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
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.