# Room EQ Wizard Help - Feedback



## MatCam (Mar 13, 2014)

Hey guys,

Another rookie here looking for help with Room EQ Wizard.

I've been following GIK Acoustics tutorial on Room EQ Wizard but every time I try to calibrate the sound card and the mic I get this piercing feedback when the levels approach the suggested levels.

Audio Interface: Yamaha MR816X
Mic: Behringer ECM8000

Any idea what's going on?

Some help would be swell,
Mat


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## EarlK (Jan 1, 2010)

"Feedback" is caused by the monitoring of the input of your record channel ( into the same output that the REW test signal is using ) .

ie; Stop sending the input signal to the output ( where it then mixes with itself & becomes a recirculating loop of sound-energy called "Feedback" ) . 

:sn:


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## MatCam (Mar 13, 2014)

Earl thanks for the quick reply. Doesn't the calibration call for a feedback loop?

Anyway, I continue to get feedback when I check the levels of the ECM8000 making it impossible to approach -18.

I should mention I haven't used a SPL meter yet as the GIK tutorial hasn't mentioned it.

Check out the photos to see what I mean.

As you can the mic is going into input 3, the outs are 1 and 2 (monitors) and the ECM 8000 is at the listening position pointing upwards.

Should I be adjusting the monitor output volume as well as the microphone preamp?

Thanks again.


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## EarlK (Jan 1, 2010)

( When calibrating the soundcard ) the GIK video talks about the connecting of a cable to create a loop-back circuit ( ie; wiring output to input ) . 

The video does not instruct the user to create acoustic feedback, such as you have done .

( As I directed in my first post ) you need to stop routing the input back into the output .

( It appears that to accomplish this ) you may need to use CuBase or your favourite DAW software to turn-off input monitoring ( since your hardware doesn't _seem to _come bundled with it's own soft-patch capabilities ( ie; soundcard specific, routing & mixing software ) .

If you can't prevent this ( feedback from occuring ) , then you'll need to use something like the following ( here a simple switch on the soundcard disables direct monitoring/feedback ). 

:sn:


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## GCG (Aug 22, 2013)

I think what Earl was referring to is the monitor function in the computer interface. If you monitor the mic it plays through the speakers along with the test signal/sweep and that's where your feedback is coming from. Turn this monitor function OFF. Below is a PC based example. Don't know what the comparable control is in a MAC.


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## GCG (Aug 22, 2013)

You ninja'd me Earl and I wasn't aware of the monitor switch. The computer monitor path still applies though.


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## GCG (Aug 22, 2013)

OK one more cup of coffee and I might wake up and actually read the whole post.


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## Wayne A. Pflughaupt (Apr 13, 2006)

MatCam said:


> I should mention I haven't used a SPL meter yet as the GIK tutorial hasn't mentioned it.


I see you’re using upright the mic orientation shown in the GIK Tutorial. That’s fine as long as you’re doing measurements for acoustics data or subwoofer frequency response. For full-range frequency response measurements, you want to point the mic directly at the speaker you are measuring, and use a 0-degree calibration file for the mic.

Regards, 
Wayne


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## MatCam (Mar 13, 2014)

Thanks chaps! I managed to mute the input in MR Editor (The MR816X software controller for the interface).

Worked like a dream.

Wayne cheers for the advice regarding mic orientation.

Mat


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