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Cash Cas

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Hey Audio Science forum!

I recently got more into audio and I want to treat my room.
So I bought an electret measurement microphone to know what frequencies are the worst in my room to try and treat them.

This is my current gear:
-Scarlett 2i2g3 audio interface
-Adam sub10mk2 subwoofer
-Adam a5x near-field monitors
-Dayton Audio EMM6 Electret measurement mic.

Audio interface is connected to my subwoofer TRS -> XLR
And the subwoofer is then connected to the A5x's xlr -> xlr
EMM6 is connected to input 1 through XLR

The EMM6 arrived yesterday, today I was downloading REW and I can't get the calibration started even, it makes me feel kinda stupid to be honest haha
What I did thus far:
Put the calibration file that I downloaded for the EMM6 in the Mic/Meter tab.
I let the output in input be set on default, as they are both set to use the focusrite 2i2 as default in windows.

When I click on measure it gives me the following error:
1.png


But I don't use a SPL meter, just the mic.
If I go to calibrate SPL it will ask me to use a seperate one.


2.png

The -14.7 value doesn't really change. Even If I use some crappy SPL meter app from my phone as my own SPL meter value and play around with it.
I thought maybe the EMM6 could be broken, so I tested it and it does record my voice, so I think it works properly.
I tried testing the "levels", when I turn up the sounds, the ref In level changes accordingly, so that actually works great. (see pic below)
I assume that's the reference input, which in my case is the EMM6. (with gain set to 12 o' clock position)
So why doesn't it work with the SPL meter function?

3.png

I thought it could be maybe cause I didn't calibrate the sound card? Which in my case is the focusrite 2i2g3.
So I wanted to create the audio loop but I have absolutely no clue what to connect to what, everyone seems to be using an AV recorder or something else on youtube and I can't figure it out.
How do I set this thing up with my gear? I don't mind buying a cable or two if that's needed.

Any help at all would be greatly appreciated!!
 

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AnalogSteph

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Absolutely SPL calibration does nothing but tell the system what the correspondence between acoustic level and digital input level is, i.e. the overall gain. In your case, it is influenced by both mic sensitivity and the input gain setting on the 2i2. Without a known reference, all you can do is take an educated guess, e.g. get mic sensitivity from the datasheet or calibration chart and look up interface system gain at full tilt (@Julian Krause generally mentions it in his reviews). Then you just have to generate a constant sound level, back off input gain to your normal setting and determine how many dBs lower you are. [1]

At the end of the day, for what you are trying to do you don't need absolute level calibration at all. Your measurements may be offset up and down by an unknown amount of dBs if you are just using the default value but relative levels will still be accurate.

[1] I may try and derive a formula for the whole thing, maybe even a little JS calculator. Seems useful enough.
 
Last edited:

JohnPM

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Looks like you have the mic connected to the left input but you have told REW to listen on the right channel.
 
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