SPL Meters | Mic's | Calibration | Sound Cards

**Nuance** · **08-25-09, 04:37 PM**

I had to format my HD and lost my soundcard cal file. Upon redoing the calibration I noticed something I hadn't last time on my M-Audio MobilePre: I had to keep the right channel gain (the knob on the front of the sound card) about half way up, while keeping the main volume (output) in the sound card properties window within Windows XP below the half way point. This allowed me to get the input and output #'s within tolerance. However, after completing the .cal file, when I then went to "check levels" I had to turn the output volume knob on the soundcard back up to almost full, else the levels were WAY too low. I also had to increase the output volume in the M-Audio properties window. Is this normal? If I didn't do it REW would tell me the output was way too low, even though it was not (I had an SPL meter to verify 75dB at the measuring position).

Finally, just to be clear (since I have not seen this discussed in detail or with a picture), the "Direct Monitor" needs to be muted when taking measurements and creating a sound card calibration, and the "output" and "input" levels that REW talks about matching are the ones I've circle in red in the below picture?

In other words, if using the right channel to create a calibration, I'd use a combination of adjusting the sound card's gain knob (on the front of the card itself) and the volume output in the sound card properties (in Windows XP) to ensure the column that says "right" matches the -9 and -12 in the left column (the one that says "out")? Or at least as close as I can get, anyway.

Does that all sound right? Sorry for the dumb questions, but better to be safe than sorry. I haven't seen this clearly explained yet, probably because it's common sense.

I just want to be sure, though. I apologize if there is already a post concerning this that I overlooked.

Thanks!

**brucek** · **08-25-09, 04:57 PM**

Quote:

Does that all sound right?

I am missing what your question is?

First you do a soundcard calibration and save the file. Remove the loopback cable.

Then connect the mic and receiver and you do a Check Levels and set the output level of your receiver to obtain 75dB at the listening position. Then adjust the input level of REW to get about -12dB to -18dB in the VU meter. Then run Calibrate and finally take a Measure.

What's your question?

brucek

**Nuance** · **08-25-09, 05:02 PM**

My questions are mostly regarding the soundcard calibration process, ensuring I am adjusting the proper settings, and wondering why I have to raise the volume of the soundcard using the gain knob and the windows properties (after I have already made a calibration file) when performing the "check levels" test?

You mentioned adjusting the input level of REW to get between -12dB and -18dB when performing the "check level" test. I want to be sure I am doing this correctly, so my question concerning that is: am I correct in the process of using the output gain of the soundcard and the output level in Window's properties to initially get me to 75dB (or about -18dB on the meter), and then from that point on I can leave those levels as is and use the preamp to adjust the volume up and down for future level tests?

Does that make more sense?

**brucek** · **08-25-09, 05:34 PM**

Quote:

wondering why I have to raise the volume of the soundcard using the gain knob and the windows properties (after I have already made a calibration file) when performing the "check levels" test?

The soundcard calibration file has nothing to do with levels. It corrects for soundcard response anomalies after a measurement is taken.

Quote:

am I correct in the process of using the output gain of the soundcard and the output level in Window's properties to initially get me to 75dB (or about -18dB on the meter), and then from that point on I can leave those levels as is and use the preamp to adjust the volume up and down for future level tests?

The output level is adjusted as you mention to a reasonable starting point (along with setting the REW sweep level to -12db).

Then when the Check Levels routine is run, you set the volume control on your receiver to obtain the 75dB at the listening position. Then you don't touch those levels.

Now the Input level to the soundcard is adjusted to get about -12dB on the input VU meter. That's it.

brucek

**Nuance** · **08-25-09, 05:37 PM**

Quote:

brucek wrote:

The soundcard calibration file has nothing to do with levels. It corects for soundcard response anomalies after a measurement is taken.

The output level is adjusted as you mention to a reasonable starting point (along with setting the REW sweep level to -12db).

Then when the Check Levels routine is run, you set the volume control on your receiver to obtain the 75dB at the listening position. Then you don't touch those levels.

Now the Input level to the soundcard is adjusted to get about -12dB on the input VU meter. That's it.

brucek

Great, that's exactly what I was looking for (just a confirmation, basically). So then I was correct in assuming the two meters I circled in red (in the picture I posted) are the two that need to be matched when performing the soundcard calibration?

Thanks again!

**brucek** · **08-25-09, 05:38 PM**

Yep....

**Nuance** · **08-25-09, 05:40 PM**

Thank you. See, I told you they were stupid questions

, but I could never find a precise explanation, so I am glad I asked. Thank you, Bruce.

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