First, I have a 2012 A3 TDI Sportback, US model, so it may have differences from other country models. It is the "Titanium" edition, which I think is called the Black edition in other countries, as all of the trim is blacked out. I purchased it with the RNS-E with navigation. All I wanted to do is replace the factory Bose subwoofer with a decent one. First option was AndyMac's system, however my understanding is that it does not fit in the Sportback because Audi reshaped the side trim area quite a bit. While looking around in the car, I noticed that there was a lot of room over the spare tire. They put a tiny temporary spare instead of a full sized one, but the the tire well can fit a full sized spare. Measuring from the spare up to the flat foam surround is about 4 inches. That is quite a bit of usable space. So I started looking around at thin subs, and ran across the JL Audio 13.5" 13TW5-3 Thin-Line Subwoofer. It only needs 2.5 inches of depth, and 0.80 cu. ft. if air space in an enclosure. Around the same time, I ran across Nik Brewer who has been making custom sub enclosures mainly for VWs, like Golfs, Jettas, etc. His enclosures typically replace the Styrofoam that surrounds the spare tire well, where the jack and other tools are kept. One of his enclosures would have worked fine, however I wanted to try and use a much larger sub than the small enclosures can handle. He custom made an enclosure that exactly fit on top of the spare tire. With the thin sub, I didn't want to take a chance on the speaker getting damaged, so I purchase the metal mesh grill for it. The grill went higher than the stock floorboard, so I created another floor board made of 3/4" MDF, with a hole in the center for the subwoofer grill. I then purchased one of the Audi trunk mats to make it all look stock. Nik created the enclosure with a separate area for me to install the sub amp. I used a JL Audio JX500/1. It won't win any SPL contests, but it sounds much better than stock with a nice deep bump in the bass. I hooked up the amp the same way others have done, based on the instructions from AndyMac, and unplugged the stock Bose sub. I don't know if it's a requirement for Nik to be an approved vendor on the forum, so I have not included any contact info, but people can PM me. If it's OK to post info here, like his website and email address, someone please let me know. I think he did an outstanding job on the enclosure.