Weird problem doing REW measurements? Help needed!

[andyr]

I've been using REW for a few years - but am certainly not an expert user.

But I've successfully measured frequency sweeps on several occasions (to set relative driver volumes in my active spkrs) and never previously had the problem I am about to describe. Which has me absolutely stumped!

I was wanting to do a sweep from 20 - 200Hz in the R channel (ie. across the XO region of sub to woofer).

I started off with sub off and woofer amp on; the LP filter for the sub was bypassed, in the miniDSP plug-in - as was the HP filter for the woofer. (So they were each running full range.)

I clicked on the "Measure" icon on the REW screen - then clicked 'Start". Result was a graph of the woofer response over the range 20 - 200Hz ... as I've done many times before.

Then I turned on the sub and turned off the woofer amp. Clicking on "Measure" and "Start" ... the result was also a graph - this time of the sub's response!

IOW - things were working as expected!

But then, a short time later, trying subsequent sweeps with just the sub turned on ... I could not get any sound from the sub!

But the sub would play the radio when it was selected as the input into my miniDSP - it's only when the Steinberg UR242 was selected (to create the sweep) that I got zero sound out of the sub.

Can anyone suggest where I might've gone wrong?

Thanks,
Andy

 

[John Mulcahy]

Did you select the UR242 as the output device in REW? If you left the output as Default device the default may have changed.

 

[andyr]

Aah, thanks, John.

No, I don't remember ever actually selecting the output device - so I will try that soon, when I start measuring again.

Thank you for the suggestion!

Andy

 

[andyr]

John,

"Output" is greyed out ... so I have no ability to make a selection?

EDIT: I closed REW and re-opened it. This time, after clicking on "Measure" and getting the "Make a measurement" window, "Output" is not greyed out ... but there is only 1 option in the drop-down ("Default output")!

Rgds,
Andy

 

[John Mulcahy]

Input and output devices are selected in the soundcard preferences, per the help.

 

[andyr]

Thanks, John - I will read that document.

Rgds,
Andy

 

[andyr]

Alas, John - after reading that doc, I did the following:

1. Selected the Output device in "Preferences"

... which lead to this, when I hit 'Measure':

But still the same result :
* no sound from the R sub (despite the radio coming through that sub, outside of REW)
* but sound coming from the R main spkr

... when I do a Measure sweep.

Any more suggestions, John?
(BTW, I had selected "No timing reference" for these 20-200Hz sweeps as, when I had "Use acoustic timing reference" selected ... I found the sweep would hang??)

Thanks,
Andy

 

[John Mulcahy]

If you have sound from the speaker then the problem is outside REW. REW has been asked to send a signal on the R channel of the output device, which it has. Where that signal goes afterwards isn't something REW can control.

When the acoustic timing reference is used a short, high frequency sweep is sent to the channel selected as the ref output. That needs to go to a speaker than can reproduce it, one with a tweeter. The Measure dialog waits to hear that timing signal (that message is shown above the progress bar), if it doesn't hear it it will wait until you decide to cancel.

 

[andyr]

Yes, that makes sense, John, - except that sound comes from the main spkr when I turn on the amp driving it. Only when I turn on the R sub and turn off the R main-spkr amp do I get no sound - despite the radio coming through the sub when that source is selected instead of the UR242.

That's why, as I said earlier - I'm stumped!

Andy

 

[John Mulcahy]

Perhaps a diagram of what is connected where would help. You spoke about selecting the radio as input to the miniDSP, is the UR242 also set up as an input to the miniDSP? Do you have different miniDSP signal routing arrangements for different inputs? If you connect the UR242 to the connections you are using for the radio what happens then?

 

[andyr]

Thanks John, I'll respond with a diagram in a few hours (I'm away from home atm).

 

[andyr]

Hi John,

Hopefully, the attached schematic of my system explains it to your satisfaction:

When radio is selected in the 4-way source selector ... music plays through the sub - and the R channel main spkr.
When the UR242 is selected:
* the sweep comes through the R mid, when the R sub is switched off and the R amp is switched on
* but no sound comes from the R sub, when it is switched on - and the R amp switched off.

Note: In previous REW sweeps, I did get sound from the sub!

Regards,
Andrew

 

[John Mulcahy]

Maybe there is a problem with your ADC or its settings.

 

[andyr]

Thanks, John - yes, that is a possibility.

However, the 20-200Hz sweep comes out of the R mid when the R amp is turned on ... just does not appear from the sub, when it is turned on.

The ADC has no knowledge of what amps are on - or off - further down the signal chain ... hence my befuddlement.

The only setting I can change on the ADC is the speed it is running at. I will find out what Hz the UR242 runs at and set the ADC speed to that (currently, it is set to 96kHz - as that is the speed the nanoDIGI is running at).

Thanks again,
Andy

 

[John Mulcahy]

Swap the inputs of the Subs DAC and the R ch DAC and see what happens then, and try a sweep that goes to 20 kHz. A mistake in the crossover or routing configuration for the miniDSP seems a good candidate, a full range sweep may more easily reveal that.

 

[andyr]

Thank you for your patience with me, John. It seems that I had the R&L sub channels reversed, on the sub DAC output. When I changed to another DAC, I (accidentally) reversed the outputs - and that solved the lack of noise problem. So then I realised where I had gone wrong - corrected it ... and it's all working as it should.

Andy

 

[andyr]

Well for the 10 days between my last post and today ... it was all working as it should!

But today, I am not getting the "cheep'n'sweep' noise from the spkrs! I made no changes from yesterday - simply turned on my computer this morning.

I've even taken my Steinberg UR242 back to the shop where I bought it, several years ago, and they proved that sound did come out from the UR242 (and through their loudspeaker).

Here is my 'Preferences' screen ... have I got anything wrong here?

And here's the "Measure" screen:

Any advice gratefully received.
Andy

 

[John Mulcahy]

You could connect the UR242 output directly to an amp input to make sure that's working, if so the signal must be getting lost along the chain somewhere. Just need to go through it methodically. Worth power cycling the miniDSP and making sure that is set to the correct input.

 

[andyr]

Thanks for those suggestions, John.

Yes, I will try:
a. power-cycling the miniDSP, and
b. connecting the UR242 direct to an amp.

I'll let you know how I go.

Andy

 

[andyr]

Tried connecting the UR242 direct to the left amp (with 'L' selected in the "Measure" screen) - still no sound!

Which I guess is good in a way ... in that it indicates that all the other items in the sound chain (that were bypassed for that test) are not causing the fault?

So then I:
* turned the miniDSP off and on - still no sound.
* turned the UR242 off and on - same
* re-loaded REW v5.20.5 to my PC - no difference
* changed the USB cable between UR242 and PC - several times ... no difference
* bought and plugged in a new output cable from the UR242 - which could've been the cause of no sound, when going directly into the amplifier ... again, no difference.

When I click 'Start' on the "Measure" screen, normally:
1. the blue bar starts to go to the right
2. then you hear the timing "cheep"
3. then the sweep starts
4. then, after the sound has gone above your hearing-frequency ... a couple of seconds later, you hear the final timing "cheep".

However, what happens now is just #1! No timing cheep and so the screen just stays like this:

It's almost like either the UR242 can no longer do the timing cheep ... or the REW software has stopped sending the "cheep" instruction to the UR242?

So ... any further suggestions, John?

Andy

 

[John Mulcahy]

Check the output level knob on the UR242 and the output level in the Windows audio properties for the UR242. Check the Windows mixer volume setting for REW (when REW is running right click on the volume icon and select Open Volume mixer).

 

[andyr]

Check the output level knob on the UR242 and the output level in the Windows audio properties for the UR242. Check the Windows mixer volume setting for REW (when REW is running right click on the volume icon and select Open Volume mixer).

Bingo - thanks John.

I had no idea the computer's "spkr icon" level would affect the output of the UR242 ... but it does! (Spkrs had been set to 'mute'! )

Onwards I go with measuring!

Andy