Subwoofers that do both L/R & LFE simultaneously?

Not sure why all subs do not work this way, but suspect it is a cost issue. The speaker level inputs on REL go into a switch selectable filter. Purpose is to fine tune the integration of speakers and room with the sub. It is not really a crossover, as the filter has no effect on what is sent to you main L/R speakers. And then the REL sub mixes LFE and speaker level.

In any case, it works well!

With REL subs, the speaker (high-level) input is the
PREFERRED method. It integrates better than with
low level signal inputs.

I have two REL Strata III subs which I use with both my
home theater system (low level input) and with my two
channel stereo system (high level input). They are
excellent and integrate seamlessly with my Magnepan
speakers.

Just my opinion of course, but adding two more (mechanical) electrical connections and another pair of speaker cables between my amp and my main speakers just doesn't say "high end audio" to me. It's OK for a modest HT system, but at best a compromised result for 2-channel audio.

Nsgarch,

Then you misunderstand how a REL is connected at speaker-level.

With the REL, the sub is connected in parallel with the main speakers. It presents such a high impedence (100K Ohms, I believe) that it doesn't significantly affect the impedence "seen" by the amplifer. The speakers and the sub are both connected to the speaker terminals on the amp.

Nrenter, what you describe is technically the same circuit as I describe (except tied together at the amp instead of at the sub) And it's a little better, yes, for the same reason bi-wiring can be. But with the scheme you describe, you could really be buying lots of speaker cable!

Either way, the sub is sampling the amp output through a filter circuit of it's own. I guess that's OK, but being the stickler for cleanliness and simplicity that I am, I insist the sub have its own direct line-level feed out of the preamp.