Capnbob,
I believe the way this is done "manually" is to convert millivolts to db, then you would do a left minus right and right minus left calculation to determine crosstalk. A straight reading of channel output would not account for channel imbalance. Also, it is possible that the Fozgometer does more than just measure voltage output (e.g., it could include filters to attenuate frequencies outside of the 1khz test signal so that the effect of extraneous surface noise is reduced. I don't know if this has actually been incorporated in the design, but, I do note that the needle does not jump around a lot whereas readings done with a VOM are more equivocal. I also don't know if the Fozgometer does or does not incorporate some kind of analysis of phase relationships (aside from doing the L-R and R-L), but that is possible since Fosgate is an expert in that field (one of the pioneers of early SQ matrix form of four channel sound).
I believe the way this is done "manually" is to convert millivolts to db, then you would do a left minus right and right minus left calculation to determine crosstalk. A straight reading of channel output would not account for channel imbalance. Also, it is possible that the Fozgometer does more than just measure voltage output (e.g., it could include filters to attenuate frequencies outside of the 1khz test signal so that the effect of extraneous surface noise is reduced. I don't know if this has actually been incorporated in the design, but, I do note that the needle does not jump around a lot whereas readings done with a VOM are more equivocal. I also don't know if the Fozgometer does or does not incorporate some kind of analysis of phase relationships (aside from doing the L-R and R-L), but that is possible since Fosgate is an expert in that field (one of the pioneers of early SQ matrix form of four channel sound).