Why 0,04ms acoustic timing reference dealy?

[FargateOne]

Hello,
I always use front right channel (Asio4All hdmi 1.2 output) for acoustic timing reference (FR speaker never moves and left speaker is in the corridor, so it moves everyday!).
Sometimes I have ) 0,04ms delay and sometimes I have 0,00ms. Why? Is it a problem?

 

[John Mulcahy]

There is no way to tell why without seeing measurement data and having some information about the measurement setup.

As to "is it a problem", that would depend what use you were making of the information. In most circumstances 40 us of delay would make little practical difference to anything.

 

[FargateOne]

I understand that this short delay makes no practical difference and don't want to waste your time. Maybe the following info could be of any use.
Measurement setup: Asus laptop to receiver via hdmi. Rew, preference panel, analysis, box "use acoustic ref" checked all others settings to default. When I open Rew, in the measurements panel, Channel 1.2 for front right is already checked as timing reference channel. I measure front left channel the box "wait for timing ref" is checked. I hear the sweep to the front right and the signal to the front left. Then I measure the Front right, the center etc. always in the same order.
Thank you again for your fantastic software.

 

[John Mulcahy]

Looking at the impulse response of the front right there is a large negative swing to about 90% of the peak value then the positive swing to the peak. Those negative and positive peaks are 40 us apart. The impulse response of the timing signal does not form part of the captured data, but I would suspect that for the high frequency timing signal the negative and positive parts of the response may be even closer in level than they are for the full range measurement so the timing signal peak may sometimes be the first negative swing and sometimes the subsequent positive swing, with the 40 us difference depending on which has the peak level for a particular measurement.

 

[FargateOne]

Thank you for the clear explanation.

 

[FargateOne]

Hi,
I have installed the latest 5.19 version and I have of course the "problem" but worst (maybe because I use an external amp for front right and left speakers?) is there a way to get 0,00 delay for the reference output?. In the following file you will see different delay but all impulse seem correct!?

 

[John Mulcahy]

That's fine, there is just a very small offset between the frequency range used by the timing reference signal and the overall impulse response.