I've owned a few squareback SVTs - still have one. The other day I came across a used 70s box (the later one with the towel bar handle). As is my custom, I popped out a couple of speakers - they were all alnico CTS, but appear to have been reconed. I've always been told that when you push in on a speaker cone in an SVT, the opposite unit's cone should pop out a bit, because each pair of speakers is in its own sealed 2x10 enclosure. My own SVTs have borne out this theory. In this case, the second speaker doesn't move. What would cause this to (not) happen?