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Discussion Starter · #1 ·
I am trying to set up REW and am having a problem with my freq response beginning to fall off at about 1k. By the time it gets to 10K it's already 20+ dBs down. I'm not sure what I may have done wrong, playing an external pink noise CD as opposed to the REW pink noise yields the same result. I've used other measurement software and never got this type of reading and listening to the speakers obviously does indicate the roll off shown in the graph. The pink noise from REW even appears to have less high freq content vs the pink noise from a test CD I used.

I have the calibrated Behringer ECM 8000 mic and the M-Audio Fast Track Pro. Sound card calibration went OK, the levels were lower than desired with about a 65dB reading on the mic calibration SPL. Trying to get to 75dB meant turning things up much louder than necessary. So something could be wrong there. I'll try to redo from the beginning tonight but just thought I'd check for some feedback that may help.
 

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If you are looking at the pink noise response on the RTA make sure it is in RTA mode and not spectrum mode, a spectrum view of pink noise drops at 10dB per decade. Sounds like you may have something different going on, however.
 

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Discussion Starter · #3 ·
Yeah John It must be something else. I am sure the RTA mode was correct.

The sound card calibration seems to go fine, that gave me a reading out to 20kHz. The mic calibration also gave me a reading out to 20kHz. When I do the RTA and just isolate the high freq. anywhere from 1kHz to 20 kHz I can hear those fine (although I can't recall what dB they were but I'll check later) The sweep sounds fine when it plays and doesn't seem to decrease in volume at the higher freqs. REW Pink noise however does reveal a more bass heavy sound but it sounds (more) normal when using an external pink noise source. I even put mic close to the speaker and got the same results so I am confused by this.
 

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Discussion Starter · #4 ·
I started over and the issue I'm having is not getting enough output to the mic from the M-audio unit. I did the loop back and that looked fine, the M-Audio unit saw the signal and the LED lit up and I calibrated the sound card. But when trying to check the levels for the mic everything is very low, not even or barely registering. I checked the PC OS system to mute other devices not used etc... When plugging in the mic I don't get the LED to light up showing there's a signal like during the loop back process. In order to get a signal light I need to turn up the gain to max and then I get feedback. Cranking the volume on my processor doesn't even get me close to 75 dB. I'm at a loss, everything look to be right. I'm tried two different laptops, different cables, even a different mic but the same result.
 

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In order to get a signal light I need to turn up the gain to max and then I get feedback.
You would expect to have to turn the gain knob up fairly high for a mic input. You should not get feedback however, the mix knob needs to be turned fully clockwise, to the "PB" position, to ensure your output contains only the test signal and none of the input.

Beyond that, check the input settings are correct (INST selected) and phantom power is on, per the manual: Make sure the associated channel’s Inst/Line button is set to the out (Inst) position for microphone or instrument input, or to the in (Line) position for line level sources. If you are using a condenser microphone, be certain to slide the 48V PH Power switch to the On position (after connecting the microphone to the XLR input). If your microphone input signal is too hot (Clip LED lights steadily), press the Pad button to lower the input level.
 

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Discussion Starter · #6 ·
Making progress. I ended up rechecking and testing every option I could think of, not sure which one(s) solved the issue but we are getting results now. End up where yo suggested John, signal level maxed, Mic level fully clockwise, level knob about 1 o'clock. Loop back on the left channel and moving to making some measurements on the mains.
 
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