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I’m in the early stages of incorporating acoustical treatment into my theater. I downloaded the REW software with the intention of using it to identify a relevant baseline to compare post treatment results. I’m running windows 7, am using a Radioshack 30-2055 SPL meter and a BehringerUCA202 as my soundcard. I’ve used both the REW help index and the guide by AustinJerry to assist in calibrating both the soundcard and the meter.

After calibrating the UCA202 soundcard I took a measurement and the results are flat and consistent with the pictures in the manual. However, when I uncheck the C weighted SPL box under preferences and measure the results as a confirmation procedure the delta is much greater than the 0.1db in the manual. My test comes back at 109.8db while the soundcard curve is just over 60db. These were my settings when calibrating the UCA202:

Output volume: .50
Sweep: -12.0
Input: .10

In the windows 7 settings I set the mic volume to 10%/10db per the AustinJerry guide for Windows 7, turned off the monitor switch on my UCA202 and used the UCA202’s volume dial to adjust the input/input ref levels to -12dbfs to match the output. My headroom comes back as 8.5 db when running a measurement. I saved this calibration file.

While I was concerned about the large delta from the confirmation procedure I did move on to calibrating my SPL meter. I’ve calibrated the meter multiple times with headroom to measure 110-122db but when I proceed to checking the levels they come back as too low (-59.4). As such, I adjusted the input volume controls in REW to the maximum of 1.000 but the best that does is get the level to -27db. The manual states it should be somewhere between -12db and -24 with -18 being preferable for non-USB mic’s like the RadioShack 30-2055.

Finally, I made a measurement for 20hz-200hz and it’s clearly not right. Here are some photos of the card calibration and the 20-200hz measurement

Not sure what my next step should be.
 

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The soundcard cal measurement looks fine. The check measurement is to make sure the flatness is good, not the level - the level is governed by the SPL Meter calibration.

What input setting are you using on the RS meter? If you are measuring with a test signal that produces 75 dB (nominally) the meter would normally be on the 80 dB range.

Where do you have the RS meter connected? Should be to an input on the UCA202. The UCA202 loopback connection gets removed when you move on to measuring.
 

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Discussion Starter #3
The soundcard cal measurement looks fine. The check measurement is to make sure the flatness is good, not the level - the level is governed by the SPL Meter calibration.

What input setting are you using on the RS meter? If you are measuring with a test signal that produces 75 dB (nominally) the meter would normally be on the 80 dB range.

Where do you have the RS meter connected? Should be to an input on the UCA202. The UCA202 loopback connection gets removed when you move on to measuring.
RS meter is set to 80 (to test at 75db), C weighting and slow response. The meter's phono/line out goes straight into UCA202 RCA inputs (cable has phono on one end; dual RCA on other) so the closed loop was removed. I run the UCA202 RCA outputs to my Lexicon preamp AUX RCA inputs.
 

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Sounds OK, but I'm not sure about your description of the cable from the meter to the UCA. The meter output is RCA, needs an RCA to RCA cable to connect it to the UCA202. Make sure the UCA202 monitor switch is turned off and the input channel selected in REW is the one the meter is connected to.
 

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Sounds OK, but I'm not sure about your description of the cable from the meter to the UCA. The meter output is RCA, needs an RCA to RCA cable to connect it to the UCA202. Make sure the UCA202 monitor switch is turned off and the input channel selected in REW is the one the meter is connected to.
Yep, the monitor switch is off- noticed that in your guide. The input channel is also the one the meter is connected to. This is the cable connector I'm referring to:

http://www.homedepot.com/p/Unbranded-Electronic-Master-6-ft-3-5-mm-Stereo-to-Dual-RCA-Audio-Cable-EMHD121006/301790878

The output on the meter is designated as phono but that's essentially the same as RCA. I also have a single RCA cable (used for composite video connections) which I first tried running from the RS meter to the right RCA input on the UCA202. It didn't make any difference.
 

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You definitely don't want that cable, the meter output is not a 3.5mm socket. The composite cable you mention should be OK, or half an RCA-RCA stereo pair.
 

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You definitely don't want that cable, the meter output is not a 3.5mm socket. The composite cable you mention should be OK, or half an RCA-RCA stereo pair.
Okay, will give a try shortly with standard RCA and report back. Thanks
 
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