Timing reference at end of sweep not detected

[davebullet1050]

TL;DR The odd thing here - is REW can detect the end timing reference from an acoustic timing measurement when I apply a 1500Hz LR2 lowpass to the right channel, but not a 1500Hz highpass to the right channel (left channel is unfiltered and same in both cases).

My setup is shown below. I am using the Measure from file option in REW, using a 256K 10 to 20,000Hz sweep file generated with REQ, with timing reference added (trim set to either 0.0 or higher = no difference) - 44.1KHz throughout (no resampling)

Scenarios:
1. If I measure the left channel - REW detects the timing reference at end and I get a nice dead straight measurement (i.e. like a loopback)

2. If I measure the right channel with a 1500Hz LR2 lowpass applied - REW detects the timing reference. Note: the left channel is unfiltered

3. If I measure the right channel with a 1500Hz LR2 highpass applied - REW misses the end timing reference (it finds the first one). The left channel is still unfiltered.

Does anyone have anyidea why REW would miss the end acoustic timing reference under scenario #3?

 

[John Mulcahy]

The timing reference is meant to be acoustic so that it can be heard on the measurement input, that's where REW is listening for it. With a wired connection that no longer works. The surprising thing is that it is detected at all when you measure the R channel, maybe there is enough crosstalk in the X6000 for it to be picked up.

 

[davebullet1050]

Thanks John. I didn't think the timing reference played on the right channel - only left? when I listen to it - without any filtering at all, I can only hear it on the left channel not the right. Are you saying the timing reference plays on both channels? I thought you had the option of either left or right - not both. I'll try right generation. HEre's what I used to generate the sweep:

 

[davebullet1050]

Ok - so that was my problem. I should have added the timing reference to the right channel as that is the one I am measuring - doh!

Interesting point about crosstalk.

 

[John Mulcahy]

If you filter that channel you will still have issues. The only reliable way to handle that would be for REW to listen for the timing reference on a different channel, which isn't supported. I'll have to think about that.

 

[John Mulcahy]

I have added a new wired timing reference option in the latest V5.20.14 early access build to deal with that situation.

 

[davebullet1050]

Wow! Now that is what I call service thank you John! I'll look forward to trying that out (donation paid