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Discussion Starter · #1 ·
Hey guys,
im trying to take a measurement with REW in my new room. I did it in my previous room aswell and altough the average dB seemed a little high i didn't realy have any problems with it. Now however it seems some setting is set waaaay off. which makes the REW give the freq. response up in the 140dB area. Unreadable. I've added a picture to make my problem more clear. Does anyone have an idea as to what's wrong?
 

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Discussion Starter · #3 ·
Not that i know off. But i've used it in a lot of occasions and some other measurement programs. Never had a problem. So i dont see why that should be a problem now...

Could it be something in REW at all?
 

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There are so many variables that could alter your results that it's a good practice to re-calibrate the sound add and mic before taking any measurements when it's been any substantial amount of time between measurements.
 

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Discussion Starter · #5 ·
I've now correctly calibrated my soundcard. Connected the ins to the outs of the Soundcard. And the strange thing is dat the average here isn't 0dB as it should be. its around 84dB 0_o. I have a M-Audio Delta 1010LT sound card by the way...

What's causing all this?
 

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Discussion Starter · #7 ·
well i just have a regualr condenser mic (included in the ARD measurement box if that rings a bell). I thought that calibration menu was only for spl meters. since it says "calibrate SPL" and next asks me to set the amount to the same amount my spl is giving... How do i go about that with my own mic?
 

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> Delete your REW preferences ( that should reset your soundcard calibration to zero ) & then run another soundcard calibration ( loopback ) to be safe .

The measurement is still at an average of 90dB instead of 0dB. But atleast now i can read it.
> A "real" acoustical measurement of a system within a room, will always be above the zero mark ( typically in the 70 to 90db range ) .


> Here's a link to REWs' help files, in pdf format ( if you feel a need to review how things work within REW ) .



:sn:
 

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Did you calibrate the mic?
Not that i know off. But i've used it in a lot of occasions and some other measurement programs. Never had a problem. So i dont see why that should be a problem now...
Nothing to do with your scaling issue, but you do know that you can't get accurate measurements unless you have a calibration file for your mic, right?

Regards,
Wayne

 

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Discussion Starter · #17 ·
Oke guys, I've mailed IK Multimedia with the request to send me the microphone cal. file as suggested. In the mean time, i've made a measurement. Can anyone tell me how i'm supposed to know what the average is? In order for me to know the sizes of my dips and peaks.

and thanks for al the help so far!

 

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Can anyone tell me how i'm supposed to know what the average is? In order for me to know the sizes of my dips and peaks.
> I recommend that you apply 1/6 octave smoothing to each of those three sweeps ( That's the smoothing I use when analysing full-range sweeps ) .

> Then open up the "All SPL" window .

> Click on "Average the Responses" ( bottom left of the "All SPL" window ) to see the average of your 3 sweeps .

:sn:
 

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well i just have a regualr condenser mic (included in the ARD measurement box if that rings a bell).
Well, I couldn't find any online mention of the "ARD measurement system" but looky look, IK Multimedia does market this ;



For those paying attention; REW will do what this product does ( for free ) , measure your system , create correction filters ( EQ ) , that are then exported as Wave files, which can then be "hosted" in a VST convolver ( among other things ) for EQ correction of your playback sources .

:sn:
 

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snip,,,,,Does anyone have an idea as to what's wrong?

Yes, the ( so-called ) soundcard calibration ( seen in your picture ) is clearly not valid .

> I'm confident that your skewed db readings were caused by you loading an "actual speaker measurement" ( instead of the required soundcard calibration file ) .

> Apparently REW version 4.xx allowed noob mistakes like this to be made ( while downloading version 5.0x very likely corrected the issue by deleting the existing preferences files containg the erroneous info ) .

> FYI ; You're still reading measurements in the high 90s because you haven't given REW a more reasonable reference level to work to ( by telling it something like 75db, when you "calibrate" the SPL meter function ).
> This db calibration protocal is still worth executing even if you don't have a SPL meter .

<> :sn:
 
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