REW Forum

**wildchild22** · **09-10-09, 05:14 PM**

I bought a mx882 as an alternative to the samson or art cleanbox. I am going to post the results hopefully the experts can chime in to give understanding as if there is any problems with the frequency response.
I measured the soundblaster live external usb with a loop back and saved the soundblaster jpg of the graph. then I inserted the mx882 into the loop and measured the calibration and saved the graph. The only difference is I swapped cables as I needed 1/4 to rca. The cables for the loop back of the soundcard was aprox 1 foot. the cables going to and from the mx882 are 15 ft.

**wildchild22** · **09-10-09, 05:19 PM**

here are the graphs
and the link to what the mx882 can do. It can do the work of 3 samson or art cleanboxes. I am going to use it to convert my yamaha rx-v661 preouts to match my ep2500's

**wildchild22** · **09-10-09, 05:31 PM**

first graphs is loop without mx882. Second is mx882 added to the loop. Next are the mdats first without mx882 and second mx882 in the loop. I had to zip them.

**brucek** · **09-10-09, 05:38 PM**

Quote:

I measured the soundblaster live external usb with a loop back and saved the soundblaster jpg of the graph. then I inserted the mx882 into the loop and measured the calibration and saved the graph.

I'm not sure of your technique here.

Generally, when we want the response of a device. we first do a soundcard calibration and save the file so REW is pointing at it. Then as a check to see if the file is valid, we take a normal response measurement of the loopback cable to ensure that it returns a flat response. If so, we know the test equipment won't influence the measurement of the device.

Then we remove the loopback and do a normal response measurement of the device. That way we're looking at the devices response only (and not the device plus the soundcard).

Is this what you did? If so, great......

brucek

**wildchild22** · **09-10-09, 06:03 PM**

Here are the revised measurements

**wildchild22** · **09-10-09, 06:05 PM**

the first is a measurement of the soundcard and the second is a measurement of the mx882. They look identical to me.

**wildchild22** · **09-10-09, 06:09 PM**

I calibrated the soundcard then I reopened rew and measured the soundcard then I saved the graph then I used the mx882 and remeasured. I had to adjust the level before I could get it to work as it was clipping it said. I done this by adjusting the wav slider in windows till rew said level was okay. I did this for the soundcard only as rew said the level was okay for the mx882

**brucek** · **09-10-09, 06:26 PM**

You have a meter or mic calibration file loaded. It must be removed - there is no meter.....

Then redo the device measurement. We don't need to see the soundcard. We'll assume it's correct.

**wildchild22** · **09-10-09, 06:26 PM**

Okay I think I finally done it right. Thanks brucek for the help.

first soundcard measured thenm mx882 measured. I hope this is right. A bit of a learning curve not the way I thought of doing it at all but it works! If I click the cal file it just shows a line above the green line dead flat at 75db instead of the green at 67db

**brucek** · **09-10-09, 06:45 PM**

Yeah, that's good, but if you want to show a response of the device, you can't use the standard vertical scale of 45dB-105dB or the horizontal scale of 15Hz-200Hz.

You need to expand the vertical scale until we see get an idea of the response, and you need to offer the horizontal axis down to at least 5Hz and up to 20KHz.

Use something like a vertical axis of 70dB-80dB and a horizontal of 2Hz-20000Hz.

You do need to run the Calibrate routine after the Check Levels routine and set the Calibrate level to 75dB. That way you graphs will come out at 75dB...

brucek

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