Are your mains ported? Seal them.
It won't be as good as a true crossover, but it will extend the dynamic range and help integrate with the sub.
Regards,
Erik
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.