After nearly 9 years at last I decided to investigate why the rear door speakers sounded so dreadful. They were quiet and lacking in any detail.

Well its simple. The door is designed for a 5x7" oval speaker and Fiat thought that a 5" round speaker held on with two screws would be ok.
Well as you can imagine, the door doesn't act as a baffle and it sounds awful.

Once I removed the plastic trim from the inside of the door it was obvious. It just looked so ridiculous. If I hadn't owned the car since new and, if the correct speaker mounting holes look like they had been used before, then I'd have guessed that some prat thought it was a smart upgrade to put these 5" round Blaupunkt speakers in. But this is definitely the original fit.

So, if your rear door speakers sound quiet and muffled then this might be why. Just ordered some Fli 5x7 speakers for flea bay for £25. hopefully will be easy to fit and make it sound sooooo much better.