Best Way to Split Amplifier Output Frequencies to Main Speakers and Subwoofer

Is there a decent stand alone active or passive stereo frequency divider that can take the speaker outputs from my vintage receiver and send mids/highs to my main speakers and lows to my subwoofer?   I want to relieve my main speakers from deep bass responsibilities. The crossover frequency should be user adjustable.  Neither my receiver or sub have the capability to do this.


Does your receiver have preamp outputs and power amp inputs? Make and model would be helpful.

Rel has a  high level input. IOW you just connect the sub to the speaker terminals on the back of the receiver. Then adjust accordingly. They integrate well and make the mains sound better. The trick is to keep the volume & crossover as low as possible so as to blend with the mains

Yes, but the REL doesn't have a crossover to keep bass from the mains.  Keeping the amp from having to replicate low bass may help with headroom???

Pass, First Watt, Bryston, Marchand. Both low pass and high pass filters, variable frequencies and slopes.

+1 elevick. And running through low-level inputs give you deeper bass. No answer from OP on separable preamp outputs and power amp inputs. I'm stopping.