[Blueeyedfrog]

Thanks for your relies.

At the moment I am still in the process of obtaining a BFD, so I'm a little unclear as to measuring/accounting for the effect of the BFD filters you refer Otto. Presumably, I just connect the BFD inline between the receiver output and sub amp input, then do measurements (cal. file loaded). I.e. the BFD is not used in the inital calibration of the soundcard/receiver loop. However, after cal. the SPL meter just plugged straight into the soundcard line in when measuring sub, and I can measure the effects of the BFD filters?

From memory, FR for the receiver was virtually flat from 10-20,000hz as you say Otto.

Sorry Otto, you lost me on your last post!

"For the sake of discussion, suppose that the receiver has some really goofy and exaggerated frequency response (FR). Do the calibration, and apply it in REW. Now do your sweeps and get everything perfect with REW and a BFD. Now, remove REW from the picture, and bring in a "perfect" spectrum analyzer, but that doesn't use a cal file (i.e., it's been calibrated on its own, and it flat from DC to infiinty at both input and output, etc.). If you remeasure, FR won't be flat due to the imperfectness of the receiver that was calibrated out with the REW cal file. That's what I'm thinking."

I guess I'm thinking that if I got everything perfect initally using a 'perfect' specturm analyzer (not REW) when using the analogue soundcard output (via the receiver), then played music to the receiver via the soundcard's digital output (which is what I only use), then the 'perfect' filtered sound/FR that I had using the analogue soundcard signal (soundcard's DAC signal) is lost due to the different response/output of the receiver's DAC analogue output?

Cheers,
Paul