Bose subwoofer replacement

[KoukiS14]

Okay, so most of us would agree that the stock Bose subwoofer sucks for several different reasons. I wanted better bass, but not at the expense of losing any trunk space. Besides that, I like to keep things as stealth and stock looking as possible.

So, I found a nice, inexpensive, infinite baffle capable subwoofer from Elemental Designs, that would work quite nicely with the help of a 1/4" thick MDF trim ring. The sub is the Elemental Designs e3.8, and I got the trim ring from EliteInstallerSupply.com. The ring is 10" outside diameter, and 7.25" inside diameter, and 1/4" thick.

Other 8" subs would probably work, as long as the cutout diameter is under 8.3", which is the diameter of the hole in the sheet metal of the rear deck. It's not easy to find an infinite baffle sub, though, and the ED sub is pretty nice, inexpensive, has a low Q, and low resonant frequency, which lets it sound tight and play low.

Here's a pic of the finished project. Of course, the grill is off just to show off the driver and illustrate the fact that there's plenty of clearance, even for this little sub with its 14mm x-max.



I documented the entire sub installation on my Mazdaspeed 6. Other models will vary slightly.

The first thing to do is to take things apart so that you can work on fitting the new sub.

Remove the rear seat by putting your hands under the 1/3 points and pulling up HARD. Seriously, pull really hard. You're not going to break anything, but it takes a lot of force to pop it loose.



Slide the seat out enough so that you can remove the 14mm bolts holding the bottoms of the side bolsters.



Slide your hand behind the upper part of the bolster and push the little release lever to free up the bolster.



Wiggle out the bolsters and set them aside someplace.



Remove the clips from the trim piece from the trunk that hides the sliding seat latches so that you can fold down the rear seats. Note that the centers of the clips pull out first, then the entire clip will come out. Optionally, remove the entire trim piece from the trunk that covers the back side of the seats.





Remove the SRS Airbag bolt covers from the C pillars with a buttner knife or some other prying tool.



Remove the bolt securing the C pillar trim with a 10mm socket with extension.



Remove the C pillar trim by grasping it firmly and pulling it out. There are several trim clips holding it on, but they come loose without breaking with a firm tug.



The trim overlaps with a piece of door trim that will need to be loosened up in order to free the last clip from the C pillar trim.



Unclip the seven "center pin clips" from the lower edge of the rear deck trim and reroute the seatbelts through the slots in the deck trim so that they're behind the trim.



Begin lifting the entire rear deck trim.



There are two trim clips at the rear corners that are slightly difficult to get loose. I just shoved my arm under the deck trim and popped them up with my hand.



Carefully pull the rear deck trim free and set it outside of the car.



Here's the silly little stock Bose sub with it's 2 ounce inverted magnet.



Make sure to unplug the amp harness before pulling out the sub.



Unbolt that POS with an 8mm socket and toss it or sell it to someone who thinks Bose is the bomb.



The hole in the rear deck is about 8.3", or really closer to 8-3/8".



Here's the blank trim ring. It's 10" outside diameter, and 7-1/4" inside diameter, 1/4" thick MDF.



Here's a comparison of the Elemental Designs e3.8 sub and the stock Bose sub. Note that the Bose is really much smaller than it looks, since the bottom half of it is the amp and its mounting bracket.



Here's the trim ring with all of the holes drilled. Lay the ring against the deck and mark the holes from underneath for the deck mount holes, and lay the ring on the sub and mark it the same way for the sub holes. Make sure to offset the different sets of hole sufficiently. The deck hole spacing is approximately 9.25", and the sub holes were 7.75" center to center.



Here's the sub installed in the rear deck. I used allen bolts for the sub to the trim ring. I was going to redrill the holes in the deck for allen bolts and nuts, but decided just to reuse the stock screws instead.



Here's a bottom view of the sub.



I'll skip documenting the amplifier installation, since it's been covered before. I used an inexpensive Boss Audio mono amp, driving both 4 ohm coils in parallel, for a 2 ohm load. The amp should put out about 375 watts RMS and 1100 watts peak into that load. Probably more than is necessary, especially for an infinite baffle sub, but for $85, why not? As you can see, I mounted the amp to the underside of the rear deck. I used three #8 allen bolts with locking nuts. I was going to use nylon spacers to allow for the fourth bolt, but it's plenty solid as it is. The amp has a subwoofer level control which I mounted in a convenient location with double sided tape. I used the power connection for the stock Bose amp as the remote turn on signal.



The whole project cost under $200, and I'm pretty happy with the results. It doesn't hit like a trunk full of 18s, but it improves on the stock sub in every way and plays nice and tight and deep. If you've already got an amp and subs in your trunk, you might as well go ahead and replace the little Bose driver with this guy and kick it up another notch.

Thanks to the girlfriend for taking all of the pictures and having the patience to put up with me while I wasted a day on the damn car.

[Mcfly013]

That's an ingenious solution to the Bose Sub FAIL!
Remember, there are things a garbage can lid can do that
the OEM Sub can't! lol Nice job.

[bmorrisj]

make sure you have the gains for those voice coils matched and dont run it in stereo (or just bridge them), but that sweet. what are you doing for rattles?

[Drizz-OH]

Badass. I'd love to rig up something like this. My huge sub box is annoying coz it takes all my trunk space and slides around like crazy.

[KoukiS14]

Edit for full how-to with pics.

As far as rattles, I haven't done anything yet, but I probably will somewhere down the road. That little 8" sub with it's 14mm x-max can definitely set things abuzz. No worries about the dual voicecoils, since it's a mono amp and the coils are in parallel.

This setup really doesn't take up much more space than stock, and since it's all up high under the deck, it's pretty much not noticeable at all, both from the space perspective and visually. If you look into the trunk from where you stand when opening it, you can't even tell it's there.

[jmhinkle]

Since when do amps work upside down? I've seen a few mounted this way and don't understand. I wouldn't make it down the street before that thing was overheating. I have enough trouble when they are mounted the right way. Actually, my current Eclipse and an old PPI were the only amps I've had that didn't overheat.

Nice clean installation for sure if it will deliver what you need. Good job.

[KoukiS14]

Well, I hope it survives. It's got a ton of airspace between it and the deck, so hopefully that will help. Besides, that's what warranties are for.

[jmhinkle]

It's not a matter of surviving, it's a matter of annoyance. The heat radiating back into the amp will constantly shut it down if it has a thermal ciircuit. Amps cutting on and off during songs is annoying as hell. The heatsinks need to face out or up to get the heat away. I guess if it had a powerful set of fans then it might work upside down, but it would be noisy for sure. If you never use it hard then it probably won't matter anyway.

[KoukiS14]

Thanks for the positive feedback guys. I like this little setup, for sure.

If the amp starts acting up, I can always flip it and use some tube spacers as standoffs. I'll report back if I have to do that.

[lacuna]

Nice clean set up, I really like the fact that it still looks OEM.

Hinkle he probably doesn't have to put up with your NM heat.