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Here's what I did for the front stage. Naturally, I have covered the "L" brackets with trim to hide them, but the sketch is cleaner without that shown.

If at all possible, try to avoid this kind of step around the speaker - install them flush with the wall or free-standing in front of it. Anything else will result in a very lumpy frequency response, even a gap has bad effects.

Frank
 

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I have intentionally drafted the front face of the speaker at 10 degrees off normal, and added 1 3/8" rounded corners to avoid this. The added depth shouldn't take anything away from the compromises that have already been made, and compensated for.
Not to be argumentative, but you're thinking of the wrong effect and have not compensated for wall spacing. This is a wave interference effect.

The reflection from the wall next to the speaker will be out of phase at some frequency, so you'll get a dip in frequency response. In round numbers, 1 Hz has a 231.5 ft. 1/4 wavelength. If a speaker is 1 foot from the wall, you'll see a dip at 231Hz. Yours profile looks like this on one side and bit more on the other, so the first peak will be in this range toward the center and a bit lower outboard. 1/2 wave differences come in as peaks, starting at twice this frequency. About the only thing you can do accoustically is to damp the reflection; front wall damping nearly always sounds good.

Frank

Ps Floyd Toole's book, Sound Reproduction goes into what's happening in detail. It should be required reading for any one doing their own home theater IMO.
 

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I'm not at the North Pole, I just did the math in my head... poorly.

You're right about standing waves resonating at 1/2 WL, but this isn't a resonance I'm talking about but rather a wall reflection.

Speakers mounted on a wall experience destructive interference starting at frequencies whose wavelengths are 1/4 the distance from speaker to wall (and harmonics at (2n+1)/4). Since the distance is traversed twice, you get the 1/2 wave required for destructive interference.

I wanted to be sure the OP was aware of this phenomenon. It appears he is and has made the tradeoff consciously, which was my only goal.

Frank
 
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