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Discussion Starter · #1 ·
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.
 

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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?
 

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Discussion Starter · #5 ·
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.
 

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Risickulous
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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.
 

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Discussion Starter · #7 ·
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. ;)
 

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Risickulous
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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.
 

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Discussion Starter · #9 ·
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.
 

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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.
 

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Discussion Starter · #12 ·
Edit: Joel's too quick to the punch, and already answered before me.

Actually, I live in Albuquerque, about 15 miles away from Joel. So, yeah, I have to put up with the same heat. We're kings of the Speed 6 write-ups here in the land of enchantment, if you haven't noticed. Matt, Dustin, and Joel, all contribute a lot here and are great guys to hang out with.
 

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I have my audisons upsideown on a MFD deck I build below the rear metal deck. One time the LRX 1.1K overheated and I had to turn the car on and off to restart it as I had killed my remote in my HU and had it hooked to the ignition. So Ya im going to mount some fans back there some day. Im sure lower end amps could have much more problems with overheating in NM when mounted upside down. I like the write up, but I would think youve got to have some bad vibs now. Ill add this to my FAQ, or joel can do it. im lazy.
 

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Lol didn't know you were in NM to. That's what I get for assuming.

We need a smiley that smacks himself in the head, I'll add this guy instead just because I think he's funny. :irate:
 

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Discussion Starter · #15 ·
I played around with input sensitivity levels this morning. I found out that the stock Bose amp under the seat does not roll off low frequencies to the mids in the doors, nor does it roll off highs to the sub input. I ran some test tones and measured 300 mV at a volume level of 20, and 500 mV at a volume level of 25. I didn't want to go any higher for fear of stressing out the stock Bose components. I would guess that at a volume level of 30, the sub input would be around 1 volt. Has anyone else ever measured this?

I ran 40 Hz test tones really loud for about 5 minutes, and the amp never even got close to warm. I hope that's a good sign for things to come.

I do want to stiffen up and deaden the rear deck. I can see a full 1 or 2 mm of travel in the deck itself when the party really gets started. That's a project for another day though.

<a href="http://www.youtube.com/watch?v=-PtfN5Qeq5U" target="_blank">Here's a YouTube clip of the e3.8's predecessor, the 9Kv.2.
</a>
The changes from that driver to the e3.8 are a carbon/nomex cone, longer/thicker voicecoil leads, better voicecoil and motor venting, and a chrome, instead of black, backplate.
 

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I'm thinking that power wire to your amp is cutting power.
That's not a very thick wire, and was wondering if the power
was run straight from the battery or not? If you're not letting
the amp get all the juice it needs, it will never run full bore,
or heat up.....which could also work to your advantage!
 

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QUOTE (jmhinkle @ May 10 2009, 09:20 PM) index.php?act=findpost&pid=1559162
Since when do amps work upside down?[/b]
You just gotta make sure to do the wiring backwards so the electrons know which way to go. Or mount the subwoofer upside down too. Then everything is good to go. If there are still problems, often installing the radio upside down will fix it.

All kidding aside, conduction doesn't care what orientation the amp is in, and convection doesn't allow for some heat bubble to develop under an amp and sit there keeping the thing warm. It's not a bowl shape underside keeping the hot air there like a balloon.

If you want to maximize convection, you can even mount your amps vertically to facilitate air movement through the fins. But realistically I usually tell folks their amp is underpowered or subject to poor sink design from the OEM. Either of those can explain basically any heat problem and either way the solution is the same.

I liked the build too.
 

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Discussion Starter · #18 ·
QUOTE (Mcfly @ May 11 2009, 01:38 PM) index.php?act=findpost&pid=1559406
I'm thinking that power wire to your amp is cutting power.
That's not a very thick wire, and was wondering if the power
was run straight from the battery or not? If you're not letting
the amp get all the juice it needs, it will never run full bore,
or heat up.....which could also work to your advantage![/b]
It's 8 gauge, straight to the battery with a fuse right by the battery. Not garden hose thick, but enough to get the job done.
 

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Ya thinking of it know, the only time my amp/amps cut out was when my car was packed to the brim with 4 people and all their stuff in the trunk so that is why it overheated once when reelly bumping it. So ive not worries. Even in extreem heat the trunk stays fairly cool but you could always mount a fan like this:
http://www.newegg.com/Product/Product.aspx...N82E16835185004
At 9db its to quiet that you could not heat it.
 
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