In Reply to: RE: Echo threshold posted by josh358 on August 12, 2010 at 16:29:35:
>Also -- and I'm not sure why you didn't hear this -- the effect of adding diffusion or absorption at the first reflection points.<
As I said, these experiments were without any controls. My speakers are on the long room wall, so maybe the reflection level is already close to audibility threshold so that any additional measure won’t have audible effects.
>I'm particularly puzzled as to why you didn't hear the presence of the doors, assuming they were at the reflection point from the perspective of your listening position.<
I checked the reflection points with a mirror. As far as not hearing the presence of the doors is concerned, any image shift could have been “masked” by localisation blur, the generated comb filters could have been below detection threshold. I’m not generalizing here, but in my case reflections don’t seem to have a detrimental effect.
>I've heard the effects of proximate boundaries many times. For example, console bounce is a common problem when setting up mini monitors.<
If the desktop reflection is the only reflection, which probably is the case for nearfield listening with desktop monitors, one could, in view of the corresponding statements in Salomons’ thesis, expect an audible problem. Genelec probably has taken that particular boundary into account (http://www.aes.org/e-lib/browse.cfm?elib=13683).
>>I don’t know of any research that shows that first reflections affect tonal character and alter imaging, other than corresponding cues being used for determining perception thresholds for the single reflection scenario.<<
>I believe that Haas demonstrated this in 1949.<
I’ve looked at the original paper and the setup Haas was using was two loudspeakers at 45º, half to the left and half to the right, one as direct sound source, the other as source for the single reflection. Both loudspeakers played at the same SPL. Once again, the single source/single reflection scenario. What happens in 2-channel stereo (phantom source, see also http://www.aes.org/e-lib/browse.cfm?elib=12718) with multiple natural reflections, has not yet been thoroughly investigated, to the best of my knowledge that is.
Klaus
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Follow Ups
- RE: Echo threshold - KlausR. 22:03:04 08/20/10 (1)
- RE: Echo threshold - josh358 06:34:16 08/21/10 (0)