Are you original speakers showing signs of having given up the ghost? Having upgraded countless A2s with Bose, I've removed more than my fair share of standard speakers. Only very rarely have I found a defective unit.
The most common cause of a defective speaker is a broken door check strap. If the check straps are allowed to make the cracking noise for too long, eventually there's enough free play to start wearing away the speaker housing.
Occasionally I'll see a water damaged diaphram or worn diaphram suspension, but only very rarely.
Replacing the A2's speakers with afterarket alternatives is tricky because they're an abscure size.
Cheers,
Tom