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Discussion Starter · #1 ·
Hi
I am using the Jriver's MC17 software in conjuction with REW sweep measurements to build crossovers and frequency corrections for an 8 channel multiamp audio system.
I had great success in REW measurements for these purposes, including XO slopes and frequencies low/high-pass filtering, by the uses of a time reference loopback taken from XLR outputs from the DACs left outputs (I have 4 DACs in //, one for each 2ch). Phases at XO location are quite acceptable so far.
However while trying to add delays in MC's EQ delay option to fine-tune between channel XO's, there is no modification of the signal showing on the REW overlay graphs for neither phase or IR. I have fixed 5ms-10ms and more without any changes.

There must be a subtility over here that I've overlooked. Could come from Jriver or REW?

Thanks for your help.

jacques
 

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One guess is that you didn't give REW a clean loopback ( for Time Reference ) .
- I would avoid ( if possible ) sending REWs Time Reference loop through MC17 ( where that timing loop could get delayed by misadventure ) .

:sn:
 

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Discussion Starter · #4 ·
Hi EarlK
Yes the preference analysis page is well setup with the loopback checked right.

Concerning MC17, all my channel managing are built in it, so I want to be able to use this delay option.

Every other MC's EQ features are very effectives and "STABLES", I mean they repeat exactly the same measurement after any changes, except for delays:huh: I had curious randomly delay changes that did not behave properly, with or without loopback??

I tought that mabe REW made timing correction for these delays but I could not think how?.
 

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Discussion Starter · #5 ·
I could have been unclear
Every other MC's EQ features are very effectives and "STABLES", I mean they repeat exactly the same measurement after any changes, except for delays:huh:
when I say they repeat, it is for the same changes, not that changes do not makes differences in measurements....

just for delays, I do not have changes in measurements
 

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Discussion Starter · #6 ·
I finally have something going better with a little inconsistancy.

My BIG mistake was that my reference loopback channel "left" was checked also for delays in MC17.... So REW took it as a variation to be corrected resulting in the neutral effect of delays settings.

Big step in comprehention thow.

It still has some flaws, delays from 0 to 50, 75 and 100ms are not regularly spaced on IR graph and definitivelly do not show that amount of delays??? A lot less....

Should they are supposed to be moved with the applied delay?
 

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rewjack said:
My BIG mistake was that my reference loopback channel "left" was checked also for delays in MC17.... So REW took it as a variation to be corrected resulting in the neutral effect of delays settings.
Yeh, I figured it was something like that .


rewjack said:
It still has some flaws, delays from 0 to 50, 75 and 100ms are not regularly spaced on IR graph and definitivelly do not show that amount of delays??? A lot less....

Should they are supposed to be moved with the applied delay?
I would assume that the delay shown within REWs IR window should match the delay amount dialed up over in MC17's dsp section .

I have not tested this out in practice yet so it's just conjecture .

:sn:
 

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Discussion Starter · #8 ·
You are right EarlK

Now all delays are measured with great precision.
The REW sweep signal is passing through MC17 using the URL Asio loopback option.

The reference time loopback for me as to use one of the DAC output since the virtual cable "VAC" is set in the REW preference soundcard output to work with the MC's URL Asio opttion (my multi channel RME soundcard has no analog outputs, only digital)
This way I could not use the PC realtech soundcard output (used for the MIC input) to perform the physical loopback.

It is then a little more complicate, but I'm working on something to reduce amount of plug-unplug manipulations.

jacques
 
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