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Does a room mode impact distortion?

2K views 5 replies 3 participants last post by  AudiocRaver 
#1 ·
This is the basic response of my sub in room, I have a big mode at 40Hz.

Text Blue Line Plot Slope


I can take that down with a single PEQ filter easily enough and get a response like this

Text Line White Green Plot


If I look at the distortion view at higher output levels, I see this

Text Line Plot Map Diagram


2nd harmonic distortion spikes at 20Hz
3rd harmonic distortion spikes at ~13.3Hz

i.e. the distortion spikes coincide with the room mode

Is it possible to determine if this a measurement artefact or is it "real" distortion? For example, the analysis of the IR that extracts the harmonic distortion can be thrown off the scent by a room mode. If it is a measurement artefact, is there some way I can dial this out through tweaking the analysis parameters?
 
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#6 ·
At very low frequencies, driver and room characteristics can become somewhat interdependent. Room modes correspond to room loading of the subwoofer and driver, so driver excursion and distortion can be affected. At subwoofer frequencies, room modes and distortion can go hand in hand. I am not saying that is what you are seeing, only that it might be.

I am not aware of a way to separate out that effect other than remove the subwoofer from the room and take measurements outside as a reference point. EQ - a high-Q band - might tame such an effect partially, but never as effectively as room treatment.
 
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