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Hey Brian,

Unfortunately, the REW Downloads page – and the video - neglects to mention the need for a proper calibration file when taking measurements with the mic in an upright position.

It’s a well-known fact that the mic’s off-axis response is depressed in the upper frequencies compared to its on-axis response. For reference, see the graph below of measurements for a Dayton EMM-6 mic as performed by Herb Singleton of Cross Spectrum Labs. As you can see, when the mic is oriented 90-degrees of-axis from the signal source, its response at 20 kHz is a full 8 dB down.

Thus, room measurements taken with the mic upright, without the proper 90-degree calibration file, will show a droop in response above ~2 kHz that will not accurately reflect the speaker’s response or what the user actually hears. We've seen it happen here many times over the years, REW users perplexed about their poor measured response in the upper frequencies, only to find out that they weren't using the proper calibration file when they measured with the mic upright.


EMM-6 On and Off Axis Response.jpg
Dayton EMM-6 On and Off Axis Frequency Response
Courtesy of HiFi Zine
Regards,
Wayne
 

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Above 2k i'm not too worried about. What we're trying to really tame is primarily below say 400Hz where the response is pretty much identical. If a 90 degree file is required, then it's something we should have on the site.

Bryan
 

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Isn't the iso curve used by many professionnals supposed to decrease gently above 2K ?
This would mean that the given curve (as wayne highlighted) is near to what it should idealy be and poor measurements of the treebles doesn't mean that it simply doesn't exist or that you can't hear it.
A treeble uprising its power above 2k measured at 90 degrees would be dreadfull to hear and challenging to listen to more thant a few minutes.

After mesuring, when you start equalizing your room, feel free to push it up a bit just to have your own idea, it sometimes can make beautifull enhancements and sometimes can make everything sound really bad. It depends of the tweeter quality/softness/crisspiness. ;-)
Everything may sound good out of the ideal curve, just give it a try after you've reached it.

Ideally for me, I try to flattent the more I can to stick to the ideal curve and then I unleash it to different point from what I am hearing and what I wish to reach.

So reaching the ideal curve is simply where the real work begins for me.
 

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I'd like to ask a question, when I understand that Room eq can allow to put cut frequencies for each speaker, can I consider this software as a full active filter ?
 

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Above 2k i'm not too worried about. What we're trying to really tame is primarily below say 400Hz where the response is pretty much identical. If a 90 degree file is required, then it's something we should have on the site.
At 400 Hz and below the mic is omnidirectional, which makes upright orientation of the mic - and the proper calibration file - moot.


...can I consider this software as a full active filter?
REW is a measurement program, not an equalizer program.

By the way, welcome to the Forum!

Regards,
Wayne
 

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Great video, thanks for posting.. got my uMIK a couple months ago and my DSP1124 is on it's way.. now I just need to wrangle up the necessary cables and I'm off and running.. :bigsmile:
 

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Great video, thanks for posting.. got my uMIK a couple months ago and my DSP1124 is on it's way.. now I just need to wrangle up the necessary cables and I'm off and running.. :bigsmile:
 

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I'm definitely going to check out this video, I'm curious as to how this all works and would like to try it out but not before understanding how to use it. From reading all the post above it sounds complicated.
 

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pddufrene, I was right there with you.. I've been sitting on my uMIK for months now.. but, I've finally made moves to get started, got my DSP1124 today - my monoprice order of wires is coming in tomorrow.. so hopefully with some help from videos like these and the Shack/AVS forums I can get up & running in no time.. fingers x'd :gulp:
 

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pddufrene, I was right there with you.. I've been sitting on my uMIK for months now.. but, I've finally made moves to get started, got my DSP1124 today - my monoprice order of wires is coming in tomorrow.. so hopefully with some help from videos like these and the Shack/AVS forums I can get up & running in no time.. fingers x'd :gulp:
I wish u luck, ill end up giving it a try once I figure out everything I need to get it going. Maybe by then you'll be able to coach me through it. Lol
 

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I have a UMIK-1 and MBP. I was wondering how and if one needs to you perform the sound card calibration and level setting procedure as depicted in the video.
 

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I'm not a studio guy so I'm not familiar with that equipment - sorry. Basically you need to let the system measure whatever equipment will be used to record and generate the sound by creating a loopback for the calibration.
 

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I have a UMIK-1 and MBP. I was wondering how and if one needs to you perform the sound card calibration and level setting procedure as depicted in the video.
In REW 5.01 beta page 30, it says:
Calibrating the Soundcard
This step is not required when using a USB microphone as the input, skip directly to
Check levels
 

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In fact, with a USB microphone, it is a lot simpler
quote from REW 5.01 beta page 28:
The initial steps required to make room measurements are:
1. Choose the audio input and output
2. Calibrate the soundcard (not required when using a USB microphone)
3. Check levels
4. Calibrate the SPL reading (not required when using a USB microphone that has
REW-compatible sensitivity cal data)
 

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My mistake. Don't understand WHY one would still not be concerned about the frequency response of the sound card though.
 

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My mistake. Don't understand WHY one would still not be concerned about the frequency response of the sound card though.
You are right about that, I do not think that it would be flat down to 10 Hz, sound card has probably a high pass filter on the low range (DC- protection) and a low pass filter at the high end for anti-aliasing
 

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You are right about that, I do not think that it would be flat down to 10 Hz, sound card has probably a high pass filter on the low range (DC- protection) and a low pass filter at the high end for anti-aliasing
I just had a second thought, the output is not completely flat across the range, but the input reading is not ruler flat either, so if you calibrate it, you will still introduce an error because with a USB mic, you do not use the input of the sound card.

If there was a cal file for the sound card input, then it would be perfect
 
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