# why does my microphone calibration file look like this



## Guest (Apr 5, 2008)

it seems to get noisier at the higher frequencies
equipment
macbook
rew (latest version)
mic behringer ecm 8000
preamp maudio fast track pro

i also tried to make adjustments in the 
Applications>Utilities>Audio Midi Setup application but there are restrictions.
Even when i set all the drop down menus for the fast track pro (input,output,properties),
I cannot configure the Audio Input or output sections much.
I can set source and format for audio input and only format for audio output.
I cannot set levels. Is this because thesignal is digital from the laptop
and the actual analog parameters are set in the maudio box?


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## brucek (Apr 11, 2006)

The microphone calibration file is simply a file of values loaded in REW to compensate for mic inaccuracies. There's no measuring involved.
The ECM8000 mic has a calibration file we provide on the download page.

Can you explain what you're doing - I'm confused?

brucek


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## Guest (Apr 5, 2008)

i am following the 'getting started' instructions for REW.
First get a loopback cable. In my case it goes from the RCA output on the back of the maudio fast track pro to a TS jack that fits into the combo jack on the front of the maudio fast track pro. 
Then i go to settings and start with the sound card calibration. The first step is setting the level. I do this by adjusting the knob on the front of the maudio box so that the measured level matches the output level in the little vu meter bars.
Then i hit calibrate and the thing gives me a curve which sort of looks like the thing i posted but rolls off at the high (>20khz). What bothers me is how the 'noise' (jiggliness?) increases during the frequency sweep.


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## brucek (Apr 11, 2006)

> Then i go to settings and start with the sound card calibration


So this is a soundcard calibration you're having trouble with and not a microphone calibration as your thread title indicates?

If that's a soundcard calibration response chart you've posted, I would say you're not getting any signal over the loop.
Are you selecting the correct channel in REW as you are using for the loopback cable - right channel ?

brucek


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## Guest (Apr 5, 2008)

sorry, yes, this is a soundcard calibration.

yes, the loopback cable is properly inserted. when i intentionally select the wrong channel, the db is much lower, i cannot match it to the output signal on the vu meter that pops up, and the program warns me that the level is too low if i try to calibrate. have you ever seen such a problem before?


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## brucek (Apr 11, 2006)

Did you select the RCA output that your cable is plugged into on the back of the unit (1/2) or (3/4)?

I see the switch that toggles between line and mic. Did you set it for line?

_Instrument/Line Selector Button (Inst/Line) – This button selects the input level of the front panel 1⁄4” inputs. In the out position,
the inputs are set to accept an instrument level signal (such as that from a guitar or bass) while in the in position they are set to
accept a line level input (such as that from a keyboard or drum machine). Please note that the XLR input level is unaffected by
this switch._

brucek


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## Guest (Apr 5, 2008)

i repeated the same process on a windows machine (in fact it ws the same macbook booted into windows) and without changing anything on the fasttrack pro-here is the result








this is the expected graph. obviously the mac os (leopard) is not handling things properly. 

and btw, flipping that little switch does not change the result-same curve is obtained.


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## brucek (Apr 11, 2006)

That's what it is supposed to look like. Save it..............

brucek


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