Thanks andrewt, yeah I had the speaker apart again last night to make more measurements and checked it all over again and didn't find anything loose and the cone travel seems find.
I did find, even with the driver out, that its position does have some effect on the problem as it does do it less if I turn the speaker facing up and in other positions.
I guess I will have to go for a replacement driver and was looking at a Peerless unit, are these any good?
