A little back story, I've been driving my EO speakers and subs with a shop-installed PDX-5 and 3Sixty.2 and they sound pretty damn good. When you REALLY turn up the volume and turn the sub control to 10 you almost feel like you're listening to a full aftermarket setup.
However, I have noticed that the OE sub, even under additional amplification is a little boomy, not as crisp or punchy as I'd like. It just never gets to the point where it feels like you're being punched in the colon as in a true high powered aftermarket setup (my last setup had 2x JL 12W6v2-D4 running 1100 watts total for reference).
The fact that my system is already setup with amplification tremendously simplified this process. I used these two guides
http://www.e90post.com/forums/showthread.php?t=163804
http://www.e90post.com/forums/showth...=145075&page=2
so I'm only going to post my observations in support or in addition to what they've already provided the community.
A ratcheted socket wrench is a MUST HAVE and the seats come out extremely easily. I also used the ratchet to remove the black speaker cover and the bolts holding the enclosure.
Removing the fins on the bottom of the enclosure does not require a dremel. I actually used an adjustable wrench and by the second enclosure, I was removing entire ribs, not just fragments. The technique is to start at one end and flex the rib, sliding the wrench progressively down the rib until the rib base is stressed along the entire length. At that point it can snap off whole, nearly flush with the base of the enclosure.
After stripping the ribs, I covered the entire interior of the enclosure in dynamat, or as nearly as I could. Since the seats are so easy to get out, I declined to dynamat the ports into the side skirts, deferring that project to another day. Dynamating the enclosure isn't a requirement, but as I was taking the original sub out I noticed the enclosure seemed kind of hollow and resonating to the tap, so I figured a little dampening was appropriate. Sorry, no pictures of my nasty dynamat job.
I ran dynamat around the lip where the sub sits to improve dampening and help seal the enclosure. I also ran thin strips around just the lip to increase the standoff from the bottom of the enclosure. The Earthquake SWS-8 does not mount flush in the enclosure; it fits, but with some tweaking to get a proper seal. For this reason,
foam weather stripping is KEY. I bought some 5/16 thick foam and it worked LIKE A CHARM. Highly compressible, it completes the seal without using glues, goop, or anything that would make the installation more permanent, or at least a hassle to remove.
The keyhole gap where the OE speaker wires clip in is a bit of a problem, but nothing unmanageable. It certainly doesn't require lexan like the guy in the top link used.
I simply used small pieces of dynamat then after running the power cable through and mounting the subwoofer, I hot glued the whole area about 1/2" thick. I figured thats a pretty good seal.
The OE power cables to the subwoofers are very heavy stuff, solid core or very thick strands, at least 14 guage. The clip assembly posed a bit of a problem since I wanted the install reversible. I wound up using some U end crimps to insert into the clip. It works well, holds in place, and keeps things stock as possible without resorting to cutting and soldering.
I haven't had time to re-tune my 3Sixty.2 but initial impressions are very good. There is still an element of boomy-ness to the system but the punch and raw power are way up. I can turn the system a lot louder before I hear the distortion creeping in. Its powerful enough that it vibrates my pants and kinda tickles the hairs on my legs. Its a bit crashy when listening outside the car but I have to do some tuning. I have yet to figure out a way to keep the sub from tapping the foam bottom on the carpet. Any suggestions are welcome that don't include cutting the carpet. The seat rails are the biggest hinderance, since they force the carpet down closer to the sub. When REALLY cranking it I can hear the sub flutter against the carpet producing distortion. Anything below about 2/3 maximum gain its not noticeable.
Is this upgrade worth it over amplifying the OE subs? Hard to say. I did it because I like doing these projects, as stressfull as they can be sometimes. If you don't listen to base heavy music, definitly not; amplify the stockers and leave it at that. If you listen to a lot of hip-hop, electronic/techno/pop, hell yes. There is definitely a MORE than noticeable difference in the low end extension and overall volume. I'll post more impressions as I fine tune the install and review more of my favorite songs.