LFE vs High-level subwoofer connection, for FIDELITY

The "extra fidelity" from speaker level connections is some extra foolery propagated by the REL guy...

If the preamp has xlr pre-outs and the sub takes xlr input...I would go with those and call it a night...If that's not possible, use the rca preouts and don't worry about it.

I'll eat my hat if anyone on this forum can tell the difference.

What subwoofer connection method offers higher fidelity, and why? The LFE, 75 ohm unbalanced RCA cable. Or high-level, speaker wire to the binding posts of the amp.

Subs with built-in dsp can add a tiny bit of lag....it was discernible on some older subs with built-in dsp..if you didn’t have the ability to delay the main speakers to compensate (as would be the case in a purist rig). It had gotten better these days.

Does one add to "lag time" and does this even matter?

@kr4 I’ve got the same experience as the other responder. My sub has eq knobs, low pass filters and room gain filters on the back panel. So my bookshelves roll off at 50 hz, so I set the sub to 60 hz and under. Even on high pass, the sub filters it 

@kr4 

Night & Day difference in my system between low level and speaker inputs.

The difference is in the tonality and integration with the mains. Via high level you can’t tell there is a sub playing at all on my system. 
via the low level, the tonality did not match and the bass  sounded disconnected from the music. My amps are type 45 monoblocks. I’m sure they impart a specific sound across the board.

When I tried it, I expected it to be a 6 in one hand-half dozen in the other type of situation. It wasn’t. 

i remember one YouTube reviewer who had his sub configured via the low level inputs because it sounded better. He wasn’t a tube guy.

Fortunately it’s really easy to try. For me it involved buying long rca connectors to try, but they are now sitting storage. which is just to say you too should try it for yourself. It’s part of the fun.

jbuddha882 OP wrote:

@kr4 I’ve got the same experience as the other responder. My sub has eq knobs, low pass filters and room gain filters on the back panel. So my bookshelves roll off at 50 hz, so I set the sub to 60 hz and under. Even on high pass, the sub filters it 

Granted and, many years ago, that would be acceptable, assuming you have a tool to measure and analyze what's going on. Nonetheless, there is still no control of the low end of the main speakers and there is considerable overlap between them and the sub(s).   You should try, if you can, the Arcam SA35 or similar.