Lolow

Hi
i am a complete newbie at this so please bear with. I have a Mazda 6 with a bose system.
The near side door speaker is crunching really bad. The separate tweeter is fine. Initially I presumed it was just that speaker that was blown but if I send audio to just the back speaks the bass sounds okay but all the mid range is crunching, on both when panning left and right
the driver side door is completely fine.
I am not sure if it could be the amp AS well as or instead of the speaker that's blown. Can anyone please give me some advice about how I'd find out? I don't want to shell out for new speaker and find out it's the amp.

many thanks