So I've recently replaced the stereo for a bluetooth stereo. And I still have a muffled sound coming through the speakers. At first it was just on bassy songs but now it seems to be whatever it listen to!

Any suggestions on what it could be?

Also what size are the speakers in the panda 169? (2007)

Had something similar with our 169. In our case poor speaker connections in the doors were to blame. A bit of extra crimping of the connectors was required. You need tp be careful not to over do this as these are fragile. I think they may have been removed unplugged and not gone back together as they should have. Good luck.