Low end SPL variations between acoustic reference and loopback

[Mike0815]

Hallo,

trying to reproduce timing variations in this thread: question-regarding-jumping-distance-with-acoustic-reference
I did notice something odd:
The low frequency part differs between acoustic timing reference and loopback.

Regards
Michael

 

[Mike0815]

Hey,

think I found the cause: My loopback signal went through the AVR's Ch7 (surround back) and was set to small with 60Hz x-over. Setting it to large gives same SPL for loopback and acoustic ref.
But why is this affecting the SPL of the measured signal? Shouldn't just the phase be affected in that case?

 

[sm52]

But why is this affecting the SPL of the measured signal? Shouldn't just the phase be affected in that case?

You have the answer.

My loopback signal went through the AVR's Ch7 (surround back) and was set to small with 60Hz x-over.

 

[Mike0815]

Hi,

just the loopback channel was set to small not the one for the measured speaker.

 

[Mike0815]

Hi,

could it be that "Use loopback as timing reference" and "Use loopback as cal and timing reference" are mixed up?

 

[John Mulcahy]

No, but the signal sent out on the loopback channel (a copy of the measurement sweep) may be affecting the behaviour of the AVR, e.g. it may be summing it through its bass management.