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On Tuesday, September 5, 2017 at 9:29:29 PM UTC-4, Geoff wrote:
On 6/09/2017 12:42 PM, Scott Dorsey wrote:


Delay isn't an issue. Group delay isn't an issue. What is an issue is when
you sum signals that are shifted in time together and get comb filtering.
It's the _comb filtering_ that is the issue, not the phase shift.
--scott

Nice that it is trivial to realign them to sample exactness !

geoff

the semantics can be confusing

a time delay that is constant over frequency is the same as a phase shift that is NOT constant with frequency.

For example, a constant 1 ms delay is =360 deg at 1 kHz and 180 deg at 500 Hz and 90 deg at 250 Hz etc.

That is why combing the same signal over two paths that have a 1 ms time difference will create comb filtering with nulls spaced every 1 kHz.

m