Newbie - am I doing something wrong?

[THB]

Just installed REW + UMIK-1 and ran my first test, and is apparently showing a very steep rolloff at around 11kHz -- not what I was expecting! Am I doing something wrong, or do I have some issue with my system? Is wired Airplay an issue? Are my KEF tweeters fried? How to tell? See chart below.

Signal path: REW on MAC --> Airplay (all wired) to router to Hegel Rost amp --> KEF LS50 and HSU ULS-15 MK2

 

[THB]

If I start the sweep at a higher frequency, then the drop-off occurs at a higher frequency. See plot below. Seems like a REW software issue?

 

[THB]

It looks like both starting frequency and length impact where the drop-off starts...is this expected/normal behavior?

 

[John Mulcahy]

There may be large latency through your replay chain causing the end of the sweep to be played out after capture has stopped. Use the acoustic timing reference, that will synchronise the capture to the replay and counter any latency.

 

[THB]

Thanks for the tip!

I had been connecting to Hegel through the network (wired AirPlay); the response curve looked more what I was expecting when I connected via USB. So apparently larger latency going over network was causing the issue. At one point I had also maxed out the buffers, which also added latency. Going back to 16K buffers also seemed to help. See chart below.

I'm not sure how to use the timing reference; do I need additional cables? Or just control settings in REW?

 

[THB]

Never mind; figured it out...used acoustic timing reference and timing signal just came through speaker. Didn't really help with network latency issue, so I'll stick with USB for now.

 

[THB]

Problem went away with REW V5.20 beta 24 (had been using latest "production" release - V5.19?). Anyway, more or less expected response now with either Network (wired Airplay) or USB. Now on to EQ!