REW rephase convolution IR delay 'centering'

hibikijin

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Jan 30, 2018
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Hi everyone,

I use REW and rephase to create a param gain EQ IR for a convolution in JRiver mostly for attenuating some bass peaks (no changes up from 300Hz) .

A pretty basic use I thought I understood until I decided to run REW to check the convolution using the very useful functions John implemented, playing from file a sweep with 2 acoustic references (one before and the other after the sweep for clock adjustment).

Without convolution the sweep and the two acoustic refs would play nicely.

With a convo using an IR for gain EQ only, generated with the rephase default ‘middle’ centering option (about 16k samples later), the last acoustic reference would not play, clearly indicating a problem with the convoluted sound, and an incorrect IR for this case.

First I thought it could be something related to the number of taps but to no avail. I then changed the default centering from 'middle' to 0ms and the convoluted sweep played nicely with both acoustic references, and the REW SPL for the convolved curve showed the expected effect of the gain EQ filter.

Could anybody be so kind to explain why the 'middle' did not work (why the second acoustic ref did not play with this large delay) but with a 0ms or a small delay it did? Or to point to a link to some documentation about it?

Many thanks

PS: I posted this in the rephase thread but since so many REW users use rephase too I posted here.
 
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