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RE: Echo threshold

Posted by KlausR. (A) on August 11, 2010 at 22:35:03

In Reply to: RE: Echo threshold posted by josh358 on August 4, 2010 at 05:59:14:

>>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 don’t have the Haas paper with, so I can’t comment.

>I've noticed three main phenomena as speakers were moved away from room boundaries: changes in the bass and midbass response, clearer sound (correlating to intelligibility), and better (or sometimes just different) imaging (correlating in part to differences in image spread and location).<

When moving the speakers away from room boundaries you are changing several parameters simultaneously (i.e. boundary reinforcement, room mode coupling, delay and possibly spectrum of early reflections, probably also the interaural cross-correlation), so you don’t know for sure that it’s the early reflections that are responsible for the perceived effect. In my experiments I added absorption at lateral reflection locations (Klein+Hummel) and I placed the Genelecs on a table in the middle of a large room, and placed room doors against that table to generate lateral reflections. In the first case reverberation time might have changed slightly due to the absorbers, in the second case the reflections were generated geometrically, hence without any changes to the acoustics of the setup.


Klaus

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