12" Premier Sub Behind the Seat Install

So this weekend I found my motivation and started what has to be one of the most challenging installs I have ever attempted. I have a Pioneer Premier 12" Shallow mount sub that I am installing in a sealed box behind the seat. I am using fiberglass, which is a first for me. I used a tutorial I found on the internet as a guide, and so far it seems to be going okay. It is much messier than I ever anticipated. Also, since it was in the 60s this weekend, it is taking a long time to dry. Anyway, I test fit it behind the seat and it fits. I am pretty sure that I have about an inch of space for forward excursion of the woofer so it should not hit the seat back. The problem is that the only place to put the woofer is also the place behind the back seat where the two seats come together and there is the most stuff in the way on the seatback. Anyway, I held me digital camera back there and took pics to make sure I would clear okay.

I started by removing the seat and factory sub and applying tin foil to the back wall. I then put my first layer of glass on and let it dry. From there I peeled it off and added layers. I lost track of the number of layers exactly but it is about 1/4" thick and will not flex when I stand on it so I figure it is good. The pics tell the rest. Hopefully I can get this project finished in the next few weeks.

More Pics Added

The way that you made the back of the box was the right way to go about it. I did it in wood and used a router to remove the wood needed to go around the metal brace on the back wall. (I'm sure you know which one I mean.) If I had to do it again, I think I would make the back wall on my box a different way. Great job so far.

BTW. I think that the shape of your box sonically is better than some square ole' box. It matter less with material that is less than 90 hz but it still helps. What is the volume of your box?

Thanks!. I actually studied the install you did where you routered out the back side of the box to make up for that bracket. That bracket eats up a lot of useful space in an application as tight as this. I knew there was no way that this 12 was gonna fit if I had to do that. It barely fits as it is. I would go with a 10 if I had to do it over, but who knows, this may kick some serious a$$ if it works.

I dont know the exact volume of the box since it is so oddly shaped. From taking very rough measurements, I would guess it is around .75 to .8 cu ft. But the speaker itself is going to eat into that quite a bit. The specs for that sub are from .5 to 1.0 sealed, so I should be okay. I am going to poly fill it also to make it think the box is bigger.

I had originally made the mold to extend all the way to the driver side wall, but I cut it off so that I could have room to mount my amp over there. I am gonna drive it with 450W RMS from a Polk amp that I have. It should do the job nicely.

awesome job, man if you could make a template and sells those you would make a fortune. Great job again.

Thanks! I actually was considering making a template of the back side before I put it all together, but as much work as this is, and as much fiberglass as this is already taking I gave up on that plan. If this was made out of wood, I would not mind making some for other folks, but this is kicking my butt!

Seems to be that something like this is what JL should have done with their stealthbox instead of that under the seat concept that has been done before (and better) here so many times.

Just an idea that I heard once for calculating air space in an unmeasurable enclosure.

Well we can measure volume in a cylinder. If we fill the unusual shaped enclosure with water, the pour the water out of it into a cylinder, you can mark how high the water came up on the cylinder (I'm thinking 5 gal bucket) Calculate the airspace from where the water is on the bucket and it will represent the volume of the unusual shaped enclosure.


Now I don't know how accurate this is, but the guy that told me this had just won several awards at and IASCA sanction just weeks before he told me this. He had placed 3 JL 10" in the spare tire well of a civic using fiberglass, and I was curious how he calculated airspace. It makes sense to me, maybe it's dead on, maybe it's not. See link and it shows how to calculate airspace in a cylinder shaped enclosure.

http://www.the12volt.com/caraudio/boxcalcs.asp

Your theory in calculating volume is correct. The only thing you are not compensating for is the space that is occupied by the woofer. I'm sure it is minimal since this particular woofer has a very shallow profile. Looks like we know who was awake in their physical science class. :cool:

Plus, the speaker manufacturer gives you the displacement volume, so it's a snap to get it right. Nice, job, BTW. I hope you didn't inhale too much of the fumes. That's the one thing I hate when working with fibreglass and plastics.

Thanks. I actually thought of using water, but since the front panel is MDF, I dont want to mess that up since it would swell and be ruined. Or I could use packing peanuts, or dirt, or anything small and packable, but, it would be a PITA to clean out the inside, so I gave up on that idea too...

Hey this looks very good. Nice job so far!

Very nice work. Keep the updates coming.

I have not had time to make any updates to the sub box but I wanted to also share with everyone the 12 Disk MP3 changer that I installed. I posted this once before, but it was in kind of an obscure thread so I wanted to put my whole audio system together in one post. It is a JVC RF CD changer. However, I modified the RF output by adding RCA connectors to the sound output from the changer. I installed the Blitzsafe AUX input adapter and connected this unit through there so I would not have to settle for crappy FM modulation. I still control the unit through the supplied JVC controller that I sanded down to fit inside the cubby hole below the factory deck. The changer fits perfectly under the passenger seat, though I may move it to the driver side so I can change disks easier.

I did the center console power outlet mod so that it is live all the time. I tapped into that to provide my constant 12v power and tapped into the dash mounted power outlets for the switched 12v turn on signal.

I now have over 8 GB of easily changeable MP3s at my fingers at all times, so this has sure made music surfing easier.

damn that is great. Ill pay you to do a 10 inch for me :)

I appreciate the good words. Man, I would love to build more of these if I had the time. Going to UT now for grad school and with that and full time work, it is kicking my a$$. I have had this sub in hand for 6 months now and am just getting around to it.

Well, I finally finished the install this weekend. Well most of it anyway. I messed up some threads on one of the bolts for the backseat, so I am gonna have to find me a shop that sells metric bolts. Hopefully I dont have to tap the holes too. Anyway, here is the final product. It seriously pounds. It is truly amazing to get this kind of bass from a box that is probably not much more than half a cubic foot after the speaker is installed.

I finished all sides with at least 6-8 layers of fiberglass mat. Since I had to attach the back of the box to the front wood panel, I had to lay the new pieces of glass over the old. There were some seams internally, so I took some silicone and sealed them all up. After about 2 hours of trying and re-trying, I finally got it sealed so tight that I could not get the cone to compress into the box at all without immediately springing back out. (I mean NO leaks, not even a little one).

I sprayed the interior and exterior of the box with rubberized undercoating to help deaden it. I also filled the box fairly densely with polyfill.

The signal is coming from the factory sub signal. I never could find on this site whether it was the green or the yellow wire that was the + signal, so I just guessed and it sounds good to me, so I figured that is all that matters. I just poked some bare wires into the ends of the factory harness and taped the hell out of it to hold them in place. Not very high tech, but it was 10pm and I did not care at the time.

The amp is rated at 450W RMS on its "birth certificate" from Polk. It has high level inputs so, it was a snap to hook up. I ran the power through the boot above the gas pedal like was recommended on this sight and sealed it further with silicone.

By biggest fear was that the cone would slap the seatback, however it does not do that at all. Very clean bass. The only problem I have is that at one certain frequency the box will resonate the rear cab wall. I plan to take the whole truck apart soon and RAAMmat or Fatmat it, so that should take care of the problem.

damn that is great. Ill pay you to do a 10 inch for me :)

x2! I have the eD 10" shallow-mount sub in-hand, hoping that someone will build and sell me a proper behind-the-seat enclosure for it.

Troy

Well, I finally finished the install this weekend. Well most of it anyway. I messed up some threads on one of the bolts for the backseat, so I am gonna have to find me a shop that sells metric bolts. Hopefully I dont have to tap the holes too. Anyway, here is the final product. It seriously pounds. It is truly amazing to get this kind of bass from a box that is probably not much more than half a cubic foot after the speaker is installed.

I finished all sides with at least 6-8 layers of fiberglass mat. Since I had to attach the back of the box to the front wood panel, I had to lay the new pieces of glass over the old. There were some seams internally, so I took some silicone and sealed them all up. After about 2 hours of trying and re-trying, I finally got it sealed so tight that I could not get the cone to compress into the box at all without immediately springing back out. (I mean NO leaks, not even a little one).

I sprayed the interior and exterior of the box with rubberized undercoating to help deaden it. I also filled the box fairly densely with polyfill.

The signal is coming from the factory sub signal. I never could find on this site whether it was the green or the yellow wire that was the + signal, so I just guessed and it sounds good to me, so I figured that is all that matters. I just poked some bare wires into the ends of the factory harness and taped the hell out of it to hold them in place. Not very high tech, but it was 10pm and I did not care at the time.

The amp is rated at 450W RMS on its "birth certificate" from Polk. It has high level inputs so, it was a snap to hook up. I ran the power through the boot above the gas pedal like was recommended on this sight and sealed it further with silicone.

By biggest fear was that the cone would slap the seatback, however it does not do that at all. Very clean bass. The only problem I have is that at one certain frequency the box will resonate the rear cab wall. I plan to take the whole truck apart soon and RAAMmat or Fatmat it, so that should take care of the problem.

I was going to mention the fact about the back seat at the 60/40 split. There is a bar that bends in towards the back wall about an inch and a half. I Put a grill over mine before i reinstalled the back seat just in case. i wish that i could have kept my 12" but i dint feel like being bothered with the fitting issues.i just got finished installing my door speakers i will post pics of that install soon.