range, and then really falls off under 30Hz. I have had a pair of ID8's run in another ported box, with 300W to each sub and using a 20Hz subsonic filter, with no problems, but I did not measure SPL using the dual sub box.
> 
> What is the SPL reading in the thumbnail graphed from (is that in-car response?), and at what input power? I am trying to understand what advantage(s) your enclosure design would have over a simple ported box for the ID8.


Well we are really out on the bleeding edge here, if you ask me. Only a handful of people have put horn subwoofers in cars, and even fewer have put tapped horns in cars.

When I built my Autotuba clone, my first impression was that the sub box got INSANELY loud, but did not play particularly deep.









Here's the in car response of my clone, which is 3.9cf, and the exact same woofer in a sealed box thats 1.4cf. The red line is the horn; the orange line is the sealed box. Both woofers were measured at the same volume level. This is NOT the tapped horn; it's the front loaded horn that I built a few years back. The tapped horn is louder, and I will post in-car measurements shortly.

We see some serious cabin gain happening here. The sealed sub is louder at 15hz than it is at 60hz. Above 40hz, the horn walks all over the sealed sub. The horn has a seven foot path length, which reinforces output from 40hz and up. At 200hz the horn has a massive 10db advantage, thats like going from a 300 watt amp to a 3000 watt amp.








This is the impedance of the three designs. Orange is the 1.6cf sealed box, red is the 3.9cf front loaded horn (AutoTuba clone), and purple is the Triple8 Tapped Horn, which is 3.2cf.

Of course, I can't ignore the elephant in the room, which is that no one gives a crap if a subwoofer has 10db more output at 200hz. It's a SUBwoofer, not a midbass. As I see it, the horn has the following advantages over the sealed box:


At the exact same volume level, the horn is drawing 25 - 50% less current than the sealed box. So the horn is louder from 40hz and up AND it's drawing less current. That's why I was able to crank up the horn sub to ridiculous levels - it doesn't soak up power like a sealed box does.
A horn physically reduces distortion. There are only three sub types which do this. By reducing distortion, the horn sounds a LOT cleaner than the sealed sub. For me personally, this is the number one reason to use a horn sub, it can make a mediocre woofer sound very VERY good, and it can make an excellent woofer sound ever more transparent.
This particular sub is the flattest measuring speaker I've *ever* measured in a car. Flatter than any midrange I've ever measured, and flatter than any tweeter. It's +/- 2.5 db over a span of three octaves, and in the harsh environment of a car, that's downright ridiculous.
Above 25hz, the tapped horn will have about 10-25% of the excursion of the sealed box. That's the BIG win - horns can soak up power like nothing else. A horn reduces excursion, reduces the current draw from the amplifier by increasing impedance, reduces thermal compression, and increases efficiency in it's passband.

In a nutshell, sealed boxes are easy to build and give excellent results in a car. A horn, or a tapped horn is more difficult to build. But they deliver higher efficiency in their passband, along with an increase in power handling and a reduction in excursion and distortion. Which means that they'll sound cleaner and play louder.


----------



## mwmkravchenko

Brian Steele said:


> Are you suggesting then that (1) an amplifier's output voltage will decrease when when a driver's impedence increases, and (2) the system's output would subsequently decrease at that increased impedance, therefore (3) you would have to turn up the volume to maintain the same output that you get at other frequencies where impedance is lower?
> 
> Just trying to understand your train of thought here.


What is this amplifier 101? 

Man you are making me work here Brian. You gotta know this stuff. So what are you trying to find out what I know? I know enough to get into trouble! LOL

Spent a year as an electronics tech just after my divorce in 1997. Some of the math is getting fuzzy so I cheated and looked it up.

This is how I can explain it one way. I think this makes sense. If something is wrong please correct me so nobody gets into any trouble. This is dangerous stuff you know.  

Here is where I'm coming from.
1) No an amp's voltage stays constant up the onset of clipping.
2) The current output with a constant voltage over a changing load will fluctuate.
3) To maintain the same power output at different frequencies the current must change with the voltage. 

To start almost all amplifiers are voltage sources. Meaning they want to keep the voltage sent into a load (speaker voice coil) constant. 

Second the premise for this statement is the 2.00 volts output setting. An amplifier gain stage needs a certain amount of voltage to get the amplifier to pass current. So the volume control on X, Y, or Z preamp circuit is set so there is a steady state signal say 500hz coming out of the amplifier terminals at 2.00 volts AC. No load variation. 4 ohm termination.

If you leave the gain setting on the amplifier alone and you change the load impedance the voltage out will be kept constant by the amplifier.

Unless I'm misapplying the formula here is what I get: 

V/R=I

V = voltage
R = resistance
I = current

V^2/R = watts

Our original example:

2^2=4/4 = 1

4 Ohm load.

2 volts multiplied by 2 = 4 divided by the Resistance 4 = 1 watt

So then we get the 40 ohm load. Here's the math.
V = 2
R = 40

V^2/R=watt
2^2 = 4/40 = .01 watt

The available current from an amplifier has a maximum limit as does the voltage output. These are the power supply rail voltages and the current spec on the transformer. To high a current draw and the transformers go into magnetic saturation. They don't give any more current. This is true in a car or a home. 

Again if I missed anything or something is wrong feel free to correct it. I've been on the go since 6:00 AM. My brain is slowly turning into mush as the evening progresses. General construction is what is paying the bills now for the most part. The days are long and hard. And it is starting to cool off these days. No rest for the wicked.

Mark


----------



## Patrick Bateman

Patrick Bateman said:


> Here's the "final" frequency response of the triple-8 tapped horn. Like the last graph, purple is the triple-8. The red line is an Autotuba clone (in this graph.)
> ​
> Here's some thoughts on this:
> 
> 
> As I see it, the ideal car subwoofer has response which is flat from about 40 to 80hz. When you combine that with cabin gain, you get in-car response for two octaves.
> The triple-8 tapped horn is flat from 50hz to 500hz - about three and a half octave.
> The triple-8 tapped horn measures +/- 5db.
> If you EQ'd out the peak at 180hz, it would measure +/- 2db. That's excellent performance for a sealed box, but for a horn, it borders on the absurd.
> The measurement of my Autotuba "clone" is consistent with the measurements of it's creator. I have a feeling that the measurements from diyaudio are suspect. There isn't a big dip at 55hz in mine, or Bills.
> My box is waaaaaay smaller than the autotuba
> The bandwidth of the autotuba is much narrower. This is normal for a front-loaded horn. The horn acts as a low pass filter, and reduces distortion.
> At 60hz, where you really want a subwoofer to kick like a mule, the triple-8 tapped horn has an advantage of nearly 10db over a front-loaded horn
> Here's the part where everyone is going to freak out: *The woofers in the tapped horn are wired in parallel.* Yes, this draws more current. Because the impedance peaks of the tapped horn are staggered, we can get away with a wiring scheme which isn't practical with a conventional horn, a sealed box, a vented box, or a bandpass. I'll measure the impedance in the next day or two, and you'll see what I mean. All the impedance "troughs" are staggered, due to pathlength differences for each woofer.
> [/SIZE][/FONT]













I found this pic on my hard drive, which shows the response of the 4.5cf tapped horn with a 12" woofer (dark red), the 3.1cf tapped horn with three eights (purple), and a 4cf horn with a single eight (red).

Measurements are outside; in car expect a big bump below 80hz thanks to cabin gain.

All three are measured at the exact same volume level on the amplifier, but the twelve is drawing the least current, due to it's higher impedance. The twelve has the highest efficiency of all of them, since Hoffman's Iron Law rules the day. The triple8 has the highest power handling and the smallest size of all of them, because it has the highest displacement. Note that the SPL level on this measurement is more accurate than the previous measurement. (IE, the twelve is more efficient than the initial measurements showed. When it comes to efficiency, bigger = better.)


----------



## Brian Steele

mwmkravchenko said:


> 1) No an amp's voltage stays constant up the onset of clipping.
> 2) The current output with a constant voltage over a changing load will fluctuate.
> 3) To maintain the same power output at different frequencies the current must change with the voltage.


I'm not sure where you're going with this, as you're not really answering my questions. 

If what you're suggesting is that the system's output will somehow decrease at a specific frequency because its impedance is higher at that frequency and the volume will have to be turned up to compensate, that's incorrect. It is perfectly reasonable for a speaker system to have varying impedance within its passband yet maintain a flat response within that passband at a constant output voltage from the amplifier.


----------



## Brian Steele

Patrick Bateman said:


> I found this pic on my hard drive, which shows the response of the 4.5cf tapped horn with a 12" woofer (dark red), the 3.1cf tapped horn with three eights (purple), and a 4cf horn with a single eight (red).


What's the measured sensitivity (dB/2.83V/1M) of those three systems?

With 3 cu.ft. to play with and an F3 around 60 Hz as a target, two pro audio 12" drivers in a vented alignment might achieve better results with less hassle.

For example, two Eminence Kappalites each in about 1.35 cu.ft. tuned to 45 Hz would be around 101 dB/2.83V/1M in the passband, -3dB down at 60 Hz and capable of over 127dB without exceeding Xmax in the passband. Of course you'll have to feed them with over a kW of power to achieve this, but... 

(FWIW, I was actually considering doing something like this for my next install. However, I'd shift box size a bit upwards and Fb a bit downwards, to around 30 Hz or so).


----------



## mwmkravchenko

Brian Steele said:


> I'm not sure where you're going with this, as you're not really answering my questions.
> 
> If what you're suggesting is that the system's output will somehow decrease at a specific frequency because its impedance is higher at that frequency and the volume will have to be turned up to compensate, that's incorrect. It is perfectly reasonable for a speaker system to have varying impedance within its passband yet maintain a flat response within that passband at a constant output voltage from the amplifier.


How about I give up!

Forget it man and lets talk about the great design that Patrick has furnished us. That is much more interesting than this carazy ( on purpose ) back and forth.

The Spl plots are for what power level Patrick?



Mark


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## GPM

thehatedguy said:


> What about dual reflex ported enclosures? Group delay go all to hell? They seem to be one of the best ways to eek out the most performance for a given foot print.


Note that all the basic tapped variants are dual reflex (6th order) alignments morphed into a common folded chamber, so group delay in their pass-band will vary depending on the variant with T-TQWTs having the lowest. In all cases it 'goes all to hell' above their HF corners, though once damped it's not an issue.

GM


----------



## Patrick Bateman

Brian Steele said:


> What's the measured sensitivity (dB/2.83V/1M) of those three systems?


I can only guess. I don't have an SPL meter. The P-Audio woofer has a sensitivity of 100db at 1khz and an Re of 5.2 ohm. The Triple8 has a sensitivity at 50hz that's basically equivalent to the P-Audio. So we can hazard a guess that it has a sensitivity of about 100db at 50hz. At 50hz the impedance of the Triple8 is 3.5 ohms.


Brian Steele said:


> With 3 cu.ft. to play with and an F3 around 60 Hz as a target, two pro audio 12" drivers in a vented alignment might achieve better results with less hassle.
> 
> For example, two Eminence Kappalites each in about 1.35 cu.ft. tuned to 45 Hz would be around 101 dB/2.83V/1M in the passband, -3dB down at 60 Hz and capable of over 127dB without exceeding Xmax in the passband. Of course you'll have to feed them with over a kW of power to achieve this, but...
> 
> (FWIW, I was actually considering doing something like this for my next install. However, I'd shift box size a bit upwards and Fb a bit downwards, to around 30 Hz or so).


It took me about a year to "wrap my brain around" the advantages of a tapped horn. Over on diyaudio, everyone is obsessed with the *efficiency* of tapped horns. IMHO, the efficiency is overstated, because nearly everyone is comparing apples to oranges, by comparing WinISD sims to Hornresp sims. (In Hornresp people are making over-optimistic assumptions about woofer loading, that's a whole seperate rant...)

The results I've posted are thorough measurements *in the real world*, and they show that the response is a lot flatter than the sims would predict *and the impedance is a lot higher.*

That last part is the key, and explains why tapped horns are trouncing vented and sealed alignments *in the real world*. The *efficiency* of a sealed or vented alignment is damn good. Look at the measurements - the sealed alignment beats *everything* below 40hz. The sealed box beats the tapped horn below 40hz, it beats the front loaded horn below 40hz.

*But the sealed box has the highest excursion, and it's drawing the most current.*









This is the impedance of the triple8. The woofer has an R3 of 3.6ohms, so three in parallel should dip down to 1.2ohms. Instead, the lowest impedance is 2.1ohms at 100hz. A five dollar inductor will low pass this box at 80hz, and raise the impedance to 3.5 ohms or higher from 20hz to 2khz! As I see it, THIS is the magic of tapped horns, being able to wire three woofers in parallel while maintaining a load that won't set your amplifer on fire. Try doing THAT with a vented box.​
If you have a modest amplifier, and you want massive output, by all means, build a vented box with a pair of eminence prosound woofers. It will deliver the goods. But if you have a giant brick of an amplifier, and you find that you're blowing up woofers on a regular basis, or your subwoofer sounds like garbage at high SPL, tapped horns are for you. Thanks to a synergistic combination of reduced excursion and increased impedance, a woofer in a tapped horn can deliver flat response and massively increased power handling.


----------



## Brian Steele

Patrick Bateman said:


> The P-Audio woofer has a sensitivity of 100db at 1khz and an Re of 5.2 ohm. The Triple8 has a sensitivity at 50hz that's basically equivalent to the P-Audio. So we can hazard a guess that it has a sensitivity of about 100db at 50hz. At 50hz the impedance of the Triple8 is 3.5 ohms.


That's a whole lotta assumptions . Better approach may be to just determine the calculated sensitivity of the sealed box sub you've got over its frequency range, then use that as a reference for your measurements. 




Patrick Bateman said:


> The results I've posted are thorough measurements *in the real world*, and they show that the response is a lot flatter than the sims would predict *and the impedance is a lot higher.*


Perhaps HornResp doesn't take box /vent losses into consideration - that would explain why the response peaks are lower than predicted. As for the impedance, my own "tapped pipe" experiment has found the impedance peaks to be lower than predicted by HornResp - again explained by box /vent losses. However, if the impedance at the troughs is quite higher than predicted by HornResp, that to me suggests another thing entirely - it may be happening because the internals of the box are not properly sealed. I've seen that happen a few times before, and in all cases it was because of improper sealing.




Patrick Bateman said:


> The woofer has an R3 of 3.6ohms, so three in parallel should dip down to 1.2ohms. Instead, the lowest impedance is 2.1ohms at 100hz. A five dollar inductor will low pass this box at 80hz, and raise the impedance to 3.5 ohms or higher from 20hz to 2khz! As I see it, THIS is the magic of tapped horns, being able to wire three woofers in parallel while maintaining a load that won't set your amplifer on fire. Try doing THAT with a vented box.


The 2 x Kappalite 3012LF alternative I proposed will have an impedance that should not drop much below 4 ohms if at all in its passband and the results should exceed that of the 3 x 8" tapped horn. Of course those Kappalite drivers are quite a bit more expensive than three of those MCM drivers . In any case, higher impedance in a car audio environment can actually be a disadvantage. 

I'm pretty sure that a TH has its merits in the pro-audio world (less cost for a given output, for example, and it's a good compromise between the efficiency of a horn and the low frequency capability of a vented alignment). I'm just not sure it's the best "compromise" for car audio duty, given the box size requirements for a given driver.


----------



## mwmkravchenko

Brian Steele wrote:

I'm pretty sure that a TH has its merits in the pro-audio world (less cost for a given output, for example, and it's a good compromise between the efficiency of a horn and the low frequency capability of a vented alignment). I'm just not sure it's the best "compromise" for car audio duty, given the box size requirements for a given driver.

Brian have you built and listened to a tapped horn? Because if you have listened to horn loaded bass you would not be hedging bets against box complexity versus performance. There is no comparison between any box and a properly horn loaded driver. Once bitten your hooked. 


Patrick:

If you are using ARTA you can go through the routine to set it up as a class "A" SPL meter. It blows the hell out of a Rat Shack meter. And you can set it up with weighting curves or flat response. You need to know the sensitivity of your microphone and measure the output of your sound card. The measurement routine is in the help section. I have ARTA to and it is one sweet setup especially when calibrated.

Nice impedance curve measurement. But if my eyes are not deceiving me you have but two peaks in the impedance. That is a classic horn for sure but not a tapped horn. Mine are the same horns but not tapped horns. A tapped horn has this type of peak as seen in the thumb nail below.

Mark


----------



## jsun_g

Hey guys, lots of interesting information on here but one comparison I am hoping to see sometime is along these lines:

Say I have 4 cubic feet (gross) of airspace available in my trunk and 500 watts on tap. With those 2 constraints in mind, I'd like to see how the horn-loaded (and TH) enclosures stack up against plain jane sealed and ported boxes, using woofers that are good for each respective application, specifically targeting the 30-80Hz range. Maybe the horn-loaded setup would use smaller (or fewer) drivers, whereas the ported may use more/larger, and the sealed setup even more/larger drivers...with the only constraints being the box can take up no more than 4 cubes and I have 500 watts available for the subs, and let's assume the drivers' impedances can be selected such that a similar final impedance can be achieved for each of these setups given that the number of drivers may differ from setup to setup (not taking into account impedance peaks). We can even assume that I only have $200 to spend on subs, hence I would purchase lower end drivers for the sealed system, because more/larger drivers would be needed.

With similar volume boxes for horn, tapped horn, sealed, and ported setups and these 500 watts, I think the following would be useful, real-world comparisons:
- what is the 1W sensitivity of each system in the car from 30 to 80Hz?
- what is the SPL curve between 30 and 80Hz in the car prior to this 500W amp clipping?
- how much power above and beyond the "500 watts" can each setup take (requires use of larger amp(s)), and what is the highest SPL achieveable for each setup and at what frequency?


----------



## Brian Steele

mwmkravchenko said:


> Brian have you built and listened to a tapped horn? Because if you have listened to horn loaded bass you would not be hedging bets against box complexity versus performance. There is no comparison between any box and a properly horn loaded driver. Once bitten your hooked.


I guess that's why horn-loaded enclosures are so popular in the car audio world... ?

I'd listened to a lot of horn-loaded bass, Mark. I haven't done a tapped horn, but I have done a tapped pipe. It does sound nice (particuarly considering how cheap the driver was), but the engineer in me is folding his arms and saying "damn - with 2.5 cu.ft. to play with, you could use two vented 10" and just blow that thing away in peak output capability".

And finally, this one should be noted for good measure - don't count on the cabin gain to be the same if you switch from sealed or vented alignments to a horn-loaded system. Horns are typically not designed to load into small enclosured spaces like a car's trunk, and their output will be affected if you do so, so you can basically throw any ideas of determining what the final response might be like by simply adding a measured cabin gain transfer function to a HornResp curve out the window. Actually, you can throw the HornResp curve out of the window too while you're at it .


----------



## Brian Steele

mwmkravchenko said:


> Nice impedance curve measurement. But if my eyes are not deceiving me you have but two peaks in the impedance. That is a classic horn for sure but not a tapped horn. Mine are the same horns but not tapped horns. A tapped horn has this type of peak as seen in the thumb nail below.


The staggered-driver config that Patrick used in his design could account for the difference. Note that the upper peak is replaced by three smaller peaks...


----------



## Brian Steele

jsun_g said:


> Hey guys, lots of interesting information on here but one comparison I am hoping to see sometime is along these lines:
> 
> Say I have 4 cubic feet (gross) of airspace available in my trunk and 500 watts on tap. With those 2 constraints in mind, I'd like to see how the horn-loaded (and TH) enclosures stack up against plain jane sealed and ported boxes, using woofers that are good for each respective application, specifically targeting the 30-80Hz range. Maybe the horn-loaded setup would use smaller (or fewer) drivers, whereas the ported may use more/larger, and the sealed setup even more/larger drivers...with the only constraints being the box can take up no more than 4 cubes and I have 500 watts available for the subs, and let's assume the drivers' impedances can be selected such that a similar final impedance can be achieved for each of these setups given that the number of drivers may differ from setup to setup (not taking into account impedance peaks). We can even assume that I only have $200 to spend on subs, hence I would purchase lower end drivers for the sealed system, because more/larger drivers would be needed.
> 
> With similar volume boxes for horn, tapped horn, sealed, and ported setups and these 500 watts, I think the following would be useful, real-world comparisons:
> - what is the 1W sensitivity of each system in the car from 30 to 80Hz?
> - what is the SPL curve between 30 and 80Hz in the car prior to this 500W amp clipping?
> - how much power above and beyond the "500 watts" can each setup take (requires use of larger amp(s)), and what is the highest SPL achieveable for each setup and at what frequency?


There are a bit more variables involved here, e.g. where are the defined F3 points and what sort of behaviour are you prepared to accept in the passband and at the cutoff frequencies. 

There's also the issue of cabin gain, which will be more effective for sealed and vented alignments than it will be for horns.

And finally, there's the questions of location and box dimension constraints. A sealed or vented box can be molded out of fiberglass and MDF to fit the sides or bottom of the trunk to make best use of the space. A horn on the other hand is complex enough as it is and you're likely going to have to settle for a butt-ugly rectangular box sitting in the middle of your trunk as you need to ensure that the mouth isn't blocked.


----------



## Patrick Bateman

jsun_g said:


> Hey guys, lots of interesting information on here but one comparison I am hoping to see sometime is along these lines:
> 
> Say I have 4 cubic feet (gross) of airspace available in my trunk and 500 watts on tap. With those 2 constraints in mind, I'd like to see how the horn-loaded (and TH) enclosures stack up against plain jane sealed and ported boxes, using woofers that are good for each respective application, specifically targeting the 30-80Hz range.


A four cubic foot trunk? What are you driving, a moped? 

My car has a 14 cubic foot trunk - that's fairly average.

Hoffman's Iron Law still rules the day, the biggest box will generally be the most efficient.

At home I tried building an uber-efficient subwoofer, by installing EIGHT subs in an infinite baffle. And as Mark noted, the horn subs just sound better. I spent two or three months building the thing, and wound up abandoning the project after a month. The sound just couldn't rival my tapped horn and bandpass subs. Remember, there are only THREE sub types that physically reduce distortion. So even if you figure out how to install eight of these in your car, you're still going to hear distortion.
Parts-Express.com:B&C 21SW150 21" Subwoofer 4 Ohm | B&C 21SW150 21" Subwoofer low frequency disco dance dj bass effects newbnc

But, anyways, long story short:

If efficiency is your top (or only) priority, just go with an infinite baffle. Due to huge box size, it will always win, as long as the woofers have gobs and gobs of displacement. (We're talking fifteens at a minimum, 21s are better. Or four twelves. Or eight!)


----------



## jsun_g

I've never tried IB in the trunk for subs. Now don't go putting ideas like this in my head 
I'd only be able to fit 2 12's for IB, unless I murder my rear deck.

I just came up with 4 cubes because my car is a daily driver and the space between wheel wells, up to the deck and down to the floor is about 4 cubes gross.

What was it about the horn that caused you to like its sound over IB? Can you relate it to freq response or some other objective measurement?
I can't hear/recognize distortion from my ported subs until they are near their limit. Maybe my ear is just not trained to hear distortion in the subbass range. I remember a mention of nonlinear distortion with subs...I'll have to try feeding a 30Hz tone and see what other artifacts pop out :blush:



Patrick Bateman said:


> A four cubic foot trunk? What are you driving, a moped?
> 
> My car has a 14 cubic foot trunk - that's fairly average.
> 
> Hoffman's Iron Law still rules the day, the biggest box will generally be the most efficient.
> 
> At home I tried building an uber-efficient subwoofer, by installing EIGHT subs in an infinite baffle. And as Mark noted, the horn subs just sound better. I spent two or three months building the thing, and wound up abandoning the project after a month. The sound just couldn't rival my tapped horn and bandpass subs. Remember, there are only THREE sub types that physically reduce distortion. So even if you figure out how to install eight of these in your car, you're still going to hear distortion.
> Parts-Express.com:B&C 21SW150 21" Subwoofer 4 Ohm | B&C 21SW150 21" Subwoofer low frequency disco dance dj bass effects newbnc
> 
> But, anyways, long story short:
> 
> If efficiency is your top (or only) priority, just go with an infinite baffle. Due to huge box size, it will always win, as long as the woofers have gobs and gobs of displacement. (We're talking fifteens at a minimum, 21s are better. Or four twelves. Or eight!)


----------



## Patrick Bateman

jsun_g said:


> I've never tried IB in the trunk for subs. Now don't go putting ideas like this in my head
> I'd only be able to fit 2 12's for IB, unless I murder my rear deck.
> 
> I just came up with 4 cubes because my car is a daily driver and the space between wheel wells, up to the deck and down to the floor is about 4 cubes gross.
> 
> What was it about the horn that caused you to like its sound over IB? Can you relate it to freq response or some other objective measurement?
> I can't hear/recognize distortion from my ported subs until they are near their limit. Maybe my ear is just not trained to hear distortion in the subbass range. I remember a mention of nonlinear distortion with subs...I'll have to try feeding a 30Hz tone and see what other artifacts pop out :blush:


It's possible that you don't *recognize* the distortion that's coming from a vented box, but you're definitely *hearing* it. Even at modest levels, the distortion in a subwoofer can be more audible than the fundamental, because of the fletcher munson curves.









A pic is worth a thousand words, so here's the measured performance of a woofer. See the fundamental at 30hz? The third harmonic is at 90hz, and it's 20db lower in level. The problem is that we're a lot more sensitive to 90hz than we are to 30hz.

_Which means that the distortion may be more audible than the fundamental, depending on the level._

To make things even more confusing, it's level dependent. That's one of the reasons that a lot of subwoofers sound better at moderate to high SPLs than they do at polite levels. At higher SPLs the fundamental begins to "crowd out" the distortion, due to the way our hearing mechanism works.

As if that weren't confusing enough, it depends on what kind of music you listen to. Real instruments produce distortion, so if you listen to a lot of acoustic music, you might not be obsessive about distortion like I am. I personally listen to a ton of electronic music and pop, which include lots of syntesized bass lines. Synthetic bass lines don't have 2nd and 3rd harmonic distortion - they're often pure tones. Same thing with movies - they have a lot of synthetic bass.

I don't think that it's a coincidence that Mark and Brian are commenting the most on this thread - all three of use have been studying subwoofers for over a decade. The perception of distortion is admittedly obtuse and confusing. It's a heck of a lot easier to build a vented box and call it a day.









Of the three subs, the Triple8 has the best frequency response. That's the one with the purple trace. *Subjectively,* my favorite is the one with the *worst* frequency response, which is the TH-Mini clone. That's the dark red trace. IMHO, it sounds the best because it has that big fat null at 140hz which basically obliterates 2nd and 3rd harmonic distortion. It also has the lowest inductance of all three subs.

Unfortunately, it's also the biggest, and has the lowest power handling.


----------



## jsun_g

This makes sense. I am guessing the nonlinear distortion plot is not necessarily of a sub in a ported box...?
Are you aware of any nonlinear distortion plots of a sub in a ported box and then the same sub in a horn-loaded setup, at the same dB SPL for the fundamental tone? I'd be interested to see how they differ.

Though in a car, especially at higher SPL, pretty much anything in the car can vibrate, buzz, shake, and contribute to the nonlinear distortion and localization.



Patrick Bateman said:


> It's possible that you don't *recognize* the distortion that's coming from a vented box, but you're definitely *hearing* it. Even at modest levels, the distortion in a subwoofer can be more audible than the fundamental, because of the fletcher munson curves.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> A pic is worth a thousand words, so here's the measured performance of a woofer. See the fundamental at 30hz? The third harmonic is at 90hz, and it's 20db lower in level. The problem is that we're a lot more sensitive to 90hz than we are to 30hz.
> 
> _Which means that the distortion may be more audible than the fundamental, depending on the level._
> 
> To make things even more confusing, it's level dependent. That's one of the reasons that a lot of subwoofers sound better at moderate to high SPLs than they do at polite levels. At higher SPLs the fundamental begins to "crowd out" the distortion, due to the way our hearing mechanism works.
> 
> As if that weren't confusing enough, it depends on what kind of music you listen to. Real instruments produce distortion, so if you listen to a lot of acoustic music, you might not be obsessive about distortion like I am. I personally listen to a ton of electronic music and pop, which include lots of syntesized bass lines. Synthetic bass lines don't have 2nd and 3rd harmonic distortion - they're often pure tones. Same thing with movies - they have a lot of synthetic bass.
> 
> I don't think that it's a coincidence that Mark and Brian are commenting the most on this thread - all three of use have been studying subwoofers for over a decade. The perception of distortion is admittedly obtuse and confusing. It's a heck of a lot easier to build a vented box and call it a day.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Of the three subs, the Triple8 has the best frequency response. That's the one with the purple trace. *Subjectively,* my favorite is the one with the *worst* frequency response, which is the TH-Mini clone. That's the dark red trace. IMHO, it sounds the best because it has that big fat null at 140hz which basically obliterates 2nd and 3rd harmonic distortion. It also has the lowest inductance of all three subs.
> 
> Unfortunately, it's also the biggest, and has the lowest power handling.


----------



## mwmkravchenko

Hi Brian and Jasun

This is for both:

The car cabin gain is independent of any type of loudspeaker. It is a function of the cars interior volume, the interior length and the seal between it and the great out doors. You will always get the same amount of cabin gain in the same car using any means to create a pressure field. The pressure field comes from the drovers that are pumping in a slightly higher air pressure wave than the steady state pressure within the car cabin. In the great out doors or in a building we hear bass in a different manner. We are in the far field in terms of bass wavelengths. In a car we are always in the near field as the longest measurement within any car is much shorter than even mid-bass frequencies.

For Jasun:

What do you get for building a horn?

Oh boy let me start here.

Headroom.


Second you get lower distortion at a given even volume comparing boxes head to head. This may not be your cup of tea. Almost all pop music relies on vast amounts of distortion in the midbass to sound impressive. Take a quick read of this review of a horn I did and see what I mean:

Tapped Horn For Car - Page 11 - diyAudio Look for Binary 110 review.

A horn sub takes apart any sloppy work done by the recording engineers or the players themselves. It separates the men from the boys. But some people hate that kind of clean bass.

What else do you gain. Headroom. Limitless ( at least it feels like that at times ) headroom. I listen to classical music. Not just the poofy stuff but the huge works by hundreds of people or enormous pipe organs that can pound like jack hammers that make the kids mouths hit the ground.

When you have a properly designed horn sub if the bass is there you get it. From the chest pounding smack of a concert bass drum to what ever the composer planned to kick your ass in the music. I like it.

What else?

You talk about power with 500 watts. Let me back this up a bit and relate power to loudness. 500 watts is 3 db louder than 250 watts. A trained musician or really good listener will hear the difference. Halve it again and you get 125 watts. A drop in 6 db. This you will notice. But the difference in power output is what 375 watts! Speakers are really inefficent ways of getting sound to our ears. They need alot of power to get them loud. Horn loading a driver makes it act as if it is more efficient. Remember that 3 db increase in sound requires double the power. Well a well done horn will get you 9 db more efficiency. That is 2 * 2 = 4 * 2 = 8 times more efficient than a standard loudspeaker. That is a real big gain.

Now think about it like this. If you like it loud in your car. The peaks are usually around 110db or maybe 116 db. I'm talking the bass peaks. How much power do you need to get a normal car sub to get to that level?

85db/watt is a standard car driver for the low end. So 110-84 = 26 db difference from one watt to where we want to get. Pour in 200 watts and you get where you want to be. Loud damn loud. 110db

Put the same driver in a horn and what happens. Plus 9 db from the get go. So you start off with 93 db/watt. How much to get to 110db? 200/2=100 watts 3db less 100/2=50 watts 3db less 50/2=25 watts the last 3 db difference. So in a horn the same driver gets you the same SPL at 25 watts. Now were cooking with gas! Your amp has huge amounts of headroom. The driver has not been sucking in wattage that will warm it up changing it's resistance and causing power compression.

The greater efficiency means that for a given SPL the driver is moving forward and backward less. Much less. So you again get less distortion.

Build it. Try it and maybe you will like it. If you can't stand the boom boxes that make everything sound like an over grown bass fart then a horn is for you.

Mark


----------



## mwmkravchenko

Hi Patrick

Some thoughts on distortion.

A distorted bass note always sounds louder. It's a trick used for centuries. Wind bands to pipe organs when you add some growl it sounds a lot louder. The growl is a distorted pure tone. Unfortunately it is getting overused. I think that when more people get to listen to clean actual low bass notes from subs that can actually do it with less distortion will grow to like it. We have had for years these wanna be subs that growl but have no bite. Time to get something with teeth!

Mark

P.S. About the years of fooling around with subs. I had hair when I started! LOL
That me with my smallest horn loaded sub design ever.

Patrick where are the design drawings for your triple? I bet quite a few folks would like to take it for a test drive?


----------



## jsun_g

Mark,
Thank you for the detailed reply. Someday I gotta build myself one of these so I can compare it with my ported box. If I also get to 144dB with 2 10's and 1200 watts as I did with a ported box (it's probably a 3dB or so hump centered at 49Hz, but all around very good SPL from about 30 to 60Hz - box is tuned to 35Hz), or perhaps even louder and less distortion, then I am sold 




mwmkravchenko said:


> Hi Brian and Jasun
> 
> This is for both:
> 
> The car cabin gain is independent of any type of loudspeaker. It is a function of the cars interior volume, the interior length and the seal between it and the great out doors. You will always get the same amount of cabin gain in the same car using any means to create a pressure field. The pressure field comes from the drovers that are pumping in a slightly higher air pressure wave than the steady state pressure within the car cabin. In the great out doors or in a building we hear bass in a different manner. We are in the far field in terms of bass wavelengths. In a car we are always in the near field as the longest measurement within any car is much shorter than even mid-bass frequencies.
> 
> For Jasun:
> 
> What do you get for building a horn?
> 
> Oh boy let me start here.
> 
> Headroom.
> 
> 
> Second you get lower distortion at a given even volume comparing boxes head to head. This may not be your cup of tea. Almost all pop music relies on vast amounts of distortion in the midbass to sound impressive. Take a quick read of this review of a horn I did and see what I mean:
> 
> Tapped Horn For Car - Page 11 - diyAudio Look for Binary 110 review.
> 
> A horn sub takes apart any sloppy work done by the recording engineers or the players themselves. It separates the men from the boys. But some people hate that kind of clean bass.
> 
> What else do you gain. Headroom. Limitless ( at least it feels like that at times ) headroom. I listen to classical music. Not just the poofy stuff but the huge works by hundreds of people or enormous pipe organs that can pound like jack hammers that make the kids mouths hit the ground.
> 
> When you have a properly designed horn sub if the bass is there you get it. From the chest pounding smack of a concert bass drum to what ever the composer planned to kick your ass in the music. I like it.
> 
> What else?
> 
> You talk about power with 500 watts. Let me back this up a bit and relate power to loudness. 500 watts is 3 db louder than 250 watts. A trained musician or really good listener will hear the difference. Halve it again and you get 125 watts. A drop in 6 db. This you will notice. But the difference in power output is what 375 watts! Speakers are really inefficent ways of getting sound to our ears. They need alot of power to get them loud. Horn loading a driver makes it act as if it is more efficient. Remember that 3 db increase in sound requires double the power. Well a well done horn will get you 9 db more efficiency. That is 2 * 2 = 4 * 2 = 8 times more efficient than a standard loudspeaker. That is a real big gain.
> 
> Now think about it like this. If you like it loud in your car. The peaks are usually around 110db or maybe 116 db. I'm talking the bass peaks. How much power do you need to get a normal car sub to get to that level?
> 
> 85db/watt is a standard car driver for the low end. So 110-84 = 26 db difference from one watt to where we want to get. Pour in 200 watts and you get where you want to be. Loud damn loud. 110db
> 
> Put the same driver in a horn and what happens. Plus 9 db from the get go. So you start off with 93 db/watt. How much to get to 110db? 200/2=100 watts 3db less 100/2=50 watts 3db less 50/2=25 watts the last 3 db difference. So in a horn the same driver gets you the same SPL at 25 watts. Now were cooking with gas! Your amp has huge amounts of headroom. The driver has not been sucking in wattage that will warm it up changing it's resistance and causing power compression.
> 
> The greater efficiency means that for a given SPL the driver is moving forward and backward less. Much less. So you again get less distortion.
> 
> Build it. Try it and maybe you will like it. If you can't stand the boom boxes that make everything sound like an over grown bass fart then a horn is for you.
> 
> Mark


----------



## Patrick Bateman

mwmkravchenko said:


> Patrick where are the design drawings for your triple? I bet quite a few folks would like to take it for a test drive?


If I *had* plans, I'd post 'em!

I literally built it because someone on the forum was complaining about the notch in the output of the 12" version.

I'd been screwing around in Akabak, and realized that Tom Danley, the inventor of the tapped horn, seemed to be using multiple woofers to smooth out the response.

So based on a hunch, and an interest in eliminating the notch in the twelve inch version, I built the triple8.

I didn't buy as single sheet of wood, and all the drivers were laying around the garage. The whole thing came together in under eight hours, including the measurements. I've probably invested more time writing about it, and encouraging people to try tapped horns, than I've spent building it.

If I'd "trued" all the horizontal pieces, to insure their height was absolutely perfect, the box would have come together in less than four hours. The most difficult part of the build was filing down half the pieces, which varied by a fraction of an inch here and there.

Anyways, the plans for the 12" version are here, and the 8" version uses the exact same mouth and throat. The only difference is the addition of extra paths. If you look at the pic, it's easy to figure out where the pieces go. If your off by half an inch here or there, it won't make any difference.

http://www.diymobileaudio.com/forum...65945-small-tapped-horn-car-2.html#post839067


----------



## Brian Steele

mwmkravchenko said:


> Hi Brian and Jasun
> 
> This is for both:
> 
> The car cabin gain is independent of any type of loudspeaker.



Um, I don't think so. I've seen more than one report of the years of persons testing out horn loaded systems in a vehicle and not getting the gain they expected to see. 

I suspect a lot of this is likely due to the horn playing the part of a transformer, the output being very dependent on the loading at the mouth. The closed environment of a car's cabin is VERY different to that of a room, hall or open air environment where you are more likely to see horns used.




mwmkravchenko said:


> 85db/watt is a standard car driver for the low end. So 110-84 = 26 db difference from one watt to where we want to get. Pour in 200 watts and you get where you want to be. Loud damn loud. 110db


You've forgotten one thing - cabin gain. Makes a HUGE difference in response capabilities. There's a reason why you see "standard" car drivers having that efficiencies around that level - it's part of achieving a good compromise between box size and output in a vehicle.




mwmkravchenko said:


> Put the same driver in a horn and what happens. Plus 9 db from the get go. So you start off with 93 db/watt. How much to get to 110db? 200/2=100 watts 3db less 100/2=50 watts 3db less 50/2=25 watts the last 3 db difference. So in a horn the same driver gets you the same SPL at 25 watts. Now were cooking with gas! Your amp has huge amounts of headroom. The driver has not been sucking in wattage that will warm it up changing it's resistance and causing power compression.


That's actually one good argument for horns, but unfortunately it's not enough IMO for car audio environment.

In any case, if anyone wants a good idea of what the best compromise is for getting good bass in a vehicle, simply look at what's available in the market or in use by car audio fanatics. I'll bet that you'll find that 1% or less car audio fanatics are using bass horns for that purpose. And it can't be just the complexity that's the cause - SQ fanatics are typically not fazed by that . If there was a significant and noticeably positive reason for using bass horns in a car, I'd expect to see a lot more of them in use by now, particularly as horns have been around for decades, as has been car audio.




mwmkravchenko said:


> The greater efficiency means that for a given SPL the driver is moving forward and backward less. Much less. So you again get less distortion.


This is not exactly true. Like all other alignments, it depends on the implementation. If you don't do it right, you can end up with horrible excursion control at the lower end of the horn's passband. And this can be a BIG problem if you select too high a cutoff for your horn, assuming that the car's "cabin gain" will fill in the rest.


----------



## Brian Steele

Patrick Bateman said:


> So based on a hunch, and an interest in eliminating the notch in the twelve inch version, I built the triple8.


An easier way might have been to simply loosely stuff part of the horn .


----------



## mwmkravchenko

Um, I don't think so. I've seen more than one report of the years of persons testing out horn loaded systems in a vehicle and not getting the gain they expected to see.

I suspect a lot of this is likely due to the horn playing the part of a transformer, the output being very dependent on the loading at the mouth. The closed environment of a car's cabin is VERY different to that of a room, hall or open air environment where you are more likely to see horns used.

Brian I think you are agreeing in one way with me and misapplying the term in another way.

Your completely correct about horn in car location and response variations. I posted a bit about that myself. But cabin gain is independent of the source. It is a function of the cabin's interior dimensions when excited by a pressure wave. No matter what kind of a box produces that wave you will get the attendant gain. I think you agree on that point. I only factor that part of the response in when I can measure the car and the person wants a really flat system. And that "flat" response is out the window as soon as there is any road noise. Cars are a pain in the butt. 

Jasun: Sometimes it helps to add the details sometimes it is an exercise in boredom.

Originally Posted by mwmkravchenko 

Put the same driver in a horn and what happens. Plus 9 db from the get go. So you start off with 93 db/watt. How much to get to 110db? 200/2=100 watts 3db less 100/2=50 watts 3db less 50/2=25 watts the last 3 db difference. So in a horn the same driver gets you the same SPL at 25 watts. Now were cooking with gas! Your amp has huge amounts of headroom. The driver has not been sucking in wattage that will warm it up changing it's resistance and causing power compression.

That's actually one good argument for horns, but unfortunately it's not enough IMO for car audio environment. 

Not good enough for who? You maybe.  

But please leave the thinking to the people reading this thread. The reasoning in the posts I made is based on sound logic and experience. Out of your own accord you have said that you have not built a horn nor listened to one in a car. When you have tried it and not liked it then you can knock it. Until then it is but an unsubstantiated opinion.

And I mean no disrespect in the comment about you not having heard a horn in a car. Some of these horns are pretty damn small as you know from my thread in diyaudio and from Patricks thread there and here. These boxes pump out sound at volumes you could never achieve with a box the same size using any other means. Some horns are monsters that would make anyone with an ounce of sanity say no way man not in my car! The trick is in getting the most for the least. That is where the real engineering comes into play. I enjoy the learning curve and the pay-off when I get to listen to the results. I share the results because I enjoy them so much myself. 


Quote:
Originally Posted by mwmkravchenko 

The greater efficiency means that for a given SPL the driver is moving forward and backward less. Much less. So you again get less distortion.

This is not exactly true. Like all other alignments, it depends on the implementation. If you don't do it right, you can end up with horrible excursion control at the lower end of the horn's passband. And this can be a BIG problem if you select too high a cutoff for your horn, assuming that the car's "cabin gain" will fill in the rest. 

Man I think you like to disagree just to get me up on my little soap box. 

How about this line of reasoning:

If a driver has a greater mechanical efficiency because it is in an acoustical transformer ( horn ) it has less excursion than the same driver in a vented or sealed enclosure. So it therefore has to move less in a horn to develop a given SPL than in a conventional box.

A properly constructed horn that has been measured and presented in this thread is here for the discussion. It works as specified. Any box can be fubarred into not working. And almost any alignment for a given loudspeaker can be built by most people if they put their mind to it. And if attention to detail is given it will work as planned, modeled and tested. A horn has particular needs. A high pass filter if plan on going loud and proud is a needed item. Trying to drive a horn below it's passband will quickly kill as both of us know Brian  And to be very fair to your comment a well designed horn is not as easy as it may appear. There is a lot of tweaking that has to be done to get them to work as optimally as can be achieved.

Your website is a testament to that concept right? A good box design is presented and there for all to see admire and build. You are an experienced person when it comes to sound reproduction to be sure.

So I'm quite sure that at some point you will take some of your well thought out horn designs that you have presented and build one. Remember I have offered to make up a fold for you if so choose. So I'm throwing down the gauntlet.

You post the design and I will post a fold for you. If you are to collaborate on the design I'm guessing that Patrick may want to take a kick at this to. Maybe between the three of us there is a full brain! 

May I suggest a four driver horn ala Patrick Bateman concept using the well thought of MCM 8" driver. Four of these puppies will get you an ability to absorb 800 watts without a hickup. The ultimate SPL capability is through the roof. The box size will be dictated by the desired low end response. And if you want louder and prouder you can switch out the MCM drivers and insert the TRIO8's or the ID 8's. Options my good man are always a good thing.

The only pain in the butt is that it is not so easy to model in Hornresp. But it can be done now that you can bounce the box design in Hornresp to a design to look at in Akabak with relative ease. 

Mark


----------



## mwmkravchenko

Some fuel for a healthy fire. If any one wants to take a poke at these two designs be my guest. I've built working versions of them in a different format. With different drivers. I just plunked in the drivers that were talked about here quickly. The larger box has had 5 minutes worth of optimization. A bit more could be squeezed out if there is any interest. Patrick this is your thread if there is any interest in this you say the word and I will start another thread. If you are interested in a collaboration then lets go for it. I know you could build this puppy. If you have better ideas then by all means your the boss. Brian has some good ideas as well. Maybe we can twist his arm to give this try.

Mark


----------



## Brian Steele

mwmkravchenko said:


> Brian I think you are agreeing in one way with me and misapplying the term in another way.


Um, no. When designing a subwoofer system for my car, I measure the transfer function first with a test box, then design the subwoofer accordingly. Normally I'm within a few dB of the target with this approach - but then I again I normally stick to direct radiator designs. From what I've read, I cannot use this approach with a horn because the response of the horn itself is significantly and sometimes adversely affected as soon as you place it in-car.



mwmkravchenko said:


> Not good enough for who? You maybe.


Me and I'll bet about 99% of the car audio crowd . I think a quick survey of the respondents here should quickly indicate what percentage have even considered using bass horns in their cars, much less actually chosen that approach over simple sealed or vented alignments.




mwmkravchenko said:


> Out of your own accord you have said that you have not built a horn nor listened to one in a car. When you have tried it and not liked it then you can knock it. Until then it is but an unsubstantiated opinion.


I actually tried out my tapped pipe in-car. It did Ok, but frankly the 2.5 cu.ft. it took up could have been put to better use with a simple sealed or vented alignment. Then again it was a cheap 6.5" driver. Even then, if I replaced it with an 8" with significantly more excursion potential, I still couldnt touch the capability of two 12" sealed in the same volume, and the latter offer more flexibility in terms of box design AND provide protection against over-excursion below Fb.

This coming weekend I'll pull out TrueRTA and do some actual measurements to see how it compares to a few other subs I have lying around. My first impressions though were clean but peaky bass with no real low bass to speak off unless I opened a door. However, the meter doesn't lie, so I'll deploy it this coming weekend to see what it says.




mwmkravchenko said:


> Some of these horns are pretty damn small as you know from my thread in diyaudio and from Patricks thread there and here. These boxes pump out sound at volumes you could never achieve with a box the same size using any other means.


I saw your thread about your "unhorn". You quoted 112dB in car? How much did it actually produce before one of the drivers was damaged? Did you measure its peak SPL capability?

Bear in mind that a cheap 12" like the Hsu Research ASW1203 is capable of over 120dB sealed in the same volume AND you are in absolutely no danger of damaging it by overexcursion below Fb unless you use really ridiculous power levels. And that's not even a driver designed for high SPL levels. 




mwmkravchenko said:


> Trying to drive a horn below it's passband will quickly kill as both of us know Brian


Oh certainly. Which means that if you're going to be designing a horn for the car audio crowd, you'd better be considering designing for an Fb of 35 Hz or below with good excursion control throughout the passband, unless you want to be replacing drivers every time the guy behind the volume control wants to play some really deep bass through his system. Considering that the target Fb significantly impacts horn length and mouth size, and therefore box volume, this isn't a trivial requirement by any means.




mwmkravchenko said:


> You post the design and I will post a fold for you.


Actually, I think I did that already - a TH with a slightly different approach to the throat configuration. See post #254 on your thread. However, that alignment I came up with wasn't designed with car audio in mind. If I was designing with car audio in mind, I'd go for something a little different.





mwmkravchenko said:


> If you are to collaborate on the design I'm guessing that Patrick may want to take a kick at this to. Maybe between the three of us there is a full brain!
> 
> May I suggest a four driver horn ala Patrick Bateman concept using the well thought of MCM 8" driver. Four of these puppies will get you an ability to absorb 800 watts without a hickup. The ultimate SPL capability is through the roof. The box size will be dictated by the desired low end response. And if you want louder and prouder you can switch out the MCM drivers and insert the TRIO8's or the ID 8's. Options my good man are always a good thing.


Ok, if I was going for a TH alignment for in-car use, here's what I'd be aiming for.

1. Fb = 30 Hz. Any higher and we're in danger of some idiot at the controls destroying the driver by playing his bass CD and cranking the volume to see how high it can go. I may settle for a 35 Hz corner but certainly not any higher. I also want the driver to remain within its excursion limits for Pe throughout the passband, and I want the Fb low enough so that 98% of all music fits within the passband and therefore the excursion target.

2. Flat but rising response from Fb to 100 Hz, somewhere around 6dB/oct. This should allow most persons to achieve flat or near flat in-car response with simple EQ.

3. Box size 2.5 cu.ft. (net) or less. Yes, box volume IS a definite limiting factor for the car audio world. Not many of us like BABs in the trunk . In fact, one of the major reasons I purchased my current SUV was because it was one of the few small SUVs that had an internal spare tire well, which I now use to house my subs, so my entire trunk space is still available for other uses .

4. I'd allow for the implementation of the horn as a stepped horn, as this would likely not introduce and response variations within the design passband.


----------



## GPM

FWIW, I did a TH Vs BR comparison using Brian's TP 6.5" Pyle driver awhile back and never got around to posting it, so not exactly what you're looking for, but does show a trend of what to expect.

Anyway, the TH sim of course is bigger than a BR for the same gain BW, like 3x bigger, and to get ~ the same sensitivity the multiple drivers must be wired in parallel, so as the impedance plot shows, they're sucking more current, ergo heating up/distorting quicker. Not knowing its Pe, Xmax, I don't know which would limit the 3x BR, but the TH would most likely be Xmax limited.

The TH isn't an optimum one though for this BW, so while its SQ should be higher due to a much larger radiating area than the three drivers combined with it being almost an order of magnitude larger than the BR's 6" diameter vent it's not going to win the SPL race for a given bulk if there's plenty of power on tap along with a multiple driver budget.

I haven't worked out an optimum TH for the BW beyond it needing a ~82.75 Hz Fs, but such alignments typically are ~35-40% efficient (~107.4-108 dB), ergo so highly damped that its excursion is very low through its pass-band, so if the driver has the right specs to fit in the same bulk it should in theory not only 'blow the doors' off the 3x BR, but do it at very low distortion to boot.

GM


----------



## Brian Steele

GPM said:


> FWIW, I did a TH Vs BR comparison using Brian's TP 6.5" Pyle driver awhile back and never got around to posting it, so not exactly what you're looking for, but does show a trend of what to expect.
> 
> Anyway, the TH sim of course is bigger than a BR for the same gain BW, like 3x bigger, and to get ~ the same sensitivity the multiple drivers must be wired in parallel, so as the impedance plot shows, they're sucking more current, ergo heating up/distorting quicker. Not knowing its Pe, Xmax, I don't know which would limit the 3x BR, but the TH would most likely be Xmax limited.


The 3xBR may be sucking more current, but now input power is spread across three drivers instead of one. What in terms of power is each driver in the 3xBR going to see, compared to the 1 driver in the TH at the same SPL level?

What is the predicted net Vb for the TH alignment?


----------



## mwmkravchenko

Hi Brian and Greg

I did not do ultimate SPL with any tapped horn I have in my car. I don't have the power. I attached a pic of my head unit. I have the rear channels bridged for the sub so I like to use something that has high efficiency. If I could squeeze out a real 40 watts I'd be pushing it.

As for SPL I did get 112 with 5 watts steady state sine wave. That was not killing the drivers. What killed the driver was a voice coil rub that I did not really pay attention to until it got so bad that it was very obvious. I always do impedance tests before and after putting drivers into the box and the rear driver had a nasty spike that PAtrick already posted. Not what the doctor ordered.

As for ultimate SPL the latest horn with the relocation of the drivers to properly match the simulation tracked the simulation within 1 db when I used 5 watts so ultimate SPL I posted below.

I know the guys reading this are thinking. Just a computer simulation. But I have to admit I have come to respect this program a great deal. It is quite accurate in the way it predicts the way a horn works if you take the time to understand how the program models the driver in the box. I can attest to it's accuracy over a couple of designs. 

Mark


----------



## Brian Steele

mwmkravchenko said:


> I know the guys reading this are thinking. Just a computer simulation.


Not me - I have great respect for computer simulations. The old adage is "measure twice, cut once". The new adage is "simulate ten different versions, select one, measure twice, cut once" . That's even more important when you live in a country that's so far away that transportation costs and duties ensure that the final cost of any driver you buy will be 2~3 times its purchase price. 




mwmkravchenko said:


> But I have to admit I have come to respect this program a great deal. It is quite accurate in the way it predicts the way a horn works if you take the time to understand how the program models the driver in the box. I can attest to it's accuracy over a couple of designs.


The one time I've built an enclosure that I use HornResp to model suggests to be that it's a pretty decent modeling tool. However, to more accurately compare its results to those predicted by other software that uses t/s parameters to model direct radiator systems, you need to use 2xPI space modelling, otherwise you end up with a misleading result that's significantly biased towards the HornResp model wrt efficiency. A possible alternative is to simple use HornResp to model the direct radiator systems too, but I haven't tried that yet (my spreadsheet offers a bit more flexibility than HornResp, as it allows me to model the effects of active filtering and measured room gain, so I haven't been tempted to use HornResp for direct radiator systems).


----------



## mwmkravchenko

The one time I've built an enclosure that I use HornResp to model suggests to be that it's a pretty decent modeling tool. However, to more accurately compare its results to those predicted by other software that uses t/s parameters to model direct radiator systems, you need to use 2xPI space modelling, otherwise you end up with a misleading result that's significantly biased towards the HornResp model wrt efficiency. A possible alternative is to simple use HornResp to model the direct radiator systems too, but I haven't tried that yet (my spreadsheet offers a bit more flexibility than HornResp, as it allows me to model the effects of active filtering and measured room gain, so I haven't been tempted to use HornResp for direct radiator systems).

This is modeled in a car environment or a corner environment. 1/8th space. No cabin gain included as it is not available in Hornresp. But to compare any other driver you add 6 db to it's response and your rather close to actual when you put it into a car.

I hate using Hornresp to model normal boxes. It's not worth the effort. I use Bass box, SoundEasy, LEAP, LSPcad and WinISD. They are designed for the normal boxes. I tried some spreadsheet programs like Unibox to. It depends on the math that they use to make the simulations. I may know a thing or two about drivers and boxes but when it comes to complex math shoot me please! A quick way to insanity. I can do the math it just takes me forever. I started horns when I had to do the calculations for each inch of length. Then I found some wonderful BASIC program by some dude in Speaker Builder magazine that made my life a whole lot easier. We have come a long way from there. I've done 50 designs in the past month and I have only committed two of them to wood and saw dust. The rest are in the wings waiting for a purpose.

Mark


----------



## Brian Steele

mwmkravchenko said:


> This is modeled in a car environment or a corner environment. 1/8th space. No cabin gain included as it is not available in Hornresp. But to compare any other driver you add 6 db to it's response and your rather close to actual when you put it into a car.


I think it's a bit higher than that at the frequencies we're talking about here.

As programs that do modeling for direct radiator systems typically assume 2*PI space, I prefer to simply stick to 2*PI modeling in HornResp for quick comparison purposes, rather than add a fudge factor to the output from the direct-radiator models. The difference between measured vs. actual is then "room gain" .


----------



## jsun_g

I think it was Andy W. who posted a picture of in-car transfer functions for several vehicles. The cabin gain in the lowest octaves is very vehicle-dependent. You may get a LOT more than 6dB depending on the vehicle, location of sub box, and firing direction of the sub.
If I'm getting 144dB at 49Hz with 1200 watts, that equates to a little under 114dB at 1 watt at that frequency. I am praising cabin gain and a ported box for that.



Brian Steele said:


> I think it's a bit higher than that at the frequencies we're talking about here.
> 
> As programs that do modeling for direct radiator systems typically assume 2*PI space, I prefer to simply stick to 2*PI modeling in HornResp for quick comparison purposes, rather than add a fudge factor to the output from the direct-radiator models. The difference between measured vs. actual is then "room gain" .


----------



## mwmkravchenko

Hi Brian

We both agree but I will state a bit more about what I mean. A direct comparison in 2 Pi space or a floor only, no walls or ceiling. That is how a normal loudspeaker modeling program should work. But a horn as well as a direct radiator enclosure (normal woofer in box) are more efficient when you add a wall you can add 3 db add another wall to get two walls and a floor that meet in a corner add another 3 db. Add the ceiling and you add the final 3 db. So in a confined corner space with a floor and ceiling you get quite a boost in efficiency. The last kind of space is what a car works out to. That is until as Brian said you add in the difference in cabin gain and you get another different animal. A normal room has cabin gain as well. It just starts a bit lower in frequency in a house.

Here is a cool study in how cabin gain works:

The Subwoofer DIY Page: Measuring a car's transfer function

Couldn't resist Brian!

Mark


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## blamus

mwmkravchenko said:


> Here is a cool study in how cabin gain works:
> 
> The Subwoofer DIY Page: Measuring a car's transfer function
> 
> Couldn't resist Brian!
> 
> Mark


A drop of cold sweat actually emerged from my forehead, and then I was laughing and rolling all over the floor!!!! Indeed, how could you resist!!


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## mwmkravchenko

That's Doctor Evil to you! Not frickin Mr. Evil Did'nt go to frickin evil school for seven years to be called frickin Mr.Evil! 

Mark


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## Brian Steele

mwmkravchenko said:


> Hi Brian
> 
> We both agree but I will state a bit more about what I mean. A direct comparison in 2 Pi space or a floor only, no walls or ceiling. That is how a normal loudspeaker modeling program should work. But a horn as well as a direct radiator enclosure (normal woofer in box) are more efficient when you add a wall you can add 3 db add another wall to get two walls and a floor that meet in a corner add another 3 db.


Actually, it's closer to 6dB per halving of the space. Going from floor to floor+wall adds about 6dB, and moving from that to corner adds another 6dB. This can easily be checked using the HornResp modeling wizard, set it to "Response" and "Other", then using the Ang slider to vary the radiation space. 




mwmkravchenko said:


> So in a confined corner space with a floor and ceiling you get quite a boost in efficiency. The last kind of space is what a car works out to.


Not quite - a car's cabin is an *enclosed space*, which changes the issue somewhat. I may be wrong, but I don't think the HornResp model can actually model the response of horns in fully-enclosed spaces of a specific volume. HornResp assumes the horn's mouth exits into free space, albeit with a restricted radiation angle of your choosing.




mwmkravchenko said:


> Here is a cool study in how cabin gain works:
> 
> The Subwoofer DIY Page: Measuring a car's transfer function
> 
> Couldn't resist Brian!
> 
> Mark


Yeah, my diysubwoofers site seems to be a veritable wealth of knowledge on DIY subwoofer design - who would've thought? .

To be pendantic though, that's a study in a car's transfer function, which could be interpreted as cabin gain (caused by the cabin's dimensions as you previously mentioned) plus the impact of other effects (like the notch around 70 Hz for example, which varies based on listening position), but the two are used interchangeably by many, including myself, LOL. 

In any case, I now use a much updated version of that spreadsheet that allows me to enter and use the actual measured transfer function, rather than using a theoretical cabin gain model (which doesn't take into account the above-mentioned effects).


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## mwmkravchenko

Hi Brian

I realise that what you have posted fits the text books. But what I have found for better or worse that eeach boundary from open space no obstuctions in any dimension is this. Add a floor or wall whatever you get a 3 db increase. The only difference is in a car I fully agree that you can get a plus 6db over same placement in a house.

More or less thinkin out loud I guess.

Mark


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## Brian Steele

mwmkravchenko said:


> I realise that what you have posted fits the text books. But what I have found for better or worse that eeach boundary from open space no obstuctions in any dimension is this. Add a floor or wall whatever you get a 3 db increase. The only difference is in a car I fully agree that you can get a plus 6db over same placement in a house.


Mark, you do realise that this basically invalidates the 0.5*PI HornResp peak SPL predictions, right? You're looking at a difference of almost 6dB between the HornResp prediction and actual results, if we assume a real-life gain closer to 3dB than 6dB when the radiation angle is halved. That's not an insignificant amount. In fact, it's even more justification to take my suggested approach to modeling the things, i.e. model for 2*PI space for easy comparison with direct radiator systems modeled with the usual box programs. With this approach, actual output is in this case is likely going to be more than predicted (due to room again, <2*PI space, etc), and for subs it's usually good to end up with results that are better than predicted, rather than worse .


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## mwmkravchenko

Brian I hate it when we agree

But it's hard to argue when you are right.

Mark


----------



## Patrick Bateman

Brian Steele said:


> An easier way might have been to simply loosely stuff part of the horn .


That doesn't work in a tapped horn.









This is the in-car response of my TH-Mini clone. It uses a single 12" woofer. There's a deep null at 150hz. I tried stuffing the enclosure, but the null remained, and the overall efficiency suffered. Stuffing improves the response above 1khz, but at low frequencies, it's all about the geometry.









Purple is the triple8, dark red is the TH-Mini clone. Note the null is gone, with the use of staggered woofers.

If I'm not mistaken, all of the new tapped horns being sold commercially are using multiple woofers. One of the new ones uses EIGHT twelves in a single cabinet.









And of course there's THIS one...


----------



## Patrick Bateman

Brian Steele said:


> Um, I don't think so. I've seen more than one report of the years of persons testing out horn loaded systems in a vehicle and not getting the gain they expected to see.
> 
> I suspect a lot of this is likely due to the horn playing the part of a transformer, the output being very dependent on the loading at the mouth. The closed environment of a car's cabin is VERY different to that of a room, hall or open air environment where you are more likely to see horns used.
> 
> 
> 
> 
> You've forgotten one thing - cabin gain. Makes a HUGE difference in response capabilities. There's a reason why you see "standard" car drivers having that efficiencies around that level - it's part of achieving a good compromise between box size and output in a vehicle.


A couple weeks ago I measured all three subs in this thread, outside AND in-the-car. Then the stupid program I use to do the plots crashed 

So I wish I could bust out a bunch of graphs and demonstrate that cabin gain works with horns too, but unfortunately, the measurements are gone.















Though most of the measurements in AND out of the car are AWOL, I *do* have the measurements of the AutoTuba clone. The red line in the top graph is the AutoTuba clone outside; the red line in the bottom graph is the AutoTuba clone in the car. Both measurements are done at the identical volume, so we can make a fair comparison. Here's what we see:


At 200hz, the horn is 3db quieter in-car than outside. This is the attenuation from the rear seat.
At 160hz, the SPL is identical in and out-of-car.
At 80hz, the horn is 9db louder in the car than out. This is unusually high; with a sealed sub I normally get a bump of about half that.
At 40hz, the horn is NINETEEN DB louder in the car. Did someone say that cabin gain doesn't work with horns? Check out the graph - that's a ton of gain.
At 20hz, the horn is TWENTY SIX DB louder in the car. This is fairly normal for my car.
The most interesting thing about the measurements is how FLAT they are. I have never measured a speaker in-car that measured this flat. It's amazing.

These measured results sure put an end to the myth that cabin gain doesn't work with horns. If anything, _horns seem to pick up more cabin gain than even a conventional sealed or vented subwoofer._ Admittedly, they're complex to build, but the bump in efficiency combined with a reduction in distortion is well worth the trouble IMHO.

In defense of the sealed box, it DOES have higher efficiency from 20 to 30hz. The horn is tuned to 40hz, and below that frequency, the horns efficiency advantage dwindles.


----------



## Brian Steele

Patrick Bateman said:


> That doesn't work in a tapped horn.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This is the in-car response of my TH-Mini clone. It uses a single 12" woofer. There's a deep null at 150hz. I tried stuffing the enclosure, but the null remained, and the overall efficiency suffered. Stuffing improves the response above 1khz, but at low frequencies, it's all about the geometry.



Here's a picture comparing the FRs of my tapped-pipe, stuffed and unstuffed.










It's clear from the picture that stuffing does work. The deep nul between 150 Hz and 200 Hz has basically disappeared. In fact, the effects of the stuffing appear to start at early as 110 Hz or so. The first half of the tapped-pipe was stuffed.

Now, admittedly I didn't measure the change in efficiency, but my ears told me that it was not significant. I'll make a note to repeat the tests when I have some time, but this time keeping an eye on efficiency. The design of the pipe gives me access to all sections, which makes it easy for me to repeat the measurements.

Where did you place the stuffing in your tapped-horn?

With respect to your FR measurements, aren't you comparing horns of entirely different geometries? 

A more convincing experiment to show the positive effect of staggered drivers would be to use a horn with the *same* geometry, but with the option of varying the driver location (perhaps a square baffle plate with two drivers mounted side by side on it - just rotate the plate to change the orientation of the drivers in the horn).

I suspect that Tom uses multiple drivers in some of his designs (like the Matterhorn, for example) simply because it might be difficult, even impossible, to obtain a single driver that has the optimum combination of parameters, including physical dimensions, that's required to make the design work best.


----------



## Brian Steele

Patrick Bateman said:


> These measured results sure put an end to the myth that cabin gain doesn't work with horns. If anything, _horns seem to pick up more cabin gain than even a conventional sealed or vented subwoofer._ Admittedly, they're complex to build, but the bump in efficiency combined with a reduction in distortion is well worth the trouble IMHO.


Good stuff. I don't think the question was about if cabin gain works with horn, but how well it works with horns. but it's good to see measurements that back up results, particularly when they challenge existing "myths" .


I'll take a more detailed look later on at your measurements (work calls!), but I've got some questions:

1. Was the cabin properly sealed (i.e. windows up, doors closed) when you did the in-car measurements?

2. Did you repeat the measurements with the rear seat down to determine that the -3dB loss was actually due to the effect of the rear seat? In my last sedan, a Mazda Protoge, the filtering effect of the rear seat actually started much lower - around 60 Hz if I remember correctly. I may even have the actual measurements floating around somewhere - will take a look for them later. I keep a lot of my old measurements, but we are talking over a decade ago. Back in those days I actually had to unscrew the seat from its frame to remove it for the tests - no folding down seats like you have today .


----------



## mwmkravchenko

Hi Brian

I'm not so sure that a tapped pipe is the same thing as a tapped horn. A tapped pipe has some attributes of a transmission line. So it can benefit from stuffing. Geitmans (Dual 8" tapped horn = TH-SPUD - diyAudio) in his tapped horn thread used stuffing to great effect. He did a redesign of the SPUD. But what he ended up with in the terms of stuffing was to tame the upper resonances if I remember correctly 

That being said Danley's tapped horns do have some lining but not stuffing. He also uses resonators to get the third impedance peak that is not present in Patrick's design or the ones I have posted. I have simulated real tapped horns it's just that I don't like stepping on the fingers of people that need to make a living off of their designs. There are other people I have spoken to and e-mailed that have done true tapped horn designs and I think they feel the same way.

Mark


----------



## Brian Steele

mwmkravchenko said:


> Hi Brian
> 
> I'm not so sure that a tapped pipe is the same thing as a tapped horn. A tapped pipe has some attributes of a transmission line. So it can benefit from stuffing. Geitmans (Dual 8" tapped horn = TH-SPUD - diyAudio) in his tapped horn thread used stuffing to great effect. He did a redesign of the SPUD. But what he ended up with in the terms of stuffing was to tame the upper resonances if I remember correctly


Actually, that's more like lining than stuffing, but if you look at the before/after FR charts he published, you'll see that the notches above 100 Hz are reduced in depth - exactly the kind of effect I'm suggesting would happen. 

I used a LOT more stuffing in my tapped pipe, but only for part of the pipe, near the throat. The before/after FR chart suggests it works very well. You might want to try it out in your dual-Trio8, now that you're planning to leave one panel free.


----------



## mwmkravchenko

You might want to try it out in your dual-Trio8, now that you're planning to leave one panel free.

I'm with you on that one. But initial testing on the other one did not show a huge amount of problems up above where you would setup a crossover point at any rate.

Hey Patrick

I have been studying your triple 8 design. It has quite a few similarities to the designs that I have been fooling with. The similarity being the negative flare at the half way point. The difference being the negative flare at the beginning. Have you modeled it as built?

And for the gents on this forum do you have max SPL figures for your box?
Mark


----------



## Patrick Bateman

Brian Steele said:


> Actually, that's more like lining than stuffing, but if you look at the before/after FR charts he published, you'll see that the notches above 100 Hz are reduced in depth - exactly the kind of effect I'm suggesting would happen.
> 
> I used a LOT more stuffing in my tapped pipe, but only for part of the pipe, near the throat. The before/after FR chart suggests it works very well. You might want to try it out in your dual-Trio8, now that you're planning to leave one panel free.



I agree that stuffing can smooth the response. In an offset horn, there's a big price to pay unfortunately.

I spent Sunday doing a TON of measurements - literally about eight hours worth. In a horn with an offset driver, the low frequency response took a real hit with stuffing.

Unity Horns and Tapped Horns are a strange beast in this respect. Because the woofers aren't located at the throat, the low frequency response DEPENDS on reflections.

Anyways, measurement after measurement, stuffing an offset horn raised the F3 by a significant amount. Even an octave or so.

One "neat" thing about horns and transmission lines is that there's a ton of options to smooth the response without hurting efficiency. Here are a few examples, off the top of my head:


After noticing that all the new Danley subs use arrays of woofers, I tried it myself. HUGE improvement. The additional woofers smooth the response. You can see this in my measurements of the TH-Mini clone and the Triple8. The Triple8 doesn't have any severe peaks and dips like the TH-Mini clone does.
In my 'natural bass' thread I've been discussing the use of multiple woofers to smooth the in-room (or in-car) response. Another neat thing about horns or transmission lines is that you can use multiple mouths on a single horn. I tried that with a design that I built over the weekend, and it appears to work. So the sims don't show an improvement, but you can see an improvement in the in-room polar response.
Stuffing the horn *does* fill in the dips in the response, but at the cost of efficiency. One idea I've toyed with is that stuffing could "tame" the behavior of a woofer that's not appropriate for a horn. For instance, if you had a driver with a high QTS it would be very peaky in a horn. Stuffing could tame the "hump" at the low end, while filling in the dips in the midrange. A better driver would be more efficient though.


----------



## Brian Steele

Patrick Bateman said:


> Anyways, measurement after measurement, stuffing an offset horn raised the F3 by a significant amount. Even an octave or so.


Where did you place the stuffing in the horn?


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## mwmkravchenko

Hi Patrick

Whats up with weekends and getting stuffed?

I did the same test two weekends ago. Sad results. I lost 6 db over the pass band. But the impedance smoothed out so much it looked like a transmission line. The Qts went all over the place to. So for what it is worth I agree in the utmost terms. Leave stuffing out of the horns. But localized padding is a different story. It can tame some of the nasty higher frequency garbage we can get out of a tapped horn. But so can an inductor at the expense of some efficiency. 

The box I'm working with is fairly even in response. It is just not as efficient as your design.

With my foolings around I have come close to copying your designed box myself. Interesting if you do a bit of manipulation of some of the panels you can clean up the peaked response. It also models more like a tapped horn ( at least the older ones with the three impedance peaks).

Have you noticed as of latest tapped horn designs have only two impedance peaks similar to your design?

But I have to say that these boxes with these little drivers can do a whole lot of shaking. Thanks for the info you have posted so far.

Mark


----------



## Brian Steele

mwmkravchenko said:


> Hi Patrick
> 
> Whats up with weekends and getting stuffed?
> 
> I did the same test two weekends ago. Sad results. I lost 6 db over the pass band.


Whoa, that is a significant difference. I'll have to repeat my tests when I get the opportunity to see how much loss my TP actually suffers due to stuffing. 

Can you provide some details about where you applied the stuffing in the enclosure?


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## mwmkravchenko

Brian Steele said:


> Whoa, that is a significant difference. I'll have to repeat my tests when I get the opportunity to see how much loss my TP actually suffers due to stuffing.
> 
> Can you provide some details about where you applied the stuffing in the enclosure?


Stuffed as in T-Line. From the rear resonant chamber up to the pinch point and loose fill but complete fill. To many people asking stupid questions about what would happen if.... So I gave it a shot. Bad idea. The only benefit as in a T-Line is the flattening of the impedance. The peak was 12 ohms. Pretty easy load. But the rsponse fell by 6 db and the low end went away. Died after 30 hz. As a untouched box it behaves as I posted about 96 db corner loaded. I have yet to rigorously test it in a car. The SPL/ 1watt 1 meter will be higher in a car. But so is every other driver box combination as compared to a house or normal 2Pi model.

Mark


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## Patrick Bateman

mwmkravchenko said:


> Have you noticed as of latest tapped horn designs have only two impedance peaks similar to your design?
> 
> But I have to say that these boxes with these little drivers can do a whole lot of shaking. Thanks for the info you have posted so far.


I did a bunch of measurements that were very revealing yesterday. I built a front-loaded horn and a tapped horn, both with the same drivers. The tapped horn had about 12db more output at low frequency! Even in an ideal world, you would only expect to see an extra SIX db.

Just crazy crazy efficiency.

One thing that was interesting was that the efficiency at high frequencies was comparable.

Here's what I think is going on:

In car audio, we've seen a number of front loaded horns. The AutoTuba is the most obvious example. It appears that at low frequencies, the horn is basically non-existent. The woofers behave as if they're in a sealed box. So they sound ULTRA loud, but that's because of all the gain that occurs at high frequencies. The microphone doesn't lie, and the mic shows that there really isn't any gain at all from 20-80hz.

There's one BIG BIG caveat though. The horn raises the impedance and lowers the excursion. That allows the woofer to drink voltage like it was coming out of a fire hose.

If I were running an AutoTuba, I'd use a low pass to get rid of all the high frequency output, then power it with a monster of an amp, and enjoy it's high power handling and low distortion. I think a lot of people are doing the opposite - they're using small amplifiers and treating it like a "conventional" sub. It's not - it has some peculiar advantages.

The tapped horn is delivering a TON of gain at low frequencies. I think what's happening is that there's a plethora of reflections, which basically create a "comb filtering" effect at high frequency. This lowers output above 200hz or so. But below 280hz, we're in "pressure mode". The wavelengths are so long, they don't even reflect any longer. The woofer is simply pressurizing the car, and the low frequency output at the front AND the back of the cone is summing. Which means that at low frequency, it's basically as if there are four woofers playing, not two. Note that I was seeing 12db more output though. I think the other six db is because the length of the line loads the woofer lower than a sealed box would. (And a front-loaded horn acts like a sealed box at low frequency, not a horn.)

You'll have to see the measurements - the amount of gain at low frequency is a jaw dropper.

Anyways, back to my original point. Small drivers DO get very loud in a tapped horn. I'm starting to think that an array of three or four inch woofers would have lower distortion and a smaller footprint than three eights.

Have you seen the TH-SPUD? Danley uses push-pull in that design. I made one over the weekend that's push-pull, and the measurements appear to indicate that it does indeed reduce distortion.


----------



## SSSnake

> The microphone doesn't lie, and the mic shows that there really isn't any gain at all from 20-80hz.


This is what I have seen with front loaded horns... I would not have expected to see any difference with the TH. I am interested to see what the advantages of a TH may be over the front loaded. I may build one just to experiment.

Have you considered the 8NDL51s in a tapped horn? They seem to meet most of the TH criteria (Fs may be too high???) and I have a pair laying around.


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## marstedt

Not small, and not 'for car' ... but some interesting juice on the latest TH from Danley.

Danley DTS-10 "Super Spud" DIY kit - AVS Forum


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## Brian Steele

mwmkravchenko said:


> Stuffed as in T-Line. From the rear resonant chamber up to the pinch point and loose fill but complete fill. To many people asking stupid questions about what would happen if.... So I gave it a shot. Bad idea. The only benefit as in a T-Line is the flattening of the impedance. The peak was 12 ohms. Pretty easy load. But the rsponse fell by 6 db and the low end went away. Died after 30 hz. As a untouched box it behaves as I posted about 96 db corner loaded. I have yet to rigorously test it in a car. The SPL/ 1watt 1 meter will be higher in a car. But so is every other driver box combination as compared to a house or normal 2Pi model.
> 
> Mark


Below are the results of some measurements I performed tonight on my POC TP. The first image shows the graphs superimposed on one another. The second shows them staggered by 10dB for a bit more clarity. The response of the unstuffed TP is in dark-blue. The brown graph represents the TP's response with the first 1/4 of the pipe loosely stuffed. The pink graph represents the TP's response with the first 1/2 of the pipe loosely stuffed. All measurements were taken close-miked, with the mike and TP fixed in the same location, driven by the same pink noise source, a continuous loop left running at the same level. To ensure that temperature variations were kept to a minimum, the source was played through the TP for several minutes before performing the measurements.

As the graph clearly shows, there isn't any significant loss in the TP's passband, certainly not in the range of 6dB. In fact, the 1/2 stuffed version actually shows a slight gain at lower frequencies. 

More telling though is that most of the major response changes occur above 100 Hz - exactly as I would expect when the pipe's partly stuffed, as stuffing ability to filter sound only starts to become significant above that frequency. The upper response starts to smooth out as the output from the rear of the driver is significantly attenuated before it emerges from the TP. The dip around 180 Hz or so almost disappears at 1/2 stuffing. The huge dip @700 Hz for the 1/2 stuffed version of the TP is curious though. 

Note, as per my previous measurements, these were taken with the TP driven by the subwoofer output from my HT receiver, which means an undefeatable active filter @100Hz, 12dB/oct is applied to the signal before it's fed to the subwoofer. The out of band noise for the unstuffed pipe is clearly audible even with this filter applied, and I can't see how it can be acceptable as a subwoofer if only an inline inductor is used in an attempt to filter out the noise. The 1/4 stuffed pipe and 1/2 stuffed pipes sound a lot smoother and better... less "honky" and "resonant".

Now, I'm not disputing your observations, or Patrick's observations. I'm simply curious as to why such a significant difference in our observations. Maybe, for example, the stuffing needs to be kept away from the narrowest parts of the TH to prevent significant reduction in the passband response. As a TP has constant cross-section, this isn't an issue to worry about.


----------



## mwmkravchenko

Hi Brain

What I made is not a tapped horn. It is more like a tapped tapered pipe. But as you understand it not exactly that either.










Tapped horns and the crazy conjunction of concepts I called an unhorn for lack of a real name rely on both path lengths that are real and that are functional. They also operate on resonance principles or a delay in the time it takes for a pulse of air driven by the woofer cone to get out of the box and excite the air in the room. Thus the term functional path length. I think that at some frequencies the functional length of the enclosure is coming from a combination of the front and rear wave that has been summed due to the time delay created by the length of the enclosure between the two wave fronts ( front and back of the woofer cone). The rear wave has been delayed enough that it is no longer 180 degrees out of phase ( or a mirror image of the front wave that partially cancels the wave from the back when they meet in an unenclosed driver in free air). Then when the correct point is determined to tap the front wave into the horn mouth we get a reinforcement from the rear wave.

When you design a tapped horn you can create an enclosure that has a response that has a trough in the middle. The better placed the tap location in the horn the better the response. Not an easy thing to balance out but when it works it works well.

It is the only way I can explain how such a short enclosure can reproduce such low bass. Then again I stress that this is only a guess. 

My design really relies on resonances to create the low end. The size of the rear chamber has quite and effect on the response. From what I have gathered in terms of "stuffing" this type of cabinet it is a dead loss. I'm not totally sure that your tapered pipe is analogous to a tapped horn. Because both of us with tapped horns found that stuffing was detrimental. The tapered pipe may be behaving like a transmission line more than a horn. Just a guess. Heck I'm not even totally convinced on how either Patrick's or my designs are working. But work they do!

Mark


----------



## Brian Steele

mwmkravchenko said:


> Hi Brain
> 
> What I made is not a tapped horn. It is more like a tapped tapered pipe. But as you understand it not exactly that either.


Whoa - that's a lot of stuffing! I would have probably experimented with half of that or less, and certainly avoided putting stuffing in or near the restricted area just before the expansion into the mouth. That would likely be the equivalent of stuffing the vent of a ported box, with similar detrimental effects. Care to try repeating the experiment under slightly different conditions, e.g. stuffing only half of the section containing the two drivers (from the midpoint until down past the lower driver), or stuffing just the rear volume behind the driver section?





mwmkravchenko said:


> I think that at some frequencies the functional length of the enclosure is coming from a combination of the front and rear wave that has been summed due to the time delay created by the length of the enclosure between the two wave fronts ( front and back of the woofer cone). The rear wave has been delayed enough that it is no longer 180 degrees out of phase ( or a mirror image of the front wave that partially cancels the wave from the back when they meet in an unenclosed driver in free air). Then when the correct point is determined to tap the front wave into the horn mouth we get a reinforcement from the rear wave.


This likely describes the operation of a tapped-pipe as well. FWIW, I consider a tapped-pipe as simply a tapped-horn with a specific boundary condition - constant cross-section across the horn. The process of modelling them is basically identical to modelling a tapped horn, except for this boundary condition, of course.



mwmkravchenko said:


> I'm not totally sure that your tapered pipe is analogous to a tapped horn. Because both of us with tapped horns found that stuffing was detrimental. The tapered pipe may be behaving like a transmission line more than a horn. Just a guess. Heck I'm not even totally convinced on how either Patrick's or my designs are working. But work they do!


Actually, I'm not sure that any of our designs are operating as true horns within the useful passband . More like enhanced 6th order bandpass alignments. But even then, the effects of stuffing part or all of the enclosure should be quite predictable. In my test case, the effects on the response are basically what I would have predicted. In your case, they are apparently not, so I'm just curious as to why, e.g. is there another factor involved that needs to be considered.


----------



## mwmkravchenko

Hi Brian

Care to try repeating the experiment under slightly different conditions, e.g. stuffing only half of the section containing the two drivers (from the midpoint until down past the lower driver), or stuffing just the rear volume behind the driver section?

Been there done that. All I can say is that with any type of fibrous tangle business in this type of box all I get is a loss in response. I did not measure to the degree you did I did so at 5 hz increments. But none the less I still stick to the notion that properly placed absorbing padding will work when there is significant out of band high frequency noise coming out of the box. 

As for not true horns you are right to the nth degree on that one. They are the closest approximation of true horns that anyone of us tinkerers and inventors (Danley) can come up with.

I'm messing around with a true front loaded horn for a client right now. I'm working on fold type and width. Decisions decisions! It is more efficient than a tapped horn by far! Actually it has the output equal to two of the drivers in a tapped horn configuration. But the box is almost the size of the new Danley tapped horn sub that has been posted above. The output is actually the same or a bit better at most points so I have a bit of an interested audience because of that little detail!

From what I have come to believe in building and designing horns this is my theory in a nutshell ( albeit a rather big nut shell ). 

Horns can massage more molecules of air per given movement of the cone than any other box configuration that I know of. Because they can do that they are more efficient than any driver directly radiating into a room or space. Because they do more with less they can also when properly designed do it it much less distortion. You just have to look at the cones in a horn when it is pumping out crazy volume and the cones are barely moving.

The explanation for this effect that I have read that makes the most sense and that I can attest to from my own observation is that the molecules of air that get vibrated or excited by the cone movement want to dissipate their little bit of energy.( No I can't see molecules of air ) That is true with any driver radiating into any space. In a horn they have to do that with a very controlled amount of air molecules. Less close to the driver as the horn area is smaller there. These little air molecules are most energetic when closest to the driver and as they are pushed along because they are being corralled and herded by the horn structure from a very confined space to a more open space. The originally excited molecules of air excite more molecules of air on their way out of the horn. They loose a bit of energy from each exchange of energy molecule to molecule. But the greater the number of molecules that are excited to a higher energy greater the potential sound pressure level at the mouth of the horn. 

We know from basic physics that every object acted upon by an outside force wants to dissipate it's energy and return to a state of rest. So all the excited molecules of air within that horn structure are a captive system that has a given mass of air within it. That given mass of air when excited by a driver wants to get back to it's resting point. So all that energy gets shot out of the mouth of the horn and it dissipates into the room. But the efficiency lies in the trick that a great big amount of trapped air within that horn has been driven into vibration by that loudspeaker cone. That is why the horn is more efficient. No directly radiating cone could ever push around as much air . That is also why when you simulate horns you usually find that the larger the volume of the horn the greater it's efficiency. It really Sucks because everyone wants a small horn that acts like a big horn. But a big horn with a few watts can blow away any normal box be it sealed or vented with much less distortion in the sound than any normal radiating box with even kilowatts of power behind it. 

I think one of the problems is this. I have run into this way more times than I care to admit to. I get unhappy people who have a horn loaded sub that has vanishingly low levels of distortion and can play louder than they will ever need and they don't "like" the sound. They don't get their booom boom boom.

I hate to say this but I will any way. I'm pulling out the musician card! I played in an orchestra for years. In the back row really close to the bass drum. I played French Horn. When a good percussionist beats the hell out of a concert bass drum or tympani drum it is a feeling that literally smacks you when you are that close. Guys a gals who have played any live music know this. When they listen to properly setup systems I repeatedly get this comment. A horn is the only type of box that truly can reproduce this effect. I never really hear this done right when I listen to vented or sealed boxes.

I also enjoy pipe organ music. And when the bass gets thick and complex where there are huge transients in the music at the low end of the musical spectrum sealed or vented systems run at the same level as horns just cannot keep up. They start to amalgamate everything into a thick bass mush that we had all come to think of massively low bass. But what we have been accustomed to is massively high levels of distortion that overpower the real music.

Any way that is the end of my rant. Hope it makes some sense.

Mark


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## Patrick Bateman

Patrick Bateman said:


> If you don't want to read the whole thread, here's a summary of it:
> 
> I've built a few tapped horns, and I've noticed that the computer simulations are a lot rougher than how they measure in the real world. I built a tapped horn a few months ago which is quite similar to the Danley TH-Mini. If you're not comfortable building crazy enclosures, I'd highly recommend BUYING the TH-Mini - it's a great box.
> 
> Someone on this forum noted that my TH-Mini clone has limited bandwidth, due to the notch between 100hz and 200hz. I think the notch has some benefits - it reduces 2nd and 3rd harmonic distortion.
> 
> But if you don't want the notch, and you want a sub that has more excursion, this one's for you.
> 
> This one uses three eight inch woofers, the MCM 55-2421. Personally I used three woofers because I can run two off my stereo channels, and one off my sub amp. That maximizes my SPL while using a minimum number of channels.
> 
> 
> 
> 
> 
> 
> 
> If you want to build one yourself, here are the plans for the twelve.
> 
> The sub with triple eights is EXACTLY the same, with three exceptions:
> 
> The box with the twelve is 12.5" across; the box with the eights is 8.5" across
> The box with the eights is designed to play a lot lower than the box with the twelve. Yes, most people think a twelve would play lower, but in this case, the eights do. The twelve is a lot more efficient.
> I didn't design the second box on the computer, I just did it by eyeball. So if you want to build this, you'll have to make some guesstimates on the dimensions. The footprint is 24" x 24". The measurements in the simulation from a few days ago are 100% accurate; I measured the box dimensions after I built it.


MCM sent me a 20% off coupon this week. The code is WMY710. It expires in one week.

It's been about a year since I built this sub, and I am still running it in my car. For me, that has to be some kind of a record, since I'm in the habit of building new subs every three months it seems 

There are three versions of this subwoofer. The first was inspired by the Danley TH-Mini, and it's documented at diyaudio in the thread "the smallest tapped horn." At first, that sub was my favorite, because it's very VERY efficient, it's one of the cleanest subs I've ever built, it's easy to build, and it gets ridiculously loud. The Achilles Heel of this one (and the TH-Mini) is that it won't play much below 40hz. So it's kind of useless for home theater. It works nicely in the car, because cabin gain fills in the low end. And I tend to play music a lot louder in the car then at home. It's a great sub.

The second version of this sub uses the MCM 55-2421. It is cheaper, but it is also much more difficult to build. That is the sub that is pictured above. It's smaller than the first sub, plays lower, and handles more power. Due to the small dimensions, and long path, it takes about twice as long to build. If you're handy with a table saw, you could build it in a day. The first one could be built in four hours, maybe faster.

The last version of the sub is a variation on the one that's pictured above. In the last version, I removed one of the three drivers. So instead of three drivers, it has two. (I removed the one that's closest to the mouth.) Then I inverted one of the two woofers. So picture the sub above, but with two woofers, and one of them is inverted. This is called "push pull", and it reduces 2nd harmonic distortion. *This made a hyooooge improvement.* Up until I did this, I really preferred the first sub by a wide margin. Because the first sub was clean and clear and dry, and the 2nd sub sounded kinda "grungey." The reduction in 2nd harmonic distortion fixed the only real drawback to the sub. What we end up with is a subwoofer that's relatively compact, handles more power than I can throw at it, plays deep, and is noticeably more efficient than a sealed box or a single reflex bandpass. It's not the easiest sub to build, but it's do-able in a day. Even with a modest amplifier, you can feel the car flexing from this subs output. A side benefit of the complex tapped horn path is that the enclosure is *incredibly rigid.* It doesn't flex at all, which contributes to it's efficiency.

Anyways, enjoy the discount code, and let me know if anyone builds one.

Oh, one last thing. BE SURE THERE ARE NO LEAKS. I spent more time fixing leaks in this box than I spent cutting the wood. Even the smallest leak will screw it up - those panels have to be absolutely airtight. I even went so far as to use wood glue to treat the woofers cones, on the off chance that air might be leaking through the pole piece. (That will change the FS and the QTS ever so slightly.)


----------



## grecon144

Hello,
I've followed your trials with the 55-2421 and now in this version I have a few questions.
I'm wondering which driver did you reverse and how did you make room for the basket/magnet assembly?
Does this version have better extension than your previous dual mcm mini?
Did you switch to 3/8" internal panels? With all the internal folding I suppose 1/2" would take up too much internal volume.
thanks, Greg


----------



## Brian Steele

Just a quick one: a few days ago one of my friends showed up at home with his latest build - two 6" JL 6W3v3 drivers in a transmission line alignment, using some specs he got of the 'net. The line was basically a pipe, with the same SD from start to finish. End result was an Fc of around 50 Hz if I remember correctly, and a peaky in-car response.

While he was there, I engaged him in a chat about tapped horns, then mentioned the "proof of concept" tapped-pipe I'd built with a cheap Pyramid W61 6.5" driver that must be about 15 years old or more. Then I suggested that we try it out my POC in place of his double-6 TL. 

When we powered it up, his eyes opened wide. 

Then we corrected the phase, and his eyes opened wider.

He spent the rest of the weekend working on a tapped-horn design for his 6W3v3s, and then turned up a few days later to demonstrate it. I was in a rush to go to the beach, so I didn't have a chance to take a good listen to it, but initially it seemed to sound a lot better and go a lot deeper than the transmission line he'd tried before. And a smaller box too. On the minus side, the box did take up quite a bit of the trunk floor, but it was only about 7.5 inches high, so technically he had quite a bit of usable trunk space left.


----------



## Patrick Bateman

grecon144 said:


> Hello,
> I've followed your trials with the 55-2421 and now in this version I have a few questions.
> I'm wondering which driver did you reverse and how did you make room for the basket/magnet assembly?
> Does this version have better extension than your previous dual mcm mini?
> Did you switch to 3/8" internal panels? With all the internal folding I suppose 1/2" would take up too much internal volume.
> thanks, Greg


The driver closest to the mouth is now completely removed. I glued a panel in it's place.
The next one is reversed. I made a spacer out of MDF so that it will fit, since the magnet wouldn't fit otherwise.

It actually *does* sound like it goes a little bit deeper. The sims said that it should only play a few Hz lower, so YMMV.

All of the wood is 1/2" thick. The box is rigid as hell. You could probably hit it with a sledgehammer and nothing would happen.

I have a 30 cubic foot tapped horn in my living room (good thing I'm not married) and it flexes like crazy. The need for bracing definitely increases as the box size does, and also as the F3 gets lower and lower. Since this box is relatively compact as tapped horns go, you don't really need to use 3/4" stock, or MDF for that matter.


----------



## blamus

Ok, a long shot, since apparently patrick doesnt even drive anymore. I wonder if I'm going to get any attention, but I'm going to try.

1. Has anyone actually built one yet?

If not, I might have to be the first - as I have run out of options, I need the most efficient sub, as I only have 70W into 2 ohms to play with. I know Patrick says I'm going the wrong way, TH should get tons of power because they can take it, but I don't have a choice, I only have a headunit now.

2. I won't be able to build the triple 8, there are no plans for it, but looks like after all patrick ended up going back to just 2 woofers anyway. So this is what I'm going to build:

The Smallest Tapped Horn - Page 7 - diyAudio

At the very end of post #63, there is a scaled drawing of the dual 8".

But since patrick found that "push-pull" helps to eliminate distortion, I would like to put that into the design too. But I do have a question:

If you simply inverted one of the drivers, isn't that the same as simply reversing the polarity? So why bother reversing the driver physically? Why not just wire the woofers out of phase?

Well, thats it! I have the drawings for the dual 8 (which is actually the same as the 12" orginal TH mini clone) and the drivers at $25 each. Any further advice before I begin?

Oh, and if mwmkravchenko eventually post the drawings of his most recent improved UNHORN, I'd be building that too, which is much smaller and can use the same MCM8" (which I will have many many of anyway), but without drawings, I can't do it.


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## mwmkravchenko

Hi Blamus

Pushing or pulling will make no real difference. Drivers are designed to center the voice coil in the gap. Wether they are pushing or pulling is a function of the connection. I have done many a box where drivers are almost touching each other but are in different sections of a horn. They function perfectly in a reversed polarity push pull configuration.

Mark


----------



## blamus

And then I just found THIS dual mcm 8" from patrick:

Collaborative Tapped horn project - Page 353 - diyAudio

post 3521. This design looks even simpler, with 2 mcm 8", but again, no dimensions, well, he did provide the akabak model so it could be re-engineered into drawings. Where is he putting that shiva?


----------



## Patrick Bateman

blamus said:


> Ok, a long shot, since apparently patrick doesnt even drive anymore. I wonder if I'm going to get any attention, but I'm going to try.


Two cars and I work at home. I am a silly goose.



blamus said:


> 1. Has anyone actually built one yet?


I did! lol



blamus said:


> If not, I might have to be the first - as I have run out of options, I need the most efficient sub, as I only have 70W into 2 ohms to play with. I know Patrick says I'm going the wrong way, TH should get tons of power because they can take it, but I don't have a choice, I only have a headunit now.


If you only have 70watts the Triple8 is overkill. Your money would be better spent on an amplifier. The Triple8 was basically designed to combine the high efficiency and low distortion of a tapped horn with the smallest possible box that can dig into the 30s in a car.



blamus said:


> 2. I won't be able to build the triple 8, there are no plans for it, but looks like after all patrick ended up going back to just 2 woofers anyway. So this is what I'm going to build:
> 
> The Smallest Tapped Horn - Page 7 - diyAudio
> 
> 
> At the very end of post #63, there is a scaled drawing of the dual 8".


The twelve inch version of that sub that you posted is basically my favorite sub that I've ever built. I can't get over how loud it is, how much power it handles, and how clean it is. It's fantastic.

I never built the dual 8" version. The Triple8 is based on it, but it has a much longer pathlength. The longer pathlength lowers the efficiency. I did that on purpose, because I have about a thousand watts available in the car, but at home I have a lot less power. (And the sub you posted was originally intended for my house IIRC.)



blamus said:


> But since patrick found that "push-pull" helps to eliminate distortion, I would like to put that into the design too. But I do have a question:
> 
> If you simply inverted one of the drivers, isn't that the same as simply reversing the polarity? So why bother reversing the driver physically? Why not just wire the woofers out of phase?


I have no idea why anyone WOULDN'T do a push pull sub. Push pull mounting lowers 2nd harmonic distortion, and it doesn't cost a penny. The Triple8 sub sounds sooooooo much cleaner as a push-pull sub. It's night and day.

Those MCM woofers are kinda grungy sounding. If you don't believe me, just go to zaphaudio and check out his driver reviews. You'll notice that the MCM woofers consistently have higher distortion than the drivers from Peerless, Seas, Vifa, etc... They're cheap, but you get what you pay for...

So push-pull mounting is a cheap and effective way to improve the sound quality of these admittedly grungy woofers.

Also, you're inverting the driver AND reversing the polarity. If you only inverted the driver, you wouldn't get much bass would you? 

Wayne Parham talks about this here:

double 18 reflex - Speakerplans.com Forums - Page 2



blamus said:


> Well, thats it! I have the drawings for the dual 8 (which is actually the same as the 12" orginal TH mini clone) and the drivers at $25 each. Any further advice before I begin?
> 
> Oh, and if mwmkravchenko eventually post the drawings of his most recent improved UNHORN, I'd be building that too, which is much smaller and can use the same MCM8" (which I will have many many of anyway), but without drawings, I can't do it.


If your goal is to produce a lot of output with just 70 watts on tap, you're going to need an extremely large box. Amplifiers are cheap; I'd strongly advise buying a big one.

I'm a fan of re-donk-u-lous subs. One of my home subs is over eight feet tall, and weighs more than a refrigerator. And it's just one of four. (I couldn't live with a single sub.)

So....

The Triple8 is kinda beastly for your application, honestly.

If your goal is to produce a ton of output with 70 watts, I'd consider the following:


A relatively efficient ten or a twelve in a box with a REALLY big port. Ported boxes are much more efficient with very VERY large ports. I'm talking six inches minimum, and preferably eight or even ten inch port.
Same as above, but a single reflex bandpass. BIG ports are your friend.
You might be able to come up with a very efficient and small tapped horn, but you're going to need an infrasonic filter to keep the woofer from getting trashed. One of the reasons that the Triple8 uses such a long path is to keep the woofer from unloading and getting trashed.

Hope that helps!


----------



## blamus

Hi Patrick, 

Here is the thing - I have a clarion DPX 11551, what is that? A 1.5kW RMS mono block into 2 ohms. I also have a planet audio BB150.4 - [email protected] or [email protected]

I have the power. But cannot use it. I used those amps for a ported RSDC102 a year ago, 2xACI SV10 sealed 6 months ago. Today, I am subless. Why? Noise.

I have been moving things around, changing things up over time, and recently, something went very very wrong. If I connect ANY amp, I get huge noise problems, sub exploding poping sound, just unbearable. Ground issues? Sure, I've moved more things and cleaned things up to try to solve the problem, I spend days and days in the freezing cold, ripped my HU and amps out 1500 times, changing grounding locations, upgrading the big 3, whatever, it has only been getting worse. So I gave up. My guess is that its actually the HU RCA outputs that are messed up. Because the HU speaker outs are fine, which is what I am using now. But its one of those $1k HU touchscreen computer with navigation and makes me coffee etc. It does everything, and I can't just "replace it".

So I decided to simplify. I ditched all the amps, turned the front stage from a time aligned active 2 way with the kenwood X4R into a first order passive that I just smacked together (peerless 2" full range + peerless HDS 6.5", first order passive XO at 2kHz)

Now I need a sub efficient enough to get LOUD at [email protected] And here is the thing - if I succeed, then I will know how to build complete systems without spending a penny on amps in the future, for me or friends. And I NEVER EVER have to battle ground loops, amp installs, amp noise, alt whines and all that junk.

If Panasonic still make those class T amp integrated HUs I'd be using them. They do like 100Wrmsx4

I have read every TH thread on diyaudio and here. More than once, every single post. From this triple8, the unhorn, DIY Spud, HT mini clones, to Jbell's single sheet etc. etc. I probably should have spend half the time reading threads and more time learning hornresp.

So that explains why I am looking at THs and why I only have 70W to play with.



> I never built the dual 8" version. The Triple8 is based on it, but it has a much longer pathlength. The longer pathlength lowers the efficiency.


What about this guy:

Collaborative Tapped horn project - Page 353 - diyAudio

looks like dual MCM in a ~20"x~20"x9" using the real THmini fold (Staiper design)

That looks just like what I need.

unless you say otherwise.

Thank you for your attention! Glad you are alive


----------



## blamus

further more, in reply to the bandpass suggestions,

There has been very little activity on bandpass designs compared to THs, I wouldn't even know where to start. I have the impression that with well designed THs using small bass/midbass drivers, a TH has higher efficiency, less group delay/phase/port issues etc. to consider and just as big. And finally I'd like to hear a DIY bass horn that everybody is raving about.

Well, I'm reading up on sonotube bandpass subs as we speak.


----------



## blamus

Hey Patrick, would you happen to still have the hornresp input for the dual or triple 8? I am learning how to use hornresp and made a few simulations. I'd love to have some working examples to compare etc.


----------



## Patrick Bateman

blamus said:


> Hey Patrick, would you happen to still have the hornresp input for the dual or triple 8? I am learning how to use hornresp and made a few simulations. I'd love to have some working examples to compare etc.


Blamus, I believe you are correct. There is a mistake in my folding scheme. I don't think it will affect the response much, but it *will* make it easier to build if you fold it differently. Details here:

Audio Psychosis • View topic - One Hundred Dollar SQL Sub

Right now I'm going back and forth between doing a dual 8 tapped horn with the Soundsplinter RLI-8, or a front-loaded horn and using them for midbass. If I can find a bit of time I'll try and throw together a diagram and an Akabak model using the correct folding scheme, the one that you noted a few months ago.

*note that the folding scheme i posted doesn't seem to screw up the response - it's just a p.i.t.a. to build.*


----------



## Patrick Bateman

Yesterday I met John Whitledge, and listened to 'The Magic Bus' for the better part of the afternoon. As I've mentioned on other forums, my favorite sub of all the subs I've built over the years is my TH-Mini 'clone.' (Documented on post #115 of this thread, and also over on diyaudio in a thread named 'smallest tapped horn.'

For the past couple years I've spent a lot of time pondering why the TH-Mini sounds so good. Is it the group delay curve? Is it the phase? Is it the efficiency?

It was hard to pick one aspect, because the Mini isn't the best in any of these respects. It's group delay is GOOD, but not as good as a sealed box. It's efficiency is good, but so is the autotuba, and I think the Mini sounds better than the Autotuba.

But John's Magic Bus got me thinking -

Maybe it's the ISOLATION!

You see, one thing I hadn't considered in all these years of running the mini is that I generally place it on the back seat of my car. Because the box is made of plywood, and the driver is neodymium, the sub box is light enough that it won't tear up the seats. So when I run it, I typically just toss it on the back seat. *So the sub is basically 'floating' on 10cm of foam.* (IE, the seats are isolating the sub from the rest of the car.

Something to consider.

Here's one way of looking at this:

If you take a sub box, and throw it in the trunk, there *will* be vibration between the box and the car. Even worse, that rattling will excite a lot of high frequency energy. Even a fraction of a millimeter of movement will generate noise, as the panels are resonant, and their large size makes them efficient.

The reason that I never ran *any* of my other subs on the back seat was due to their weight. For instance, a couple of Diyma 12s in a plywood box weighs about 120lbs.

Think I might try throwing one of my other subs in the car, but 'float' it on memory foam.


----------



## chithead

Interesting observation there. It does make sense though. Vibrations do lead to localization.


----------



## axiom26

Has anyone tried out the Anarchy Tapped horn DIY kit? 
Anarchy Tapped Horn - Subwoofer Cabinets - Flat Packs DIY Sound Group

I'd been thinking about a building a pair of these for a hatchback, but found no one using one in a car even though several have brought up it might be really good in a car. They are kind of small compared to some large ported boxes and don't require thousands of watts.


----------



## Patrick Bateman

axiom26 said:


> Has anyone tried out the Anarchy Tapped horn DIY kit?
> Anarchy Tapped Horn - Subwoofer Cabinets - Flat Packs DIY Sound Group
> 
> I'd been thinking about a building a pair of these for a hatchback, but found no one using one in a car even though several have brought up it might be really good in a car. They are kind of small compared to some large ported boxes and don't require thousands of watts.


The Anarchy drivers are fairly similar to the Alpine SWR-824D, and my tapped horn with those drivers turned out well. I'd say it's a safe bet the Anarchy TH would work well too. (Theoretically the Alpine is an 8" woofer, but the basket is so beefy, the cone isn't much bigger than the Anarchy.)


----------



## axiom26

Well i'll be going with atleast 2 of the tapped horns stacked since they are only 8.25" high maybe even three high. A pair of Anarchy drivers have alittle bit more surface area than the 8 and almost a 10 so I should have plenty of output and headroom. Even though I may not end up needing a third its nice to have alot of extra headroom for dynamics and lower distortion.


----------



## Patrick Bateman

axiom26 said:


> Well i'll be going with atleast 2 of the tapped horns stacked since they are only 8.25" high maybe even three high. A pair of Anarchy drivers have alittle bit more surface area than the 8 and almost a 10 so I should have plenty of output and headroom. Even though I may not end up needing a third its nice to have alot of extra headroom for dynamics and lower distortion.


Wicked! Probably the best bass you can get from a 7" in the world.


----------



## jwsewell01

Diggin' up bones! 

Hey Patrick, I am wanting to build a clone of your dual 8" TH-mini to replace an isobaric pair of 12's sealed in .75 ft3

I have a single cab ranger. And 54x20x14 to play with and a 14"x14" blow through on the passengers side that can be cut wider if needed.

I wanted to build a TH-Spud clone but at 48x45 it will not fit between my wheel wells in the bed.  There is only 40 inches between them, the 48" length is not an issue. Oh well.........

I have a pair of Rockford RFP2408 XLC's That look good on paper for your TH-mini clone enclosure. 
Even the Fs is higher than the MCM 55-2421, which if I am not mistaken you have stated many times in several threads on the web that Fs was too low on them.

If you don't mind and have the time could you please model these for me in HR.
I would give HR a try and learn it IF I had a currently operational windows machine, as it stands now I have two iPads. Yuck!

Here are the specs. http://www.rockfordfosgate.com/rftech/library/1998/5_Subwoofers/LIT10191_RFPXLC_MAN.pdf


----------



## thehatedguy

Why would you take up the bed of a trunk for a pair of 8s from 1998? I owned those 8s back then and they were decent.


----------



## jwsewell01

thehatedguy said:


> Why would you take up the bed of a trunk for a pair of 8s from 1998? I owned those 8s back then and they were decent.


Hell why not?! I thought is was understood that we are all kinda weird here.......


I really just like trying new things and learning.  

If I could learn Horn Res. I would try to re-fold the Th-Spud clone so it's no wider than 40".


----------



## thehatedguy

Touche'

Hornresp isn't that hard to learn...but folding one of those guys can be a PITA.

When I made one for my house, I only had one fold...I didn't want to deal with that folding mess...lol.


----------



## GPM

If you can do one fold accurately, then you can do multiples.

FWIW, a couple of new folding worksheets being developed: 

Spreadsheet for Folded Horn Layouts... - diyAudio

A different TH fold... - diyAudio

GM


----------



## GPM

Sheesh! That RFP2408 wants a tiny TH, ~35.25 L net/Fs damped and only ~17.9 L for a max output ~43 Hz tuning. Not sure the driver will fit in the former without a bit of creative woodworking.

GM


----------



## oabeieo

jwsewell01 said:


> Hell why not?! I thought is was understood that we are all kinda weird here.......
> 
> 
> I really just like trying new things and learning.
> 
> If I could learn Horn Res. I would try to re-fold the Th-Spud clone so it's no wider than 40".


I'm just now figuring out horn resp. It's a bit diffrent than winisd. I had a hard time learning what everything means. I'm starting to get the hang of it now . If you do get it , be patient and keep messing with it and it will eventually click. 

It's easy to use once you teach yourself what everything is.


----------



## Lycancatt

now you guys have me curious..would anyone like to undertake a tapped horn design for the jbl gto 1514d? I've got a pair and am bored with the 6.5 cubic ft boxes they are in..


----------



## jwsewell01

Oabeieo, Oh I thought my head was going to explode when I first tried WinISD. 
But it all became second nature pretty quickly.

GPM, you ain't kidding, 1.25 - .7 ft3!!!
I'm pretty sure I have come across many of your posts on the web researching these things. Lol


----------



## oabeieo

Lycancatt said:


> now you guys have me curious..would anyone like to undertake a tapped horn design for the jbl gto 1514d? I've got a pair and am bored with the 6.5 cubic ft boxes they are in..


I could probably get you a BASIC design, the fold would take hours to draw out and do the conversions. ... I'm sure there's a faster way....anyone else wanna take a crack at it? I can use horn resp, I wouldn't consider me a expert tho. 

I did a rubber throat single 10" for the shop stereo as a compition with one of my techs who is a t-line guy. Mine was a success , the horn beat him in overall sq but he squashed me in output in the low end by about 6db. I also think our identical subs were better suited for him tho , but again idk . I'm still haven't figured out it 100% . 

But it is fun to make a horn sub and actually have it work! Kinda accomplished feeling... Sorta .


----------



## Patrick Bateman

jwsewell01 said:


> Diggin' up bones!
> 
> Hey Patrick, I am wanting to build a clone of your dual 8" TH-mini to replace an isobaric pair of 12's sealed in .75 ft3
> 
> I have a single cab ranger. And 54x20x14 to play with and a 14"x14" blow through on the passengers side that can be cut wider if needed.
> 
> I wanted to build a TH-Spud clone but at 48x45 it will not fit between my wheel wells in the bed.  There is only 40 inches between them, the 48" length is not an issue. Oh well.........
> 
> I have a pair of Rockford RFP2408 XLC's That look good on paper for your TH-mini clone enclosure.
> Even the Fs is higher than the MCM 55-2421, which if I am not mistaken you have stated many times in several threads on the web that Fs was too low on them.
> 
> If you don't mind and have the time could you please model these for me in HR.
> I would give HR a try and learn it IF I had a currently operational windows machine, as it stands now I have two iPads. Yuck!
> 
> Here are the specs. http://www.rockfordfosgate.com/rftech/library/1998/5_Subwoofers/LIT10191_RFPXLC_MAN.pdf


I don't see any Thiele Small parameters online. This was the best I could do:
http://autosound21.co.kr/shop/board_data/automanual/rockford-1999_Color_catalog.pdf

I'd also think long and hard about trusting the specs of a fifteen year old woofer. I have some TC Sounds woofers, from twelve years ago, and their parameters are WAY different now than 12 years ago. Basically the spider and the surround dries out, and that shifts the parameters quite a lot.


----------



## thehatedguy

I probably could do something...but translating what is designed to something you could build, I dunno about that lol.

There was an interesting patent from Bose in last month's Voice Coil about smoothing out the response of a tapped horn.


----------



## oabeieo

jwsewell01 said:


> Oabeieo, Oh I thought my head was going to explode when I first tried WinISD.
> But it all became second nature pretty quickly.
> 
> GPM, you ain't kidding, 1.25 - .7 ft3!!!
> I'm pretty sure I have come across many of your posts on the web researching these things. Lol


Horn resp isn't hard , what's hard is knowing what sub wil sound good, it just gives you the basic horn in one shape, it's really brain racking to try to make it fold . If your good at geometry and math , you'll have a much easier time. 

Download it and try a few designs . Than make it fold . You'll see it's just time consuming as hell .


----------



## oabeieo

GPM said:


> If you can do one fold accurately, then you can do multiples.
> 
> FWIW, a couple of new folding worksheets being developed:
> 
> Spreadsheet for Folded Horn Layouts... - diyAudio
> 
> A different TH fold... - diyAudio
> 
> GM



Lol! 

Ha , yeah...... Those links take me to nothing short of Chinese to me.
Bunch of number crunchers.


----------



## jwsewell01

Patrick Bateman said:


> I don't see any Thiele Small parameters online. This was the best I could do:
> http://autosound21.co.kr/shop/board_data/automanual/rockford-1999_Color_catalog.pdf
> 
> I'd also think long and hard about trusting the specs of a fifteen year old woofer. I have some TC Sounds woofers, from twelve years ago, and their parameters are WAY different now than 12 years ago. Basically the spider and the surround dries out, and that shifts the parameters quite a lot.


 I posted a link to the owners manual, did it not work? No matter..... 

I get what you are saying 100% about the T/S parameters and had not even considered that until now.

Now I need a woofer tester along with a new windows machine. My GF told me that this project would cost more than some wood and glue. :blush:

SEE, total success! I learned something!


----------



## oabeieo

jwsewell01 said:


> I posted a link to the owners manual, did it not work? No matter.....
> 
> I get what you are saying 100% about the T/S parameters and had not even considered that until now.
> 
> Now I need a woofer tester along with a new windows machine. My GF told me that this project would cost more than some wood and glue. :blush:
> 
> SEE, total success! I learned something!


 You could still build it with those parameters and expect a high 60% success rate. (Guess) it would still sound pretty good is what I'm saying . It wouldn't be a total failure that I could immagine. 

I heard a 40 year old set of altec subs in a theatre of sound rig . It sounded amazing . I'm just sayin


----------



## jwsewell01

I hear ya. 

I ordered Autotuba plans and am building a 14x32x32 2x8". If I don't like it I'll shove my 3 ft3 sealed box with two 12's n the hole. Lol

It's not a tapped horn, but whatever. It's a cheap project.

Link to my build, not much done yet. Lol

http://billfitzmaurice.info/forum/viewtopic.php?f=30&t=23332


----------



## Patrick Bateman

jwsewell01 said:


> I posted a link to the owners manual, did it not work? No matter.....
> 
> I get what you are saying 100% about the T/S parameters and had not even considered that until now.
> 
> Now I need a woofer tester along with a new windows machine. My GF told me that this project would cost more than some wood and glue. :blush:
> 
> SEE, total success! I learned something!


Ack! I missed that. Sorry.

Are those numbers correct? That's 8.75 cubic feet?


----------



## jwsewell01

Yes they are correct. And that's not even the max width that it could be built. Lol


----------



## Patrick Bateman

I just got assigned to a new client and I'm going to be flying to the bay area to stand up their cloud. Looks like I'll have to take a shortcut on this design. I've posted plans and sims for a tapped horn with your sub here:

Tapped Horn for the Lazy and Impatient - Page 5 - diyAudio


----------



## jwsewell01

OH wow. Thank you Patrick. I had no idea you were going forward with it. Thanks again for your time and effort. I'm off to check it out.


----------



## Patrick Bateman

It's not the size you spec'd, but it IS simulated for your woofer.

I reverse engineered Bill's Autotuba, and ran it in my 2005 Accord for a while. Both designs are good. The Autotuba doesn't play remotely as low as the Insubnia, but it should get louder. To me, the main achilles heel with the Autotuba clone that I built was that the MCM woofer isn't anything special. For the price, there's nothing as good, but if one is willing to spend $100 the Alpine SWR is really nice.

As a general rule, tapped horns and back loaded horns require smaller boxes than front loaded horns. FLHs advantage is more output.


----------



## jwsewell01

I'm thinking of trying the Insubnia tapped horn you modeled first. It will not require any more cutting of my bed and cab to try it out. The Autotuba requires some metal removal.


----------



## jwsewell01

Y'all gotta check this out!

I ran some simulations in Hornresp 

1 of Patrick's 8" tapped horns for one of my Rockford subs (200W @ 3.7 ohms, about 3.2 ft3 gross)
VS
3 Alpine SWR12D2 sealed (1500W @ 1.3 ohms, about 4 ft3 gross)

The 3 Alpines are only 2 dB louder than the single 8" tapped horn at 30 Hz in half space, (2Pi)
Of course the Alpines run away from the horn above that.

One of the Alpines in 1 ft3 sealed with 500w was 7 dB down from the same horn above on 200w at 30 Hz, and the horn held the advantage until about 55 Hz. (Again in half space)

I'm still trying to figure out how to post up the graphs from HR. I'll get them up as soon as I can.


----------



## Patrick Bateman

Yup, Hoffman's Iron Law in action. Output is mostly dictated by box size.

I've come up with some really bizarre designs due to this; I once made a tapped horn that could only handle about one watt, because the box was so oversized!










It makes me wonder what one of these beasts can do. (Danley BC-218)


----------



## jwsewell01

Patrick Bateman said:


> Yup, Hoffman's Iron Law in action. Output is mostly dictated by box size.
> 
> I've come up with some really bizarre designs due to this; I once made a tapped horn that could only handle about one watt, because the box was so oversized!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> It makes me wonder what one of these beasts can do. (Danley BC-218)


 I showed that to my girlfriend. All she had to say was gross! Lmfao!


----------



## jwsewell01

This is still a work in progress so keep that in mind. The interior folds are not even complete at this time.

Anyway here is the beginning of the "HORNy Snork" 



This is a Snork BTW, lol


----------



## Patrick Bateman

Cool!


----------



## jwsewell01

I'm making some progress. Still learning as I go.
I'm having trouble getting the sub hole to "punch" through and the bottom panel is hollow for some reason. Lol


----------



## james_spearo

Your design looks well designed, here's my 1st attempt at a TH, it's a 25Hz design using a DLS nobelium 12i. It's absolutely massive lol, I had to remove the rear seat of my 4 door Toyota hilux, and it takes the place of the rear seat. Not heaps flat measured response firing into the passenger door, but after a bunch of Rew EQ I got it sounding pretty smooth. Biggest disappointment was the group delay was much higher than I originally accounted for, had to delay front stage by 12ms+ to get the impulse response to match up


----------



## SPLEclipse

Patrick Bateman said:


> Yup, Hoffman's Iron Law in action. Output is mostly dictated by box size.
> 
> I've come up with some really bizarre designs due to this; I once made a tapped horn that could only handle about one watt, because the box was so oversized!
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> It makes me wonder what one of these beasts can do. (Danley BC-218)


Bass vagina. :laugh:


----------



## jwsewell01

james_spearo said:


> Your design looks well designed, here's my 1st attempt at a TH, it's a 25Hz design using a DLS nobelium 12i. It's absolutely massive lol, I had to remove the rear seat of my 4 door Toyota hilux, and it takes the place of the rear seat. Not heaps flat measured response firing into the passenger door, but after a bunch of Rew EQ I got it sounding pretty smooth. Biggest disappointment was the group delay was much higher than I originally accounted for, had to delay front stage by 12ms+ to get the impulse response to match up


 I didn't really design anything, just took some ideas and suggestions from Patrick Bateman and jbell to modify the Insubnia and threw it all together in SketchUp. I am learning a metric **** ton though. :laugh:

Group delay is the one thing keeping from just going with a pair of 12's in a bass reflex, (ported), enclosure. And I want more output and low end than sealed thus the tapped horn. Plus it's fun to try something new first hand.


----------



## james_spearo

It certainly caused a stir when I arrived arrived at the SQ comp rocking a horn sub  scored really well, the judge said he really liked the sound of the sub bass and it has a tonne of authority even down at 25-30hz, off 400w. I've actually pulled it out for now and just running 10" sealed, it's a PITA when I wanna use my car for camping & fishing


----------



## jwsewell01

I wanted to see if I could re-fold it an get a smaller foot print. The goal was to fit the tapped horn in the 54x20 rectangle in the top left. 
And see if I could find a way to use the current 14x14 blow through I already have on the passengers side.

So I un-folded the Insubnia and got busy.



Once I had a new fold I re-measured everything on the model and re-entered the data in Hornresp to account for any differences.



It's looking good so far. 
At 13 inches internal depth, 
loaded with both 8's, (still working on that detail LOL)
it does 114 dB from 30-80 Hz in 2pi on 400 W @ 1.85 ohms, (hoping for 130dB in vehicle)


----------



## Patrick Bateman

I've put my beloved th-mini clone up for sale for $79

It's listed in the San Diego craigslist

I won't post the link as this is the wrong forum, but if anyone's interested in a well documented tapped horn for under eighty bucks, LMK


----------



## Patrick Bateman

When I originally published this thread, I'd built a couple of horn subs. One was based on the Fitzmaurice 'autotuba.' It worked well. The other was my own design, the "Triple8." That worked terribly.

With a few more years of experience under my belt, here's how I might do it today.









It's still a tapped horn, but this time I made it isobarik. The reason that I went with isobarik is because it reduces the box size by half, same idea as isobaric vented subs. When I did the 'Triple8' sub, I wanted a small box with a lot of output. If that's your goal, isobaric is tough to beat. This tapped horn is 1.5cubic feet in airspace. Once you factor in the displacement of the woofers and the wood, you're looking at 2.5 cubic feet, or a package that's about 21" x 21" x 10".









Here's the response. With cabin gain, it will easily reach 20hz. This would make a nice home theater sub also. This response curve includes a 4th order highpass at 21hz and a 4th order lowpass at 65hz.









The MCM woofers are good for 8mm of xmax, and this box design uses all of it. The response curve is with 500 watts into 4ohms, which gives each woofer 125 watts.









Here's the response curve of the tapped horn, versus the response of the same four woofers in a QB3 vented box. You'll be surprised to see the vented box is actually more efficient! The reason for this is because the vented box needs a HUUUUUUUUGE port. No joke, the port is FIVE times bigger than the box itself(!) This is the challenge with modern woofers that have a tiny VAS; the port sizes get ridiculous. I've seen a lot of SPL boxes where the woofer is in something the size of a cereal box, and the port stretches from the back of the car to the front. The MCM has similar issues in a ported box. The VAS is tiny. In this vented box, the "box" is six liters, the port is 30 liters. The port is 6" in diameter with a roundover at the mount and at the throat.

Oh, the reason that the vented box has those 'spikes' in the response is because you get standing waves in the port. WinISD can't model those, but hornresp can. The standing waves get worse and worse as the volume of the port gets larger and larger.









Here's the displacement of the tapped horn versus the ported box, with the same woofer. The ported box has lower displacement because the F3 is higher.









One 'trick' that I did with the tapped horn is that I flared the throat. The reason that I flared the throat is that it reduces compression on the woofer. One issue that I had with some 8" horns that I built recently was that the compression was so high on the cone, the woofers started making strange noises even at low power levels. Flaring the throat allows you to lower that compression ratio. The pic above is from the Danley TH-SPUD horn, which has a similar layout as my horn, but is much larger because the Danley design uses two woofers that *aren't* isobaric. So it needs to be twice as large in volume for the same F3.


----------



## ParDeus

Going grave digging here, forgive me!

So, I've spent two days reading this thread, and I'm massively impressed with everyone's talents and intelligence. More through trial, error, sawdust and curse words, I've finally got my single 18" tapped horn where I like it... Structurally destructive output from 24hz-40hz, while still sounding good enough @80hz to blend well.

To the point, I've decided to pursue a full blow-through (ext cab truck), utilizing 2-18" (possibly a single HST24, 2 would be impossible, no?) in a tapped horn configuration.

The most important thing I've learned reading this thread is... I'm not as smart as I like to think. I'd rather make an offer of financial compensation to any of the Horn-Gods that may see this and be willing to help. Everyone names there horn design, I'm thinking we call this HornDeus? Anyhow...

Patrick, if you happen to read this, I'll be in San Diego some time in May, and I'd love to pick your brain on this.

Thanks y'all!


----------



## Patrick Bateman

My TH-Mini clone never sold lol. Still sitting in my garage.

Though I have a tapped horn in my Mazda, I'm not sure if it's worth the hassle. The owner of Stereo Integrity argued that a sealed or a vented box is the way to go, and I'm kinda leaning that direction.

For the home or the club, I think that front loaded horns and back loaded horns make sense. But in the car, the Schroeder Frequency is so high, you might as well build a nice sealed box and call it a day.

I put my money where my mouth is and I bought a Stereo Integrity 18"  I will likely build a dipole or a sealed box for my car.

Again, I'm not against subwoofer horns in general, just against them when the room is small. Such as a home or a car.

(If anyone's curious, the Schroeder Frequency is the frequency when the wavelenghts become so long, they exceed the dimensions of the room. For instance, when you're listening to a subwoofer in a car, the longest dimension is about 3.7 meters. That means that any output below 94Hz is longer than the car itself. This causes a couple things to happen:

1) efficiency goes through the roof. (cabin gain)
2) The rigidity of the room/car becomes really important. Go to any SPL show and you'll see SPL cars where the body panels are vibrating like a passive radiator.


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## Brian Steele

The advantage of the TH approach is the amount of SPL you have on tap for the wattage applied. The disadvantage of course is the larger box requirement. 

My POC3 loaded with the Eminence Kappalite 12" with its 9mm Xmax causes the trunk of my car to behave very badly with only a few watts (compared to the two 12" Type R drivers in the sealed cabinets that I normally use for car audio duty), but of course peak SPL is limited (one driver with 9mm Xmax vs. two drivers with 20mm Xmax.). The attached image is a comparision of the output of the POC3 and the POC6 (a 48 Hz slot-loaded offset TL) compared to my Type Rs. Bear in mind that the imedance of the POC is 4 ohms and the POC6 is 8 ohms, and the combined impedance of the two Type Rs is 2 ohms. 

At the moment I'm leaning towards slot-loaded offset TLs using low Q drivers (which unfortunately excludes almost every car audio subwoofer from consideration, LOL) as being the best compromise, e.g.

1. Lower achievable Fb for the same box volume (compared to vented)
2. inherent bracing (due to internal panels)
3. Smoother rolloff at midbass frequencies = better midbass integration
4. Lower group delay, approaching performance of sealed alignments
5. Box size comparable to or slightly larger than vented alignment with the same driver (depends on how much you compromise on the vent area).
6. Wider bandwidth than a TH, and no funky organ pipe resonance peaks that are too close to the passband.


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## Patrick Bateman

Someone on Facebook asked me about bass horns, so I thought I'd sum up my views here, since FB isn't a good medium for technical discussions.

First off, *I don't think bass horns are a good idea for the car, and probably not for the home either.* In this respect, my views are aligned with Geddes. I believe that the owner of Stereo Integrity summed it up in this thread, years ago. It basically took me a while to come around. There's 191 posts in this thread and I'm too lazy to find his lol.

The reason why bass horns are a bad idea is because of Hoffman's Iron Law. Basically the bass horn must get larger and larger for you to see gains in output.










With something like the Danley BC218, you can see the virtues of a horn: _though the Danley BC218 is enormous, something like 500lbs, it makes sense because it's being used in an environment where there isn't a premium on space. If you are building loudspeakers that are being used in rock concerts and stadiums, a five hundred pound horn isn't completely ridiculous. Just go and rent a forklift, put the giant horn in place, and enjoy the fact that you can hit 130dB with one thousand watts, whereas a vented box might need TEN thousand watts to do the same.

In the car, having a five hundred pound sub box just doesn't make sense. It wastes space, it wastes gas.

Here's where things get tricky:

There's a ton of box types that live in a grey area between "front loaded horn" and "sealed box." Box types like Tapped Horn, Transmission Line, TQWT, etc. All of these boxes are generally LESS efficient than a front loaded horn, MORE efficient than a sealed box, SMALLER than a front loaded horn, and LARGER than a sealed box.

It's in that grey area where things get really tricky, because you can juggle the parameters a thousand different ways and come up with a thousand different results. 

I love to tinker, and I've tried nearly every box type. Sealed, front loaded horn, tapped horn, single reflex bandpass, isobaric, dual reflex bandpass, ported, etc.

If YOU like to tinker, have at it, it's fun.

If you just want something that works, I think that bandpass, sealed and ported boxes are pretty difficult to beat. I generally lean towards single reflex bandpass because it has the same or better efficiency than ported, while also having less harmonic distortion. *But that doesn't mean bandpass is the best!* Bandpass boxes are very difficult to get right, and if you don't have gear to measure them, I wouldn't bother. 

As Brian noted in post #190, "the advantage of tapped horns is the amount of SPL you have on tap for the wattage applied." I like tapped horns a lot; I'd argue that it's fairly easy to make a tapped horn that behaves as predicted. Tapped horns might even be easier to build than vented or bandpass boxes. (The ports on ported and bandpass boxes frequently aren't tuned properly, and the only way to know is to measure it, and 90% of the people building sub boxes don't measure them, they just listen to them.)

Anyways, here's the TLDR:

1) if you can't measure the impedance curve, think long and hard about building a sealed box

2) if you CAN measure the impedance curve, ported boxes and bandpass boxes are nice

3) if you like to tinker, consider the other box types. Be sure to purchase some measurement gear

4) tapped horns are an interesting option, and may possibly be easier to build than vented or bandpass. Obviously, you'll need to learn hornresp to build one, or use an already published design.

_


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## Patrick Bateman

Update : 

Some of the most interesting discussion in this thread, including the Stereo Integrity posts, are on this page:

https://www.diymobileaudio.com/foru...n/65945-small-tapped-horn-car.html#post837800

Also, I put my money where my mouth is: I have a Stereo Integrity 18" sitting in my garage, and the original subject of this thread was thrown in the trash. I tried to sell it on Craigslist for nearly a year, with no success.


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## TJ Mobile Audio

Good conclusions. Many years ago when I had customers who were more interested in the output of their system than the practicality of their vehicles, I often used Hoffman's law to my favor, which lead to some interesting designs.

One box type I deployed with great success was a dual chambered ported enclosure, as described here on Brian Steele's DIY Subwoofers page. I remember being surprised at both the efficiency and power handling of this enclosure, achieving (at least subjectively) greater output than many multiple-thousand-watt systems I've heard with only 500 watts and a single (cheap no-name-brand) 15, but still keeping the cone safely within the limits of excursion.



Another time I built a large 4th order bandpass for three 10" that someone wanted in the trunk of a Mercedes CLK, of all things. The enclosure was a massive cabinet (seen here) of baltic birch, and weighed about 85 lbs before loading the 20-pound-each drivers.

But while enclosures like this, or the tapped horn, or transmission lines, are great fun to figure out and build, and I've had a variety of transmission lines in my own cars, I can't imagine using anything like that again in an automotive environment. There are so many viable options, and class D tech has made bass amplifiers so cheap per watt (and with considerably less strain on electrical systems than the older A/B amps) that I just don't see the point anymore.

My new priority, at least in my current build is coming up with something that sounds good and don't sacrifice the usability or fuel economy of the car. There are so many tradeoffs already baked in to the automotive environment that I can't see optimizing efficiency at the expense of usability as a viable position anymore --- and yes that makes me sound old but such is life.

PS, I was greatly inspired by your tinkering years ago and used it as motivation to try some of the novel designs I've mentioned. Although based on my own parallel experiences, I'm not surprised to see the bass-horn-in-a-car idea fall by the wayside.


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## Patrick Bateman

Thanks!

And one of the reasons I've been such a lunatic about measurements is because it took me so long to figure out that many of the sub boxes that I built weren't functioning as planned.

For instance, a few weeks ago I built a bandpass box for a pair of five inch woofers. After I measured it, I could see that the impedance curve didn't have a deep null at the measurement frequency.

At that point, you're basically ****ed. The impedance curve could be off for a number of reasons:

1) the box may be leaking

2) The walls may be flexing

3) possibly a bad driver

Whatever it is, *the box will never work as predicted* and unless you figure out how to fix it, *it is never going to play 100% as well as it should.*

And I'm not talking about a loss of a decibel or two, if the impedance curve is "off", you could be off by as much as 3-6dB.

A few years back I had two identical midbasses that I built, and the impedance curve of one suffered from a similar issue. After tinkering with it for hours, I convinced myself that Parts Express must have sent me a 4ohm driver and an 8ohm driver. Because the two boxes were "off" by about 3dB.

After literally sawing the enclosure in half, I checked the parts, and they were identical.

I fiberglassed it all back together, added a layer of mortite, some more fiberglass, etc...

It turned out the fundamental issue was just leaks. Even the TINIEST leak can screw up a ported or a bandpass box, which is particularly funny when you consider that those boxes have a giant hole in the side of the box (for the port.)

But ported boxes of all kinds simply don't work if the box has even the tiniest leak.

In 2018, I realize that a lot of my initial fascination with exotic enclosures had a lot to do with the fact that they're often more difficult to **** up. For instance, a tapped horn still needs to be carefully checked for leaks, but a tiny leak in a tapped horn isn't quite as catastrophic as it is with a ported box. 

I basically built a lot of bandpass and ported boxes from 1990 - 2010ish that weren't performing as designed, and I imagine that this happens to a lot of people. Dayton DATS should be in everyone's tool box. 

With a carefully built ported box, I (mostly) don't hear the overhang and sloppiness that I used to associate with ported boxes. I think a lot of those old ported boxes weren't performing as designed. 

Still, I'm not 100% finished with exotic boxes; I actually kinda like them for midbass. Because it's hard to get good midbass output and midbass horns don't get as crazy in size as sub bass horns. Plus, y'know, it's fun. A few years back I made a fourteen liter horn with two 3.5" woofers that was something like 6dB more efficient than an 8" woofer in a 28 liter box.



EDIT :

Once in a while you're going to run into someone who says "I built this horn and I dumped five thousand watts into a 8" woofer and it took it like a champ." _This is actually an indication that they built the box wrong!_ For instance, I made a clone of a Bill Fitzmaurice Autotuba. When I first built it, I was just dumping power into the thing, and it was taking it like a champ. I was literally maxing out the volume knob, and that woofer should have exploded. It's a $25 woofer. The thing is, when you build these boxes wrong, the impedance curve is off. So you would expect to see a 4ohm load with a properly built box, but when it's built wrong, the impedance could be as high as eight or even twelve ohms. *So that's why they take so much power.* The impedance curve is raised by the leaks, and the amp isn't delivering even close to the rated power. In fact, that's why the maximum output isn't as high as expected; the amp needs to see that deep deep null at the tuning frequency so that it can dump all of it's power into the woofer.










The purple curve here illustrates this. It SHOULD be about two ohms at it's lowest, but it's four. That means the amp will be putting out half as much power. And that's why it SEEMS that the box can take a lot of power.










Here's a measurement from Steele's site. The deep nulls indicate that he built his box properly. https://www.diysubwoofers.org/projects/other/impresp/


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## JCsAudio

Patrick,

I’m curious about these leaks you are referring to in the boxes you built and then found out had leaks. How did you verify the type and size of those leaks in a physical means? When you built these boxes, what kind of methods did you use to make an attempt to seal the box and what thicknesses and type of wood did you use? Did you caulk the joints or just glue them together? I’m not trying to challenge you or you methods but just trying to learn something I may not know from your experiences.

Also, I’m curious to know how one can test a ported box to determine its tune. I can measure mine with REW and my microphone but is there a more accurate method that can be used with REW and a microphone? 

Thanks in advance.


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## Patrick Bateman

V8toilet said:


> Patrick,
> 
> I’m curious about these leaks you are referring to in the boxes you built and then found out had leaks. How did you verify the type and size of those leaks in a physical means?


Measuring the impedance of the loudspeaker will show you the issues. In particular, you want to see a deep trough at the tuning frequency, like Brian's measurement shows, and mine doesn't.



V8toilet said:


> When you built these boxes, what kind of methods did you use to make an attempt to seal the box and what thicknesses and type of wood did you use? Did you caulk the joints or just glue them together? I’m not trying to challenge you or you methods but just trying to learn something I may not know from your experiences.


My old boxes were unnecessarily complex, with a lot of crazy bends which are error prone:










From page one of this thread, nine years ago



















From two years ago. (https://www.stevemeadedesigns.com/board/topic/204082-maximum-bass-for-1000/?page=4)
A lot of effort sealing off every last path in the sub box. Doing everything possible to prevent the box from leaking, and also from air from leaking from one path to another.



V8toilet said:


> Also, I’m curious to know how one can test a ported box to determine its tune. I can measure mine with REW and my microphone but is there a more accurate method that can be used with REW and a microphone?
> 
> Thanks in advance.


Check out the impedance curve. If the impedance curve isn't right, the subwoofer won't work properly.


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## Grinder

V8toilet said:


> Patrick,
> 
> I’m curious about these leaks you are referring to in the boxes you built and then found out had leaks. How did you verify the type and size of those leaks in a physical means? When you built these boxes, what kind of methods did you use to make an attempt to seal the box and what thicknesses and type of wood did you use? Did you caulk the joints or just glue them together? I’m not trying to challenge you or you methods but just trying to learn something I may not know from your experiences.
> 
> *Also, I’m curious to know how one can test a ported box to determine its tune.* I can measure mine with REW and my microphone but is there a more accurate method that can be used with REW and a microphone?
> 
> Thanks in advance.


Just for fun. 

Actually works quite well.


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