# "Improve Your Loudspeaker for a Buck" aka "Loudspeaker Hell"



## Patrick Bateman (Sep 11, 2006)

In a recent thread I demonstrated how to improve your stereo for about a hundred bucks, by measuring the polar and the frequency response. In this thread I am going to demonstrate how to improve your speakers for a buck. The other thread is here:

http://www.diymobileaudio.com/forum...um/65046-improve-your-sound-quality-80-a.html

Before I dive into this, I gotta warn you:

_This is a time consuming process, and when you're finished, you might have a ruined speaker. If you do it right, you'll have a better speaker though._

According to Dante's Inferno, the gates to Hell are inscribed with the words "Abandon All Hope Ye Who Enter Here." Without further ado, welcome to loudspeaker hell


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## Patrick Bateman (Sep 11, 2006)

_At the end of this thread, I will demonstrate how a one dollar modification to a loudspeaker can improve the sound. Before we reach that point, I'd like to share a few of my opinions on loudspeaker design, since it will help explain why I've made some of these engineering decisions._

The ideal set of stereo speakers would be small, located equidistant from the listener, and would cover the entire audible bandwidth, from 20hz to 20khz. A good set of headphones are an excellent example of the ideal; you can hear details in the music that are often obscured over loudspeakers, and headphones make excellent monitors.

Unfortunately, headphones can only be properly listened to by one person, and they become uncomfortable after extended listening.

So what's the alternative?


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## Patrick Bateman (Sep 11, 2006)

One alternative to headphones would be a loudspeaker which can deliver the full frequency spectrum, with dynamics and finesse.









The JM Lab Utopia is an excellent example. It covers the entire spectrum, from 20hz to 20khz, with real authority. The reviewer at Stereophile said they were "the best speakers he'd ever heard." (Stereophile: JMlab Utopia loudspeaker)

So I traveled to San Francisco, curious to give them a listen. The first thing that I noticed were the dynamics, it was like the band was playing in the room. Such dynamics!

One little problem though... As I moved closer to the speakers, the sound began to fall apart. At the back of the room, it was exquisite. As you moved to the front of the room, the sound was barely tolerable. There was a distinct difference between the sound as you moved around, and the speakers were downright offensive at any distance short of ten feet.

This is a simple physics problem. Remember how our "ideal loudspeaker" is a single driver, covering the entire spectrum? Now look at the picture above. The Utopia is over TWELVE cubic feet. And sound waves are extremely long. (The lowest note on a bass guitar is longer than a car!)

Due to the very long wavelengths of sound, the Utopia cannot "sum" properly at close range. With various drivers covering various frequencies, you have to sit way WAY back for a convincing illusion, and my listening room is not a basketball court.

So what's next?


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## Patrick Bateman (Sep 11, 2006)

After the Focal was such a disappointment, I listened to a lot of "cost no object" speakers over the years, like the Pipe Dreams, Avantgarde Acoustics, and McIntosh.



















Year in and year out my impression of these expensive speakers was the same: _Big speakers were dynamic, but imaged poorly. Some big speakers sounded better than others, particularly ones with an excellent power response. Yet even if cost was not a factor, I started to realize that I preferred the sound of small speakers._

That last part was a shocker - even with a blank check, it was easier to live with a set of Sonus Faber monitors than a set of behemoths from Wilson.

It's important for me to stress that point, which is that I *prefer* the sound of a two-way, or even a one-way if that was practical. On this forum I've noticed a preference for three-way and even four-way systems. That preference implies that the quality of a stereo goes up as you add drivers. I am coming at the problem from the other direction, and saying that if possible, ONE speaker per side would be ideal.

So the prolog of this thread is intentional, because the goal of this thread is to wring every last ounce of performance out of a single driver. If your personal preference is the use of three or even four woofers per side, *this solution is not for you.*


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## aztec1 (Jun 13, 2008)

You definitely have my interest! I've been toying with the idea of using a fullrange in a two-way for the truck after reading your sphere diffraction thread and it sounds like this will dovetail nicely with that. Looking forward to the next installment.


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## Patrick Bateman (Sep 11, 2006)

aztec1 said:


> You definitely have my interest! I've been toying with the idea of using a fullrange in a two-way for the truck after reading your sphere diffraction thread and it sounds like this will dovetail nicely with that. Looking forward to the next installment.


Yeah, the prolog is a bit lengthy, but necessary I think. It's important to make the distinction that we're going to treat a woofer to extract every last ounce of performance out of it, not to save money. In audio there seems to be a misconception that "more" is "better". IMHO, a lot of this is driven by marketing, since there is definitely more profit to be found by selling people six drivers and three amplifiers.

People tend to look at me as if I'm a lunatic when I recommend spending $100-$200 on a single midrange, instead of $500 on a three way component set.

There's a method to the madness


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## masswork (Feb 23, 2009)

Can't wait to see the full how-to


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## Mless5 (Aug 21, 2006)

Oh come on, don't leave us hanging like that?!


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## Patrick Bateman (Sep 11, 2006)

If you've made it this far without dozing off, you've read that:


I'm looking to build a cost-no-object two-way speaker
I'm going with a two-way because I believe it's the best solution, not because it's cheaper than a three-way.

So what's a good candidate for a two-way? The most common configuration is to use a 6.5" woofer combined with a 1" tweeter.









Here's Focal's offering, at $4700.

I've listened to these, and while they're pleasant enough, their dynamics cannot match my home speakers. My home speakers have a fifteen inch midbass with an efficiency of 95db. Though the Focals are certainly well-engineered, a 6.5" woofer can't match the displacement of a good fifteen.

So what then?


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## 94VG30DE (Nov 28, 2007)

...glue a larger stiff paper cone to the existing cone, thereby increasing your cone area and costing $1


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## Mless5 (Aug 21, 2006)

94VG30DE said:


> ...glue a larger stiff paper cone to the existing cone, thereby increasing your cone area and costing $1


Plastic tapper ware?


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## Notloudenuf (Sep 14, 2008)

94VG30DE said:


> ...glue a larger stiff paper cone to the existing cone, thereby increasing your cone area and costing $1


Buy $1 screwdriver
Jam it through each ear drum
All speakers now sound the same.


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## Patrick Bateman (Sep 11, 2006)

At this point, I've listened to the $30,000 JM Lab Utopias, and though impressive, they require a room the size of a basketball court to work their magic. Even when cost is no object, I prefer two-way speakers. Putting "my money where my mouth is", my home speakers are a set of two-ways, which use a fifteen inch midbass. Here's that midbass:









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

I've listened to Focal's $4700 car speakers, but their 6.5" woofer can't keep up with the dynamics of the 15" B&C.

At this fork in the road, you have two solutions:


Compromise, and buy the Focal. There's nothing wrong with it. It can't match the B&C, but then again, how could it? There isn't a 6.5" woofer in the world that can match the dynamics of a fifteen (at least not yet  )
Go the gonzo route, and see how close we can get to the B&C. This way is the path to madness, aka "loudspeaker hell." 

Everything else being equal, an eight inch woofer will give you one quarter of the output of that big ol' B&C woofer, and twice the output of the Focal woofer. We know that by looking at a spec called "SD" on the spec sheet from the manufacturer. The B&C weighs in with an SD of 855, and the Focal has an SD of 127. The typical SD for an eight is about 220.

That spec sheet shows us that an eight will give us twice the output of the Focal, and a quarter of the output of the B&C, as long as all woofers have the same XMAX. Note that efficiency doesn't play a factor here - it's all about displacement, just like the pistons in an engine.


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## bassfromspace (Jun 28, 2016)

94VG30DE said:


> ...glue a larger stiff paper cone to the existing cone, thereby increasing your cone area and costing $1


Whizzer cone!


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## aztec1 (Jun 13, 2008)

Does this mean there's some sort of relationship between Sd and room size?


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## [email protected] (May 14, 2009)

Hi!

Remove the Dustcap and put a Tweeter in the VoiceCoil :surprised:
Custom made Coaxial Speaker.


Greets


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## req (Aug 4, 2007)

cmon guys, enough with the rediclious comments.

im interested in seeing how you plan on getting an 8 inch to be efficent enough to play that high and that low at the same time.


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## jpswanberg (Jan 14, 2009)

Hey Patrick,
3 more speakers to listen to: Magnpan 20.1, Dynaudio Evidence Master, and the Gallo Reference Series. Three different price ranges/sounds. Personally, I've been seduced by Maggies (not the 20.1's - cost being a factor). JPS


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## savagebee (Sep 12, 2006)

c'mon PB, Im dying for the punchline. Im not too with you on the waveguides or TH stuff (yet, but Im following you there), but this is definately gettin my interest


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## Quickshift (Feb 28, 2009)

Anything to do with Bud's process?


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## Patrick Bateman (Sep 11, 2006)

Quickshift said:


> Anything to do with Bud's process?


Nah, this isn't anything "magic" or exotic. I'm just going to show how to extend the frequency response of a woofer by treating the cone.

The reason I called the thread "loudspeaker hell" is that I would much rather BUY a good eight. But a lot of the time you find that there are three or four good candidates for a speaker, but each one of them is defective in one way or another.

I wanted to differentiate the thread from some of the other projects out there, where someone modifies cheap woofers to make them sound more expensive.

The idea here is to take a woofer which isn't really designed to play into the midrange, and twist it's arm until it cries "uncle"


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## 94VG30DE (Nov 28, 2007)

Patrick Bateman said:


> Nah, this isn't anything "magic" or exotic. I'm just going to show how to extend the frequency response of a woofer by treating the cone.
> 
> The reason I called the thread "loudspeaker hell" is that I would much rather BUY a good eight. But a lot of the time you find that there are three or four good candidates for a speaker, but each one of them is defective in one way or another.
> 
> ...


Well let's see it! If my gf was this much of a tease, I would find a new one :laugh:
So release the documentation on this crazy treatment process so I can get to ruining my spare speakers


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## chithead (Mar 19, 2008)

Subscribed yet again.


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## ginster6 (Aug 19, 2009)

the setup I have at home is both dym, staging and most important musical... you should that a listen to Verty Audio and Nagra Electronic par up together..... musical bliss..

I have own Wilson Audio, Revel, b&w, Paradigm ref, martin Logan, Thiels, and Totem....


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## western47 (Nov 17, 2008)

Stop the insanity PB!!

Seriously, you have a lot of people very interested as your posts are all very well based. The WG on the dash will be a difficult sell for quite a few people. The tweeter or small FR driver in the sphere to reduce diffraction effects is a brilliant 'why didn't I think of that' moment. The measurements, well, if people aren't measuring these days but just using their ears then they really aren't serious about good sound.

My goal is probably like that of most around here; great sound based in science using the KISS principle as much as possible. Knowing that your Summa's are the mark makes me feel pretty good about your efforts. This all leaves the question for me of what would you say is the best achievable system using realistic approaches in everyday drivers?

I, as usual, await your next post.


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## Quickshift (Feb 28, 2009)

Patrick Bateman said:


> Nah, this isn't anything "magic" or exotic. I'm just going to show how to extend the frequency response of a woofer by treating the cone.
> 
> The reason I called the thread "loudspeaker hell" is that I would much rather BUY a good eight. But a lot of the time you find that there are three or four good candidates for a speaker, but each one of them is defective in one way or another.
> 
> ...


OK, so somehow you're going to need to increase the stiffness of the cone and / (or damp resonance)? to move the breakup higher up the frequency range. Maybe something like a carbon fiber lattice bonded to the cone or coating it with layers of something like epoxy or maybe a composite coating of some kind. (can you tell I've never really thought about this before   )


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## BigAl205 (May 20, 2009)

If this ends like "No Country For Old Men", I'm gonna be pissed.


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## jedc (May 4, 2009)

BigAl205 said:


> If this ends like "No Country For Old Men", I'm gonna be pissed.


Yes please none of that crap.


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## Excellrec (Oct 22, 2007)

No Country for Old Men had a great ending. Some people just can't stand things not being wrapped up into a nice tidy little package. Let a little mystery into your life.


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## mattyjman (Aug 6, 2009)

okay, i'm piqued...teach me more!!!


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## reindeers (Mar 7, 2008)

Subscribed...


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## Patrick Bateman (Sep 11, 2006)

aztec1 said:


> Does this mean there's some sort of relationship between Sd and room size?





aztec1 said:


> Does this mean there's some sort of relationship between Sd and room size?


Great question!

There IS a relationship between the size of the speaker, and the room. But the relationship isn't immediately obvious.

This was something that frustrated me when I was demoing all these speakers, and noticing that the small ones were often more listenable than the big ones. And the big ones were demo'd in auditoriums.

For instance, the last demo of a Wilson speaker that I've heard was done in a 5000sf auditorium, with Halcro amplifiers that cost as much as a house.

The reason that Wilson and JM Lab demo their big speakers in BIG rooms is they understand that relationship exists.

If I were a salesman, I might say that the Utopia speaker needs a big room to "breathe" or that the big speaker needs an amplifier with enough "balls" to "open up", or some other marketing nonsense.

But that's all a distraction from the *real* issue, which is a technical one. _As you get closer to a big speaker, the frequency response goes to hell._ The technical term is that you are transitioning from the _far field_ of the speaker to the _near field._

When you're in the near field, the frequency response is hellish, and unpredictable. The frequency response varies wildly, exhbiting peaks and dips that appear and disappear as you move even an inch or two.

You can check this one out yourself, it's easy.


Get yourself a set of two-way or three way speakers
Listen to them from a distance of ten feet or more. Note how the treble is smooth, the bass is well integrated, and the location of the midrange and the tweeter isn't obvious.
Now take the exact same speakers, and sit two or three feet away. Notice that the treble sounds hotter, the bass is leaner, and the integration between the highs and the lows is poor? That's due to the transition from the near field to the far field.

Anyways, to make a long story short, this is one of the reasons that small two-ways work well in small rooms.


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## huckorris (Sep 2, 2009)

No no, we want the long story.

You're such a tease. I wanna know why it does this, even though it's probably over my head.:smart:

It's not like you have a life or anything, I mean, c'mon, teach me teach me. 

I pity da foo' who don't wanna learn. :Mr-T:


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## Patrick Bateman (Sep 11, 2006)

About every day on the forums, there's a new thread asking which is the best seven inch woofer, or if a tweeter from a particular manufacturer sounds good.

This has always struck me as odd... The parameters of a loudspeaker will affect how it sounds more than the origin.

For instance, the upper limit of the woofer in this project will largely be determined by just two factors:


*Diameter* - More than any other parameter, the diameter of the piston will set the upper limit of it's response. Doesn't matter if it's a subwoofer, a midrange, or a tweeter. The diameter trumps nearly all other variables. As the wavelength of sound approaches the diameter of the piston, the sound narrows, and begins to roll off. For an eight inch woofer, that frequency will be 1688hz. (speed of sound / 8) = (13500 inches per second / 8) = 1688hz.
*Inductance* - The voice coil of a speaker has inductance, just like an inductor does. As the frequency rises, inductance increases. As inductance increases, the woofer draws less power from the amplifier. And less power equals less output. So the output of the woofer falls as the frequency rises.

To sum it up, it doesn't particularly matter if your woofer is from Dynaudio, Focal, or even Goldwood. The response of the woofer will largely be determined by inductance and diameter.


















This frequency response of an eight inch dynaudio woofer illustrates the points above. A typical eight inch will start to beam at 1688hz. Note where the response of the Dynaudio begins to narrow "in the real world."








This is the impedance of the same woofer. Note that the response begins to droop at 1khz, which is exactly where the impedance begins to rise. *This is not a coincidence.* You might be wondering why it doesn't fall faster, since the impedance is rising very quickly? The reasons it doesn't decay faster is because the beamwidth of the speaker is narrowing at the same time as the impedance is rising. The narrowing of the beamwidth concentrates what energy is left into a smaller angle. Aren't loudspeakers fun? (ok not really)

YES, there are some tricks to get around this. Shorting rings lower inductance and distortion, and it's possible to extend the response of a woofer by changing the shape of the cone. But the second trick basically modifies the speakers diameter, by damping part of it at high frequency, to extend the response.

Yes, this thread is long-winded, but I'm hoping the technical information will help others select the very best loudspeakers for their projects. I learned a lot of this off other people, and a great deal of it is poorly documented, or rarely discussed. Until I developed a good grasp on directivity and inductance, many of my own projects were largely based on whatever seemed to be a good deal at Madisound or Parts Express. With a solid grasp on what makes a loudspeaker tick, it is possible to exceed the performance of Focal or Dynaudio for a fraction of the cost.


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## huckorris (Sep 2, 2009)

:bowdown::bowdown::bowdown:

Every post is well appreciated.

So the seven beams around 1928hz? I've heard of tweets playing that low, and horns do it without a sweat. I'm interested how this turns out, of course.


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## dtm337 (May 28, 2009)

c'mon man were all dying for an answer .... i like the screwdriver comment my self ..im so sick of tuning systems ..and being dissapointed .mostly in my own cars .


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## subwoofery (Nov 9, 2008)

I know that the higher frequencies radiate from the center of a cone and the lower from the outer... Should we try to make the center of the cone lighter to play higher? 

My comment sounds stupid I know  

Kelvin 

PS: subscribed


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## western47 (Nov 17, 2008)

So, we want a cone of larger diameter to play as a smaller one at increasing frequency. Making the motor structure to do so is pretty straight forward these days. My guess would be that you would want to dampen the outer edges of the cone towards the surround termination. I would think that as the sound propagates from the voice coil you would end up having to dampen the breakup as the frequency rises. The outer portion of the cone also has the majority of the surface area to it. 

Beyond this issue I am wondering where we are planning on mounting this thing. As you said, the diameter will dictate a lot of where this driver will start to narrow it's sound pattern. At 8", mounting of such an item on the dash or anything crazy might be an issue. Having a tweeter that integrates well with higher xo point is a no brainer. Getting this same 8" which now plays pretty well into another octave to act like a good woofer sounds like another issue to discuss.

Either way, I am along for the ride as my future system is at a stand still for now.

My vote would be for a pro driver such as the B&C 8 PE 21.


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## BigAl205 (May 20, 2009)

So Patrick, what kind of "dope" are you selling?


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## ItalynStylion (May 3, 2008)

Standing by for conclusion....


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## andy335touring (Jan 25, 2009)

Subscribed, sounds like another excelent thread


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## Lanson (Jan 9, 2007)

While watching American Psycho I just smiled and remembered all the PB threads I've read over time. It is ERIE how reading these threads feels a lot like the personality Christian Bale presented in the movie. Detail oriented, completely nuts, etc. 

And you know, PB, whenever I read your threads I read them in my head in a Bale voice. I never really noticed that 'till now.


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## stills (Apr 13, 2008)

i always think about the naked w/ the chainsaw and tennis shoes scene.


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## npdang (Jul 29, 2005)

It may be a shock to some, but I've almost sworn off tuning with respect to in-car measurements. I've tried many things over the years, gotten some decent results, but nothing has yet to approach what I've achieved doing it the old fashioned way of listening to a reference source and tuning over time subjectively.

Even assuming that you do have relevant measurements, do you have the proper tools to adequately correct for supposed deficencies in the system sensitivity?

I always keep an open mind to new solutions however. I just don't have the motivation to experiment myself any longer.


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## huckorris (Sep 2, 2009)

stills said:


> i always think about the naked w/ the chainsaw and tennis shoes scene.



I love the "Mergers and Acquisitions" part.


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## TREETOP (Feb 11, 2009)

npdang said:


> It may be a shock to some, but I've almost sworn off tuning with respect to in-car measurements. I've tried many things over the years, gotten some decent results, but nothing has yet to approach what I've achieved doing it the old fashioned way of listening to a reference source and tuning over time subjectively.
> 
> Even assuming that you do have relevant measurements, do you have the proper tools to adequately correct for supposed deficencies in the system sensitivity?
> 
> I always keep an open mind to new solutions however. I just don't have the motivation to experiment myself any longer.


Same here, well said. No amount of electrical or acoustical measurements will compensate for how my own brain interprets what my ears allow in, or for my listening preferences.


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## masswork (Feb 23, 2009)

Where's PB btw???
I'm curiously checking this thread hourly


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## 2500hd (Aug 22, 2009)

In the washroom choking out Carruthers...
Seriously though I'm very anxious to see the $1 mod


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## western47 (Nov 17, 2008)

npdang said:


> It may be a shock to some, but I've almost sworn off tuning with respect to in-car measurements. I've tried many things over the years, gotten some decent results, but nothing has yet to approach what I've achieved doing it the old fashioned way of listening to a reference source and tuning over time subjectively.
> 
> Even assuming that you do have relevant measurements, do you have the proper tools to adequately correct for supposed deficencies in the system sensitivity?
> 
> I always keep an open mind to new solutions however. I just don't have the motivation to experiment myself any longer.


I think that a lot of tuning in a car is horrible because of the power responses. The vast majority of home systems that really top my list all have great control over their polar fields. In a car it is not only very difficult to do but it is almost never even looked at. When one is tuning they are often looking at one position or axis. As you well know, adjusting this axis is not an isolated event.


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## WLDock (Sep 27, 2005)

Patrick Bateman said:


> It's important for me to stress that point, which is that I *prefer* the sound of a two-way, or even a one-way if that was practical. On this forum I've noticed a preference for three-way and even four-way systems. That preference implies that the quality of a stereo goes up as you add drivers. I am coming at the problem from the other direction, and saying that if possible, ONE speaker per side would be ideal.
> So the prolog of this thread is intentional, because the goal of this thread is to wring every last ounce of performance out of a single driver. If your personal preference is the use of three or even four woofers per side, *this solution is not for you.*


OK, I gotta say that this exact thought has been on my mind for the last month! I just dumpped my supposed 3-way + sub system and was thinking about the what would I replace it with if i started all over again. Well, a single 15" or two would be a must for the sub. But upfront what would I use? Those new 8" Tang Band full range drivers at Parts Express really caught my attention.

If I had the means I would try it...two 8" fullranges and a single 15" with solid power might be fun to play with?










OK, you caught my attention...I am subscribed.


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## WLDock (Sep 27, 2005)

Patrick Bateman said:


> It's important for me to stress that point, which is that I *prefer* the sound of a two-way, or even a one-way if that was practical. On this forum I've noticed a preference for three-way and even four-way systems. That preference implies that the quality of a stereo goes up as you add drivers. I am coming at the problem from the other direction, and saying that if possible, ONE speaker per side would be ideal.
> So the prolog of this thread is intentional, because the goal of this thread is to wring every last ounce of performance out of a single driver. If your personal preference is the use of three or even four woofers per side, *this solution is not for you.*


OK, I gotta say that this exact thought has been on my mind for the last month! I just dumpped my supposed 3-way + sub system and was thinking about the what would I replace it with if i started all over again. Well, a single 15" or two would be a must for the sub. But upfront what would I use? Those new 8" Tang Band full range drivers at Parts Express really caught my attention.

If I had the means I would try it...two 8" fullranges and a single 15" with solid power might be fun to play with?










OK, you caught my attention...I am subscribed.


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## Patrick Bateman (Sep 11, 2006)

npdang said:


> It may be a shock to some, but I've almost sworn off tuning with respect to in-car measurements. I've tried many things over the years, gotten some decent results, but nothing has yet to approach what I've achieved doing it the old fashioned way of listening to a reference source and tuning over time subjectively.
> 
> Even assuming that you do have relevant measurements, do you have the proper tools to adequately correct for supposed deficencies in the system sensitivity?
> 
> I always keep an open mind to new solutions however. I just don't have the motivation to experiment myself any longer.


That IS shocking!

I've been building loudspeakers and doing car audio for close to twenty years now. Until 2009, measurements were always an afterthought for me. I've done them for half a decade, but I would typically do three, maybe five measurements over the span of a project.

Basically on a whim I built a PC and dedicated it to measurements, using a bunch of old parts I had lying around. Literally invested nothing to build it.

And THAT really took everything to "the next level."

If I wanted to measure my car a year ago I had to dig up my microphone, hook up a preamp, hook up an amplifier... See what I mean? In 2008 it would take 30-60 minutes to do one measurement.

Now I have a PC running 24/7 for measurements. I can literally measure a driver in under three minutes, and do a full set of polars in under five.

Being able to do measurements so easily, and doing literally hundreds at a time, has uncovered a lot of things for me. Some of these are just common sense, but having measurements to back it up is satisfying. Over the years I've worked on a series of car stereo projects which were not satisyfing. I would say that 80% of my projects were a disappointment, maybe even 90%. For instance, a few years back I had a system with four inch woofers in the doors, and the midbass was lacking. To fix it, I built custom doors, with dual woofers. It was a lot of work... And there was no bass. The four inch woofers actually played deeper than the dual woofer setup, even with completely new doors. Back then, I just scrapped the project, having flushed hundreds of hours and hundreds of dollars down the drain. *That's a lot of work that went to waste!* Nowadays, I would just measure the car, and figure out why the bass was so light. For instance, you'll get a reflection off the floor in a car, and that reflection will create a notch in the measured response, and that NOTCH could have made the woofers sound bad, not the woofers themselves.

Even with close to twenty years experience, I am routinely confused by the measured results I see. For instance, a couple of months back I nearly scrapped my current install, because I couldn't isolate a notch and a dip in the midrange. I did EVERYTHING I could think of to fix this stupid response problem, it was driving me NUTS. Replaced the midrange, tried a DIFFERENT midrange, at one point I even laid down egg crate foam at various spots near the midrange, trying to absorb the sound.

Can you picture what a lunatic I was, sitting out in my car in the middle of July, with giant sheets of eggcrate foam? I'm surprised my neighbors still speak to me.

Anyways, while doing this, with the music playing, I detected a veeeeery faint vibration coming from the horns. We're talking about a fraction of a millimeter. You could FEEL it if you touched the horns, but you sure as hell couldn't HEAR it while listening to music.

But the mic caught it, and that was critical. I cross braced the horn, added about a pound of dampening, and sure enough, 50% of the peak and the dip disappeared. Of course it would have been great if I'd elminated 100% of the peak, but that's a thread for another day. I don't think people appreciate how many things rattle and buzz near their midranges, and how much those resonances contribute to the systems frequency response.

For me, THAT is the key to measuring a speaker. To use the measurements to pinpoint a problem, and then PHYSICALLY fix the problem. I would never encourage anyone to measure their car, then EQ it so it's relatively flat. That's foolish - the microphone is a way to pinpoint resonances and reflections, and often the only solution is to physically move the loudspeaker.


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## aztec1 (Jun 13, 2008)

Any more news on this mod Patrick? 

I'd also like to know more of your thoughts on the Sd/room size relationship and how it might apply to a vehicle. Is there a golden ration that you've found? I'm thinking of trying some Fountek FR88's in some spheres.


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## psycle_1 (Aug 4, 2005)

I think the mod is similar to this, but of course I may be wrong.

Speaker Tweeks -- Puzzlecoat & Ductseal


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## Mless5 (Aug 21, 2006)

Curious minds demand part 2


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## ItalynStylion (May 3, 2008)

So....what happened?


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## Patrick Bateman (Sep 11, 2006)

ItalynStylion said:


> So....what happened?


The program I use to merge the measurements together crashed. (You get what you pay for - The Gimp is free.)

So I lost all the measurements 

I think I have them on one of my laptops here, I'll dig them up soon.

In a nutshell, the use of cheap damping on the cone allowed this 8" subwoofer to play into the midrange. The reason that this "trick" works is that the XBL^2 motor has very low inductance. So even though it's a subwoofer, you can get four or five octaves out of it.

And since it has a ton of excursion, you wind up with a "woofer" that can take some serious abuse.

For less than $100, it's pretty compelling as a midrange.


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## Blake Rateliff (Jul 12, 2008)

Are you eventually going to tell us what type of "cheap cone damping" was use, and how it was applied?


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## bafukie (Nov 23, 2007)

awaiting updates


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## CGG318 (Apr 9, 2007)

Patrick Bateman said:


> _At the end of this thread, I will demonstrate how a one dollar modification to a loudspeaker can improve the sound. _


End of thread?


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## ItalynStylion (May 3, 2008)

Yeah....I wanted to know how this story ended as well


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## SSSnake (Mar 8, 2007)

Wow, five star rated thread?!?


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## 94VG30DE (Nov 28, 2007)

SSSnake said:


> Wow, five star rated thread?!?


5-stars with no finale even...


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## WRX/Z28 (Feb 21, 2008)

What happened? Updates still in the works when the measurement machine is back up and running? 

Skimming the thread seemed to indicate that you're attempting to extend the upper FR of a larger driver (8") by adding mass/deadening? Why are the drivers made without that mass built in to begin with? Efficiency? 

I have a set of Mpyre 65m's (adire extremis). They play midbass with authority, but will not extend high enough to be used in a two way situation, this even though they are 6.5's. Will your process allow these to extend higher as well? 

Waiting for more clarification. I'm going to go back and re-read this thread.


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## Patrick Bateman (Sep 11, 2006)

It took a lot of digging, but I managed to find some of the measurements. (As I mentioned previously, one of my apps crashed, and I lost most of the measurements for this project.)

Here's a summary of what I'm trying to accomplish here:

I've listened to speakers at every price level, from $100,000 line arrays to $200 two-ways. I've found that a lot of the "cost no object" speakers don't image very well. They have dynamics to burn, but they don't image. Small inexpensive speakers tend to image quite well, but they can't compete with the giant megabuck speakers when it comes to dynamics.















So what I'm trying to do here is find a sweet spot between the two speakers above.

I believe the best way to find that "sweet spot" is to combine the dynamics and low distortion of a megabuck speaker with the simplicity of a good two way.

Up until this point, most people would do that by using a 6.5" woofer and a 1" tweeter. I believe that there are a handful of 8" drivers which can be pushed up another half an octave.

Please note that these woofers are VERY rare. In fact, the technology that enables this kind of performance is quite new. Innovations like split voice coil gaps and shorting rings are what makes this all possible. This is because large woofers are _physically unable_ to play above a certain point. For instance, an eight inch woofer with a _perfectly rigid cone_ will begin to roll off about 2000hz. (The math is in the link below.) The upper limit of a woofer is dictated by it's diameter and it's inductance. That's the bad news. The good news is that we have technologies that can reduce inductance by a LOT, and these technologies allow us to push an eight inch woofer to 1500 or even 2000hz.

For more information on how we do that, see this post:

http://www.diymobileaudio.com/forum...r-buck-aka-loudspeaker-hell-2.html#post849153

So the first thing we have to do is find a woofer with very very low inductance. The one that I wound up using is the Creative Sound Trio8. It's inductance is 0.6, which is 75% less than an average eight.

There are other good candidates too. Peerless, Dayton, Seas and even Pioneer offer models with inductance that's VERY low. The reason that the Trio8 trumps the competition is that it has the most xmax of all. This is VERY important for our application. Making bass is all about moving air. Even though the Trio8 is only an eight inch woofer, it can move as much air as the average ten or twelve.

That's key here - that's how we get massive dynamics out of the Trio8, it can move a lot of air.

There's one big problem with using the Trio8 up to 1500hz. It's not a midbass, it's a SUBwoofer! So it was never designed to play to 1500hz. It has the low inductance that we need, but the cone wasn't designed to play that high.

In fact, the manufacturer hasn't even published a frequency response graph. But I could see from the specs that it had the potential to play to 1500hz.







Here's the measured response of the Trio 8 on a baffle. There are three graphs. The top one is "out-of-the-box." The next one is with mass added to the cone. The bottom graph is with even MORE mass added to the cone.

As mentioned above, if this 8" woofer was perfectly rigid, it would roll off about 2000hz. What these measurements demonstrate is that adding mass to the cone is getting us closer to the ideal. The grey area in the graph is my target - I want the woofer to rolloff at 1500hz, with a 12db/octave slope. The untreated woofer isn't ideal - there is a 12db dip at 1200hz! Now look at the treated woofer. We can see that the dip is half as deep and half as wide.

Besides improving the on-axis response of the woofer, there are a number of other improvements in the response, which aren't immediately obvious:


There is no way to electronically reduce distortion. But you can *physically* reduce distortion by manipulating the rolloff of a loudspeaker. For instance, if a speaker naturally rolls off due to it's physical size, _distortion will also be rolled off._ For instance, let's say you have two woofers. One is four inches, one is eight inches. The four incher rolls off at 4500hz, and the eight inch woofer rolls off at 1500hz. *Both have an electronic crossover at 1500hz.* Because the eight is *physically* rolling off at 1500hz, it will have less 2nd and 3rd harmonic distortion above 1500hz. This can make a tremendous difference in the clarity of a loudspeaker, and it's one of the reasons that large loudspeakers often sound very "clean." Believe me, I love those small full range speakers. I just wish they could play loud and clean. While this thread is a bit confusing, I hope it illustrates some of the "tricks" we can use to make a clean and dynamic loudspeaker.
The rolloff of the treated woofer is getting close to our target. The untreated woofer has a 10db peak at 7khz which could make a crossover difficult.
While the efficiency of the woofer is very low, keep in mind that SPL is determined by the xmax of the driver. Efficiency only dictates how loud a woofer will play with one watt; the maximum SPL of a woofer is generally limited by it's xmax. In other words, reducing the woofers efficiency does NOT reduce it's maximum SPL.

The next step in this project is to determine what parts of the cone are resonating the worst, and then re-arrange the damping so that the dip at 1200hz is completely eliminated. All of the damping that I've applied so far was arranged equally. The trick is to find the parts of the cone that resonate the worst.


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## WRX/Z28 (Feb 21, 2008)

Wouldn't reducing it's efficiency would increase the amount of power it would take to acheive that spl though? Possibly even increasing it past it's thermal power handling capability's?

Also, how careful do you need to be when placing the damping material? Can't it throw the linearity out of whack?


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## Patrick Bateman (Sep 11, 2006)

WRX/Z28 said:


> Wouldn't reducing it's efficiency would increase the amount of power it would take to acheive that spl though? Possibly even increasing it past it's thermal power handling capability's?
> 
> Also, how careful do you need to be when placing the damping material? Can't it throw the linearity out of whack?


I've built a lot of speakers, and the only time that thermal power handling has been a big issue for me is when I'm using drivers with extraordinarily small voice coils, or when I'm building subwoofers.

Basically, as long as I'm limiting a driver to 100hz and up, I generally run out of xmax before I run out of power handling IF I'm using a fairly large woofer.

Now admittedly, with a three inch or a five inch woofer, it's easy to blow through the thermal limits in a hurry.

But beyond those sizes, the limitation always ends up being xmax. For instance, I have some B&C eights here, and they'll play to absurd levels, but they just can't generate any bass at all because the xmax is too low. One of the most "extreme" examples of this is the Galaxy Audio 5". It can soak up a hundred watts without breaking a sweat, but due to it's limited displacement it runs out of XMAX at just ONE watt if you use the wrong enclosure! Crazy huh? 

So the goal was to find a "sweet spot", where we have lots and lots of displacement, but not so big that the woofer is rolling off at 500hz.

As for "throwing it out the linearity", I'm not sure how that would come into play. Guys like Dan Wiggins or John Janowitz could help me on this one. As I understand it, improving the rigidity of the cone to reduce resonances is always a good thing.

Note that I believe that the weight of the cone is completely irrelevant; I do not believe that light cones are "faster." Dan Wiggins has convinced me that transient response depends on the frequency response and the inductance, not the weight of the cone or the driver's sensitivity.

Dan's motor has already fixed the inductance, which means that all we need to do is fix the frequency response.

And then we're done.


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## huckorris (Sep 2, 2009)

:2thumbsup::beerchug::ears::snacks:


How low is this 8" supposed to play?


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## SSSnake (Mar 8, 2007)

Any reason you wouldn't just apply EQ to get the same response? That way you are not burning efficiency. 

Also, adding weight usually manifests as an increase in inductance with the subsequent roll off in higher freq response. As a matter of fact your measurements show that behavior as well (-5db at almost 3Khz in the unmodified speakers and 1.6khz in the modified). 

Adding cone mass to increase high freq response is typically a non-starter.


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## Patrick Bateman (Sep 11, 2006)

SSSnake said:


> Any reason you wouldn't just apply EQ to get the same response? That way you are not burning efficiency.


A peak or a dip in a speakers response can be fixed with EQ. But a peak NEXT to a dip is basically a no-win situation. If you try to boost the dip you boost the peak and if you try to cut the peak the dip gets so deep that the speaker becomes unusable above that frequency.

Now you *could* cut the peak, and lower the crossover to 500hz or so, and you'd be fine. But I want to get this thing to play above 1000hz!



SSSnake said:


> Also, adding weight usually manifests as an increase in inductance with the subsequent roll off in higher freq response. As a matter of fact your measurements show that behavior as well (-5db at almost 3Khz in the unmodified speakers and 1.6khz in the modified).
> 
> Adding cone mass to increase high freq response is typically a non-starter.


You could add twenty pounds of lead to the cone and the inductance wouldn't change - it's a motor parameter.

The reason that the speaker is playing to 3khz when it's unmodified is due to resonances. If the speaker was a perfect piston, it would begin to rolloff around 2khz. Once you deal with the inductance problem, the high frequency limit of a speaker is based on the speakers diameter, and to a small extent, it's shape.

There are a number of tricks that a loudspeaker designer can use to extend the response above the pistonic limit. For instance, a 3" woofer _should_ roll off around 7khz. But the shape of the cone can be manipulated to provide a bit of horn loading at high frequencies, which increases the efficiency in the last octave, and the apex of the cone can be modified so that it resonates at a very high frequency, acting a bit like a whizzer cone.


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## Patrick Bateman (Sep 11, 2006)

huckorris said:


> :2thumbsup::beerchug::ears::snacks:
> 
> 
> How low is this 8" supposed to play?


The spectrum is split in half basically. Five and a half octaves from the woofer, and four from the tweeter.

So that's 30hz to 1500hz for the woofer, and 1500hz to 24khz for the tweeter.

There are 6.5" woofers which can cover 30hz to 1500hz, but they don't have as much displacement as the Trio 8. So your maximum SPL with the Trio8 is about 5db higher than a comparable 6.5". (You'd need a 6.5" woofer with about 16mm of xmax to match it.)


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## Hernan (Jul 9, 2006)

WRX/Z28 said:


> I have a set of Mpyre 65m's (adire extremis). They play midbass with authority, but will not extend high enough to be used in a two way situation, this even though they are 6.5's. Will your process allow these to extend higher as well?


A bit Ot but I use the Mpyres and they have a nice flat extended FR. Measured.
I like these drivers very much. (I'm still using 3 ways because I have them at the doors).


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## SSSnake (Mar 8, 2007)

> You could add twenty pounds of lead to the cone and the inductance wouldn't change - it's a motor parameter.
> 
> The reason that the speaker is playing to 3khz when it's unmodified is due to resonances. If the speaker was a perfect piston, it would begin to rolloff around 2khz. Once you deal with the inductance problem, the high frequency limit of a speaker is based on the speakers diameter, and to a small extent, it's shape.
> 
> There are a number of tricks that a loudspeaker designer can use to extend the response above the pistonic limit. For instance, a 3" woofer should roll off around 7khz. But the shape of the cone can be manipulated to provide a bit of horn loading at high frequencies, which increases the efficiency in the last octave, and the apex of the cone can be modified so that it resonates at a very high frequency, acting a bit like a whizzer cone.


You are making the assumption that L is time invariant which is NOT true. The majority of the L value is time invariant and and a function of the motor design but there are other time variant portions of inductance. I believe this has been pointed out as a fallacy in Dan's woofer speed paper. Is it a solid 80-90% approximation, sure, but not entirely correct.

There is a solid realtionship between efficiency and bandwidth and you can trade one for the other. One method, as you mentioned, is to add mass. Typically, this helps you more on the low end of the FR than the high end (the whole delta mass method of determining Vas is based upon looking at the effect of added mass on the resonant freq). However, the same effect can be attained with proper equalization without causing the inefficiency or potential thermal issues. Now if the mass is added strategically so that you damp resonances then you can eek out a little more on the high end. This is something that you can't do with an EQ. However, IME it is not as simple as just slapping some weight on the cone.


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## Patrick Bateman (Sep 11, 2006)

I agree that slapping a bunch of weight isn't ideal, but the measurements demonstrate that it gets you halfway there.

The only real problem with the response of the Trio8 is the dip at 1200hz. In all other respects, it's just about perfect. Because of it's huge xmax, it can generate 3db more SPL than the best 6.5" woofers, or play half an octave lower. Due to it's low inductance, it has the motor to play up to 1500hz.

I literally can't name another woofer that can do all these things. I have one of the Dayton RS200s here, but it can't keep up with the Trio8's displacement. (BTW, the RS200 actually measures better than the specs on the Parts Express site - it appears that they've modified the cone at some point to improve the rolloff, because my measurements show that it's now better than what they've shown, and better than the prototype that Mark K published.)

About the only alternative to the Trio8 that I can think of is a ten inch woofer, such as the neo models from B&C or the Aurum Cantus tens.

All the other candidates have too much inductance, or cost four times as much (Seas, Scanspeak.)


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## dnvm84 (Nov 8, 2009)

PB, as I was looking at CSS's website I stumbled upon the SDX7 which is a 7" woofer. Comparing it to the Trio8 specs and the response graph you created I believe this could be potentially a substitute for the Trio8. Inductance is .75 and an xmax of 11.1. And according to CSS it is efficient from 200 Hz up to quite possibly 3 KHz plus. I realize that it has about half of the xmax but frequency response looks good.
If I am seeing this wrong please let me know otherwise could the SDX7 work for your 2 way setup?
Link for pdf spec sheet: http://www.creativesound.ca/pdf/CSS-SDX7-data-261207.pdf
I also would like to thank you for all of your technical write ups. I have been designing my own systems for some years now but what I have learned in the 2 or 3 days since I became a member is amazing.


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## vactor (Oct 27, 2005)

this thread needs updating. i LOVE reading PB posts and i learn a lot everytime.


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## lycan (Dec 20, 2009)

SSSnake said:


> You are making the assumption that L is time invariant which is NOT true. The majority of the L value is time invariant and and a function of the motor design but there are other time variant portions of inductance. I believe this has been pointed out as a fallacy in Dan's woofer speed paper. Is it a solid 80-90% approximation, sure, but not entirely correct.
> 
> There is a solid realtionship between efficiency and bandwidth and you can trade one for the other. One method, as you mentioned, is to add mass. Typically, this helps you more on the low end of the FR than the high end (the whole delta mass method of determining Vas is based upon looking at the effect of added mass on the resonant freq). However, the same effect can be attained with proper equalization without causing the inefficiency or potential thermal issues. Now if the mass is added strategically so that you damp resonances then you can eek out a little more on the high end. This is something that you can't do with an EQ. However, IME it is not as simple as just slapping some weight on the cone.


The problem with Dan's paper on woofer "speed" is that he defined "transient response" in a non-standard, and virtually meaningless, way.

The industry standard, and meaningful, definition of transient response is the ENTIRE time domain response ... from t=0 to t=infinity ... to a transient input. Transient inputs including impulses, steps, etc.

Dan's definition was simply the initial _rise time_ of time-domain response to a transient input. That's why his conclusion focused on coil inductance, instead of the other major energy storage elements (mass & suspension) which, in addition to Q, _dramatically_ impact VERY important aspects of the industry-standard transient response ... like overshoot and ringing. Focusing on coil inductance alone can be very misleading ... it "reduces" the Dan-defined transient response in the same manner as the *low-pass* crossover on a woofer "reduces" its transient response. You'll find that the *high-pass* dynamics of the woofer-in-enclosure are MUCH more impactive, when you analyze the _complete_ time-domain response to a transient input (the industry standard definition of "transient response").

In short, there are many aspects of the true transient response of a woofer-in-enclosure ... like overshoot & ringing, determined by mass, suspension and Q ... that are completely ignored by Dan's definition of transient response.

EDIT : good summary and more info :

http://www.diymobileaudio.com/forum/diyma-tutorials/9579-loudspeaker-inductance.html

http://www.diymobileaudio.com/forum/diyma-tutorials/30-transient-response-stored-energy.html


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## Lars Ulriched (Oct 31, 2009)

been reading page 1 n 2 but didnt get the $1 solution....skip to page 4....now im blank....


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## SSSnake (Mar 8, 2007)

Jeff,

Thanks for the link and discussion. I was actually looking for your thread when responding on this thread. I forgot about the whole "leading edge" definition used in the woofer spped paper. I'm getting too old to remember all of the things I've forgotten 

Inductance variance with stroke has been a pet peeve of mine for quite some time. I guess that is why I tend to focus on it and ignore the other aspects.

Charles


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## SSSnake (Mar 8, 2007)

IMO - there is no $1 solution


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## lycan (Dec 20, 2009)

SSSnake said:


> Jeff,
> 
> Thanks for the link and discussion. I was actually looking for your thread when responding on this thread. I forgot about the whole "leading edge" definition used in the woofer spped paper. I'm getting too old to remember all of the things I've forgotten
> 
> ...


Yes ... there's inductance, a _linear_ term, that limits high frequency extension. Just like the LPF we typically put on the woofer limits its high frequency extension  Same frequency-domain artifacts, same time-domain artifacts: rise-time is "slowed down". If the cutoff frequency formed by coil inductance and resistance is at last twice the intended LPF that you'll put on the woofer, feel free to IGNORE coil inductance. Period.

Then ... there's inductance VARIATION with stroke, a _non-linear_ term. Causes distortion at higher frequencies within the woofer's passband.

Then ... there's mass, compliance, BL product and resistive loss terms that define the classic HIGH-PASS dynamics (Fs, Vas, Qts). These will absolutely impact transient ringing and overshoot, VERY significant parameters of a woofer's transient response.

There are no "fast woofers". Woofers are *LOW-PASSED*, being intended for use at LOW frequencies. Low frequencies are SLOWER than high frequencies, by definition. HOWEVER ... there are "tighter sounding" woofers, compared to "sloppier sounding woofers". For the difference, look to the classic T/S *HIGH-PASS* behavior of the woofer-in-box. Mass & compliance, being the major energy-storage elements, will have substantial impact on the COMPLETE transient response


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## vactor (Oct 27, 2005)

any more on this? looking for more gold. c'mon patrick


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## Patrick Bateman (Sep 11, 2006)

vactor said:


> any more on this? looking for more gold. c'mon patrick


Ugh I slept four hours last night, and worked all three days of my three day weekend. I miss having a life


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## Sex Cells (Jul 21, 2007)

Patrick Bateman said:


> Ugh I slept four hours last night, and worked all three days of my three day weekend. I miss having a life


Don't. They're beyond overrated.


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