# Rew measurement help



## Gingerone (Jun 3, 2012)

Hi all, 

I've been trawling this forum for the answer to my problems to no avail so hope you can help.

I've been trying to get rew set up for weeks now with no success, I've got a generic usb soundcard which I have calibrated using the loopback connection and I'm using a radioshack 33-2050 soundmeter with calibration file.

When I run sweeps all I get is this;

I'm sure you will know the answer straight away but I'm tearing my hair out so any advice will be greatly appreciated:sweat:


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## JohnM (Apr 11, 2006)

Can you post a pic of your soundcard calibration measurement? Or attach the .mdat files from the soundcard calibration and this measurement.


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## Gingerone (Jun 3, 2012)

what are the .mdat files and how to do i locate them?


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## JohnM (Apr 11, 2006)

When you make a measurement in REW you can save that measurement to a file (by clicking the Save button on the measurement panel or Save All in the toolbar), the file is given the extension .mdat. See http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/rewoverview.html#top and http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/measurementspanel.html#top


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## Gingerone (Jun 3, 2012)

here's the soundcard measurement


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## Gingerone (Jun 3, 2012)

Here's the measurement as requested


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## JohnM (Apr 11, 2006)

Soundcard measurement looks fine, but the measurement with the SPL meter has a huge DC offset on the input signal.

- When you connect the RS meter to the soundcard input does the meter needle continue to behave normally?
- If you go to the Scope plot after making a measurement is the Captured trace offset from 0?
- Are you running Windows or OS X?

You could try ticking the "High Pass" box on the REW soundcard preferences, that might allow a measurement to be made, but the offset shouldn't be there and it would be best to figure out where it is coming from.


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## Gingerone (Jun 3, 2012)

I have the meter set up to c weighting and slow, and the needle behaves normally.
Using windows 7
I will check the scope plot now


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## Gingerone (Jun 3, 2012)

I get this in the scope when I run a sweep


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## JohnM (Apr 11, 2006)

That step upwards is odd and a problem, but try the REW High Pass option to see if you can then get a measurement. Please also post a pic of the scope plot zoomed out to cover the whole span of the sweep, but with the output signal not selected so the input is easier to see.


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## Gingerone (Jun 3, 2012)

This is with the high pass enabled,

Do you think it's an issue with the spl meter?


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## JohnM (Apr 11, 2006)

Can you expand the range on that plot to show the whole period of the sweep instead of just the period up to 1.00s?

Worth attaching the .mdat file of a measurement made with the High pass selected.


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## Gingerone (Jun 3, 2012)

The rest of the sweep looks exactly the same, just disconnected it all but the sweep with high pass enabled looked the same as without, I'm stumped any idea what is causing it? 
Do you want me to run another sweep and upload them.. Mdat file?


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## Gingerone (Jun 3, 2012)

Out of curiosity I've tried using an audyssey mic, here's the results with high pass enabled, without it enabled it errors.


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## JohnM (Apr 11, 2006)

On the scope plots untick the box for "Sweep" (the purple trace), that is the signal REW is generating. What we need to see is the red "Captured" trace, over a time span of about 6 seconds.

Also go to the Windows sound properties for the input (right click on volume icon, select Recording Devices, click on the line in from your soundcard, click properties, then click on the Listen tab and make sure "Listen to this device" is *not* selected.


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## josh96 (Jan 21, 2013)

I get these same results when i try. Except i use an audigy sound card.


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