My Tumult sucks (v. Don't believe the model / What to do with a paperweight?) - AVS Forum
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Old 10-08-2012, 12:33 PM - Thread Starter
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I have a Tumult from the first batch of drivers. I pre-ordered it almost a decade ago. Back then I built a ~220L box with 4 Adire PR-15 passive radiators massed up to the max 1500g. I played with the resulting box a bit and wasn't real impressed but I never dug into why. The sub ended up in storage collecting dust for the past 7+ years. I got the sub back in my hands last Friday and found it was just as disappointing as I remembered. Modelling for the sub based on the published T/S parameters gives this: (Click the thumbnail for full size)



I used the close mic technique to measure the sub and summed the results (driver + 4 passives) in REW after compensating for the Sd differences between the passives and the Tumult and got this response in the blue trace: (Click the thumbnail for full size)



The measured result isn't even close to the model. Trying to track down the cause of this disaster I pulled the Tumult and did a close mic free air sweep of it and got this: (Click the thumbnail for full size)



The response seems to show at least a serious inductance "problem" with the driver. While I had the driver out of the box I used my DATS to measure the T/S parameters of the driver: (Click the thumbnail for full size)



Feeding these parameters back into the model gives this: (Click the thumbnail for full size)



Still not close to the measured response. As a final sanity check I put an Acoustic Elegance AV15-H D2 in the box in place of the Tumult and measured the box response and got this response in the red trace: (Click the thumbnail for full size)



The AV15-H measures well in the box matching the model (not posted) fairly closely and audibly sounds much better. But, it seems my Tumult doesn't perform even little bit like how the model predicts and it sounds bad (presumably due to the frequency response). Obviously, since Adire closed their doors years ago, so I can't exactly go ask them why. Do I have any options to rescue this heavy paperweight? Or, should I find a more suitable high power 15" driver (that performs like its model predicts) for the box + PRs I already have and consider this another lesson learned in not pre-ordering audio products on hype?
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Old 10-08-2012, 12:39 PM
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You've posted quite a bit about your dislike for your old Tumult. wink.gif

Besides trying it in a sealed box and using plenty of signal shaping, why not just sell it off and buy something new?

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Old 10-08-2012, 12:42 PM - Thread Starter
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Originally Posted by Scott Simonian View Post

You've posted quite a bit about your dislike for your old Tumult. wink.gif
Besides trying it in a sealed box and using plenty of signal shaping, why not just sell it off and buy something new?
Yeah, imagine the audacity of trying to understand why the models that everyone uses in the DIY section as gospel don't always accurately predict the actual response of the driver + box. rolleyes.gif

Nearly everyone seems to operate from the belief that the model is always accurate. I rarely see people measure their finished products and compare them back to the model to close the loop.
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Old 10-08-2012, 12:46 PM
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I didn't say that. It just seems pretty obvious that you are unhappy with it which is why I'd suggest to just move on or try something new instead of the PR system.

Also, MANY drivers do not model correctly in Unibox...unfortunately. frown.gif There is more to inductance than just the one stated listing which is why I practice using Unibox's complex Inductance which even then isn't always super accurate. Look at many drivers tested on Data-Bass compared to their specs. You'll see the same massive hump caused by tons of inductance.

Imo, your Tumult measurements look pretty accurate to their specs. The roll up high kind of sucks but you can shape that out.

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Old 10-08-2012, 12:52 PM - Thread Starter
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Originally Posted by Scott Simonian View Post

Also, MANY drivers do not model correctly in Unibox...unfortunately. frown.gif
What other program is more accurate?
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There is more to inductance than just the one stated listing which is why I practice using Unibox's complex Inductance which even then isn't always super accurate. Look at many drivers tested on Data-Bass compared to their specs. You'll see the same massive hump caused by tons of inductance.
Unfortunately, it seems only TC Sounds gives the extra Le2 / Lp and Re2 / Rp parameters to more accurately model the sub driver's response. I know most drivers have an inductance hump. I just haven't seen one as large as I measured or centered at 30Hz before.
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Old 10-08-2012, 01:27 PM - Thread Starter
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Originally Posted by Scott Simonian View Post

I didn't say that. It just seems pretty obvious that you are unhappy with it which is why I'd suggest to just move on or try something new instead of the PR system.
I'm very willing to try something else, but it seems pretty clear from the data that my Tumult is the poster child for why you shouldn't blindly trust a software simulation, so what similar 15" drivers are there that will match the software model much closer and give the sort of performance I get with the AV15-H but with more power handling / SPL output? How's the TC Sounds LMS-R 15 for example?
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Old 10-08-2012, 01:54 PM
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Originally Posted by Stereodude View Post

When I posted I knew you'd be along shortly to claim user error.

Wow, you must be psychic.

The Tumult MKI wasn't designed for a flat-to-200 Hz response. It's a SUBwoofer driver, made to cross around 60 Hz, although, as I've already shown about 2 billion times, it works just fine with proper signal shaping giving a very formidable 5.5 liters of displacement to the bottom of the room/signal chain.

The CSS-SDX-15 is the Tumult MKII. With a redesigned basket, it looked to be a spiffy 15, but never appeared for purchase, and probably never will. Sundown has adopted XBL^2/Wiggins designs and one other I can't recall, so similar performance there with a bit less displacement. Good stuff in any case. Certainly not paperweight, which really is a rookie thing to say.

PR ain't my cup-o-tea, so I can't help you there, but signal shaping is an inevitable part of low end reproduction in-room. Whether you do it pre or post, you'll do it. I obviously prefer no post EQ and prefer to shape the signal before the room with a signal shaped response that is predictable as working best with the room and listening preferences. Afterward, placement, delay and crossover selection options will fine tune well enough in most every case.

Build a sealed box and a simple L/T from Linkwitz's spreadsheet (or some outboard EQ if you prefer a costlier pre-built outboard solution), use a good amp and there ya go.

Also, when you measure close-mic, put the LPF in line that you use in your HT. That'll save you a lot of fretting over nothing. So the AV Vaporware-after-I-waited-2-years=for-it driver is relatively flat to 300 Hz, what does that mean in actual use? Nothing.
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Old 10-08-2012, 03:00 PM
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Originally Posted by Stereodude View Post

I'm very willing to try something else, but it seems pretty clear from the data that my Tumult is the poster child for why you shouldn't blindly trust a software simulation, so what similar 15" drivers are there that will match the software model much closer and give the sort of performance I get with the AV15-H but with more power handling / SPL output? How's the TC Sounds LMS-R 15 for example?

Yeah. It's too bad the AV15X/H's aren't still available.

Other low Le smooth response 15's I can think of would be the LMS-R15, JBL w15gti, Aurasound NS15, Sundown SA-15...to name a small few.

Honestly, to me, the response you're getting from the PR system looks good on the deep end. It's just lacking the top end goodness. Maybe mate the PR with a sealed pro-style woofer system for the midbass punch? Sounds like fun to me. smile.gif

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Old 10-08-2012, 03:00 PM - Thread Starter
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Originally Posted by bossobass View Post

Wow, you must be psychic.

The Tumult MKI wasn't designed for a flat-to-200 Hz response. It's a SUBwoofer driver, made to cross around 60 Hz, although, as I've already shown about 2 billion times, it works just fine with proper signal shaping giving a very formidable 5.5 liters of displacement to the bottom of the room/signal chain.
Except there is no user error. The fact is the driver doesn't perform anywhere like the model says. Can I EQ it flat? Sure. But if I want relatively flat output to ~80Hz I need >5x as much power at 80Hz as I do at 30Hz since the driver rolls off that much. Or, I have to reduce the output down low to the SPL it can produce at 80Hz. Neither is particularly desirable IMHO.
Quote:
The CSS-SDX-15 is the Tumult MKII. With a redesigned basket, it looked to be a spiffy 15, but never appeared for purchase, and probably never will. Sundown has adopted XBL^2/Wiggins designs and one other I can't recall, so similar performance there with a bit less displacement. Good stuff in any case.
Unless I'm mistaken there already was a Tumult MkII and the "vaporware" driver is the SDX15 MkII, which seems interesting, but anyhow...
Quote:
Certainly not paperweight, which really is a rookie thing to say.
Well, with regards to the box I built to it sort of is a paperweight. A cheaper & "lesser" driver (bench racing specs) from AE takes it to the cleaners.
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Old 10-08-2012, 04:45 PM
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Hi Seth,

I've been harping on DIYers for years to actually measure and verify the behavior of what they were building, especially with respect to real world inductance. I first ran into the more extreme examples of this with the TC built HE-15 drivers Stryke sold, and later again with first generation Ascendant XLB^2 drivers. In years past many would carefully calculate L/T and similar filtering based on simple T/S models, and even set up external devices like a Marchand Bassis without a single measurement. Such suggestions were most often dismissed as being alarmist in what are rather small deviations. Ilkka's measurements gave some insight into this with a few examples, and Josh Ricci has posted much more information about this for DIYers, most importantly correlating simulated vs. measured performance.

Most cases can be approximated plenty close with a 3 element Le approximation, but even then you really need to correlate it to an acoustic measurement, where an impedance curve fit gets in the ballpark, but can be misleading either direction for unique cases.

To be fair, high Le can have a very significant effect, but it doesn't automatically mean a driver is useless. It is important to watch for excessive upper octave distortion, but that is a possible symptom, not a guarantee. In the case documented here, it lowers efficiency and creates a very non-flat response. Careful correction of the frequency response shape and additional power would likely provide a hugely improved subjective response.

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Old 10-08-2012, 05:07 PM - Thread Starter
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Just for Bosso... Free Air Model (based on Adire T/S) vs. Reality: (Click the thumbnail for full size)



I look forward to hearing about how this discrepancy is "user error". tongue.gif
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Old 10-08-2012, 05:09 PM - Thread Starter
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Quote:
Originally Posted by imagic View Post

It seems to me that you are the poster child for mangling subwoofer data.biggrin.gif
Uh okay, thanks for your valuable input on the topic.
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Old 10-08-2012, 05:57 PM - Thread Starter
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Originally Posted by Mark Seaton View Post

Most cases can be approximated plenty close with a 3 element Le approximation, but even then you really need to correlate it to an acoustic measurement, where an impedance curve fit gets in the ballpark, but can be misleading either direction for unique cases.
Too bad us DIY'ers can't even get the 3 element Le approximation for most of the drivers on the market. frown.gif
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Old 10-08-2012, 06:02 PM
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Quote:
Originally Posted by Stereodude View Post

Just for Bosso... Free Air Model (based on Adire T/S) vs. Reality: (Click the thumbnail for full size)

I look forward to hearing about how this discrepancy is "user error". tongue.gif
I may have missed it, but how did you measure the free air response? What kind of baffle was it mounted to, how far was the mic from the dust cap, and what gating delay did you use?

If my subs had a free air response like that, I'd be unhappy too.

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Old 10-08-2012, 06:11 PM
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I have been fortuitous to have my designs match simulation very well. I'm a bit curious if this is because I work mostly with lower inductance pro drivers. The Zv3 18" has exhibited similar dissonance between simulation and measurement in a few of my test runs.
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Old 10-08-2012, 06:22 PM
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Nothing fortuitous... IMO you are doing it right. When people can't get a match (most of the time) they really need to look at their measurement methods first - before questioning published specs and accusing subwoofer designers/engineers of being pathological liars and masters of obfuscation.
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I have been fortuitous to have my designs match simulation very well. I'm a bit curious if this is because I work mostly with lower inductance pro drivers. The Zv3 18" has exhibited similar dissonance between simulation and measurement in a few of my test runs.

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Old 10-08-2012, 06:32 PM - Thread Starter
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Originally Posted by imagic View Post

Nothing fortuitous... IMO you are doing it right. When people can't get a match (most of the time) they really need to look at their measurement methods first - before questioning published specs and accusing subwoofer designers/engineers of being pathological liars and masters of obfuscation.
Are you going to delete this post in a few minute too like several others you've made in this thread?

The fact is that the T/S parameters don't always accurately predict the behavior of a subwoofer because they are inadequate in some cases. My experience with the Tumult is a perfect example. If you have something valuable to add like suggestions as to how the measurement were done wrong feel free to post them. Otherwise please keep your vague 3rd person straw man attacks out of my thread.
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Old 10-08-2012, 06:41 PM
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It's fair to say that you have provided no proof that your conclusions are justified, Occam's razor still points to user error... and this is not the first time. rolleyes.gif

That will be all from me. I did not want to litter up your thread so I deleted a couple of posts. So what, big deal. I'm sure you are busy uncovering the great subwoofer conspiracy.tongue.gif
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Originally Posted by Stereodude View Post

Are you going to delete this post in a few minute too like several others you've made in this thread?
The fact is that the T/S parameters don't always accurately predict the behavior of a subwoofer because they are inadequate in some cases. My experience with the Tumult is a perfect example. If you have something valuable to add like suggestions as to how the measurement were done wrong feel free to post them. Otherwise please keep your vague 3rd person straw man attacks out of my thread.

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Old 10-08-2012, 06:47 PM - Thread Starter
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Originally Posted by imagic View Post

It's fair to say that you have provided no proof that your conclusions are justified, and this is not the first time. rolleyes.gif
I've provided way more proof than you have that they're not justified. The measurements show the subwoofer doesn't match the model. I've got other measurements (done the same way) of the same configuration with another driver that are pretty close to the model.

Yet, you claim there's a problem with the measurements. I'm sure you have measurements of your DIY subs and comparisons to the models right? Can you link me to your thread please?
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Old 10-08-2012, 06:51 PM
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StereoBro just sell the Tumult and get something more to your liking. I doubt it would take long to sell.

I've been saying this for a while but yeah you can't accurately model a system without the inductance effects and a single frequency spec isn't worth a velvet painting of a whale making love to a dolphin. Unfortunately you rarely get measurements or even an impedance curve from many manufacturers. So stick with drivers that are a known quantity or roll the dice. Either way measurement capability is a must. So far inductance seems to mainly have a negative affects on top end output and sensitivity sometimes drastically but also the deep bass sensitivity as well in some cases. Lower sensitivity comes with increases in distortion too usually. It can also increase sensitivity around the peak though which is useful in some cases for example if you just want to be as loud as possible over a limited bandwidth like 30-70Hz.

Justin most of the pro woofers have inductance combatting measures and lighter coils and lower moving mass. Also note that they usually publish measurements and impedance curves. Also it's not just inductance that can cause a hump in the response. The driver parameters and enclosure can contribute as well.

Extreme close mic measurements will exagerate the hump a little more than an anechoic or ground plane measurement.
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Old 10-08-2012, 06:55 PM - Thread Starter
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Quote:
Originally Posted by Looneybomber View Post

I may have missed it, but how did you measure the free air response? What kind of baffle was it mounted to, how far was the mic from the dust cap, and what gating delay did you use?
If my subs had a free air response like that, I'd be unhappy too.
I had the mic pointed down at the dustcap from above. The mic was about as close to the dustcap as was possible without the cone hitting it during the sweep. I used the default settings of REW other than increasing the length to 1M points so I'm not sure of the gating. There was no baffle. I measured the AE AV15-H the same way and it measured much better.

AE AV15-H close mic free air sweep: (Click the thumbnail for full size)

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Old 10-08-2012, 07:08 PM - Thread Starter
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Originally Posted by imagic View Post

...Occam's razor still points to user error... and this is not the first time. rolleyes.gif
That's pretty ironic coming from you... What's Occam say about this?

AV15-H Sub vs. Model: (Click the thumbnail for full size)



Must be more user error. wink.gif
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Old 10-08-2012, 07:15 PM - Thread Starter
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Originally Posted by imagic View Post

Maybe yours is a lemon, have you considered that?
I'd say that's a strong possibility. Other measurements of a Tumult in a box I've seen show the inductance hump at a higher frequency with a much less severe roll off above the hump. Unfortunately, the only person who has posted in the thread with a Tumult dismissed my observations out of hand as another attack on his favorite subwoofer driver.
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Old 10-08-2012, 07:16 PM
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This thread caught my interest...

StereoDude, you say that you have been disappointed with the driver but you don't say *how* you were disappointed by it. Put aside all the analytical measurements made and ensuing bashing that seems to have resulted please, What is it about the speaker that you heard (or didn't hear) that made you throw it in the corner.

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Mark

You guys are crazy....
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Old 10-08-2012, 07:17 PM
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Occam changed his mind and thinks it's a faulty driver (your Tumult).
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Originally Posted by Stereodude View Post

That's pretty ironic coming from you... What's Occam say about this?
AV15-H Sub vs. Model: (Click the thumbnail for full size)

Must be more user error. wink.gif

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Old 10-08-2012, 07:24 PM - Thread Starter
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Originally Posted by mrogowski View Post

This thread caught my interest...
StereoDude, you say that you have been disappointed with the driver but you don't say *how* you were disappointed by it. Put aside all the analytical measurements made and ensuing bashing that seems to have resulted please, What is it about the speaker that you heard (or didn't hear) that made you throw it in the corner.
Thanks,
Mark
I'd say the most telling characteristic is that the sub lacked impact and slam. I'd play a track I was familiar with and wonder where the kick to the bass was.
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Old 10-08-2012, 07:33 PM - Thread Starter
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Originally Posted by Ricci View Post

StereoBro just sell the Tumult and get something more to your liking. I doubt it would take long to sell.
Well, that's sort of the problem. As you said you can't tell squat with a single Le number measured at 1kHz. So, I'm not sure what driver will be to my liking. I'd like something like a souped up AV15-H with more excursion & power handling, but don't know what 15" driver is actually going to give that performance in box.
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Old 10-08-2012, 07:36 PM
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What enclosure was the tumult in when measured? Do you have measurements of the response of it in room from your listening position? You could have a major resonance or nulls causing big response issues.

Well off hand the 15's that I can think of are the Sundown Sa15 but it won't have more displacement than an AV15. The LMSR will be reasonably flat similar to the 12" measurements. There is the alpine type R 15" and w15gti JBL. Mtx 9515 is good if you can find one. The LMSR or mtx 9515 have the most displacement and maybe the most thermal power handling but are also most expensive. Big stroke woofers with a flattish top end are not the norm.
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Old 10-08-2012, 07:53 PM - Thread Starter
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Quote:
Originally Posted by Ricci View Post

What enclosure was the tumult in when measured? Do you have measurements of the response of it in room from your listening position? You could have a major resonance or nulls causing big response issues.
It was in a 220L box with 4 Adire PR-15 passive radiators loaded to 1500g. I don't have any measurements of it in room. The sub is in my unfinished basement right now. It was measured using a close mic technique to avoid any "room" effects since I don't have access to a field like you do or the vehicles to get it there. The same box + PRs with the AV15-H was measured the same way.

Comparison of the two drivers in box: (Click the thumbnail for full size)

Stereodude is offline  
Old 10-08-2012, 07:54 PM
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Quote:
Originally Posted by Stereodude View Post

Just for Bosso... Free Air Model (based on Adire T/S) vs. Reality: (Click the thumbnail for full size)

I look forward to hearing about how this discrepancy is "user error". tongue.gif

First, no, the AV driver did not compete with the Tumult. 34 mm bests 23 mm by 2 to 1 at 20 Hz in a sealed system.

Of course, maybe I didn't have 4 of each here and maybe I didn't test them exhaustively. rolleyes.gif

Your close mic free-air is not accurate.

Read what Seaton said. Anyone who uses a computer to design a system and expects it to match the sym is a deluded rookie, like yourself. You should have asked your question BEFORE you built.

Here's Ilk's GP measurement with my measurement overlaid in dashed black. Please note that all of Ilkka's measurements were inaccurate below 20 Hz, as they added 3-4dB that wasn't there. I have no idea what any computer sim looks like of the Tummy MKI. Never modeled it for FR, only for excursion, which is never exact either.

As Mark mentioned, I used the Marchand Bassis to get the exact L/T parameters through settings/measuring. I still do. Building an L/T signal shaper based on WinISD (or whatever) is suicide.

Below that are several drivers after signal shaping, laid over the Tumult MKI anny response. One of them is the AV15H. I'll leave it to you to guess which. The others all have the dreaded Le hump/roll off to a greater or lesser extent except the Tumult MKII, which would mop the floor with a pair of AV drivers to 500 Hz.

compareavtumbht_zpsd14a9127.jpg

After the fact, in-room, there's no chance you'd tell a difference, except if the subs were driven to the edge of their existences.
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