[John Williamson]

On 06/09/2017 13:00, Scott Dorsey wrote:
James Price wrote:

That said, comb filtering also applies to the reflection from the floor
back into the mic(instant comb filtering), though I think it keeps stuff
cleaner than multi mics.

Yes, that's comb filtering caused by phase shift. The signal is delayed by
the additional distance of the reflection. It takes about a millisecond for
sound to travel a foot in free air. Move the mike five feet, you have a
uniform phase shift of 5ms at all frequencies.

A point of order. What you have is a uniform time delay of 5ms, which
causes a different number of degrees of phase shift, depending on the
frequency. The time delay will cause phase shift at all frequencies, but
the angle of that shift will vary at different frequencies, so giving
rise to comb filtering as some frequencies add and others subtract

A phase shift of x degrees for multiple frequencies an be obtained at
any frequency, but not by using a fixed delay in the signal path.

Sloppy phrasing is what's causing a lot of the confusion in this thread.


--
Tciao for Now!

John.