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post #1 of 6 Old 11-21-2007, 06:42 AM - Thread Starter
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[ This is a split-off of the thread "DSP Best Practices" which is a continuation of the really interesting "Double Bass Array" (DBA) discussion which catapult (thanks!!) began here .]

So is the Double Bass Array the Magic Bullet, the ultimate secret to achieving ruler-flat subwoofer room response? I am finishing a round of simulations using a conventional image source modeler that I recently wrote, but which I modified to handle the out-of-phase pressure plus time delays required for the DBA. The answer so far is "no" . However, my impression is that it is about as good as what would typically be achieved by a first pass of parametric equalization.

The frequency resolution I am using (raw FFTs, no smoothing or windowing) is about 1 Hz. For my tests so far, using a fairly "live" simulated room (uniform absorption coefficient of 0.2), the data shows roughly a +/- 5 dB variation. This variation is, however, relatively slowly changing with frequency, and modal resonance appears to be controlled. Smoothed to 1/3 or 1/6 octave, this would look quite good.

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post #2 of 6 Old 11-21-2007, 09:35 AM
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Thanks for starting the thread it will be interesting to see how this works.

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post #3 of 6 Old 11-21-2007, 10:43 AM
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Hey Terry,

Thanks for running the sims. I don't know if it will help the response any but Nils noted you need to reduce the amplitude of the rear array a bit if the room is at all absorbent. That said, if it can get rid of the deep nulls, I'd think some gentle EQ should be able to take care of the wiggles in the response over a fairly large seating area.

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post #4 of 6 Old 11-21-2007, 11:06 AM - Thread Starter
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I am just playing with that parameter now. When the rear sub cancelation is too high, you can actually see one or more rear sub peaks cut into the overall response to make dips. Reducing the rear sub pressure from -1 to -0.7 seems to help for this simulated room.

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post #5 of 6 Old 11-21-2007, 12:01 PM
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I am interested more in the expanded seating area of similar response. On my todo list to model it - I did go DOH! and figure it out...
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post #6 of 6 Old 11-21-2007, 02:58 PM
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Here's a link to Nils' post where he measured at different distances. His thread was what got me interested in this stuff (thanks Nils!). Click the link at the top of his post to see the whole thread.

http://www.avsforum.com/avs-vb/showp...1&postcount=76

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