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I need to reduce some nulls and peaks in my basement home theater. The room is an l-shaped room with an open stair to the rest of the house (cannot be closed off). I have my sub and speakers optimized after 8-10 hours of trial and error. Seriously, 8-10 hours, moved a few inches, measured, over and over. This is the best location without any absorbing/trapping material.

It certainly isn't optimal in terms of looks, but it is optimized so I can see the screen and not have speakers in the way. I can also still get to the kegerator, which is key.

17' on the theater screen wall, 24' on the inside wall (right from seating), outside sections are 12' each with the l portion being 6' deep (leaving the back wall, from seating position 11' wide).

The main areas I am concerned about are a dip about 35 hz and 61.3 and the corresponding peaks around those dips. Smacks of room modes, but with the shape.. There is no way to get around all of the nodes in terms of placement, though they are minimized.

So far I have some old DIY tube traps (fiberglass I compressed and put around a round frame) and some other absorbent material in the corner and on the wall where I measured peaks. With 4 20" tubes it made about 3-5db difference depending on what frequency I was measuring. Nowhere near enough, I need much more absorption and around specific frequencies.

So the question is what next? I can sacrifice about 2' of the room where the sound peaks at the exact nulls. Membrane/panel resonators? Just go for very deep broadband absorbers?
 

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Broadband absorbers are most effective above 100 Hz. Although they absorb below this frequency, their efficiency drops off quickly.

I have spent a lot of time searching and there does not seem to be a lot of practical information on panel resonators. It seems not a lot of people use them. I gather that they are not as efficient as other absorbers, but there is not complete agreement on this. Unfortunately, I have not been able to find anything that quantifies relative efficiency. The nagging question in my mind is how many of these might be needed to be effective for a given frequency band.

If you go to johnlsayers.com and search on their studio design forum, you will find some good threads on panel resonators.
 

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Above about 35Hz, your decay times look pretty good. You could certainly build some resonant panel type absorbers tuned around the 120hz issue if you know where in the room is causing the problem.

Bryan
 
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