Author Topic: delay finder negative polarity  (Read 2240 times)

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lunamassimo

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delay finder negative polarity
« on: September 06, 2011, 10:06 »
hi,

just using satlive in the field for PA tuning. At about 20 metres from the cluster (EV Xlc), microphone with grounplane placement, i started delay finder and noticed that the polarity field read NEG. So i actually thought that was a cable between my reference signal ( output of a PM 5D) and my measurement microphone. I checked the cables and everything looked fine. So i looked again at the delay finder and i noticed that there was a positive peak , amd right after a negative peak but with much more amplitude... so what does it mean? I performed a wire-type measuremen of mi rig (both output to the inputs) and everything looked positive polarity. i measured my HS 50 at home and they looked positive polarity. Actually also the traces i captured from that system (xlc) looked pretty regular.

thanks

Massimo

TomyN

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Re: delay finder negative polarity
« Reply #1 on: September 06, 2011, 12:03 »
Hi,

the delayfinder simply searches for the peak, i.e. the highest absolute value in the impulse-response. This is where it aligns the delay to.
So it fails in such cases, because it does not notice the first positive peak.
That's why the delayfinder has gotten the small display area, where you can verify (or change) the delay.

The polarity display shows the direction of the peak.

Tomy
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DANTE Level1 certified

Jeffsco

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Re: delay finder negative polarity
« Reply #2 on: September 06, 2011, 18:20 »
So if the delay finder fails in it's aquisition of the impulse response...what do we do  to make it right?

TomyN

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Re: delay finder negative polarity
« Reply #3 on: September 06, 2011, 18:27 »
In this case you can use the MAT-Impulse-response measurement. You can define the length (as longer as better as slower) and the amount of averages (as higher as better as slower) used for the calculation.

Once you've found the desired delay, just put the cursor on it and press F3 (or the Cursor to Delay  D=C Button).
You can use the key P to put the cursor to the peak of the impulse-response trace.

Tomy
Dipl.-Ing.(FH) Thomas Neumann
SIM-II Operator
DANTE Level1 certified