For those who have listened to IB subs.... - Page 14

I was doing an exact FR match, adjusting the smaller to the larger.

Two lines became one.

Ugh. This again.

One more try;

When the LMS was tested in a 100L box, everyone proclaimed it as being the most linear driver ever, although 100L is technically already too small a Vb for that driver.

In the ASD discussion that lead to the test, my point was that Vilchur proved air spring linearity vs suspension linearity 1/2 a century ago by removing a then popular IB driver from its huge box, decimating its surround and spider and replacing it with a makeshift, extremely high compliance suspension and reinstalling the driver in a very small Vb.

The result was:

Instead of Ilkka using the 100L results and comparing them against the same driver/amp in the 200L Vb (or whatever size he preferred), he claimed that the 100L tests were a year old and, therefore, not comparable to any new test, so he fashioned the smallest box the driver could physically fit into and then added ballast to effectively shrink the Vb to 75L.

A test that would have been in keeping with the actual discussion would have entailed changing the drivers suspension from its production parameters to a high compliance driver in the same 100L box and comparing the results to the tests in 100L that were already done, or using a high compliance driver with more sensible differences in Vb.

That said, Ilkka's test was largely unnecessary, as we had already discussed the ASD formula which could easily have predicted the results and the THD by component numbers closely enough.

ASD Formula: 140 * one-way swept volume/Vb:

140 * 4.18L/200L = 2.9% THD
140 * 4.18L/75L = 7.8% THD

A difference of 2.67 times increase predicted by the formula.

Looking at the actual results, taking the average THD of max output sweeps at 10, 15 and 20Hz:

200L = 10%
75L = 23.7%

23.7% is 2.37 times 10%, showing a slight difference from the prediction via formula vs actual, which may be attributable to any number of factors, but would have saved the effort to prove something that was already known but didn't address the actual topic of discussion.

Since we have the 75L and 200L numbers, let's take a look at the numbers that no one seems to be interested in, the CEA2010 numbers, taking the average from 10-80Hz:

200L = 109.43dB
75L = 108.06dB

So, here we have the max clean output per CEA's standard. Does anyone out there actually believe that there will be an audible difference at normal listening levels?

Just for fun, let's compare the 200L CEA results with the existing 100L results, averaged from 12.5-80Hz, because there is no 10Hz number for the 100L results:

200L = 111.26dB
100L = 112.05dB

Interesting enough results to warrant discussion, IMO. A discussion which never took place.

There is an ASD rule of thumb for anyone who wants the smallest Vb for his chosen driver in a sealed. LT system. Vb = or > total swept volume/5%.

For the LMS-18: 8.36/5% = 167.2L. That's roughly equivalent to a stuffed 140L box. Take that sub and test it against any sized Vb you prefer (up to and including IB) and you'll see the same things, proportionally, that I've shown in this comparison of the 100L and 200L versions of the LMS driver:



The larger you go, the worse the performance will be below 30Hz unless you a) Use a smaller amplifier, or b) Use a HP filter to prevent severe over excursion.

Option a will limit performance above the knee and option b defeats the purpose for building a 2nd order sub. Generally, under normal use, there will be no discernible SQ or clean output difference.

Bottom line: CEA 2010 results show the LMS 5400-18" and 3KW in any of these boxes (75L + boost EQ, 100L/no EQ, 200L/no EQ), far from one being 'unusable' vs any other, in a typical room will perform similarly enough as to be indistinguishable from each other in actual use.

Except for the fact that one of them will be a whole helluvalot bigger.

Bosso

Nope - I meant efficiency, i.e. the ability to transform voltage into musical signal with less heat. IMO, good drivers have gotten good enough that the primary issue affecting fidelity to the source material is dynamic compression caused by heat. And the way to minimize the role of heat is to have a system that makes as little of it for a given SPL as possible. That means mains with big drivers.

Why? See Catapult's excellent contribution to this thread.

As an aside, I read somewhere recently here that "Pro Audio is the Darkhorse" as it relates to design trends in home audio etc... and with the likes of Permanian, Seaton, Danley and others, it's hard to disagree.







The speed of an IB driver array would be an excellent example of an audio myth.



Not meaning to split hairs and I know exactly what you intended but your statement would be more accurate if you stated "Home Audio" ... , as Pro Audio fleshes out snake oil much faster than their consumer counterparts.

When the client's off to the side watching you, and watching the money being spent, you've got to "deliver" every night. There is no room for audio myths.

Whether the client is the lead singer in a club cover band, or a promoter, watching hundreds of stagehands assemble a production over a five day period...all for a two hour show, ... then tear down and load out by dawn, if it doesn't contribute to the quality of the show in a quantifiable manner, it's not on the truck.

Not to nitpick but this is, again, wrong. Efficiency is power out/power in. Sensitivity is power out/voltage in. Small difference but its a difference.


Yes and woofers are really not efficient at all. Even the most efficient woofer in the world is not that efficient at all. Going from 0.35% efficiency to 0.50 is not much of a big leap.

If you want to minimize thermal compression with a given driver then use a bigger box.

Well, fair enough. But if a speaker is considered to be full range then do you not agree that it should be able to handle all bass information recorded in the main channels (or at least down to 20 Hz) ? Whether this is practical or not is irrelevant. I'm talking about the core definition, not the practicality of it all. The accepted definition of 'full range', to my knowledge, is extension down to 20 Hz.


No, of course I'm not. You claim that the Summa can play stupid loud between 40-50 Hz and I'm saying, 'no, it won't because it's a friggin pro-audio speaker that isn't targetting that portion of the power band. If a speaker is 12 dB/per octave down at 50/60 Hz then it's maximum output is going to be curtailed, whether you like it or not.

You are right about one thing; loudness is very much subjective.

No it's not ! ChrisBee believes that the more woofers you have working in tandem the faster your bass reproduction will be. That's surely not a myth ? This is the kind of flippy floppy, wishy washy, cookie-cutter scientific brilliance that we deal with around here on a regular basis. I mean, it's embarrassing enough when one appeals to science and then fails miserably, but fabricating your own science out of thin air takes the cake.

FYI, faster bass equals better bass articulation, better separation; the ability to smell the texture of each bass note.

This is real science man.

I am humbled to be surrounded by so many scientists. Having so much passive absorption just hanging around will save me stuffing my IB to slow it down. Though I do like a nice quick transient. None of your sloppy leading edges for me, either. Mine travel so fast they are gone before I have time to be scared. They have even been known to leave a partial vacuum in their wake. Which is quite handy for damping down any overshoot!

My cat used to sleep through the SVS playing loud music and films. When I built the IB array he was still blasé. When I built the first manifold he dashed downstairs and hid under the furniture! A week later he left home!

So, one hundred percent of cats, who expressed a preference, said they hated the speed and realism of IBs. That's science for you.

That was the placebo effect. When you told the cat that it would be startled once subjected to a full blown manafold IB installation vs a line array it naturally agreed with that assumption and was startled as you said it would be. That's the power of suggestion mate. Talking to cats usually gets you results.

Cheers mate.

Definition of "Full Range" here



3.2.1 Full Range vs. Satellite

For the purposes of this document, "full range" speakers are defined as those which are capable of reproducing frequencies of at least 18kHz or higher at the high end, and 40Hz or lower at the low end. Surround mixing should always be done on identical full range speakers of the same brand and model, plus a subwoofer.

"Satellite" speakers are typically found in consumer home theater systems. They are much smaller in size than full range speakers, and have a very limited low end response, relying instead on a subwoofer to deliver bass frequencies. Surround mixes should be checked on a satellite speaker system, preferably one that emulates a typical consumer home theater environment. (See section 2.3)

How about when someone compares a single SVS subwoofer to a 8 driver IB manifold and claims the manifold is "faster" or whatever. Is that a subjective observation or is that just a bunch of cornswaggle?

Down to 20 Hz.

It's a subjective evaluation which may have merit but not for the reasons mentioned. If 'ones' (obviously I have no idea who this 'one' is you are referencing ) SVS was poorly designed and/or ran into a compression/nonlinear state, that doesn't explain how bass could be physically faster since bass isn't 'fast'; it simply would mean that the IB was considerably more linear.

But faster bass ? One could arrive at that conclusion simply from, I don't know, changing physical positioning of IB and SVS, and faster energy storage/decay ! That could change your perception of slow, fast bass, not the operation of the mechanical system, since even if 8 woofers took 1/8th the time to reproduce a given transient, it wouldn't reproduce the transient quicker than another woofer system that took 1/6th of the time, since all that was needed was (X) amount of time. If the woofer can move quick enough to reproduce the frequency then by definition it's traveled as fast as it needs to to reproduce that frequency.

Of course, 8 15 inch woofers would lay waste to a single SVS subwoofer so I can imagine woofer excursion would be minimal at very high levels with extremely low thermal compression. So from a sound quality point of view, there is no doubt in my mind that one could hear very noticeable differences between subwoofers. My MFW-15 subwoofer sounded boomy no matter where I placed it, no matter how much EQ was applied and no matter how much treatment I added to my room so one could conclude that it was poorly designed full stop.

However, the idea that adding additional woofers creates faster bass is flippy floppy, swishy swashy cookie-cutter physics at best. What's even more preposterous is the notion that adding additional Vd to a system that is already dynamically untaxed will result in superior dynamics.

At least we all learned something interesting today concerning the placebo effect; it affects animals too !

Not singling you out at all, Penn, just citing the statement.

This statement has appeared in every sub thread since forever.

The statement should read: "People will defend what they've decided is the is the best choice, no matter what the facts are, and justify it by saying 'all systems are a compromise'."

Once you have flat response across the entire SW bandwidth, cleanly to reference levels and beyond, can dial in any in-room response or the latest boutique curve, have a system that fits the room nicely and looks very good (to yourself and she, who are the only people who matter), reproduces the most demanding source with no audible distortions and Compression is non-existent...

... and you posted the FR, comp sweeps, single sine peak holds, SLs, dBSPLs, anny FRs, signal chain loopbacks, measurement rig specs to prove it...

What exactly are the compromises?

We can discuss theoretical things like the audibility of latent release of stored energy and claim that it is audible but not measurable, or box coloration as another theoretical unknown ghost that's somehow painfully audible but not measurable and every other slice of baloney, but the truth has always been that...

All of the band pass (bandwidth limited) subwoofer manufacturers and DIYERs have consistently increased the size of their subs and lowered the bottom end of the BW of their subs. Each time they proclaim that their latest F3-by-fiat is as low as anyone needs to go because yadda, yadda, blah, blah, and every alignment has its compromises.

Bosso

Cost...

and, depending on how many subwoofers it required to get you to "enough output", perhaps size...

Cost... [edit lennon beat me to it]

For that matter Bosso, how cheaply can one get 135db from a sealed system assuming, say a 6db/oct room gain below 25hz?

Well cost as in, "it is too expensive" would not be a compromise. Going cheaper would be a compromise of your bass potential.

My question would be since he decided to throw subs all around his room to get a better response over a larger area, does he get the same measurements from everywhere?

Wouldn't a DBA be less of a compromise in this situation? What if someone else came alone with 64 18"s in sealed subs. He would say bosso's setup was compromised.

The only thing that matters is getting the bass you want within your own realities. Whatever they may be. Example, I think spreading subs around the room to get better response all over is a waste, as I only sit in one spot. I don't care that a random visitor may have a peak or null where they are. That doesn't make me right, wrong, or better than anyone else, or their setups.

There is no perfect setup for everyone, or a single ultimate setup. It's the old one+infinity bit.

I'm curious, what is your setup Soho54? Bass horns?

You are the one who seems to have a way of rationalizing your own choices. You always infer that an uncompromised subwoofer setup is the only way to go.

A lot of people simply do not have the room to place 4 - dual driver megawatt subwoofers in their rooms nor can they install an IB setup. Esthetics and normal use come into these system decisions in the real world.

The Bosso statement should read: "Bosso will defend what he has decided is the is the best choice for everyone, no matter what the facts are, and will justify it by saying 'no system should ever be a compromise'."






Mental health!

Compromises are come in two packages.

WAF and performance.

Its very hard to have a perfect solution. Bosso your solution has two big road blocks (It requires Extra $$$ in EQing functionality/power requirements + many boxes taking up space).

You may not deem those as compromises to you but others will. I posted before I will not compromise my family room with your subs when I can get the same performance out of an IB for less $$$ that is completely hidden to most people.

Points taken.

But, I could easily apply that same set of compromises to the sofa and other family room accoutrements as well.

I'm speaking of strictly end-result performance, which I don't feel is compromised in my system. That's where the discussion seems to drag on. The word game is always confusing to me, I guess.

For the record, I do agree that the IB (done well, as is assumed when discussing any system) is an equally no-compromise system.

Good points. I figured your previous posts was sticking to pure performance which I 100% agree with.

Quote:
Originally Posted by FOH
The speed of an IB driver array would be an excellent example of an audio myth.




Ok, I just realized you were joking right, ..right?

I'm thinking, "hell, I'll field this one" well, never mind.



Although, since I'm here, the more woofers working in tandem, the "slower" one's bass becomes. As I understand it, individual driver velocity would be inversely proportional to total displacement. V=pi(FD)



Also, as far are system compromises in a system such as Bosso's, .... or one like it, the compromise foremost in my mind is the Vb/eq-power, fwiw




A very good friend of mine heats his lake home exclusively with wood. During the cold winter months, he would tell me that before he and his wife would turn in for the night, he would put an "big ol' all nighter" in the wood stove,.... to "keep 'er goin' for a while". Well, here's my all nighter;
In my opinion, if one were to substitute quick bass, in an instance when one would be compelled to use the term fast bass , it would certainly be more accurate.

Transient response / slew rate is a high frequency function and will be determined in a sub, mainly by the LPF employed. Given systems of reasonable capacity and design (and no pathological faults), and both using an (arbitrarily selected for discussion) 80hz LR24 it will be predominantly the filter that determines system response.

If that were true, and since most system use just such a filter, all subwoofers would sound identical.

Though I have noticed that lowering the crossover point robs the system of life and attack. This, despite having 38Hz(-3dB) mains. Measured and confirmed with REW.

Alas, my 8 x 15" IB has lost its former speed. One channel seems to have become a shrinking violet.

The stunning realism, attack and brutality are all all absent with the remaining four drivers despite a tweak on the gain control.

Going back to an earlier point: Distributing the displacement between discrete subwoofer units would smear the phase enough to cause jet lag.

The IB suffers no such problem since all the drivers in a manifold combine to provide a coherent wavefront.

Briefly;
Despite the 38hz extension, I would guess that it's primarily the effects of the thermal compression differences, and secondarily, comb filter cancellation effects. Whether that's what robbing the life and attack out of the system with the lowering of the crossover, I don't know. But from afar, I'd bet it's contributing.

Are there any studies available that show that thermal compression can contribute to 'slower bass, slower attack, loss of life etc' ?


Of course I.....was.

You would achieve smoother bass with 4 separate subwoofers vs one manafold with 4 woofers. A flatter response may lead to subjectively 'quicker' sounding bass.

Perhaps you should think about building another manafold, or another 3; then you'll achieve bass that you never thought was possible.

Really? So now you are disagreeing with PhDs like Geddes, Toole, etc? I know some DIYers are full of BS but that was a a perfect example of an education level about equal to a stock boy building subs.

Keep digging that hole Chris! I posted before that you know very little and you are showing your true colors which makes me happy because I enjoy being proven right.

An objective scientist would gain no contemptuous enjoyment from the attempts by anybody to seek a rational explanation for the things we hear. You post with far too much emotion to be considered remotely objective. Dismissive to a fault, your open worship of your theoretical idols must cast serious doubt on your normal ear level!

Let's think about this for one moment: Multiple, discrete subwoofers cannot be spaced equidistantly from the listener and relative to the room boundaries if the listener is to avoid the usual null point in the centre of the room. In fact it is difficult to imagine a situation where the time domain is not seriously violated. EQ will not help the situation except in the crudest sense regarding FR. Reflections from the non-equidistant boundaries will only compound the mischief.

Are we knee deep in satisfactory working examples of your idol's suggestions? Or do they remain impractical theoretical models of interest only to the disciples of your revered audio prophets?