No problem at all, unless you're shooting for as close to perfection as possible.
Have you compared the same sub driver in sealed and vented boxes, where the response of the vented gets matched by the sealed using EQ's or a Linkwitz transform? When I do that carefully outdoors with proper ground plane measurements, the transfer functions look much more similar than not.
Bottom line imo, is both vented subs and EQing sealed subs to an equivalent response lead to same end, an extra two orders of so of phase rotation / group delay, vs straight sealed.
May I ask why you prefer sealed?
I think there is a growing awareness of the likelihood that phase /group delay is audible at lower frequencies.
(What happens in a room is immaterial to the question of phase audibility imnsho)
How audible, and in what situations, I have no clue. Although I hope to convert six 18" subs from vented duty to sealed, to set up outdoors for my best test yet. I do know that careful time/phase alignment across the board, including as low as possible, is yielding truly marvelous results (to my ears)
I also share John Meyer's philosophy of trying to be as technically correct as possible, whether doing so appears to be audible or not.
I think as transducers, processing, and speaker technology continues to improve, we may find out so does our hearing . 😉
(headphones are not a suitable evaluation method of phase audibility imo)
Remember when it was widely taught in school that the human eye could only resolve a bit over 200 lines-per-inch?
Funny how it eventually turned out, that the visual limitation was that our printing technology hadn't able to produce clear resolution over 200 lpi....
Hi, did you not get I advocate using enough sealed so that you don't have distortion? (something i think most folks don't do)
Im afraid i missed this part, sorry.
i wish someone would answer my question:
if you consider group delay audible. Would a better room make group delay more or less obvious?
Edit: i try to find decent comparisons between sealed vs BR. Anyone know a good test that was made? Comparing the same driver in the same cabinet but only change from sealed to BR.
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No worries.
I'd suggest no room, to make it more or less obvious. Iow, outdoors.
If you can't hear a difference outdoors with whatever comparisons you're making, I call it inaudible.
If you can hear a difference outdoors, it trains the ears what to listen for indoors, ime.
The challenge is to find a suitable woofer with the right parameters for 'vented sub bass' of the highest level.
That's why people like Jürgen Strauss and Karl-Heinz Fink decided to design their own woofers.
The moment low extension down to ± 35 Hz is sufficient (enough for 95% of all music), the choice for suitable woofers also increases.
The big deal breaker is excursion. Once excursion can be minimized, you kill a lot of birds with one stone.
My personal objectives may be different from the average reader of this thread. I mainly strive for 'realism' (credibility) and 'natural sound' in the reproduction. As a result, I have become critical of the general tendency to view audio from a strictly technology/science/measurement driven approach.
At the same time, knowledge of these fields is necessary to be able to assess what really matters.
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Thats also my instinct
have you seen some comparison between sealed vs br using same driver and same size cab In a “perfect” room?
have you tried outside yourself?
following this, i really wonder how good a room has to be to start making group delay audible at LF
then i wonder about the trade offs, along the limitations of a seal system to go as low as a bass reflex…
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I did just mention the 20hztuned BR.....There is also the option of using dampening to get to desired tuning and lower Q..... GM, you are going to have give a better description than that link if I am to learn from you how to actually achieve Critical Q with a BR....Seems that all we have to do is achieve a certain roll off character.
OK I read it again, well played......wellll played. Just to make sure I'll ask, I am correct on reverse engineering through roll off character lol.....0.5Q 2nd order low pass something like that, please advise lol!!
This is a good philosophy when there is doubt. Definitely some grey areas about what is technically correct... IR quality, seems to be an ok choice.
I think there is a cheat code for this as well.... Isobaric loading....I think that The amplitude vs GD audibility topic is a tell....BL is suffering against the pressure of the harmonics of the vent, at higher volumes. My guess
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Hi mark100,
As best as I understand it, the maximum SPL from a sealed box arrangement is limited by the design parameters, i.e., the Vb and the driver's excursion, which, for the example below, happens at input power Pi=30W:
Are you saying that if one were satisfied with, e.g., SPL=105db, dow to 40Hz, which requires Pi=5W to about 100Hz and then used equalization, e.g., Linkwitz transform, to increase the power between 40Hz - 100Hz to achieve the required SPL at these frequencies:
the group delay would increase form the case above?
Regretfully, to my knowledge, although UniBox does have means to implement the equalization, it does not show group delay.
Kindest regards,
M
Can you please explain this in greater detail?
As best as I understand it, the maximum SPL from a sealed box arrangement is limited by the design parameters, i.e., the Vb and the driver's excursion, which, for the example below, happens at input power Pi=30W:
Are you saying that if one were satisfied with, e.g., SPL=105db, dow to 40Hz, which requires Pi=5W to about 100Hz and then used equalization, e.g., Linkwitz transform, to increase the power between 40Hz - 100Hz to achieve the required SPL at these frequencies:
the group delay would increase form the case above?
Regretfully, to my knowledge, although UniBox does have means to implement the equalization, it does not show group delay.
Kindest regards,
M
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Didn't you leave out the excursion null, and increase in efficiency at tuning? I guess if you are going to increase radiation area, until excursion is gone, then you don't care.
No, GD is more or less fixed around 5ms for suitable 15" drivers (quick & dirty sim of the 515B attached).
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Hi Ro808,
thank you for the reply.
What application are you using for the simulation?
Kindest regards,
M
thank you for the reply.
I am not sure how I am to understand the group delay (GD) graph. Is the GD shown for the non-equalized case or equalized case? If so, should you not show the other case to prove your point?
What application are you using for the simulation?
Kindest regards,
M
I was suggesting that if you measure the same peak levels in your home as the front row of Imax, you will feel similar visceral impact.
I suspect the reason you are not feeling the same impact at home is simply because your front loaded sealed drivers aren't putting out near that level, as is obvious by their displacement limitations. The Imax woofer system probably has at least 10dB more peak level potential.
This does not take pages of discussion or hours in the theater to verify, you have the SLM, either it reads 123.4 dB peak at home or it reads less.
Down in the 30 Hz range, -5dB will probably seem like about half the subjective impact. If your drivers can't put that out at 1meter, than no doubt the Imax is going to have left you more impressed.
At any rate, when your eyeballs rotate in their sockets with each impact, it's not something you are likely to forget, regardless of what your SLM reads.
Here's the B&C 15TBX100 in the same cab. Note the power requirement compared to the Altec.
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App is VituixCAD.
Correction: GD is more or less fixed between 5ms and 10ms for suitable 15" drivers in the case of non-equalized sealed cabs.
The perceptibility of GD below 50 Hz is debatable.
Correction: GD is more or less fixed between 5ms and 10ms for suitable 15" drivers in the case of non-equalized sealed cabs.
The perceptibility of GD below 50 Hz is debatable.
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Hi Ro808,
thank you for the reply.
I will experiment with VituixCAD.
Kindest regards,
M
thank you for the reply.
Yes, but my inquiry was whether the equalization will (significantly) change the GD. It seems plausible that it will change it somehow, after all, it is a filter. But, the question is how much and whether it can be perceived. If the change is significant, an equalization filter could be designed to correct the GD.
I will experiment with VituixCAD.
Kindest regards,
M
This is the part that is confusing and it is important to be clear about what the EQ is doing as that will make a big difference. EQ does not have to equal a change in slope.
You absolutely can EQ a sealed box and maintain the sealed boxes natural 12dB per octave roll off, it will limit the maximum SPL and use more power and excursion to get there.
You can also EQ the sealed box the resemble a vented one pushing the F3 down lower but rolling off at 24dB/oct below it.
You can EQ to follow the sealed response in the initial roll off and then get steeper lower down, or anything else that takes your fancy.
I think you are mainly advocating for good acoustic design by choosing the right drivers to work in the box type you want because not every driver will give a good response in a sealed box without EQ.
The only way it will significantly change the group delay is if the roll off slope is made much steeper.
Hi fluid,
thank you for the reply.
Kindest regards,
thank you for the reply.
Well, if I recall correctly, the equalization, e.g., Linkwitz transform, actually decreases the roll-off slope. Hence my initial question to mark100.
Kindest regards,
Ultimately the final rate of roll off is the same 12dB/oct but it can be pushed so low that it is hard to see in graphs.
From the man himself,
"A majority of drivers exhibit second order highpass behavior because they consist of mechanical mass-compliance-damping systems. They are described by a pair of zeroes at the s-plane origin and a pair of complex poles with a location defined by Fs and Qt. The circuit above allows to place a pair of complex zeroes (Fz, Qz) on top of the pole pair to exactly compensate their effect. A new pair of poles (Fp, Qp) can then be placed at a lower or a higher frequency to obtain a different, more desirable frequency response."
Hi fluid,
thank you for the reply.
In any event, the question for mark100 stays.
Kindest regards,
M
thank you for the reply.
Ah, that is a great description. So the transform is essentially cancelling the original pair of poles, and substituting new pair of poles. However, the original zeros are left unaffected; the equalization curve raises (albeit eventually to a limit), so the resulting equalized curve should be less steep, although perhaps not appreciably so.
In any event, the question for mark100 stays.
Kindest regards,
M