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Stereo Integrity HS-24 Measurements & General Discussion


Ricci

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The formula predicts increase/decrease as Vb changes for a given driver. It does not predict THD from a sub nor is it a tool for comparison of different drivers.

This is not exactly correct either.  The formula estimates the level of second harmonic distortion (2HD) as a fraction of the sound level under the assumption that the compression and rarefaction of the air in the box is a thermodynamically reversible process and in the absence of distortion from other components.  I don't know how close to reversible the motion of a real subwoofer is, but reversibility seems like a reasonable approximation to me, especially if the box is empty.  Someone with a physics background and more subwoofer design experience than I could probably offer a strong argument for this being the case.  For now, I'll trust Linkwitz.

 

It is also possible to use a similar mathematical derivation to obtain formulas for the third and higher harmonics, which could be summed to calculate THD.  However, if 2HD is low then the level will be seen to diminish quickly for higher harmonics, so ensuring this 2HD is low is all that's needed to assure that THD is "low enough".  Of course, this formula only accounts for ASD, and being that there are many other sources of distortion in any subwoofer, it certainly does not predict the THD for a sub.

 

More importantly, the formula does not predict the relative difference in 2HD for two different boxes because it ignores other sources of distortion.  Your statement two posts prior that "2HD will double as you halve the box volume" is inaccurate.  It is only correct if other sources of distortion such as the amp and driver itself are negligible.  With that said, if the THD of each component in the system is reasonably low, then it's probably ok to assume that THD is additive as a worst-case estimate.  This estimate is worst case because phase is important and distortion generated in a downstream component could possibly cancel distortion generated in an upstream component.

 

In my previous post, I did not use the ASD formula to compare to two subs alone.  What I did do was estimate 2HD for the air spring alone for the sealed HS-24 and 2 X HST-18s at Xmax (as speced and as built by Ricci).  Comparing my calculations to Ricci's measurements, one can readily see that air spring distortion does not account more than a small part of the distortion increase, at least where measured THD is < 20% or so.  As I said, it's not correct to say that 2HD doubles with half the box because other sources (like the suspension of the woofer) contribute make their own contributions to 2HD.  Moreover, most of the distortion increase in the low bass is 3HD, which is more audible and in the measurements appears to overwhelm the 2HD present.

 

I'm not saying Vb doesn't matter.  In my previous post, I suggested that larger Vb might decrease distortion the mechanical distortion of the driver itself by altering the resonance frequency of the system.  However, I have no idea if the system resonance frequency affects driver distortion.  I'm inclined to believe that it doesn't, that mechanical distortion is a function of excursion only, and that changing the resonance frequency changes the efficiency of the system but not the excursion required for a given output level at a given frequency.

 

The formula predicts increase/decrease as Vb changes for a given driver. It does not predict THD from a sub nor is it a tool for comparison of different drivers.

 

There are 2 factors at work... Vb and amplifier.

 

Looking at Ilkka's test results of the LMS-Ultra vs Josh's test of same, the only apparent variable was the amplifier used. Josh got +3dB more output at 10 Hz with magnitudes less THD using a sine sweep. All other variables (air temperature, humidity, calibration, driver parameter tolerance difference, etc) cannot explain the difference in result.

 

504df9406716526ca526b77f56273bc7.png

 

Amplifiers act very differently <20 Hz and without data little can be assumed.

 

Josh knows my position on THD results from progressive sine sweeps. ;)  It is essentially much ado about nothing. If you look at the comparison using CEA shaped tone bursts, where the THD limits determine the results, you see better evidence that the difference is Vb and amplifier.

 

b06242b16c33cf10738ac7ef5551a5cb.png

 

You can use the ASD formula and the CEA results to predict Dave Gage's version of the HS24, subtracting for plugging the amp into a typical 110V/15A shared outlet or a 110V/20A dedicated outlet, factoring in line sag as well. B)

 

 

Illkka's test is definitely pushing the rated limits of his amp, which is rated at 3500W into 4 ohm.  At that power and load, the amp provides 118 Vrms.  The 115 dB nominal sweep that Ricci uses for the LMS Ultra is at 73 Vrms.  A 119 dB nominal sweep performed by Ricci would require 116 Vrms, but because Ricci's box is reported to be about 120 L versus 100 L for Illkka, Ricci's box is at least 1 dB or more efficient at low frequencies.  Hence, Illka's 118 dB nominal sweep is taking that amp up to and likely beyond its rated limit, which was probably quoted under overly optimistic assumptions anyway.  There's nothing at all surprising about seeing heavy distortion here.

 

In contrast, the K-10 Ricci used to test the HST-18 in his sealed box is rated to 9000W into 4 ohm, at which it is providing 190 Vrms.  The highest sweep level, where the mechanical limits of the HST-18 are found, is at 113 Vrms, and the voltage required to reach "Xmax" (in terms of CEA distortion thresholds) at low frequencies is only 58 Vrms.  The THD curves that I'm using to compare 2 X HST-18s to the HS-24 were measured with 20, 35.6, and 63.3 Vrms, respectively.  These levels are well below the limits of the K-10 amp, and the two amps we are comparing are the K-10 and K-20, designed by the same manufacturer and having only a 2X power (or 1.4X voltage) rating difference.  Do you really think the different amps are making a significant difference here?  I don't doubt that amps often fail to live up to their performance ratings under 20 Hz, but I find it unlikely that this is an issue at output levels *much* lower than the amp's rated limit.

 

In summary, I have argued here that neither the reduced ASD nor the bigger amp explains the difference in distortion performance between the HS-24 and 2 X HST-18s.  The logical conclusion to me is that the difference is largely due to the drivers.  I'm not 100% sure since there may be other factors to consider (including those that depend on Vb), but I don't think ASD or amp adequately explains the performance gap.

 

I guess we'll see what happens when the DSS 24" is tested.  I anticipate that the CEA measurements will be lower and will be limited by the amp all the way down to 10 Hz, unless the amp has some kind of burst capability > 4000W.  It will be interesting to see what the distortion measurements look like, although the results may be hard to compare directly with the DIY HS-24 because of the output differences.

 

All this has me wondering whether I should consider stuffing 2 X 24" into each of two 8 cuft boxes for a total of 4 X HS-24s run with 3500W each?  The trouble is that compared to the 18 cuft box that Ricci tested, I'd expect to lose 9 dB sensitivity at 10 Hz and 6 dB at the lowest frequencies.  That 3500W per woofer is not even enough to reach CEA limits.  Even then, I suspect it may be overkill for my room size and listening preferences as most of the time I run my subs at or below 85 dBC reference.  It could offer more faithful reproduction of a few key scenes like the HTTYD crash scene and the Space Shuttle launch recording, but not much else would benefit from the increased output.  But what about distortion?  Naturally that depends a lot on the effect of Vb.  At this point, I still lean toward going with HST-18s, but if the low distortion of the HS-24 is retained in the smaller box size, I'm sure it will be attractive to many despite its higher price.  Yet another possibility is for me to abandon the dual-opposed configuration and just put each of 2 HS-24s in their own (~8 cuft) boxes.  So many choices ...

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The air volume makes a HUGE difference. There is no doubt about that. However ASD has some effect but it is not the major component. The true cause of the increases in distortion in smaller boxes is the increased current through the coil / motor system. A lot of data points to that. I have an older test of the LMS in a VERY small box which barely contains the driver and the distortion is much higher in the deep bass since the current needed to reach the same excursion levels is greatly increased. I will be redoing that test at some point and also with the MTX 9515-44. We should see similar with the HS24 in Dgage's half sized enclosure. I expect the THD in the deep bass to increase greatly.

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Hey hey! Whatya know?! A huge Vd driver makes mega amounts of bass. Who'da thunk it?

 

Congrats to the SI guys for their star product making huge waves .... of bass. :D This is a monster driver and I hope you can continue to make it for a long time.

 

Also, don't let the reality of a drivers performance get you down. Anyone can nitpick ANY driver. Even the LMS Ultra (which IMHO is probably one of the best ever made) has it's faults and is not perfect. Your driver which is available beats it. Feel good about that, bud. :)

 

Take a load off and enjoy the great results of DB's most outrageous deep bass driver. It will be near impossible to top.

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I agree with Josh, of course.

 

Harmonic distortion<20 Hz is irrelevant. The discussions about this or that driver in this or that box with this or that amp are instructional in understanding some of the mechanics of sealed subwoofer systems, but I have yet to get feedback from anyone who could spot a difference in WOTW, etc.

 

Even in Ilkka's exaggerated test of the LMS in 75L vs 200L, in the CEA2010 results, which are THD-limited results, there was an average of 1.4dB difference in output from 12.5 Hz to 80 Hz. But that didn't stop the discussion being about the "huge" difference in THD from the sine sweep power compression results.

 

About that... in the beginning, the THD was a by product of the power compression progressive sine sweep test, which, as it's name implies, was to test power compression, not THD. The THD part was included because it 'killed 2 birds with one stone'. After the CEA2010 test was devised, the THD part of the power compression test should have been retired.

 

With music a sub that gave 100% THD and an audience of musicians yielded a 50/50 heard a diff/didn't hear a diff. Those who heard a difference actually preferred the distortion, offering subjective comments that included "tighter" types of wording.

 

The room will distort the presentation FAR more than THD, which is all but eliminated by room gain <20 Hz. This is why I prefer multiple smaller drivers over a single monster like the 21s and 24s of the world. If you decide to use multiple 24s to gain the advantages of multi-sub systems (dual opposed, smoother response, etc.), the subs will physically dominate the room scape and you will never use their output advantage save for the occasional silly demo level.

 

OTOH, when running sine sweep tests outdoors, THD is audible and much higher as a %, dBSPL for dBSPL, and there are no room modes causing 20dB dips and peaks in the response.

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Yup yup. Pretty much. In a domestic room or vehicle you see huge reductions in THD in the deep bass. I still do the sweep THD measurements because they are more detailed and can provide some info that the burst tests don't. Most of it having more to do with why the system is distorting, how, what might change in a different alignment etc...much harder to see some of that in the burst data. I like having both. It will be interesting to see what happens with some other drivers not so clean as the LMS.

 

As far as the 24 I would down size the enclosure if I were to use them myself. The big sealed is limited a bit by the amount of excursion below 20Hz. Too big of an amp could smack it around with the wrong content. I'd rather deal with a bit higher THD and compression and down size the box a bit to control the excursion more, have something much more manageable and put a bigger amp on it to compensate.

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Hey hey! Whatya know?! A huge Vd driver makes mega amounts of bass. Who'da thunk it?

 

Congrats to the SI guys for their star product making huge waves .... of bass. :D This is a monster driver and I hope you can continue to make it for a long time.

 

Also, don't let the reality of a drivers performance get you down. Anyone can nitpick ANY driver. Even the LMS Ultra (which IMHO is probably one of the best ever made) has it's faults and is not perfect. Your driver which is available beats it. Feel good about that, bud. :)

 

Take a load off and enjoy the great results of DB's most outrageous deep bass driver. It will be near impossible to top.

 

Haha, thanks. I'm very happy with the results and I hope no one takes this as me being cocky but I fully expected those results. And I absolutely knew that a particular other forum would go ape $hit negative with the results nitpicking any little detail they can. But those people were never going to purchase/use the driver anyway. I had a woo-sah moment while explaining the avalanche of negativity that I expected and I came up with this analogy: Seeing how some people seemed to be sitting at their computer wearing out their F5 key for the results only to search and search for something negative to say is like me doing the same thing to a small airplane manufacturer. That would be like me sitting there following them pointing out all of the downfalls (as I see it even though I don't know as much about airplanes as they do) of their new airplane design even though I don't have my pilots license nor do I ever plan on owning an airplane. 

 

But lets get back to this forum. :D 

 

Yes the driver is huge, yes it requires a big box, but it is not an ABSOLUTE to put it in a box as big as what Ricci tested it in. Does that big box help performance? Yes it does. Is that volume absolutely needed for use in a home? Nope. With DSP being rampant these days it is very easy to measure your initial response and then reduce or increase levels to tailor the response to your liking. Does boosting have its downfalls? Yes it does. However, as Ricci pointed out there will be an increase in distortion due to extra current required if you use the woofer in a very small box and boost the bottom end but the neatest thing about the driver is that it has the stroke and sheer air volume displacement capability to cope with the EQ necessary to flatten the response. 

 

It is a mammoth of a driver and I love its performance. I'm really happy that Ricci measured it and has the data posted on his/this site. 

 

Now if you'll excuse me I have a massive Stone IPA brew staring me in the face challenging me to a drink-off. I think I'll win.  :P

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Nick,

 

Nothing wrong with being cocky over a job extremely well done. ;)

 

I was there and heard the 24 vs 2 x 18" LMS-Ultras. I doubt the LMS-Us were suffering higher THD than the HS-24 in-room, in fact, I'm sure they were not. I suspect that the difference between two non-EQ'd subs was Qtc more than anything else. Well, I'd stake my rep on it. Most people prefer a higher Qtc to the so-called critically damped low Qtc of the LMS-U systems.

 

Had we had the time to equalize the 2 responses, the subjective preferences would have less one-sided, IMO. But, that takes nothing away from the HS-24 as we're talking about 2 x LMS-U 18s with proper amplification. :) The lesson that should have been taken away besides the high quality of Nick's drivers (Brandon's 8 x 18" HT-18 system was stellar as well) is that "critically damped system Q" has rarely been preferred over a flat response in the history of subwoofers for HT and listening tests in general.

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The air volume makes a HUGE difference. There is no doubt about that. However ASD has some effect but it is not the major component. The true cause of the increases in distortion in smaller boxes is the increased current through the coil / motor system.

 

I like this explanation, but I'm not convinced it applies to the HST-18 versus HST-24 as measured.  I'd expect to see a big dip in HST-18 distortion around the impedance peak.  Your measurements show an impedance peak at 32 Hz or so, but the lowest distortion is at around 63 Hz where impedance is rather low.  At 32 Hz, there's actually a slight peak in distortion, but only in the highest level sweep.  I wonder what other reasons smaller Vb would exhibit much more distortion.

 

With music a sub that gave 100% THD and an audience of musicians yielded a 50/50 heard a diff/didn't hear a diff. Those who heard a difference actually preferred the distortion, offering subjective comments that included "tighter" types of wording.

 

This is an interesting anecdote.  Ironically, I'm not sure musicians are necessarily more qualified to judge bass quality than anyone else, and in fact, they may prefer the harmonically distorted sound even more than other subjects.  Their primary purpose of listening is to evaluate what they are playing.  Higher harmonics are much more useful than bass fundamentals for identifying what notes and rhythms one is playing.  On top of that, rooms with good bass acoustics are rare, so lacking a frame of reference, most musicians probably have a biased preference for a sound in which the higher harmonics dominate at the expense of bottom end weight.

 

 
The room will distort the presentation FAR more than THD, which is all but eliminated by room gain <20 Hz. This is why I prefer multiple smaller drivers over a single monster like the 21s and 24s of the world. If you decide to use multiple 24s to gain the advantages of multi-sub systems (dual opposed, smoother response, etc.), the subs will physically dominate the room scape and you will never use their output advantage save for the occasional silly demo level.

 

I do agree that the advantages of smaller subs in multiple placements likely outweigh that of one large sub with lower distortion.  I'm not sure I agree that distortion is irrelevant under 20 Hz.  Suppose that at some playback level the outside measured THD is 20% and inside, we have 5 dB room gain.  The in-room distortion will be This is not an implausible situation.   In the room (and ignoring room response difference other than room gain), the 3HD will be about 11% or -19 dB.  But looking at equal loudness contours, we see that for a 20 Hz tone in the 100-120 dB range, a 60 Hz tone needs be -20 dB or less than the 20 Hz tone to be equally loud.  So even though THD is only 11%, psycho-acoustically speaking, THD may be more like 100%.

 

Now I'll admit that the equal loudness contours are only valid for pure tones in isolation and don't adequately explain what we hear when multiple harmonic tones are present.  Still, the result appears significant.  If it is not significant, then I'd like to see more data that says so or experience this for myself.

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I like this explanation, but I'm not convinced it applies to the HST-18 versus HST-24 as measured.  I'd expect to see a big dip in HST-18 distortion around the impedance peak.  Your measurements show an impedance peak at 32 Hz or so, but the lowest distortion is at around 63 Hz where impedance is rather low.  At 32 Hz, there's actually a slight peak in distortion, but only in the highest level sweep.  I wonder what other reasons smaller Vb would exhibit much more distortion.

 

 

This is an interesting anecdote.  Ironically, I'm not sure musicians are necessarily more qualified to judge bass quality than anyone else, and in fact, they may prefer the harmonically distorted sound even more than other subjects.  Their primary purpose of listening is to evaluate what they are playing.  Higher harmonics are much more useful than bass fundamentals for identifying what notes and rhythms one is playing.  On top of that, rooms with good bass acoustics are rare, so lacking a frame of reference, most musicians probably have a biased preference for a sound in which the higher harmonics dominate at the expense of bottom end weight.

 

 

I do agree that the advantages of smaller subs in multiple placements likely outweigh that of one large sub with lower distortion.  I'm not sure I agree that distortion is irrelevant under 20 Hz.  Suppose that at some playback level the outside measured THD is 20% and inside, we have 5 dB room gain.  The in-room distortion will be This is not an implausible situation.   In the room (and ignoring room response difference other than room gain), the 3HD will be about 11% or -19 dB.  But looking at equal loudness contours, we see that for a 20 Hz tone in the 100-120 dB range, a 60 Hz tone needs be -20 dB or less than the 20 Hz tone to be equally loud.  So even though THD is only 11%, psycho-acoustically speaking, THD may be more like 100%.

 

Now I'll admit that the equal loudness contours are only valid for pure tones in isolation and don't adequately explain what we hear when multiple harmonic tones are present.  Still, the result appears significant.  If it is not significant, then I'd like to see more data that says so or experience this for myself.

 

 

If a bass player is sitting in your sweet spot listening to a recording of a tune in which he wrote and played the bass line and says, "Now THAT'S what playback of my bass should sound like", you gonna tell him he's full of shit and drone on about THD and equal loudness studies done in the 50s? Probably, and good luck with that.

 

Your example of 5dB room gain, etc., is purely hypothetical. I deal in reality. When the <20 Hz part of the effect hits, I immediately know it for 2 reasons. One, I'm acclimated to the experience. It's a recent phenomenon that a human can routinely experience playback of recorded source <20 Hz. Since there is no frame of reference, it's a learned experience. Two, it isn't because my infrasonic hearing is abnormally acute. The reaction of my environment is the cue, not human hearing of steady state sine tones.

 

Here's Black Hawk Down at reference level:

 

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You can see the harmonic distortion on the mic'd version. It's <3%. I'm sure the 4 x 15" subwoofer would show very high THD outside in a cornfield with a 6 Hz sine wave tone being played at -7dBFS. Irrelevant to in-room playback with soundtrack source. This isn't conjecture, it's black and white proof. I have dozens of caps that show no discernible harmonics in the spectrograph. The latest is the square wave beginning of Edge Of Tomorrow:

 

2e3acb6c8cd8bc9ad0ef05d1474c1f73.gif

 

The system is producing <2% 2HD of the 10 Hz fundamental. The higher level harmonics at 40 Hz are from room rattles. Still, nothing over about 8%. Again, the system will show MUCH higher levels of 2HD and THD of 10 Hz outside using a pure sine tone and... that is obviously irrelevant. Odd order harmonic distortion is completely masked by the effect, which has odd order harmonic distortion in it's makeup. This is also the case in Black Hawk Down. Most of the effects we're addicted to are comprised of an infinite number of frequencies wherein harmonic distortion <30% is completely masked.

 

Here's a link to an interesting exercise that focused on HD by Axiom done a decade ago. Not saying I agree with the study methodology or results, just saying it's interesting and worth a read:

 

http://www.axiomaudio.com/distortion

 

As I say, we played a pair of LMS-U and a single HS24. There was unanimous consent that the HS24 dominated in "SQ" amongst rabidly avid low end enthusiasts, all of whom have excellent low end reproduction capabilities. THD was not an issue... it never is. Evidence to the contrary is welcome.

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If a bass player is sitting in your sweet spot listening to a recording of a tune in which he wrote and played the bass line and says, "Now THAT'S what playback of my bass should sound like", you gonna tell him he's full of shit and drone on about THD and equal loudness studies done in the 50s? Probably, and good luck with that.

 

...

 

Let's discuss this in a new thread.

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Well I hit a personal record today of 3 infractions in a single post over at avs.....on the SI 24 thread.....huh huh huh.... 

 

Man... you had to make me go there and wade through that [thread] just to see what you did wrong, didn't you? :P:lol:

 

WOW!. Nick builds the baddest ass driver of all time and there's some $#%@  quoting some $%#@ regarding the Xmax spec and calling Nick a liar over it?

 

Where's the button that kicks the dumb person in the groin on that forum?

 

EDIT: Language.

 

How much Xmax does it give? Enough. Are we done here?

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Well I hit a personal record today of 3 infractions in a single post over at avs.....on the SI 24 thread.....huh huh huh.... 

 

 

wellthatescalatedquickly.jpg

 

 

Man... you had to make me go there and wade through that shit swamp just to see what you did wrong, didn't you? :P:lol:

 

WOW!. Nick builds the baddest ass driver of all time and there's some dick stain quoting some dick stain regarding the Xmax spec and calling Nick a liar over it?

 

Where's the button that kicks the dumb ass in the groin on that forum?

 

LOL to all of the above posts!  :lol:

 

Honestly I don't care about what the neagtive nancy's have to say because it only shows that you can not appease anyone that is hell-bent on making sure they grab at least a few people's attention because their system that they've paid big money for got beat by a driver that costs 1/3 what they have spent on their subwoofer system. But more-so, people said time and time again they were waiting on Ricci's measurements to see how the driver performed. Ricci measured the driver and posted up the data. Now the driver still sucks. Specs are wrong, I'm a liar, price is wrong, voice coils come un-wound if you don't pray to them every time you fire up your system, etc. Nothing I didn't expect from AVS. 

 

There are measurements from Beast's GTG and now Data-Bass yet both of those measurements mean nothing. The depths that some people are willing to dive to continues to surpise me on a daily basis. And I am quietly saying "woo-sah" with a smile on my face and a craft brew in my hand. The numbers speak for themselves and the driver is the same thing I've been saying for a LONG time: It is BIG. Everything about it is big: big output, big size, big bass extension, etc. I continually don't get why some people get so pissy because it takes a box larger than 4 ft^3. It's a 24 inch subwoofer!! It's NOT going to take a carry-on approved sized suitcase enclosure for a box. Thinking the latter is like looking at a Dodge Hellcat and being pissy because the in-city fuel mileage isn't that of a Prius. 

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@Electrodynamic et. al.

 

I personally want to thank Nick for providing a kick ass solution/option for the DIY crowd, especially @ the price/value he offers. Now some of you may know my plight when it came to garner support from the DIY crowd only to be criticized, and my efforts downplayed since I wasn't building a Marty-whatever. It just seemed unfair that the cheerleading for a certain alignment pushes out the creativity for another. My experiences @ AVS truly took away the excitement I had for the fun of building (what I thought of as) a formidable sealed system. I'm so close to finishing this project, but as the late BB King once said, "The thrill is gone".

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How much is this driver? Is it the msrp listed on the site or can it be gotten cheaper? I don't think it would suit me anyways. It really looks like an IB sub to me. If someone could IB it would be the best option I'm aware of. I suppose the size of it could make IB difficult where 16" OC timbre framing suits 15" subs better. Then again, using a manifold fixes that small problem.

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Ok gotcha. I won't bother him as I wouldn't be buying one unless one day I moved and did have an IB. Was just curious. Pretty insane output. I could see one of these with several 12s to smooth response being enough for most. That's a lot of output. Would make an interesting system actually.

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Ok gotcha. I won't bother him as I wouldn't be buying one unless one day I moved and did have an IB. Was just curious. Pretty insane output. I could see one of these with several 12s to smooth response being enough for most. That's a lot of output. Would make an interesting system actually.

 

 

Dgage is already working on that. Loads of 24's 412's, huge horn, win:

 

http://www.avsforum.com/forum/113-subwoofers-bass-transducers/1981769-official-deep-sea-sound-thread-4.html#post33945690

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Looks like my friend Doug's plan to go with 2 massive ported 24's is a solid one compared to 2 G-Horns he was thinking about.  The purple line is the G Horn and the blue line is the sealed 24".  In a big ported box won't the 24 have at least as much output as the G Horn down low?  I think he's planning on 2 50 cu ft ported boxes.  Not sure what the port tune will be though.  Any downside to this plan compared to going with the G-horns?  

 

I don't know why I haven't been on this website much, this is awesome and I agree with some that have said that Ricci should setup a pay pal thing for people do donate.    

 

 

 

Capture_zpsvcouawre.png

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