Why is acoustic reference timing single not triggering in REW??

Socket

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Love that REW now allows IR to be measured using USB mic with a acoustic reference timing option, instead of a loop feedback.
But I have run into a problem with V5.20
When trying to do an IR measure using a sweep and ART, it comes back with a "signal at end of sweep could not be detected". At other times there is no signal produced at the start of the sweep, so it just waits, hears the end of sweep signal and then measures?? Is this a corrupted sweep generation file or have I got some setting stuffed up somewhere? I am a novice and would appreciate some help figuring out why REW is not producing a ART signal at the start and end of the sweep.
What makes this more confusing is that I was able to get IR measures yesterday using ART without a problem

Uninstalled and reinstalled V5.20, no change
Rolled back to V5.19 and had the same issue with the missing ART signal at either the start or end of the sweep

Settings
The ART option is ticked in the analysis tab
USB mic (Superlux ECM-999) plugged into laptop and selected as input device (R channel)
Output is blue tooth connection to Helix V8 DSP via BT expansion card (L&R channel) which plays the signal through the drivers selected in the AFT DSP PC Tool.
Timing reference selected (L channel)

Any help would be much appreciated
 
Last edited:

John Mulcahy

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I'm not clear whether REW is producing the sweep signal or you have saved the sweep to a file that you are playing back. Either way the timing signal needs to go to a tweeter or speaker with a tweeter, is that what the L channel provides? Beyond that make sure there is no auto power on feature that isn't engaging until after the signal has started, so missing the initial part, and that the blue tooth connection isn't somehow not active for the initial part of the sweep.
 

Socket

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I'm not clear whether REW is producing the sweep signal or you have saved the sweep to a file that you are playing back. Either way the timing signal needs to go to a tweeter or speaker with a tweeter, is that what the L channel provides? Beyond that make sure there is no auto power on feature that isn't engaging until after the signal has started, so missing the initial part, and that the blue tooth connection isn't somehow not active for the initial part of the sweep.
Thanks John. REW is producing the sweep signal. Turns out scorched earthing REW, (deleting everything including preferences and the REW folder) and then a complete fresh install fixed the problem. Clearly I corrupted the sweep generating file somehow. All good. Thanks so much for your prompt reply. Really appreciate all the support and time you give to the community. Much respect....
 

Socket

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Spoke too soon, actually is not a corrupt file issue !!!! Im guessing it is something to do with blue tooth streaming the measurement sweep to the Helix V8 DSP

Let me tell you the story

I am tuning my active 3 way car audio system and trying to measure the impulse response of my car speakers using a laptop, USB mic and REW

On the output side, I have the laptop connected to the audio system DSP (a helix v8) via blue tooth. It appears in the output menu as headphones HD-BT (which is correct designation for the DSP BT expansion card)
In REW sound card preferences I have selected headphones HD-BT (R/L channels) as the output

On the input side, I have a superlux ECM 999 USB omnidirectional mic
In REW sound card preferences I have selected USB mic (L channel)

In the REW sound card preferences I have selected timing reference output (R channel) and Loopback input (L channel)
In the REW analysis preferences I have adjust clock with acoustic ref (ticked)

I am using REW V5.20 beta (but also have the same problem with V5.19)

In the DSP the L and R tweeters are active and have all other speakers muted

In windows 10 sound settings on the laptop, I have made sure all audio enhancements are turned off, levels are at 100% and there are no other power saving or settings causing delays etc

In the measure tab, I select SPL sweep 0 - 20,000 Hz, -12.0 db, acoustic timing reference (ticked) Output (headphones HD-BT L/R) Ref output (Headphone HD-BT R) Input (USB mic L)
Sample rate 44.1 Khz (same as mic and BT connection sample rates) all other settings are default

I then run a level check in the REW measurement window and turn up the volume on the DSP control knob to get a acceptable level

I then run a sweep, I can see it measuring the floor level, then it sits for a few seconds waiting for a reference signal, then the main sweep plays through the speakers, then the end reference signal plays (it can be seen on the graph and heard in the speaker) then an error message pops up saying the end reference signal could not be detected???

I have tried using a difference lap top (same result) playing with channels and settings (same result) and hooking my laptop to a BT speaker (mono) which plays the start and end ref signal perfectly....

Will take some screen shots if it helps, but cant understand why the initial ref signal is not playing

Otherwise is the someway of using the REW generator to produce a file with the start and finish ref signal and the 0 -20Khz sweep? I can produce the sweep but not with the start and finish ref signal

Any help or advice would be much appreciated
 

Socket

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Joined
Jul 19, 2020
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once again thanks so much John, the functionality built into REW is amazing. Would never have found this without your help
 
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