A DSP processor with a digital notch filter for base control would probably help. My Anthem AVM-20 has this feature and it works very well....if you like vinyl then you can still do it.... just use the DAC to convert to digital and then apply the digital processing you require and finally convert back to analog.
Purists will of course sneer at this suggestion...but I assure you it works and digital signal filtering is sharper and better defined than analog. I find this unavoidable when using the sub and speakers to play stereo music together despite the reponse curves of my sub/speakers being engineered to be flat down to 30 Hz and -6db at 20Hz. These speaker specs are for ideal anechoic conditions and not for my room which reinforces a 40 Hz signal and hence a notch filter is unavoidable if you want to achieve a reasonably flat response in your base.
Another option is to move your sub away from both walls to say about 1/3 across the room and then shift it slightly off the diagonal room axis by a foot....good for your sound but probably bad for ergonomics and it wont completely cure the resonance but it will likely reduce it.
Purists will of course sneer at this suggestion...but I assure you it works and digital signal filtering is sharper and better defined than analog. I find this unavoidable when using the sub and speakers to play stereo music together despite the reponse curves of my sub/speakers being engineered to be flat down to 30 Hz and -6db at 20Hz. These speaker specs are for ideal anechoic conditions and not for my room which reinforces a 40 Hz signal and hence a notch filter is unavoidable if you want to achieve a reasonably flat response in your base.
Another option is to move your sub away from both walls to say about 1/3 across the room and then shift it slightly off the diagonal room axis by a foot....good for your sound but probably bad for ergonomics and it wont completely cure the resonance but it will likely reduce it.