Need a wee bit of REW assistance

**w3bby** · **07-13-09, 06:02 PM**

Goal- To find the worst frequency in my room and dial it in better using my Sub's Parametric EQ.

Equipment- SVS PC Ultra 13 | Pioneer SC07 AVR | HTPC w/ RadioShack Analogue Meter.

I have done step by step from the help files.
I am getting signal etc. I just keep hitting a point where I don't know what else to do or if what i have done is correct.

-I have the RadioShack .Cal files ready to go.

-I have the Calibration Mic plugged in to the HTCP with a mono to stereo wire, no loopback being used. (Do I need loopback without having a Behringer?)

Can anyone be so kind as to tell me the steps to achieve my goal? It would be really appreciated!!!

**tonyvdb** · **07-13-09, 06:44 PM**

Have a look here, I was in the same position just last week it should give you the information to get you going.

**brucek** · **07-13-09, 07:11 PM**

Quote:

no loopback being used. (Do I need loopback without having a Behringer?)

Well, you need to first install a loopback alone without any other cables and do a soundcard calibration routine to create a calibration file for the soundcard. Once that is complete and that file saved with REW pointing to it, then you remove the loopback and use that channel to connect the SPL meter and the receiver. Then you run the Check Levels routine and Calibrate routine and then Measure.

brucek

**w3bby** · **07-13-09, 09:07 PM**

Quote:

brucek wrote:

Well, you need to first install a loopback alone without any other cables and do a soundcard calibration routine to create a calibration file for the soundcard. Once that is complete and that file saved with REW pointing to it, then you remove the loopback and use that channel to connect the SPL meter and the receiver. Then you run the Check Levels routine and Calibrate routine and then Measure.

brucek

I am so lost on this loopback thing.
So if my PC is hooked up to my avr do I need it? All I have is the mic to the mic in on the pc and the pc out to the avr. It was generating anf picking up the tones etc. I did make the calibration file. But who knows if that is right?

Why would I connect the SPL meter to the avr?? Doesnt it need to be hooked up the REW?

THEN- Am I loading the .cal of my radioshack mic...then runing the sound card calibration and saving that as my main NEW .cal file?

Thanks guys!

**tonyvdb** · **07-13-09, 09:41 PM**

Make sure your using a PC with a line in not a mic in or the software will not function properly. Disconnect the SPL meter and the mic during the loopback calibration.

**w3bby** · **07-13-09, 10:09 PM**

Quote:

tonyvdb wrote:

Make sure your using a PC with a line in not a mic in or the software will not function properly. Disconnect the SPL meter and the mic during the loopback calibration.

I still cannot wrap my little mind around his "loopback calibration". Also isnt my mic my SPL meter?

My soundcard has mic and line inputs.

AM I completely slow on this or what??

**tonyvdb** · **07-13-09, 10:38 PM**

LOL, dont worry. It took me 5 hrs to get this figured out the first time I ran the software. Take the meter out of the equation during the calibration you are only calibrating the sound card not the software to the meter as you already have that file.
Connect the right line output of the soundcard to the line in of the soundcard and run the calibration sequence do not have the left connected to the receiver or the meter during this time..

**w3bby** · **07-15-09, 03:07 PM**

OK Ill do that this evening. Then maybe we will be smooth sailing!

**brucek** · **07-15-09, 04:09 PM**

Quote:

My soundcard has mic and line inputs.

Yes, but an SPL meter is a line level output device, so you plug it into the line-in.

Quote:

cannot wrap my little mind around his "loopback calibration"

The loopback calibration is a one-time routine to create a file (called a soundcard calibration file) that is used to compensate for your soundcards imperfect frequency response. Your soundcard will have a response that drops off at low and high frequencies. We don't want that interfering with our measurement tests. We want a perfect, flat response soundcard. To get this, we create a file that offsets all the soundcards problems that is applied to the REW measurements.

To get the file we connect a loopback cable from line-out to line-in and run a routine that creates the file. Then we remove the loopback and use that channel for all the measurements (for measurements we connect the SPL meter to line-in and the receiver to line-out).

We also know that the SPL meter is far from perfect. We also want it to be perfectly flat when we measure. To get this, we load a meter calibration file that offsets the meters problem and applies the results to the REW measurements.

Once we have those two files (the meter file is downloaded from our site and the soundcard calibration file is created by you), then we can take a measurement knowing that our test equipment will not influence the results.

Get it?

brucek

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