What size speakers can I fit in my 300tdi.
I know the originals are 4" but too small.
I was looking at 5-6" all round.

Tailgate don't work so could do with replacing them.

Any advice on modifying and fitting will be appreciated

Very difficult if not impossible to replace the front door loudspeakers with larger ones in the same position due to their depth an the space existing, although they will fit lower down with the aid of a bit of boxing on the front of the door card to accommodate them.

Depth is not so such a problem with the two rear loudspeakers.

Tailgate sub not functioning? depends on what's wrong, the 12v supplies missing (there's two) audio supply missing, faulty amplifier or loudspeakers which can be replaced but make sure that the replacements can handle the low bass of 50Hz frequency a least.


Sent via my iPad Air on a train.

If you're just trying to improve the bass & need to replace the rear subs anyway, have you considered an "active sub" ?
They're a single large speaker with a built-in amp - that could replace both your existing subs.
The bass is strong enough to be easily heard with the luggage cover in place & stuff in the boot, but without being boomy / overpowering (there is a separate gain (volume) control on the sub, which you use to match the sub to the rest of the system initially. After that, you don't need to adjust anything. If you overdo the sub setting it definitely gets out of control .
I've got 1 in the back of our D2 after initially thinking of replacing all spkrs to improve the sound.
It's worth adding that 1 would easily fit on your rear door & be more compact than the existing subs housing.
Price has gone up since I bought, but this is the 1 I have http://www.caraudiocentre.co.uk/product_m-in-phase-usw10_p-25817.htm