Subwoofer insight.

using different speaker taps directly to mains and directly to subs denies a fundamental advantage of self-powered subs. the need for bass comes from the source, the main amp will still be trying to make/send all bass, the main speakers will still be trying to make all bass.

you want to remove low bass signals going to both the main amp and main speakers, especially inefficient and range limited mains, like yours. then they both can do a better job.

preamp out to crossover, or preamp to sub with adjustable crossover, self powered subs,

then signal less low bass back to main amp or integrated amp line in. main amp now doesn’t need to deal with low bass signals. low bass signals no longer seen by inefficient main speakers, those speakers no longer ’try’ to make low bass.

ideally easy ability to adjust sub’s crossover and adjust subs volume. this has to be done while they are in their intended location, again, bass is not always mono, so I advocate a pair of front firing subs near the mains. if hard to access controls, and heavy, put them on low rolling ..., pull out, adjust, slide back in place, listen.

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One of those posts that sounds really technical and plausible... only it just isn’t so. There’s more going on than is dreamt of in your simple techno world, elliott.

In the real world all these extra circuits and wires you need, they all diminish the signal to some extent. Its just a fact. Nobody ever made the perfect component that doesn’t do this and until they do simpler is better.

In the real world the more sources of low bass the better. If you want to get all technical this is one where we can go and the tech and physics are solid as can be. Each woofer creates room bass modes based on its location. The more locations the more modes. The more woofers the less output needed from each one. So the more woofers the smoother the bass. Its been researched and tested and proven. Its science.

Also happens to work in practice. To a lot of us, this means more than any number of high falutin theories. 

So when you filter bass from the stereo pair you aren’t improving you are worsening.

Keeping track, that’s two ways your idea made the system worse. There’s a third.

Money spent on this unnecessary and counterproductive crossover and amp and all is money not spent where it could actually do some good.

About the only time this might be a good idea is in the case of a very low output SET where relieving it of low bass might actually be enough of an improvement to be worth it. Except notice, no one with a SET actually does this. Why? Isn’t this the prime example of when it should be most beneficial?

Except people are drawn to SET and low output in general because they enjoy listening for the truly subtle compelling detail that carries one away with palpable presence. The very same subtle detail all your extra circuits ruins. So the one guys who according to your view really should be advocates want nothing to do with it.

Me neither. https://forum.audiogon.com/users/millercarbon

Roll the low end out of the mains with a simple cap XOver, say 80-100Hz.

Check out  http://www.ielogical.com/Audio/SubTerrBlues.php for integration advice.

I ran a single 10" w TC-50s in 16 * 30 * 7 to good effect.

Adding good low end increases realism beyond all proportion. The operative word is good. As a composer friend opined on hearing my system "Every other subwoofer I've ever heard just boomed!"

Were I you, I'd opt for something with continous phase and a polarity inversion. Without them, integration will be problematic at best and impossible at worst.

Check out 2x ML800x as control is far more extensive than the RELs

Ignore everything millercarbon says.

As they say, you only know what you know. So far I have been impressed with my results with the RELs.  I suppose I would need to move outside my comfort zone to take the advice what many are saying here.  I do feel like the air is moving.  The only thing that seems bothersome is having to readjust the volume based on what is playing.  Sometimes to boomy.  Seems to be album to album.  Not song to song. Maybe I am doing something wrong but only had them 1 day.  

For Elliotbnewbcombjr, I think what you are saying is to come out of the 4ohm taps that the main speakers are coming out of to the high level input of the RELs.  I could easily do as I have female banana spades on the REL high level cable.  However, REL says best to come out of 8ohm or 16 ohm taps.  Appreciate your insight.  

I researched both REL and Rythmic.  I think either one is a good choice, but I think the high level connection designed by REL is genius.  The high level connection allows the subwoofers to play more like woofers.  The key is calibrate then to not play too loud.  If you can detect them you either have the volume turned up too high or you need to calibrate the crossovers to blend seemlessly.

I have a pair of Paradigm Prestige 85F towers.  Originally, I was going to buy a pair of REL T9i"s, but went with a pair of REL S3 SHO's.  Glad I went with the S3's.  No matter what you decide, go with a pair.  Much better sound than just one.  I would not get anything smaller than the REL t9i's.  Right now playing two bookshelf speakers is lacking an enormous amount of bass.  You could also purchase towers unless you have a space limitation.  If you are limited in space and have to settle for bookshelf's, spring for a pair of the REL S2 SHO's.  I can put you in touch with someone who can surprise you with a great price.  This was how I could afford the REL S2's.