Impulse response anomaly?

Tony Walters

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Hi there

Using 5.20 version. When I measure l speaker followed by r and look at impulse response, both spikes are to the left of time 0. How do I align these in preparation for creating impulse response for convolver. Do I just move t0 over to first spike and then move other spike to match that location?
 

John Mulcahy

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Are you measuring with a timing reference? A little odd to have the peaks come early. You can ask REW to estimate and then remove any delay (positive or negative) in the impulse responses using the Estimate IR delay button in the graph controls. For further comment best attaching an mdat file with the measurements.
 

Tony Walters

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Are you measuring with a timing reference? A little odd to have the peaks come early. You can ask REW to estimate and then remove any delay (positive or negative) in the impulse responses using the Estimate IR delay button in the graph controls. For further comment best attaching an mdat file with the measurements.
Yes I use the standard timing reference l for left speaker and r for right. One subtlety is that I move the recorderd measurement sweeps over to my volumio player. I start the measure and then I play the sweep and I hear the normal start chirp and the end chirp. Seems to be working fine for that at least. Measurement mic is a good 15' from speakers.

I am trying to create an impulse response for both speakers for a convolver which I this case is camilladsp that is baked into volumio.

Picture attached
20230324_142222.jpg


Thanks for the support
 

JStewart

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Yes I use the standard timing reference l for left speaker and r for right.
Perhaps I’m interpreting wrong, are you saying when you measure the left speaker the chirp is on the left and when measuring the right speaker the chirp is on the right?
If so, change the timing reference to go to the same speaker for both left and right measurements.
If not, sorry to interrupt.
 

Tony Walters

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Perhaps I’m interpreting wrong, are you saying when you measure the left speaker the chirp is on the left and when measuring the right speaker the chirp is on the right?
If so, change the timing reference to go to the same speaker for both left and right measurements.
If not, sorry to interrupt.
You are correct! I will try your suggestion and report back
 

Tony Walters

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The suggestion seemed to work thankyou. I set the reference time g to right and reran measurements. The right is dead on t0 and the left is 170 micosec ahead.
I am running the latest software and I see a lot of changes and I am having some unexpected results in other areas but I want to work with it more as they are probably my issues.
Many thanks for the support.
Tony
 

Tony Walters

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Feb 2, 2018
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Perhaps I’m interpreting wrong, are you saying when you measure the left speaker the chirp is on the left and when measuring the right speaker the chirp is on the right?
If so, change the timing reference to go to the same speaker for both left and right measurements.
If not, sorry to interrupt.
No. I found out that for the timing to work properly the timing reference must come out of the same speaker. So L refL and R ref, and if you do both speaker measurement it is LR ref L. Works perfectly i just aligned my mic to within 2 or 3 microseconds.
 
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