Newbie needs help

I'm trying to run analysis on a recording studio in my house, and I am having problems calibrating my soundcard (actually a firewire interface). The loopback works, but my graph does not have the expected shape (see graph, which is using 1/12 smoothing).

Also, when the calibration finishes, it gives this message:

Impulse peak is not where it should be, the measurement may have been corrupted.

Check the Impulse Response and the Captured Data plots.

It also seems strange that I have to turn the volume up on the firewire interface to near clipping so that it will match the level of the calibration output (as instructed by REW). Any ideas what may be wrong here?

[JohnM]

Mac or PC? Under OS X Java applications do not get access to Firewire soundcard inputs even when they have been selected as the default in sound preferences. 10.4 had the same problem with USB cards, but that was fixed for 10.5. The built-in line input works fine for measurement purposes.

Thanks for the reply, John.

I'm on OS X 10.4. I did read about the issues with firewire on mac, but I didn't have any problem getting REW to receive input through Core Audio. For example, if I talk into the mic, the level change is displayed on the REW input meter (and the mic is connected to the firewire interface). Do you think there is still some compatibility issue here that is causing the strange readings?

[JohnM]

I guess you are using a line input rather than mic input for the loopback? How is that input selected? The plot looks like there may be no input signal, and turning the gain right up is just amplifying the input noise level. If you look at the scope tab after a measurement you can see that actual waveform that was captured, may indicate whether it is a valid input.