I picked up my very first pair of SDA speakers yesterday -- 1b's -- and have been liking what I hear so far. (I upgraded from a pair of Monitor 10 Series II.) They are really delivering a bigger/wider/deeper soundstage.
However, when I play bass-heavy music, the rear panel of the left speaker is most definitely vibrating and making the sort of sound you hear emanating from a low-rider. If I press on the panel, the vibration stops and all is well.
So what's the best way to fix this?