It's an old peerless sko 10 tweeter with plastic face plate and snap-in assembly.
The wiggles disappeared when loosening one mounting screw. The routed tweeter recess was obviously slightly uneven and the distorted face plate caused some voice coil rubbing or rattling!
The wiggles disappeared when loosening one mounting screw. The routed tweeter recess was obviously slightly uneven and the distorted face plate caused some voice coil rubbing or rattling!