Vijay

What size components should I be looking for to fit under factory Bose grills for front doors, rear doors, and rear deck in a 2000 S4?

The R

Front doors:

You can get MB Quart adapters to make 5 1/4s fit easily. Only ones that might have trouble are the FOCALs cause they tend to be a little larger than 5.25"s. You can get 6.5s to fit (what i did), but at a price. It will take a serious amount of work/labor to get them to fit without doing any modification to the door panel. I did some tinkering with my panel to get my 6.5s.....honestly, it's worth it to me. You just don't get that rich of a sound with 5.25s.

Rear doors:
I have some 6.5" coaxials in there....didn't use any adapaters to get them in.

Rear Deck:
I think you need some kind of a adapter to get 6.5s to fit...not sure. I'm sure someone will chime in on this. I didn't bother....I'm using the holes to let the sub freqencies in.

Ray Khan

I have 6.5" infinity kappa coaxials in the rear dec with the quart adapters. It's really a shape adpter going from square to circle. Whereas the 5.25" adapter for the front doors is a size adapter.

Now Vijay, if you have a good shop do the work, like Sound in motion in Alsston, or Krank it up in Medford (mistic Ave), they will have all the adpters and means to make lots of speaker options work for you. You pay a bit for install, but they are both great shops with plenty of experience with working on our cars. I opted to buy a used setup froma friend when he sold his A4, and bought my own adapters from Krank it up and did the install myself. I saved a lot of money, but it took me a while. Good luck.

Ray Khan

if you want somecustom kick panels made, you can go with 6.5" components. I like having a sub. Mine is a 2x10" enclosure in the trunk. As for the rear deck, I like having the fill. But with the rear door speakers, you mae feel you don't need it and the hassle of having and extra 2 channels to power it. Ivan has an aftermarket setup with 3x10 sub in his trunk, 6.5" components in his rear doors (he had to cut a custom hole in each door for the tweeter), 5.25" components inthe front doors, and 6.5" coax in the rear deck. Sounds awesome. I'm very jealous of his JK Audio sub. Ask him for a listen and have him turn on/off the rear deck and see if the extra speakers are worth it to you.