I have a 2007 997.1 turbo with the Bose stereo from the factory. Doing a mild stereo upgrade and want a better sub enclosure. I thought I read that the bose sub box is actually part of the bracing for the rear strut tower. If true, what considerations should I make when building a slightly larger(taller) box with 2 8 inch subs firing backwards.

 

Having had mine out of the car a few times I would be surprised if it were part of any bracing / structural improvement to the car. As its optional on non turbos I would not stress about it when modding it.

 

What upgrades are you doing? Have you found useful threads on TT? Where will you place the amp? Are you using stock wiring? Active or passive crossovers? Is the Bose Sub a 6th order band pass design? Will you use the same sub enclosure?

I am also thinking of upgrading my 2012 TT using passive crossovers to minimize the number of amps. I love the neutrality and clarity of Dynaudio speakers.
- Dynaudio Esotec 362 8" 3-way
- Dynaudio Esotec MD102 Tweeters
- Dynaudio MD142 Midrange
- Genesis Series III 75W x 4 Amp or Moscone AS100.4 Amp.
- Diamond S104 10" shallow mount sub + JL 500/1v2 Amp.

 

I have a zapco 1004 which is 4 x 150 and has built in DSP. The amp is mounted to a custom and very trick bracket that goes on the floor in the boot and takes up 2.5 inches. The factory amp still powers and processes the center channel and rear speakers. I went with hybrid audio. Upgraded the center channel to a 2" ring tweeer/mid and left the rear speakers alone. Went with a 3 way set up in the doors. 8" mid bass, 3" mid range and .75" tweeter all in the factory locations. Mounted a 3 way cross over where the factory NAV DVD was located previously. The 3 way crossover actually directly connects to the factory wiring for the door speakers and we ran a separate wire for the tweeters. Not using the bose enclosure at all. Using 2 hybrid audio 8" subs firing backwards. The enclosure will have the same footpring as the factory bose but be a couple inches taller. Simple sealed enclosure. It's not built yet so I can't really comment on how well it works. If I'm not happy, I'll try something else. Keep in mind I have the GMG racing 600 horsepower package. At 3000 RPM or below(stuck in traffic) the front door set up is very nice and definitely nicer than stock. Above 5000 RPM the engine completely drowns it out.

My advice to others: the double din kit for mounting a Kenwood 9990 is a great upgrade. Talk to Loi. His $850 kit not only gives you the bracket but also interfaces with the factory amp and allows the steering wheel controls to work(volume, track up and down, mode). If I had it to do over again, I would have just stopped there. This has been a meticulous installation with a lot of challenges. It's turned out well and it's certainly better than stock assuming whatever sub enclosure I end up doing turns out. However, it's probably not worth the incremental cost over just swapping the head unit to something modern. Especially in a modified car.

In your case with 2 amps, you may have enough power to drown out a stock exhaust.