Yamaha A-S801 Subwoofer Connection Confusion

Regarding the option to use the Yamaha's Sub Out to the Subs LFE input. Does anyone know if this is bypassed when using the Pure Direct or CD Direct Mode? I know those "pure" modes bypass the tone, balance and loudness controls - I am wondering if it also bypassing any type of bass management as well.

I know - perhaps I am overthinking this

 

Yes. And it surely just sums all the bass (including LFE-this is a stereo unit, I'm sure they are not sending just LFE out that RCA jack). Then according to page 18 of the Owner's Manual
https://usa.yamaha.com/files/download/other_assets/2/332372/A-S801_om_UBL-1.pdf
it is filtered above 100 Hz. The output can hit 3.5 volts, which could clip the inputs on some sub amps, so that's something to check out.
Unfortunately, as is stupidly the case with so many stereo units, there appears to be no provision to cut the low bass out of the main amp and speakers. (There is NO "bass management" that you mention in the post right before this one). Therefore they will still be trying to put out all the low bass. If the speakers are straining, you could use the bass control to cut and jack up the sub. That will work albeit not the purest way. But the only "fix" would be a different amp.

 

Like most ported speakers, his have an acoustic high pass filter that bascially makes it a non-issue. They're response is down by more than 10db at 30Hz and the speakers are certainly large enough to handle 40Hz^ frequencies with little strain. Could they audibly benefit from further cutting? Possibly, but that also introduces more connections and parts in the signal path.

 

?? I think there is some confusion with coax cables, whose source and receiver have a characteristic impedance. If you're talking about RCA cables, they aren't 75 ohms. They're kinda zero ohms, or irrelevant ohms. The source has a low output impedance-maybe hundreds or a thousand IIRC, and the receiver maybe 10-30,000 ohms.

 

Not so strange, since the LFE channel should just be very low bass, so the crossover is already sort-of taken care of.