For those who have listened to IB subs.... - Page 12

I'd invite you over to listen to my IB... but my room is beige... I find it provides optimal balance of lighting for use as a living room with the possibility of using the projector during the day, any projector without beige walls is severely limited and anyone that likes their setup without beige walls only enjoy it because they don't know what they're missing...

Have you learned nothing from this thread? Cut off that IB and just apply an LT and more power. Won't sound any different

In the interests of fair play I think we should accept that the walls are coffee & cream coloured rather than beige.
As such, the SQ of the IB concerned is raised well beyond that possible for any other sub-bass, transducer alignment in a room of any other colour.

Physics R'us.

I just want to know how they would sound different? More distortion?

If the Response curve in the end is equal what makes them sound different?

I'm no pro on IB but I do understand the use for IB. I would believe that the effects of the room to the response of any sub system would rule over any difference between a sealed system and an IB. Just my two cents.

Its already been pointed out that is not a 100% garuntee of success even with an IB at one location. Placement isn't always perfect and without multiple placements around the room there might be peaks or dips on the response because of room nodes.

Im still curious to how 4x18" woofers in an IB with EQing and proper amplification is superior to 4x18 woofers in 4 boxes in room with EQing and proper amplification? If physics R' US then there should be no difference between the two designs, multiple boxes may even improve the in room response because of what Toole, Geddes, etc proved.

and around we go ......

Jesse S,

I want to ask you two questions. The first question is do enclosures color sound ? If yes, can you provide an explanation for it ?

Take note, I am a fervent believer in IB systems and I do agree with those who claim that enclosure coloration exists. I simply don't have evidence of my own to lend credence to that claim.

The second question is a question that I've asked ChrisBee to answer which he decided to ignore. If one adds enough displacement to their system to be able to reproduce any dynamic transient without compression would there be any benefit to adding more Vd to the system if both examples were gain matched to the same level and EQ'ed to the same level, maintaining identical frequency response curves ?

If 'yes' then please provide an explanation. If 'no' then no explanation is required. I realize that ChrisBee separates himself from the competition by providing no competition but I am curious to know what your answer will be (no sarcasm intended, I am being serious here).

To the Readership; I vow not to ask the same question again, to any member on this forum or in this thread ....except to ChrisBee....

Scott, where have you been hiding all these years ?

I don't A properly designed box has no audiable coloration on its own when we apply the proper EQing and power.

I would also like to know or see a graph of how adding Vd affects coloration? I'd assume the difference between having 10000 cf of space and 1000 cf of space is minimal or 0 but how about 100, 10, 1 etc? Where is the point of diminishing returns.

No sim will show the difference....people tend to exeggerate real audible differences never having measurements to back up their opinions.

Well how self-indulgent of you. But seriously, I can't explain it, I can't prove it; I'm simply not able to provide sufficient evidence but I do believe it. Since I've never EQ'ed an IB and a conventional acoustic suspension flat, calibrated to equal levels and in the same location, I simply don't have a reference point.

Until I have experienced both systems, EQ'ed identically, calibrated to even levels in the same location and accounting for auditory changes due to time related ear acclimation, I'll have to reserve judgment.

My real point here is that once the FR plot is the same what else can be different?

Decay? Distortion?

I'm not sure that is what I asked Jesse S. In a nutshell (sheeesh) If you have enough displacement in your system to handle any dynamic scene in a film, then would extra Vd be beneficial if you gain matched or level matched the system and EQed to similar levels ? In my opinion, no, it would not be beneficial. The only benefit to this would be to lower measurable distortion. But as we all know, what is measured and what we perceive do not always correlate 100% with one another.

So achieving 0.1% THD at 40 Hz is insignificant, but adding an addition 10 L of Vd improves this to 0.004% THD; no difference to us since we wouldn't be able to perceive such changes. We are not concerned with measurable phenomena but perceptible phenomena since at the end of the day, if we can't perceive it, then it is the equivalent of it not existing.

It wouldn't make a lick of difference except the measurable distortion would be reduced but that's a moot issue. What I want to know is how ChrisBee was able to determine how adding more Vd to his system somehow gave him greater dynamics when he level matched his system to the same levels without taxing it. It's ********e.

Adding more displacement on top of such a system would be tantamount to adding 100 megatons of nuclear energy to destroy a small city when 20 megatons would have sufficed. I realize my example is really, really crude but that is how ridiculous the claim is. Are you reading this ChrisBee ?

Don't worry Goneten, we all agree (minus chrisbee) that there is really no improvement going from 4x18s to 8x18s...just more displacement.

If we can not even hit Max SPL from 4x18s then 8x18s is a meaningless addition.

I agree. I used to think sealed subs sound better than ported. Problem was, I was just hearing better subs that happened to be sealed. After hearing good (DIY in my case) ported subs I realized that it is not the type, it is execution of the design. All of them need EQ. The location of the needed EQ just varies based on the subwoofer type (sealed, ported, IB, or horn) used.

Does Group Delay change for a driver in a sealed design with VAS of 200L vs 1000L??

Someone can sim it pretty easily to know that answer.

Remember an IB is just a HUGE sealed box

It would be interesting to test GD in both IB and a sealed box in the same position, in a real world test. It's a bit of bad omen to suggest that GD is applicable at very deep bass frequencies but who knows. I can name a few people who claim that GD is as important if not more important than general harmonic distortion, especially the icky 2nd-order kind.

As far as I can tell, there are three options :

1) All those who have owned and built IB's who claim the sound quality is the best they've heard and better than anything they previous owned have never conducted in depth testing of both in the conditions I've described, namely, EQ'ng flat, calibrating to even levels in the same position for both.

2) Those who claim that their IB's sound better than anything need to believe that the sound quality is better than anything they've heard to overcome the huge expectations of building one and the nonstop bias from places like the Cult which promote such things.

3) Perhaps no one here has done any in depth testing (as per 1) whether the claim was made or not since no one can corroborate any of this anyway, it's just subjective and being subjective is subject to critique and hence nonobjective.

4) The IB crowd who scoff at the idea of being laughed at because their beliefs are put into the same category as those believing in fancy zip cord, power cables and cable elevators can just turn around and say that until in depth testing has been conducted and a listening session has been put together which can show the difference between the two set ups, with quick changes between systems to refresh auditory memory, that they have as much credence in their belief as the nonbelievers do.

Who...the...hell..knows...

Well, sure. A small sealed box = acoustic suspension, an IB = not an acoustic suspension since a very, very large sealed box operates differently to a very, very small sealed acoustic suspension.

Doh.. you are correct. I was in a meeting reading/planning and for some reason was mixing Vd and box air space up in my head. Don't ask why.. just move on these are not the droids you are looking for.

I still would like to see real world measurements (not sims) of how increasing sealed box size affects (the as of yet unmeasurable) box coloration.

Perhaps 'box coloration' can't be identified with current measurement technology. Unfortunately if you stick with this line of reasoning then you could justify any irrational concept on the planet.

Tom Danley claims that power compression starts at 1/10 to 1/8 of a drivers rated power.

So if you want to hit reference level LFE, which is 125db (if using speakers set to small) then your subs should be able to hit 135db at the listening position.

I would agree with that.

I don't think you're correct on either of your last two points. His position on BM is conditioned on using speakers that work with his theories, which is to say large cone-area, high-efficiency, closed-box mains with reasonable LF extension (into the modal region, say at least down to 100 Hz anechoic loudly, cleanly, and with low compression) for mains. And while he's changed his approach based on subsequently-acquired knowledge - which is what one would hope anyone would do, right? - the fact of the matter is his old approach (run the mains with no LP, cross the subs up high using an "LFE+Main" or "DoubleBass" setting on the AVR) works damn well with most program material. Better than any BM scheme employing a HP on the mains and redirection of those signals to the subs, in my experience.

As for "full range speakers," pretty much by definition nobody can make a reasonably sized speaker that plays at high, uncompress SPL from DC-20kHz. And such a speaker wouldn't even be that useful. So being able to get stupid loud cleanly at 40-50 Hz - which the sealed B&C woofers in his Abbey and Summa certainly should be able to do! - is certainly close enough.


While I won't presume to know what's going on in his head, isn't any theory by definition a "work in progress." When it's no longer such it becomes a law.


I'll pile mine on top of that.


Most people claim that higher-order distortion is way more audibly deleterious than 2d order.

Well, if true, there's your difference. An IB uses so little power (nowhere near the thermal max) that you don't need that extra 10dB of headroom. You can design based on excursion and not worry about thermal compression.

That said, I haven't measured it so it's just a theory. But I've noted that more efficient speakers, like those with big pro woofers, seem to play loud with a certain subjective ease compared to their less efficient counterparts. I suspect but can't prove that the same applies to subs. STEPS (part of ARTA) lets you run sweeps with increasing power levels so it would be pretty easy to show where compression sets in. Dan Wiggins used to do curves like that with his drivers as well.

Which means Dr Earl Geddes theories are not applicable to 90+% of people on planet Earth since I think it's reasonable to assume that 90+% of people on planet Earth don't own sealed main speakers.


That idea just sounds barbaric. You are needlessly increasing distortion by using the LFE+main, whether your mains could handle it or not, since an argument could be made that the speakers would be better off without it.


Claiming a speaker is 'full range' which hits down to 50 Hz is simply asinine for so many different reasons. You literally have to redefine the word 'full range' to such an extent that it loses all meaning and value. Even if you don't agree that 'full range' encapsulates LF content down to 20 Hz (and below), you have to at least agree that 'full range' is whatever content is covered by speakers set to 'large', and that is anywhere from 5 Hz to 20 kHz. Obviously the Summa can't handle that, and it certainly isn't 'full range' by most peoples definitions, therefore it isn't 'full range' by most peoples definitions. Only Dr Earl Geddes will claim that his pro-audio speakers are full range which is a contradictory claim in and of itself.


Of course it would be ! The more sources of low frequency reproduction the better, remember ? That was Dr Geddes mantra. His slogan. His signature. The more LF sources you have in a room, the smoother the response will inevitably be.

However, I agree with you that a 'full range' speaker would be useless.....for HT applications if you use several dedicated subwoofers, since the same speaker would be better off having it's LF capability nuked and high passed to a capable subwoofer that could handle such levels with lower overall compression and at higher overall levels.


I don't agree that the 'Summa' can play stupid loud at 40-50 Hz. I would say that the lower limit would be 50 Hz and then, like all sealed designs, act like a high-pass filter below resonance, so 12 dB/per octave below 50 Hz baby ! And the Abbey is less capable than the Summa, so I wouldn't expect great LF response or capability down low. I would expect impressive mid-to-upper bass impact but for a design like the Abbey and Summa, that's par for the course.

I'm always around.

This is an interesting thread.

Excellent point ! Thermal compression. The bane of all small sealed boxes (unless, of course, you attach a refridgerator to it). Now the real question is, how much of an impact would this have on audibility...at lower levels. Seems kind of contradictory, since in order for there to be compression, you have to reach a compression state.

Another thing I've thought about lately is whether the lack of resistance acting upon the woofers mechanical suspension would have major audible benefits. It might. Who knows.

The only company I know of that talks about the effects a box has in a sealed design is Rythmik. You can find their article addressing it here.

You mean "Air Spring Distortion"? I remember a huge discussion about that about a year ago. IIRC, Bosso brought it up and I thought Ilkka did some tests on that.... hmmm...

http://www.hometheatershack.com/foru...cial-test.html