right - thanks for this: I see you did something like it with a different set-up. but does anyone have experience doing it with the LFM2? will ask a friend to come over with the SPL meter, and will try two test-tone CDs also, and then report back if findings are of interest. - background: I'm considering a second sub (instead of swapping the LFM2 from one system to another), and the purchase may depend on how well this in-line connection works.