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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Room Acoustics Technical Question posted by cuallito on September 28, 2022 at 21:43:28:
A real room will not have a cleanly decaying impulse response due to reflections and room modes.
Typically, the problems to treat are:
- Flutter echoes between parallel walls
- Early reflections from the walls and ceiling
- Bass peaks due to room modes
Flutter echoes and early reflections are broad band, and they can be dealt with using absorption, diffusion, or a mix of both. Room modes require absorption, a lot of it, and it should be narrow band.
The benefit of using absorption for flutter echoes reflections is that a relatively thin (2 inches) absorbing panel will be effective over the whole midrange and not just the treble. A diffusor that covers the midrange will be too deep for most people's rooms. The disadvantage of using absorption is that the more you add, the more you reduce the room's reverberation time.
A key metric for assessing the sound of the room is the RT60 vs. frequency curve. RT60 is the rate of decay of the envelope of the impulse response: high RT60 = long decay, low RT60 = short decay. I found it important to measure this as I was adding treatments to my room. Because my initial experiment of putting absorbing panels at every reflection point produced a very clean impulse response tail, but resulted in a dead sounding room.
After a lot more experimentation, I reached the conclusion that the frequency dependence of RT60 matters more than the absolute level. The room sounded worst with a lot of high frequency absorption and minimal low frequency absorption. But it sounded good even with a very low RT60, as long as RT60 was relatively flat vs. frequency. I guess I shouldn't have been surprised, since recording studio control rooms are made like that.
So I think you'll have to experiment and decide for yourself how low you are willing to go in pursuit of the perfect impulse response. If you want to get the best benefit from the least amount of absorption, you really should get yourself a measurement microphone so you can see the effect of a placing treatment on the impulse response.
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Follow Ups
- RE: Room Acoustics Technical Question - Dave_K 06:50:36 09/29/22 (0)
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