Non-linearity of air?

So i'm reading through one of my sound books and I came upon this:

High Performance Loudspeakers: 5th Edition wrote:

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Another potential source of distortion is the excessive compression of air in the box. If this exceeds 5% by volume, harmonic production from this source may be significant. In practice this is unlikely to occur as the ouput in the case of a medium sized enclosure would be approaching a very loud 120dB SPL at 1m. If greater levels are required, then it would be expedient to increase the box size. Sinse a larger driver with a high power rating will undoubtedly prove necessary, a larger box will in any case be employed.
Incidently, such distortion is a problem with horn systems, particularly high output mid-range drivers where the effective air compression in the horn throat is considerable.

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I was wondering how this affects the current drivers with high excursions and low air volume requirements?




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I dunno try doing the math.

Before anyone jumps down my throat, this would, of course, given parameters needed (which are not always provided honestly) and the shape of cones and what-not, a best guess sort of a thing.

Take any particular woofer, and get ur xmax and your sd in the same units. Now multiplay them together and viola!
Maximum volume displaced by the woofer.

Now get your box volume in the same unit, and multiply by .05. If the volume displaced by the woofer is smaller than that number, then it shouldn't matter... according to your book.



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"I'm finished!" - Daniel Plainview

Ok thanks.

Question: What's the recommend enclosure size for an Adire Brahma 15?

The Total volume displaced by it = 124.2163in^3

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OK... you asked for it...

Poormanq45 wrote:

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So i'm reading through one of my sound books and I came upon this:

High Performance Loudspeakers: 5th Edition wrote:

---

Another potential source of distortion is the excessive compression of air in the box. If this exceeds 5% by volume, harmonic production from this source may be significant. In practice this is unlikely to occur as the ouput in the case of a medium sized enclosure would be approaching a very loud 120dB SPL at 1m. If greater levels are required, then it would be expedient to increase the box size. Sinse a larger driver with a high power rating will undoubtedly prove necessary, a larger box will in any case be employed.
Incidently, such distortion is a problem with horn systems, particularly high output mid-range drivers where the effective air compression in the horn throat is considerable.

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I was wondering how this affects the current drivers with high excursions and low air volume requirements?

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Hmmm... interesting concept. The way I see it is this: 1 cubic foot = 1728 cu inches. 1728 x 5% = 86.4 cu inches. This is how much the box volume would have to be compressed (and/or rarified) to induce significant distortions of this type. 86.4 x 2 = 172.8 cu inches of displacement (total of ± 5%. A 5% compression or rarifaction relative to the "at rest" position of the woofer). The way to figure how much volume is displaced (or swept) requires knowledge of Sd (area of diaphragm) and Xmax. Multiply these numbers together. If this number (the swept volume) EXCEEDS 5% of your net box volume, you may need to go to a larger enclosure, or use a woofer with a shorter Xmax. My Eclipse SW9122 (a three inch throw woofer - 75.95 inch Sd) provides only 151.9 cu inches of displacement, linearly (easily, ±1 inch). If driven to it's non-linear range of ±1.5 inches (it's specified 3 inch X-max), it will provide 227.85 cu inches of displacement, but by the time I reach this range, I have a bit more than the non-linearities of AIR to worry about...

I also would like to take issue with the assumption that the enclosure WOULD be producing 120dB at 1M. This seems completely wrong to me. I say this because as the frequency goes down, (longer stroke - more compression - lower frequency - less output) so does your output. If you have an enclosure that is producing a 40Hz tone, its excursion will be X and XdB, but at 20Hz, the excursion will be 4X, and the output will (likely) be XdB -6, the standard roll-off for a sealed enclosure being 6dB per octave.

Also, WOOFER EXCURSION HAS LITTLE TO NOTHING TO DO WITH THE ACTUAL OUTPUT OF A SYSTEM. Frequency response, yes, output, no... If this were the case, then Eclipse and Adire woofers (as we all know, two exceptionally long throw, and equally capable woofers) would be capable of WAY more output than, say, a Cerwin-Vega or JBL Pro... An equally powered Eclipse or Adire woofer will NEVER exceed the output of either of these drivers. You'll notice I chose two relatively short throw woofers to compare with. This is to illustrate the fact that shorter throw will almost always equate to more output for a given input power. Output is SPECIFICALLY determined by rate of change - how fast can the woofer change direction? This factor MOSTLY being affected by 1) voice coil inductance, and 2) magnetic field strength in the voice-coil gap.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Nice post ham fist.

I also took issue with the fact that the book specified an SPL.

Oh and nice drivers you compared to there. Two of my favorites(CV and JBL)



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Poormanq45 wrote:

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Ok thanks.

Question: What's the recommend enclosure size for an Adire Brahma 15?

The Total volume displaced by it = 124.2163in^3

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i believe its 4.731 ft^3

Nice one, haemphyst.  That one gets saved into my list of explanations that I'll have to re-read over and over and over...

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

A good plasce to find info in box sixing is a program blaubox its on blaupunkts website this is only helpful if you know the specs on your sub and are looking into building a box but it is easy enough to build it and tune it

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IF YOU DONT DRIFT IT DONT DRIVE IT

Is he doing it again???

I mean just by the topic I knew who the author was.

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Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.

I've been sick lately, sorry I won't be on much.

"did I do that...?"

Now come on, am I REALLY that predictable?

BTW, it wasn't me that opened the can...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

placid warrior wrote:

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Poormanq45 wrote:

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Ok thanks.

Question: What's the recommend enclosure size for an Adire Brahma 15?

The Total volume displaced by it = 124.2163in^3

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i believe its 4.731 ft^3

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Actually that's closer to a large ported enclosure size.  We normally recommend around 2.5 cubic feet sealed for in car use. 

Steven Kephart

Adire Audio

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hamfist:    

1) My EQX is so *beautiful* ... how do you solder stuff that small anyway? How is that possible?
*cheers*

2) Well... one thing here at the bottom just doesn't make sense to me:

Output is SPECIFICALLY determined by rate of change - how fast can the woofer change direction

Isn't that... uhh.. frequency.. occilations/second? Like the woofer moves back and forth 50 times when playing 50hz? And the *distance* it is moving when doing so determines spl?
I mean.. sound volume is really a measure of air distruption right? Like.. everyone knows the louder a woofer a gets the more back-and-forth it moves.
I know from reading here the best determination of a clean woofer at significant output is a high excursion, but ultimately, wouldn't that also be the best determination of ultimate output as well?

I notice the way you word this sentence:

This is to illustrate the fact that shorter throw will almost always equate to more output for a given input power.

Isn't that speakers in general? Like.. the smaller a speakers' excusion, the more efficent it is .. louder at a given input power... likewise however, the speaker loses sq(linearity?) at volume, *as well as* ultimate volume? By that stick both the Adires' and the Eclipses' should have significant headroom on a JBL.. they just need to be plied with more power?

Am I misinterpreting this?


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"I'm finished!" - Daniel Plainview

sedate wrote:

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Output is SPECIFICALLY determined by rate of change - how fast can the woofer change direction

Isn't that... uhh.. frequency.. occilations/second? Like the woofer moves back and forth 50 times when playing 50hz? And the *distance* it is moving when doing so determines spl? 

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Actually it has more to the with the transient response, which has to do with the upper frequency extention of a driver.  The higher the inductance, the lower the rate in change will be limiting the quicker changing frequencies (higher frequencies).

sedate wrote:

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I mean.. sound volume is really a measure of air distruption right? Like.. everyone knows the louder a woofer a gets the more back-and-forth it moves.
I know from reading here the best determination of a clean woofer at significant output is a high excursion, but ultimately, wouldn't that also be the best determination of ultimate output as well?

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Unless I'm mis-reading what Heamph is saying, I've got to agree with you on this one.  There is no replacement for displacement is as true in speakers as it is in vehicles.  It was said "An equally powered Eclipse or Adire woofer will NEVER exceed the output of either of these drivers", but I think enclosure size was left out of the equation.  Put the pro sound subs in the smaller enclosures required for the Adire/Eclipse subs and you will greatly limit their output, especially down deep.  They gain their efficiency from the enclosure, not their low excursion (well partially from less mass maybe, but at what cost?) or inductance.  In fact, I wouldn't be surprised if the Brahma's inductance is similar to the pro sound units being that it uses an XBL^2 motor (shorter coil compared to the overhung units for a given excursion).  In other words, inefficiency isn't a symptom of the higher excursion, but a symptom of the small enclosure design because of their intended market.  Keep in mind that our Parthenon will do 80mm one way linear and still has a sensitivity of 97 dB. 

Steven Kephart

Adire Audio

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steven wrote:

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Unless I'm mis-reading what Heamph is saying, I've got to agree with you on this one. There is no replacement for displacement is as true in speakers as it is in vehicles. It was said "An equally powered Eclipse or Adire woofer will NEVER exceed the output of either of these drivers", but I think enclosure size was left out of the equation. Put the pro sound subs in the smaller enclosures required for the Adire/Eclipse subs and you will greatly limit their output, especially down deep. They gain their efficiency from the enclosure, not their low excursion (well partially from less mass maybe, but at what cost?) or inductance. In fact, I wouldn't be surprised if the Brahma's inductance is similar to the pro sound units being that it uses an XBL^2 motor (shorter coil compared to the overhung units for a given excursion). In other words, inefficiency isn't a symptom of the higher excursion, but a symptom of the small enclosure design because of their intended market.

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Ah, but you have to remember that those CVs and JBLs start out with a larger Sd due to the fact that they do not need a surround that can handle an extremely large excursion. This gives them the advantage right off the bat by increasing cone area.

Steven: What's the output of one of your 15s(anyone) at 25watts RMS? NM, I just graphed the 15in Brahma against the JBL W15GTi. I put them both in the same size enclosure(2.667ft^3) and tuned both to 30.49hz. Set the input power to 25w on both. The JBL shows higher SPL across the graph until above 400hz where it starts to roll off and the Brahma stays flat.

Both the Sd and the Bl are higher on the JBL then the Adire.




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Poormanq45 wrote:

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Ah, but you have to remember that those CVs and JBLs start out with a larger Sd due to the fact that they do not need a surround that can handle an extremely large excursion. This gives them the advantage right off the bat by increasing cone area.

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Huh. I never even thought of that. I wonder if that would make the difference? Like a 1/4 - 1/2 inch extra sd would, on the outside of a cone like that, translate into greatly increased cone-area... maybe the extra cone area *would* move more air than an extra few mm of xmax?

I'm gonna play with numbers for a little while I post back on this later.

What does bl have to do with output? I thought bl was a measure of motor force.. like.. it translates into cleaner sound and more woofer control.. not necessarily more output? What is the connection between bl and output?

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"I'm finished!" - Daniel Plainview

Yep, that extra cone area does indeed make a difference, but the high ecursion drivers quickly make up for that small difference once they go past the excursion limits of the short excursion driver.

Hmm, I think there's a connection between Bl and output, but I can't think of it right now

BL   Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!     

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I'll respond later -- when I am not up to my ass in alligators. My grandpa always told me "Don't make yourself irreplaceable - because you make yourself unpromotable". I have no idea what that has to do with ANYTHING, but I seem really busy at work lately.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

wow... I reaaally did it... Y'all asked for it!!!

Here's a link to a semi-recent thread here on the12volt... Some other good links to other threads and web-pages within it as well. (please excuse the rantings, tho...)

(Answers from here on out, appear as the questions did... )
sedate
1: I'm glad you approve; and practice, practice practice...
2: Yes, rate of change could be seen as simple frequency response, as a woofer DOES have to move faster for higher frequencies, but doesn't it have to move faster for low frequencies as well - because of the throw? As Steven states in his answer to this, it has more to do with the "transient response" of the woofer. (I still hate using that phrase - it, IMO, relates to something completely different) How fast can the motor structure make that woofer cone CHANGE DIRECTION from in to out? This rate of change is the AMPLITUDE of an audio signal in air.

When a woofer is moving a great distance, and the amplifier says "Move back in" by changing the electrical signal it is feeding to the voice coil(s), this change is supposed to happen as quickly as possible, right? The BIGGER the electrical signal the amp feeds the woofer, the faster it will want to move the other way, right? Well, the bigger the electrical signal the amp feeds the woofer, the faster it "turns around", the louder the woofer's output, right? And, the longer stroke observed... There you go...

Yes, generally speaking, a smaller speaker (like a mid or tweeter) will have an EXTREMELY LARGE (strong) MAGNETIC FIELD, relative to the size of the diaphragm it is expecting to move, and/or a relatively large electrical signal from the amp. This is why a smaller driver will generally have more output for a given electrical input.

I have noticed that longer throw woofers do seem to have better sound quality at extreme outputs, and this probably relates to the linearity curve... At longer excursions, a short-throw, high(er) efficiency woofer will (or should) sound not quite as good - because they begin to work in a far less linear range. Yes, I think your assumption is safe, BUT, the determination of ultimate output is determined by how much power is fed to said woofer, not it's excursion capabilities.


Steven
I was assuming EQUIVALENT ALIGNMENTS. All drivers in a sealed, and say Qtc of .707 enclosure. The enclosure size and alignment DOES ABSOLUTELY affect the output, but my statement should have put all of the drivers on a level playing field, even if it does not say it.

The Parthenon also uses so much neo magnet in it's motor, that the steel in the motor structure is this close (dave holds his hand up with forefinger and thumb with a vanishingly small gap between) to being saturated. This gives it a HUGE magnetic field to work with. Again, back to the strong magnetic field, and the mandatory control it will have over the diaphragm for a given inout signal. While it is ABSOLUTELY IMPOSSIBLE to saturate the air in the gap, you can eventually saturate the metal structure UP TO THE GAP... This, and your Parthenon has FOUR SQUARE FEET OF DIAPHRAGM... Quite the advantage there, eh? How about if the Parthenon only had 75 square inches of radiating area? Oh sure, the surround would have to be 6 inches across, but I bet with a motor structure like it has, the output would be even BETTER than the big one.

No. Inefficiency is NOT a symptom of excursion, but it is completely a by-product of excursion. The trade-offs are manifest!

Another thing I just thought of: Longer excursion almost necessarily maens more stress on a diaphragm, this mandates heavier, stiffer cones to minimize distortions... (exotic materials not completely included, but not completely excluded either - this IS a GROSS generalization) I was looking at an Eminence guitar woofer, and it has an Sd of 95 inches square, a Vd of a MERE 125cc, a MMS of 33g, but an efficiency of 96dB! (this is a guestimate, as the efficiency guide for these drivers actually specifies X efficiency at Y frequency - the sign of a GOOD loudspeaker manufacturer. These actually spec as high as 101.8dB at 3K! (Alpha-12)) Check here for the way Eminence specs their drivers.

Poormanq45
Yes the CV and JBL drivers DO have a larger Sd, but not enough to equal the kind of efficiency gains one sees between them and an Eclipse or Adire. My SW9122, for example, spec'd on the Klippel Machine at the Harman Labs, acheived an ABYSMAL 84dB! The old-school (1st gen) 10 inch Ti?, 78dB!!! No WONDER I have to beat it with 2700 watts! To HAVE TO HAVE three+ HORSEPOWER to drive a woofer is a sad state! (One horsepower, BTW, is 746 watts, so really I have almost FOUR horsepower!!!)

This goes to answer your final question/statement, too, sedate. Yes, the increase in cone area SHOULD give more output, but I still maintain that all of the above statements have FAR more to do with it than the small (25%) increase in cone area. A 100% increase in cone area nets (again - oversimplified dramatically, for the purposes of discussion) a 3dB increase, whereas these drivers are upwards of 6 to 8 dB more efficient - a 400%increase in output...

Damn... my fingers are tired, and so is my brain... sleepy-time...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

ham]Wh wrote:

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n a woofer is moving a great distance, and the amplifier says "Move back in" by changing the electrical signal it is feeding to the voice coil(s), this change is supposed to happen as quickly as possible, right? The BIGGER the electrical signal the amp feeds the woofer, the faster it will want to move the other way, right? Well, the bigger the electrical signal the amp feeds the woofer, the faster it "turns around", the louder the woofer's output, right? And, the longer stroke observed... There you go...

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I understand what you're trying to say, but the way you said it sounds like you're talking about the actually frequency changing. That would be the only time the driver would actually move faster.

well, lets look at the sine wave. AS you increase the amplitude the excursion MUST increase, correct? This occurs to move a larger volume of air.

Were you just trying to say that the driver covers more linear distance, meaning higher excursion, at higher amplitudes? If so then yeah I agree with you and this post can be disregarded.

anyways, good post. Me sleepy too.

What was that talk of alligators?

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Poormanq45 wrote:

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Ah, but you have to remember that those CVs and JBLs start out with a larger Sd due to the fact that they do not need a surround that can handle an extremely large excursion. This gives them the advantage right off the bat by increasing cone area.

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True, but you are talking about minimal cone area differences.  Especially since a lot of pro sound drivers use undersized baskets.  So the cone area is 5-10% larger, but if I'm guessing correctly (as specific models of drivers for the "low excursion" units weren't provided for me to check) we are talking about significant increases in exucrion.  My guess would be about 4 times the excursion.

Poormanq45 wrote:

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Steven: What's the output of one of your 15s(anyone) at 25watts RMS? NM, I just graphed the 15in Brahma against the JBL W15GTi. I put them both in the same size enclosure(2.667ft^3) and tuned both to 30.49hz. Set the input power to 25w on both. The JBL shows higher SPL across the graph until above 400hz where it starts to roll off and the Brahma stays flat.

Both the Sd and the Bl are higher on the JBL then the Adire.

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I don't think they were talking about the GTI sub.  It has a pretty high excursion at over 20mm.  Also, I'm going to venture a guess that you are using WinISD for the above graphing.  WinISD sets the curves based on the sensitivity from the parameters.  JBL lists their sensitivity at 91 dB, but they also specify that at 2.83 volts with an Re of 3.2 ohms.  This means that the sensitivity rating is 2 watts instead of our 1 watt rating.

This is where I wish I had LspCad on my computer since it can provide a more realistic prediction of compared output of the drivers in question.

Steven Kephart

Adire Audio

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sedate wrote:

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What does bl have to do with output? I thought bl was a measure of motor force.. like.. it translates into cleaner sound and more woofer control.. not necessarily more output? What is the connection between bl and output?

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It effects frequency response.  Here's a quote by my boss explaining how the parameters effect one another.  The last part of the quote will answer your question above:

"Vb is proportional to Vas (double Vas, double Vb). Vb is proportional to Qes squared (halve Qes, quarter Vb). This is for the same Qtc/alignment... And since Qes is inversely proportional to BL squared, if you double BL you cut Qes by a factor of 4, meaning the box volume for a given alignment is cut by a factor of 8.

Now, that is all well and good, but consider what Fb does in relation to Qts/Qes... Fb is inversely proportional to Qts, thus as you raise the BL, and lower the Qts, you raise the Fb accordingly. Double BL, cut Qts by a factor of 4, meaning Fb just jumped up 2 octaves!"

Steven Kephart

Adire Audio

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haemphyst wrote:

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the "transient response" of the woofer. (I still hate using that phrase - it, IMO, relates to something completely different)

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Don't tell me you were down town again with a stop watch and a dollar bill on a string, timing the response of the homeless people to your money.

Sorry for the tasteless joke.
 

haemphyst wrote:

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Steven
I was assuming EQUIVALENT ALIGNMENTS. All drivers in a sealed, and say Qtc of .707 enclosure. The enclosure size and alignment DOES ABSOLUTELY affect the output, but my statement should have put all of the drivers on a level playing field, even if it does not say it.

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I think you missed my point.  But it could have been because I didn't explain it well enough.  I was merely saying that they were designed around Hoffmans Iron Law, just like ours was.  They chose efficiency at the cost of enclosure size.  We chose enclosure size at the cost of efficiency.  The excursion of the subs has nothing to do with it as it isn't a physical parameter of the driver.  You can design a high excursion sub that is very efficient.  However it will require a large enclosure, or be a large midbass driver.

haemphyst wrote:

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No. Inefficiency is NOT a symptom of excursion, but it is completely a by-product of excursion. The trade-offs are manifest!

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Again, I don't think so.  It all depends on the engineering of the driver.  If you want high excursion with high efficiency, it can be done without a problem.  The reason you don't see it is because there is no market for them. 

haemphyst wrote:

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Another thing I just thought of: Longer excursion almost necessarily maens more stress on a diaphragm, this mandates heavier, stiffer cones to minimize distortions... (exotic materials not completely included, but not completely excluded either - this IS a GROSS generalization) I was looking at an Eminence guitar woofer, and it has an Sd of 95 inches square, a Vd of a MERE 125cc, a MMS of 33g, but an efficiency of 96dB! (this is a guestimate, as the efficiency guide for these drivers actually specifies X efficiency at Y frequency - the sign of a GOOD loudspeaker manufacturer. These actually spec as high as 101.8dB at 3K! (Alpha-12)) Check here for the way Eminence specs their drivers.

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Keep in mind that the guitar speaker you mention had to have a response up pretty high, probably covering most of the midrange territory.  This means it couldn't have a heavy cone.  However it probably didn't have much of a response below 40 Hz.  It had to give up low end extention for high end extention and efficiency.  But then you are talking about two completely different markets with two completely different requirements from their speakers. 

haemphyst wrote:

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Poormanq45
Yes the CV and JBL drivers DO have a larger Sd, but not enough to equal the kind of efficiency gains one sees between them and an Eclipse or Adire. My SW9122, for example, spec'd on the Klippel Machine at the Harman Labs, acheived an ABYSMAL 84dB! The old-school (1st gen) 10 inch Ti?, 78dB!!!

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Out of curiousity, are you allowed to share the reports for those drivers?  I would love to see how they fare.  If you don't want to share it publically, you can send it to skephart@adireaudio.com.

Steven Kephart

Adire Audio

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Let me see if I can dig them up... I am certain I have the 10 inch printouts, but the 12?   mmmmmm I think those were thrown away accidentally by the spousal unit. I'll search for the 10, if I DO locate them, I'll scan 'em, and get them to you...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it

Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

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Poormanq45 wrote:

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Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it

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Naw, it's cool... gives me (and others, too, I'm sure) a chance to "flex my (our) mental muscle" so to speak... Bring 'em on! Discussions like this require me to do further research and thought into what I already understand about the subject... I quite enjoy it.

Poormanq45 wrote:

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Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

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Me? I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

ham]Me wrote:

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I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume...

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I don't know. Considering that current technology is less efficient then older technology

THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range!

People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

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Poormanq45 wrote:

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haemphyst wrote:

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Me? I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume...

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I don't know. Considering that current technology is less efficient then older technology

THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range!

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You're preaching to the choir, man... I have been disgusted with the ever PLUMMETING efficiency number for as long as I can remember. My engineer buddy at Harman (just so you don't all think I am blowing smoke about my "engineer friend", Steven met him at the CES this year, and he and Dan Wiggins spoke with him at great length, so Steven knows I am not BS'ing...) has been also researching this same issue. I am not really at liberty to speak of what specifically he is working on, let's just say it's being addressed.

Poormanq45 wrote:

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People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

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Amen, brother. YEAH!!! I expect though, that a long throw, high efficiency woofer would be a cash cow for the company that comes up with it on a mass market scale. (are you listening Steven? ) I don't expect anybody is really in a hurry to produce such an animal yet - especially the companies that produce multi-kilowatt amplifiers, what would be the purpose of defeating that market angle? More money in electronics than speakers, I expect... Especially HIGH POWER electronics... Why would a company that had a 4000 watt amplifier in their line-up want to produce a high efficiency woofer, so the consumer would only NEED a 200 watt amplifier to drive it? A bit self-defeating, wouldn't you agree?

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Poormanq45 wrote:

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Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it

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One thing I like about this forum is that everyone is more mature, and respectful to one another.  They don't allow their ego's to get in the way, causing these things to escelate into a flaming war.  But instead, this allows for calm, detailed discussion that hopefully everyone learns from.  I'll be the first to admit that I don't know it all.

Poormanq45 wrote:

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Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

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Well like I said earlier, there is just no market for that type of sub.  And as a manufacturer, you have to offer what will sell if you want to stay in business.

Steven Kephart

Adire Audio

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Poormanq45 wrote:

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I don't know. Considering that current technology is less efficient then older technology

THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range!

People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

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Well, you have to understand why efficiency is digressing.  It isn't because newer technology is worse or anything.  It is simply because the market demands speakers that use smaller enclosures, but doesn't give up output or low end extension.  Because of Hoffman's Iron Law (something that NO technology will ever be able to beat) efficiency MUST suffer.  And considering that power is cheap, that isn't a bad thing. 

Steven Kephart

Adire Audio

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steven wrote:

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Well like I said earlier, there is just no market for that type of sub. And as a manufacturer, you have to offer what will sell if you want to stay in business.

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I think a little market called the Home theater market would be very interested in a sub like that.

steven wrote:

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Well, you have to understand why efficiency is digressing. It isn't because newer technology is worse or anything. It is simply because the market demands speakers that use smaller enclosures, but doesn't give up output or low end extension. Because of Hoffman's Iron Law (something that NO technology will ever be able to beat) efficiency MUST suffer. And considering that power is cheap, that isn't a bad thing.

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Yep, I completely understand that. Unfortunately women have become the dominant party in a relationship and dictate such things as how large the speakers can be.



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Poormanq45 wrote:

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Yep, I completely understand that. Unfortunately women have become the dominant party in a relationship and dictate such things as how large the speakers can be.

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That is absolutely soooooooo correct.  We like to call it the "WF" or Wife Factor.

Poormanq45 wrote:

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I think a little market called the Home theater market would be very interested in a sub like that.

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Actually unfortunately it is quite the opposite.  The Home theater market is greatly gavitating toward small enclosures.   And the main reason for it is because of the WF mentioned above.   We do a lot of OEM design of speaker systems for quite a few companies, and all of them want the subs as small as possible.  A perfect example of this is the OEM sub we are selling on our E-bay store.   It is a 10" cube.  In fact we recently designed a system for one OEM consisting of 2 of our 15" Tumults and a 2400 watt Rms amplifier in a small enclosure.

Steven Kephart

Adire Audio

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Steven Kephart wrote:

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Well like I said earlier, there is just no market for that type of sub.  And as a manufacturer, you have to offer what will sell if you want to stay in business.

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And you are so right.  The market wants BIG wattage numbers to brag about.  They'd rather say "I've got a 1000 watt sub!" then "I've got a 100 watt sub".  So if I were a manufacturer and produced a sub whose efficiency was 97...and put that up against a sub with an efficiency of 87...

...and both were identical in their abilities to produce the same SPL level; the only difference being in the efficiency...

increase in db = 10*log(p2/p1)
where p1 is the reference power, p2 is the new power level, and log is log base 10...)

...I would be trying to sell a 100 watt sub up against 1000 watt subs in a market that doesn't understand what efficiency is.

That is to say, the sub with a 87 db efficiency would take 1000 watts to equal the SPL my sub makes with 100 watts with its 97 db rating.  But the subs' continuous power handling numbers would, of course, reflect their efficiency.

Both would be loud, and either would be as loud as the other...but my sub is "only" a 100 watt sub.  Oh and yeah, that's not even considering the exponential increase in "peak" numbers!  The 1000 watt sub will get the buyers because we all know the buyer's knowledge is very limited.

My gosh, just think about how limited OUR knowledge is on the subject...and we digest this stuff on a daily basis!  (..."we" = me...)  The average buyer is pathetic by comparison.  They see that Volkswagon commercial where the guy and girl go to the store and buy a subwoofer that says "1000 watts" in big bold letters on the box, and they say "That's what I want!"  It's not even unusual that some of them think in the back of their minds that the subwoofer actually produces the power.

89 db/1 watt is good for me.  That's what I'm using.  Power is cheap but I like it cheaper.

(...I had to come back and edit my wattage numbers here because I originally screwed up the math part...)

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

stevedart wrote:

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My gosh, just think about how limited OUR knowledge is on the subject...and we digest this stuff on a daily basis! (..."we" = me...) The average buyer is pathetic by comparison. They see that Volkswagon commercial where the guy and girl go to the store and buy a subwoofer that says "1000 watts" in big bold letters on the box, and they say "That's what I want!" It's not even unusual that some of them think in the back of their minds that the subwoofer actually produces the power.

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The scary thing is that if you watch the comercial, and mazda too, they turn the HU up to 100% volume! I eeffing hate marketing bull$hhh. It is so powerful that it even affects the products that companies make. Just look at adire audio. They conformed.

If I were incharge of developement I would have chosen NOT to conform. The enclosure would be close to 10ft^3 for all my drivers. My selling point? Hmm... Sacrificing the space will save you money on your electric bill compared to other subs.

ANd it'd be true becaus eit'd only take ~50watts to drive it above reference levels.

NOw compare that to the compact subs that require 500~1000 watts to just reach refernce levels

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Poormanq45 wrote:

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It is so powerful that it even affects the products that companies make. Just look at adire audio. They conformed.

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Uh oh, trying to start another topic in this thread I see.   So I guess I will take the bait and ask you to explain this comment.  I should warn you though that we have seen many similar comments by people after making the recent changes, and it has always proven that those people are basing their opinion on very limited knowledge of the situation.

Steven Kephart

Adire Audio

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YOu are designing high power handling, low efficiency drivers that are made to go into small enclosures. That IMO is conforming to the current trend.

Note I only used Adire as an example because you're the only rep I see on here.

Do you guys make any drivers that are designed for "large" enclosures? Meaning 5ft^3 or more?



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Oh wow, I totally misread what you were saying then.  I'm sorry about that.

Keep in mind thought that if you want to sell product, you have to offer what is popular. 

I discussed this thread with our salesman, and he did mention that we used to have an efficienct sub with large throw but required a pretty good size enclosure.  It was our Maelstrom.  It had 13mm of throw one way which is huge for pro sound gear, and had an efficiency of over 92 dB.  However those drivers sold VERY slow because there just wasn't a market for them.  Ported enclosure requirements for it were in the 5-6 cubic feet area.  In fact, just recently a guy posted pictures of one he just put in a 14 cubic foot enclosure.  Here's the link: https://forceaudio.com/viewtopic.php?t=75

Also, our old Shiva and Tempest drivers were well known for their efficiency, but large box requirements.  They had 16 and 18mm of throw one way respectively.

Steven Kephart

Adire Audio

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steven wrote:

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Keep in mind thought that if you want to sell product, you have to offer what is popular.

I discussed this thread with our salesman, and he did mention that we used to have an efficienct sub with large throw but required a pretty good size enclosure. It was our Maelstrom. It had 13mm of throw one way which is huge for pro sound gear, and had an efficiency of over 92 dB. However those drivers sold VERY slow because there just wasn't a market for them. Ported enclosure requirements for it were in the 5-6 cubic feet area. In fact, just recently a guy posted pictures of one he just put in a 14 cubic foot enclosure. Here's the link: https://forceaudio.com/viewtopic.php?t=75

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Yep, I understand. High efficiency drivers trade off power handling because they don't need much power to play loud. Unfortunately people(mostly teenagers/young 20 year olld) are obsessed with huge power numbers. When I'm talking to someone about there system the first words out of their mouth are, "I've got XXX watts". My response is, "So, I've got X watts and play just as loud". WHen asked what I'm running for my mains and how I'm powering them, I respond with, "15w RMS from the stock Bose amplifiers." They're powering high efficiency Infinity Kappa Speakers to ~110~115dB

ANyways, I understand the marketing behind it. I think it's going to take a company to go out and mass market efficieny. SImilar to what Bose did, they blanketed people with mindless information to make them think their product was better. Fortunately though, in the efficiency case your product would be better

Hmm, 4~5ft^3 really doesn't take up much trunk space if you build a proper enclosure, usually custom molded of fiberglass. Unfortunately most people only use MDF, but hey, that just leaves a market for me to make low profile high volume enclosures for them

About the selling what's popular. You could market like I said. That'd surely get people to open their eyes.

WOuldn't it be awesome to have people competing to see who could have the lowest wattage and the highest output!

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Well that's just the thing, high efficiency isn't necessarily something that you want to look for.  It is important in pro sound, however you have so much working for you in car audio it really isn't a necessity to market.  It's like trying to petition people to breathe less in the forest to conserve oxygen.  What is the point?  You get so much free bass from the small environment of the vehicle, and power amplifiers are so efficient and cheap it's not an issue.  I, and a majority of the consumers out there, would MUCH prefer all the same bass (and many instances much lower bass) in a much smaller enclosure.

Steven Kephart

Adire Audio

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When I was 16 I installed my first box with a friend of mine who learned the craft from his older brother.

A pair of Pioneer 12" subs getting 100 watts a peice.. the *spec* box was like 4 cft.. in a 92 Sentra this thing took up the *entire* trunk.

Imagine the jubilation not 4 years later installing a pair of Exact 12s at 2cft... but yea.. ack.

That was a 1000watt amp he had on those.

<I'm really sleepy>



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"I'm finished!" - Daniel Plainview