I am using this external USB sound card.
So I can just use one RCA Plug (from sound card either L or R) to one RCA Plug (from AVR either L or R).
But if I am going to measure the Main speakers, then I will have to connect BOTH L + R from Sound card and AVR.
...OH..I think of a question..but might sound stupid..if I connect BOTH L + R from Sound card and AVR to measure Subwoofer freq respond, will it play louder than using just L to L from sound card and AVR? (Or REW will automatically adjust the sound level on it software side to make sure that it measure correctly? Will it affect the SPL level calibration for the subwoofer?)..
Sorry..my understanding is really bad...hope you have patience to reply my doubt... I really appreciate..Thanks.