Stereo subwoofer output to a mono sub input? (1 Viewer)

[swimtwobirds]

Hi folks,
I'm setting up a 2 channel system with a Harmon Kardon HK3470 reciever--an older model but it's got a nice phono stage built in.

The HK3470 has a puzzling Left-Right pair of subwoofer outputs. It simply instructs me to use the lower (right) output if I have a mono subwoofer input.

The manual doesn't give any indication about the crossover settings, but I'm pretty sure they're not adjustable. Which is fine, I can do that at the subwoofer stage.

But I am curious about what might be up with a left-right subwoofer output, whether the instructions are simply directing me to use the right subwoofer output (which is probably fine as most bass signal is centered, but still, weird!) or whether I should be summing the outputs before sending to the sub. Any ideas?

 

[JohnRice]

Just run the mono output from the receiver to the mono input on the sub.

 

[swimtwobirds]

The thing is, i'm not sure it's actually a mono output. It seems like it might just be a right channel output pretending to be a mono output. Additionally, there's no information about where it's crossed over (if at all) but it's way too high. I can hear the sub trying to produce stuff up into the mids. I'm clearly going to need to insert an EQ.