Fastest Subs?

dallasjustice

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Apr 12, 2011
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I am planning on adding a pair of subs to my room.(front/back walls axial modes) I will have them professionally calibrated/installed. Everything will be done inside Jriver and out an Lynx AES16 (crossover, delay etc.), then to multipe DACs with unified digital volume control inside all DACs.

I am told that so called "group delay" can be audible at lower frequencies; below 50hz. If that's really true, then it seems to me that one of the specs that would matter most would be lowest group delay (fastests subs; cringe Nyal :) Are there any valid measurements available that compare group delay? I am considering JL Audio, Velodyne and Procella. I am also interested to know how DSP on the sub affects group delay (eg. Low pass filter) and whether some subs allow the user to defeat said dsp so as to "speed" the sub up.
 

RBFC

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Apr 20, 2010
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I spent a lot of time with Barry Ober of JL Audio discussing this. He prefers to compensate for group delay by using the "distance" adjustments in your processor, which is essentially a certain number of milliseconds delay on the selected channel. I'm sure you can compensate at least as precisely, probably more, with your setup. Steve, I, and many others have been happy with JL products.

Let me know when they're going to dig the tunnel for your TRW!

Lee
 

dallasjustice

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Lee,
Maybe I need to revise and extend my remarks concerning group delay. I will easily be able to delay my main left and right in jriver to achieve perfect time coherence at the crossover frequency. However, all sub manufacturers use DSP to achieve linearity at the lower frequencies; eg. 18hz. My understanding is that the greater the DSP applied inside the sub, the longer the delay. So I might be able to achieve linearity but not time coherence all the way down to the lowest frequencies. Now, somebody is going to chime in and say something like, "but you can't hear that." I am not interested in debating what can be heard. I just want to know more about group delay specs and whether anyone can point me to reliable measurements in this realm. I know the use of the word "fast" would invite the panoply of subjective impressions. I am not really interested in that. I'll take the blame for using that word. :)
I spent a lot of time with Barry Ober of JL Audio discussing this. He prefers to compensate for group delay by using the "distance" adjustments in your processor, which is essentially a certain number of milliseconds delay on the selected channel. I'm sure you can compensate at least as precisely, probably more, with your setup. Steve, I, and many others have been happy with JL products.

Let me know when they're going to dig the tunnel for your TRW!

Lee
 
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microstrip

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May 30, 2010
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Lowest group delay below 50hz.

Perhaps I am being naive, but my idea is that if you consider it important you should want to have the same group delay as your main speakers at crossover frequency, not the lowest. Or are you addressing the variation of group delay along the bandpass of the subwoofer?
 

mojave

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Data-Bass.com has group delay info on about 50 subwoofers. Click a subwoofer, measurements, and then the static graph tab. Here is the group delay for a Velodyne DD18+:



There are measurements for about 50 subs at hometheatershack.com. Here is the JL Audio F113. You can see that it has more distortion than some other subs. Here is the group delay graph:



Like you mentioned, any EQ done to smooth the frequency response will change the group delay. Most commercial subs will have higher group delay than the DIY subs since the commercial subs have some EQ applied in the amplifier. However, a higher group delay isn't indicative of "more DSP" being applied. The room's affect on frequency response will change the group delay at the listening position more than anything else.
 

dallasjustice

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Data-Bass.com has group delay info on about 50 subwoofers. Click a subwoofer, measurements, and then the static graph tab. Here is the group delay for a Velodyne DD18+:



There are measurements for about 50 subs at hometheatershack.com. Here is the JL Audio F113. You can see that it has more distortion than some other subs. Here is the group delay graph:



Like you mentioned, any EQ done to smooth the frequency response will change the group delay. Most commercial subs will have higher group delay than the DIY subs since the commercial subs have some EQ applied in the amplifier. However, a higher group delay isn't indicative of "more DSP" being applied. The room's affect on frequency response will change the group delay at the listening position more than anything else.
This is awesome! Thanks.

From the looks of these charts, the Velodyne is more accurate in the time domain than the JL down to 20hz?
 

dallasjustice

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So, less group delay could also be achieved by using a sub that has no DSP. For example, could I DSP on the computer for the sub using Audiolense FIR filters?
 

LL21

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Hi Dallas,

You've got a great system, and I've enjoyed watching it evolve. I use a Velodyne DD18 in parallel with my X1s, and have compared it with the newer DD18+. The DD18+ is much more powerful and incredibly tight. I have used a Velodyne in parallel with all my systems going back to 1993.

What I have liked about the Velodyne is its adjustability...hi and lo Passover, plus 8-section EQ for individual boosting/lowering of any frequency from sub 20-120...phase, and all manner of other things...all on 2 screens which, once u get the hang of it, takes a few minutes to tweak each time you make other changes in the system. Also, it saves 7 different settings if you want to have different settings for some reason. Personally, I use 2 settings only...one for audio and one for movie soundtracks...I tend to find raising the crossover a bit (from 40hz to about 55-60hz) and boosting volume of sub by 20% tends to add more visceral impact for bullets and explosions without feeling much 'bass bloat or bleed'.

I've not compared with any other subs...but the proper dial-in/adjustability i am told is half the battle in subs, and I have had such good experience with the Velodynes I just keep getting them.

For all-out assault, I suppose i would also consider the Parasound Sub 2 which Jeff Fritz reviewed so positively after having the JL Gotham 213 in his system (which is the other one I would consider). Our gracious site founder could speak to JL subs well no doubt. And of course there is 2-3 subs vs just one depending on your available floor space and desire to have to set up 2-3 subs. good luck.
 

DonH50

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I use Rythmik and like their sound. I suspect most AVRs would have little problem compensating for the delay in most subs unless something is really strange about your setup.

Perfectly linear phase leads to constant group delay and that provides the best pulse (time domain) response. Frankly, that would be near the bottom of my list of criteria for a subwoofer given the frequencies involved.

Where delay matters is at the crossover point because you want the sound from the sub(s) and other speakers to be in phase and not cancel each other. As you move away from the crossover frequency the sub or mains (depending if you are going up or down in frequency) contribute less and phase matching ceases to matter.

All IMO, usual disclaimers apply - Don

Edit: Steve, I doubt anyone would hear non-constant group delay, especially in a sub. If the delay/phase is not right (in phase) you will get a "hole" or "suckout" at the crossover frequency to the extent the sound from the subs and mains cancels.
 

dallasjustice

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And of course there is 2-3 subs vs just one depending on your available floor space and desire to have to set up 2-3 subs. good luck.
I will have 2 subs; one very close to the frontwall and one very close to the back wall. They will both be run in mono and crossed over at around 50hz. This setup will (1) eliminate all remaining front/back axial modes/nulls (not very much at this point) and (2) extend my system's headroom.
 

sly30

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Jun 18, 2012
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I tested many subs.Most are good to home cinema, not to stereo couse they are too slow!
One is the best and the fastest!!! Wilson Benesch - Torus, it has 2 push pull drivers 16 inches made by carbon.
It is passive so recomended is bass ampilifre by Wilson Benesch but it has no DSP and no remote control.
I use bass amp Velodyne SC-1250 with 7 band DSP and remote kontrol and short, fast speaker cable bi-wire to Torus.
This sub is cheaper than many other top subs and....best of them...in my opinion. Sound great becouse fastest, very deep but a little soft, nice to listening.
 
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Steve Williams

Site Founder, Site Owner, Administrator
Don


I understand that completely. You're preaching to the choir. I agree that you won't hear any difference or won't be able to pick it out.

I ask this only because it took me 3 months to dial in my pair of Gotham subs and now 6-7 weeks dialing in my pair if Fathom subs. I maintain you won't hear the difference
 

dallasjustice

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Steve and Don,
I agree that group delay below the cross-over frequency may not be a top priority issue to sub integration. The very idea of sub "transient" response sounds a little wacky to me as well. But I also want to better understand it and minimize, as much as possible, it's effects before I really get started with this project. I don't really think there's any authoritative evidence one way or the other and I appreciate your experiences.
 

treitz3

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...........I ask this only because it took me 3 months to dial in my pair of Gotham subs and now 6-7 weeks dialing in my pair if Fathom subs. I maintain you won't hear the difference
Between a slow and a fast sub?

Tom
 

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