Group Delay?

Ignite · 29th October 2001, 06:14 AM

I'm considering the design of subwoofer for the mini home theatre in my bedroom area. I want the lowest bass possible in a 2-3cu ft max enclosure. The obvious choice here is the ACI SV10, as it has a huge xmax and doesn't need a lot of enclosure volume to play deep. In a ported enclosure of 2 cu ft with an Fb of 21Hz it plays impressively deep with an F3 of about 23Hz.

_BUT_ group delay reaches around 25ms at 20Hz in that alignment. Will this result in noticably 'loose' bass?

[Edited by Ignite on 10-29-2001 at 05:29 PM]

Super · 29th October 2001, 07:50 PM

I believe that the Shiva drivers can be used in enclosures almost as small as 1 cu foot. Also have a look at Dayton's Titanic series of drivers. They have good output in relatively small sealed enclosures.

ThomasW · 29th October 2001, 11:29 PM

There considerable disagreement regarding how audible bass GD is. It seems pretty safe that say that 25ms won't be audible at 20Hz.

dufre · 8th November 2001, 08:29 AM

I think it is noticeable. 25ms delay means it sounds as if the speakers should be 340*0.025=8.5m moved to the back. 25ms is 180 degress for 20Hz, which is surely audible. It also depends on the top frequency of the sub.

AudioFreak · 12th November 2001, 10:47 AM

I too face this problem .... given the wild phase changes and group delays of a ported enclosure, would it be possible to make some kind of parametric EQ that could cancel most of this out?

Ignite · 13th November 2001, 04:29 AM

Perhaps, but probably not.
The only way to eliminate group delay is to change the timing of output at certain frequencies... something I have never heard of being done aside from per-driver timing.

I've opted for the design I was talking about to have a sealed enclosure and equalize for deeper bass.

ThomasW · 13th November 2001, 05:52 AM

For those desiring more info on the GD topic here are a couple of references

Blauert, J. and Laws, P "Group Delay Distortions in Electroacoustical Systems"
Journal of the Acoustical Society of America
Volume 63, Number 5, pp. 1478-1483 (May 1978)

"The Differential Time-Delay Distortion and Differential Phase-Shift Distortion as Measures of Phase Linearity" by Marshall Leach,
JAES, Vol. 37, No.9, September 1989

29th October 2001, 07:50 PM	#2
Super diyAudio Member Join Date: May 2001 Location: Connecticut	I believe that the Shiva drivers can be used in enclosures almost as small as 1 cu foot. Also have a look at Dayton's Titanic series of drivers. They have good output in relatively small sealed enclosures. __________________ Bryan

8th November 2001, 08:29 AM	#4
dufre diyAudio Member Join Date: Oct 2001 Location: Netherlands	I think it is noticeable. 25ms delay means it sounds as if the speakers should be 340*0.025=8.5m moved to the back. 25ms is 180 degress for 20Hz, which is surely audible. It also depends on the top frequency of the sub. __________________ DuFré

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29th October 2001, 06:14 AM	#1
Ignite diyAudio Member Join Date: Jul 2001 Location: Toronto, Ontario, Canada	I'm considering the design of subwoofer for the mini home theatre in my bedroom area. I want the lowest bass possible in a 2-3cu ft max enclosure. The obvious choice here is the ACI SV10, as it has a huge xmax and doesn't need a lot of enclosure volume to play deep. In a ported enclosure of 2 cu ft with an Fb of 21Hz it plays impressively deep with an F3 of about 23Hz. _BUT_ group delay reaches around 25ms at 20Hz in that alignment. Will this result in noticably 'loose' bass? [Edited by Ignite on 10-29-2001 at 05:29 PM]

29th October 2001, 11:29 PM	#3
ThomasW diyAudio Member Join Date: Oct 2001 Location: 5280'	There considerable disagreement regarding how audible bass GD is. It seems pretty safe that say that 25ms won't be audible at 20Hz.

12th November 2001, 10:47 AM	#5
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	I too face this problem .... given the wild phase changes and group delays of a ported enclosure, would it be possible to make some kind of parametric EQ that could cancel most of this out?

13th November 2001, 04:29 AM	#6
Ignite diyAudio Member Join Date: Jul 2001 Location: Toronto, Ontario, Canada	Perhaps, but probably not. The only way to eliminate group delay is to change the timing of output at certain frequencies... something I have never heard of being done aside from per-driver timing. I've opted for the design I was talking about to have a sealed enclosure and equalize for deeper bass.

13th November 2001, 05:52 AM	#7
ThomasW diyAudio Member Join Date: Oct 2001 Location: 5280'	For those desiring more info on the GD topic here are a couple of references Blauert, J. and Laws, P "Group Delay Distortions in Electroacoustical Systems" Journal of the Acoustical Society of America Volume 63, Number 5, pp. 1478-1483 (May 1978) "The Differential Time-Delay Distortion and Differential Phase-Shift Distortion as Measures of Phase Linearity" by Marshall Leach, JAES, Vol. 37, No.9, September 1989

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