Hi all,

I'm working out my understanding with REW and taking measurements of my mixing space and running into more difficulty than I anticipated.

First off, I decided to NOT use my Babyface Pro FS nor my UCXII, for no other reason than I just don't want to do something stupid and damage any inputs with a loud loopback sweep/tone/noise/pop! Instead, I tried using my Mackie ProFX6v3 mixer today and while nothing blew up ( ) it now has me confused more than before I started.

The beginners video guides I've watched make sense until I try and duplicate what they say and it doesn't work for me. Basically, I understand I need to select an output and loop that back to the same input, turn up the levels to match the 1kHz tone and then REW runs a sweep which I will create a .cal file from. That seems very straightforward except when I tried doing that, there seemed to be a feedback loop or high frequency oscillation that pegged both the meters in REW and on the mixer. Clearly, something was not right.

I started trying a few different combinations of outputs and inputs and finally was able to assign output 3 and input 1 and get the .cal file created. It was very flat...maybe too flat, as though the software was merely reading the outgoing signal somehow through the Windows audio routing? Moving on...

So the next step is to take a measurement sweep from a microphone. Since my USB measurement microphone won't be here until next week, I thought I'd try a small diaphragm condenser I have at my desk just to get a feel for the process., I hooked it up to channel 1, turned the gain to approximately unity and turned up the channel level and main out. I measured SPL with my standalone handheld and performed the sweep. The output graph looked nothing like others I've seen in the tutorial videos. There was hardly any variation, almost as if the smoothing had been turned all the way up, except I hadn't enable any averaging or smoothing. Plus. it too was very flat...just like the calibration graph. Trust me, my editing area is nowhere near that flat or balanced.

Now, I did get more variation to the sweep measurement through my microphone as I turned up the levels on the microphone. I was very conservative in my adjustments because in the back of my head, I kept thinking that putting a microphone 2 inches in front of a Genelec monitor outputting 80-90 dB frequency sweep could potentially be VERY bad. Bad and LOUD. How is this not causing the mother of all feedback loops??? Maybe someone could enlighten me on that.

Another concern/question is...I'd MUCH rather be using one of my RME interfaces but I REALLY don't want to damage anything and so I feel like I lack the courage to proceed when I don't really understand the routing and testing of it all. Is it as dangerous as my gut tells me?

Help

Thanks for reading and sorry for the long post!

-Steve