[QUOTE=naethoven;4282123]
Quote:
By "the listener to sit 12 ft from the back wall" you mean the engineer, not the client, correct?
If so, can you tell me if I'm doing my math right? 38% point puts me 10.22 ft from my back wall. So: 10.22 x 4 = 40.88 ft wavelength, and 1130 / 40.88 = 27.6 Hz
So in that seating position I should be good down to about 28 Hz. Correct?
Just a quick question about this- that's what I've always heard/read, but the other day in Master Handbook of Acoustics he mentions that technically the diagonal is the longest dimension. Which should I use for my math above and for any calculation?
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Yes, you are doing your math right with regards to the back wall null, but there is still the matter of overall control room depth.
Everest is correct technically, but the diagonal of the room has much less surface area to resonate, so the resonance will be much less pronounced. So with all due respect and then some, in my experience, for all practical purposes the knee of the curve will follow the longest axial dimension. Like I said there will be audible sound below that, but it will not be flat. This is related to the reason that one shouldn't give as much weight to tangential modes as one gives to axial modes. They aren't equal in amplitude due to the inequality in resonating surface area.
So your 16.5 deep room will have an effective cutoff frequency of 34 Hz. This is approx. C# below E on the Bass guitar. Not bad, but there are 4 more 1/2 steps on a Steinway, and even more on a Bosendorfer. That's why we go for that 20 ft. depth if there's any way to pull it off. I think it's worth sacrificing your favorite ratio set in favor of your next favorite if it means getting closer to that critical depth.
-Wes