Steve Dallas
Major Contributor
Not sure how much the rear ports were causing your issues.
Seems the corner loading of one speaker being right against the wall, and both speakers having lots of reflective wood under the front of them, extending out 4-5 inches may have caused some of the issues also.
It was BOOM! city with rear ported speakers (not limited to the M10s--tried a few). The front ported Elac Debuts and Q100s sounded the best, but Wifey vetoed the gargantuan Elacs.
Sure, nothing is environmentally right with that location, but pumping the port into a cubby and exciting the resonances of all that wood was not a good choice for clean lows. Front ports are still not great, but much better.