There is no ringing.
That still seems one of these very deep fairy tails in audio land.
An high Q results in a peak in the frequency response.
So theoretically speaking, an higher Q speaker doesn't have to be worse in performance.
Practically speaking, woofers with a lower Q usually have a better motor system (not always true, but very often it is).
Also are much more efficient, need a lot less power, especially when actively corrected in the same enclose.
Best is to just simulate the speakers, unfortunately the newer version of WinISD has some very major bugs when it comes down to active filters, so I would recommend the older Alpha version.
Just simulate the woofers in the same enclosure volume, with a (4th order LR) lowpass on a certain frequency (80Hz or so), Linkwitz-transform at a certain parameter (eg. 30Hz, Q=0.707) and a 2nd order Butterworth at the same frequency (together they form a LR roll-off!!).
Next go to excursion and max them almost out, go to SPL graph to level them at same SPL level.
Keep on eye on excursion so one of them doesn't go over xmax.
Last, look at the power graph.
None of that matters (not none, output capability matters a lot!) if you are going to EQ each sub. Not Q, not Fs, it all gets swamped out by the other subs and the room. It's the final EQ that matters.
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A Q of 0.9 doesn't have any ringing in the time domain ? Back to the text books for you for a catch up...
Whether that's audible at bass frequencies is another matter entirely since the Q's of room modes are far worse.
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Yes an high Q will give a lot of so called shoot through.
Which results in a peak in the frequency response.
I guess you could call it ringing.
In terms of an oscillator a Q of 1 is still extremely poor.
I already said that before?
But not like the ringing people usually think of when they talk about it.
Which results in a peak in the frequency response.
I guess you could call it ringing.
In terms of an oscillator a Q of 1 is still extremely poor.
I already said that before?
But not like the ringing people usually think of when they talk about it.
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Thank you
That's very interesting, that all the little things that a lot of people worry about - me included, simply downs in the total "chaos" of sound that is going on at low frequencies - so that only the final sum of sound really matters - all individual sound sources "simply" needs to be within their limits of operation 
I always thought of ringing as a continued sound - like an echo. But as I understood it, ringing will be less, if you use EQ to reduce the problematic frequency area. BUT - nothing will be less "ringing" than the room itself - where only bass-absorbers of a rather huge size is needed to really obtain fewer peaks and dips - acoustical problems needs to be solved with acoustical solutions.
If the Q is high enough, it will.
With smaller Q's not so much, and from 0.707 and below there is no "ringing"
This can be seen in the group delay as well.
But it is the in-room response that matters in the end, right?
Thank you
I am glad that you follow, many just can't get past this idea.
Well, yes
But a tiny bit no. More from a practical sense.
You also want to make sure that the woofer can handle it.
Plus there needs to be an amplifier that can deliver the power.
So, a bit of care always has to be taken.
Again, depending on SPL's and lowest frequency.
Also, even in a multi-sub setting, the roll-off is not really being affected.
In general it is mostly just playing with delays and phase between all the different subs.
Crazy EQ'ing, especially boosting is not really advisable.
In general I like to use a LR roll-off (Q = 0.5) to get a nice transition with the room-gain and to prevent the sub of going to its limits when those lower notes are being played.
Why is that? If the subs can handle it? Which we both agree they should. With five pro subs (in my case) that's not an issue.
Seen from the subwoofer itself:
3dB extra boost costs already twice the power.
So it goes up rapidly. Same for excursion.
I am just saying that one really needs to take that into consideration when designing a subwoofer.
From an acoustic point of view:
In general just adding delays/phase shifts will in most cases be enough to get the response smooth.
Keep in mind that room modes are a result of basically relative phase between the subs (and the room)
So a dip will always be a dip, no matter how much you boost that particular frequency.
In general (parametric) EQ'ing only fixes the frequency peaks and dips, but doesn't fixes the time domain issues. Standing waves resonate, a lot!
Said in simple words, they take time which can be audible even when EQ'ed.
That being said, a notch standing wave peak is still better than non-notched one.
Anyway, there are (free) programs these days to calculate that for you.
But in general, the whole multi-sub magic lays in the fact of delays and phase shifts (between the subs/sources vs room)
Very little in EQ'ing.
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Just to be clear, I don't use delay or phase (except for polarity) in my setups, it's all EQ.
And "room modes" are not "a result of basically relative phase between the subs (and the room)" They exist with no subs present at all.
A true null cannot be EQ'd that is correct, but since no room is without damping, there are no "true nulls" in a damped room and they can be eq'd flat, although sometimes this is impractical because of headroom, but in theory it is always possible.
If I " fix the frequency peaks and dips" then I simultaneously "fix the time domain issues" - this is a fundamental aspect of the Fourier transform.
"Free programs" that calculate this (the modal response) are all incorrect. I could show you why this is true, but the math is rather complex and if you don't understand the Fourier transform, then you wouldn't follow my explanation.
I think that you need to do a little more study before you make such rash comments.
And "room modes" are not "a result of basically relative phase between the subs (and the room)" They exist with no subs present at all.
A true null cannot be EQ'd that is correct, but since no room is without damping, there are no "true nulls" in a damped room and they can be eq'd flat, although sometimes this is impractical because of headroom, but in theory it is always possible.
If I " fix the frequency peaks and dips" then I simultaneously "fix the time domain issues" - this is a fundamental aspect of the Fourier transform.
"Free programs" that calculate this (the modal response) are all incorrect. I could show you why this is true, but the math is rather complex and if you don't understand the Fourier transform, then you wouldn't follow my explanation.
I think that you need to do a little more study before you make such rash comments.
I'm starting to. But I do understand why it can be tricky for many people to accept that the so called quality of the speakers, like Q=0,6 vs Q=0,9 matters much less than the sum of the total combined output. It's like I'm still chasing the same principles that I use above 500hz, to gain sound quality beneath a 100hz - thinking that they are the same somehow - when in fact - my ears won't be able to distinct the same audio qualities throughout the entire audio spectrum. And as you pointed out most of the time - you go for the tools that gets the job done - not what sells the best or creates the best story
Maybe you should than start a comedy show as well, you're very funny.
Don't really appreciate these kind of comments at all actually, seem to be sometimes a standard thing on these kind of forums, really sad.
Not very scientific pretty disrespectful even, more over everything expect constructive.
I speak on behalf of many. It's a general statement btw.
But I see it quite often.
back on topic, hopefully we can stay on the subject and stay constructive.
I am actually more than surprised about your comment.
The whole point of a multi-sub system IS delays (phase) between different subwoofers (aka sources) in a given space.
And no, obviously I am not talking about just the room, but the interaction between the subwoofers themselves inside a room. (the space)
I never said that room modes are a result of delay.
Since you're so keen on math yourself, this can even shown in a very simple two dimensional case.
Obviously a three dimensional case is an awful lot more complex, but the same fundamentals apply.
But for that there are simulation programs out there.
There used to be a very very great one here on the forum, unfortunately it doesn't seem to work anymore
Also, to bring you up to speed, have a read an try on this;
Multiple Subwoofers: Optimize Them With Multi-Sub Optimizer Software
Verified and tested by many works absolutely awesome, 100% free.
Anyway, yes, in the end there is always some EQ'ing needed, since one can only do so much with delays.
The whole point is, is that delays are a fundamental parameter of the whole muti-sub approach.
Denying that also tells me one needs to refresh his mind on the matter.
In fact, it's part of fundamental acoustics and how waves interact with each other (which is by definition phase aka delay)
Used to be a main part of my study in physics, so yes I think I know a thing or two about what acoustic waves do and how they interact with each other.
Earl - can you please offer a few thoughts on the "Toole Critique" which says rooms have their enduring characteristics and humans accommodate/adjust/normalize to the sound of human and mechanical "speakers" in a room (perhaps after a learning period).
In his view, it is important to use a speaker which is produced to be capable of delivering "flat-like"* sound to the room (perhaps after EQ of the speaker... mechanical speakers only, of course) if not exactly flat-like to the listener's chair.
Thanks.
B.
* by flat-like, I mean which humans sense as flat. That's not accurately predictable from physical principles.
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I agree with this 100% and have made this same point elsewhere. We do acclimate to what we listen to and as such if what we listen to is flawed then we come to accept this as correct. That is why, IMO (as well as Floyd's) one absolutely has to have "flat-like" speakers as a reference or we risk making false judgements.
Thanks for helpful thoughts.
I'd only add that in psychology, sense adaptation results in a new norm (like when you are in a room with yellow lamps for a while). But not wrong to say "correct" in common parlance.
I'm not sure if you carry the new norm around to other rooms. My music room is full of old fashioned damping stuff. So any HiFi I hear in a modernly furnished room sounds bright.
B.
I'd only add that in psychology, sense adaptation results in a new norm (like when you are in a room with yellow lamps for a while). But not wrong to say "correct" in common parlance.
I'm not sure if you carry the new norm around to other rooms. My music room is full of old fashioned damping stuff. So any HiFi I hear in a modernly furnished room sounds bright.
B.