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-   -   Group Delay? (http://www.diyaudio.com/forums/multi-way/1007-group-delay.html)

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



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