subwoofer connection quandry

Hi Loomis,

Thanks for the implicit compliment. See my post here, which explains the concerns, and the rest of the discussion in that thread.

The bottom line: It might work ok, and some people do just that, but I don't consider it to be good practice and I would recommend against it. There might be adverse effects to both sonic quality and the long term reliability of the D7050, depending on the specific design of the circuit in the D7050 which drives the sub outputs. I would recommend either obtaining a separate mixer to combine the two channels, as discussed in the thread, or else connecting at speaker level.

Best regards,
-- Al

Thanks, Loomis & TLS. There's no technical issue connecting just one output channel, but obviously it won't be sonically optimal with recordings having deep bass content that is not centered (i.e., that is not recorded equally in the two channels, to a close approximation). As Elizabeth indicated in the other thread that probably won't be an issue with many or most recordings, but IME it would definitely be an issue with some.

The resistor-based approach TLS describes amounts to implementing a passive mixer, and can work well. In fact in the other thread I linked to there is a link describing exactly that, although with resistors in the 5K to 10K range. What value is optimal depends on the impedances and other characteristics of the particular components, and also perhaps on the length and characteristics of the cable (although that probably doesn't matter much if at all in an application such as this where effects on high frequencies aren't a concern).

In this case the output impedance of the NAD's sub output and the Hsu's line-level input impedance do not appear to be specified. But my suspicion is that the resistor value that is chosen is probably not very critical. If I were to hazard a guess I would say go with something in the area of 1K to 3K for these particular components, if that approach is pursued.

Best regards,
-- Al