Always hesitate before judging new speakers, especially those woofers. It takes a while to break them in and it's difficult to do that in a car.

 

Tried both ways. Now have the large spades as negative. Confirmed by tracing the black wire to the oem subwoofer amp, where it's marked as "spkr +". Have about 4 hours of break in on them so far.

On bass heavy songs, at bass + 3, the sb15mfc30-4 bump well. On half the other songs I listen to, they're barely audible. Maybe they're not hitting the low frequencies. Feeling the air pressure thump in your chest at medium-high volume, is what I'm using as the barometer. I want subs I can hear and feel all the time, at low volumes.

I ordered a Alpine MRV-M500 Mono with a remote ****
Per channel into 4 Ohms: 300W RMS x 1
Per channel into 2 Ohms: 500W RMS x 1

Planning to try out a pair of 8" Tang Band W8-740P (4 OHM) subs, since I already have a pair in my garage. Single voice coil I believe. Not sure how I'd wire them, to maximize output. Need suggestions.

The shape of the oem box is fairly simple, and think I can get close with MDF, and cover it with black carpet. 8" subs are too big to point up, but I could build a 2" taller than oem box, and have them face towards the front of the car.

On the plus side, I love how the front stage sounds now with the focals!

 

The only issue with another amp is making sure you have an adequate power lead to support the amperage of the new amp. The Oem power lead is not that robust. That's why I avoided it as others recommended running a new power lead and that didn't fit into the budget install I was after. I really thought the power line was probably good enough, but I just didn't go there. Also, I'll say again that the sub drivers I used broke in nicely and were quite an improvement after a while.

 

The power leads for the amp at the 5 pin connector going into the subwoofer box are much larger gauge wire then those that actually go to the amp. Tie into them back at that junction and you can use the compact Alpine amp I did without issue. Its RMS rating is about double that of the stock Bose amp.

 

I'd be running dedicated power to the new subwoofer amp. Looking at the spec sheet, the subs can handle 120-240 watts. From my research, single voice coil subwoofers can only be wired in parallel so that brings me to 500 watts split in 2. Definitely have to turn the gain down on that.

Amp and subs purchased. Gonna build the box next

Not much of a price increase. Amp $175. Amp kit and wiring labor $150. Material for new box - $50.

 

Sounds excellent. Be sure to report back and good luck. A dedicated amp and subs will definitely yield even better results!

 

So far I made a rough box that's 24" wide, and a few inches taller than stock. The angle of the back seat and oem box is 15 degrees, so I replicated that.

My car's at the dealer getting the clutch upgraded and coolant pipes welded, so I won't have a chance to finish the box for 2 weeks. I plan to trim it down to minimal proportions. pictures of template for 1 hole, but i'll be using 2 subs.

 

Excellent post! Thanks for the details, I've got some Focals on order and will let you know how to goes.

 

any updates on this project? Roffle did you achieve what you aimed for? Pete you have experience withe the oem wiring and the alpine 500 digital mono amp, and i suppose a subwoofer system at the back, can you share your impressions and ideas learned so we can do better?

 

All of my detail was in the PDF document I created that I thought I attached to one of my posts - it's attached here. I'm still very happy with my setup. The rear amp could probably stand to be a little stronger, but I couldn't find one that was the right physical size in the right power range and didn't want to risk blowing the expensive Focal Utopia subs, so I'm good with it as is and have moved onto other projects with the car - namely enabling the heaters in the Adaptive Sport Seats I installed back in 2012 - the journey continues.

 

I didn't get a chance to finish my project, since car is at the dealership getting some upgrades. (clutch/coolant pipes, etc). I should resume next weekend

 

Pete, thanks for sharing again brother. Will be doing this upgrade soon. I've recently upgraded the sound in one of my cars and now the 997 seems seriously lacking in quality specially in the low range areas...

 

Keep us updated Roffle... Thanks

 

Anybody discovered a good route for heavier wiring from the battery to the rear deck? Hopefully minimized disassembly of stuff.

 

I had kicked around the idea of running a heavier gauge wire by tying onto the post of the starter where it gets the heavy gauge constant 12v from the battery, but once I discovered the heavier gauge wiring that runs to that connector on the sub enclosure itself, rather than the really thin wires that run to the amp in the enclosure, determined that wasn't necessary for the slightly more powerful amp I was installing. Now if you're going crazy with the rear subs and amp, that may be a different story.