10W6 Vented Through the Rear Deck, Figured you coupe owners might like this Options

[Coomer]

Since I got my coupe almost four years ago, I've always envied how the hatchbacks have no rear deck in the way to keep lots of the bass from subs in the trunk. Today, after a couple days of working a couple hours a day, I finally remedied the problem.

The answer is a vented box, with the vent going through a hole cut in the rear deck, in my case, a JL Audio 10W6 in a 1 ft^3 vented box tuned to 34 hz.

First, you plan your box. I took measurements, thought about what I wanted, and then used LinearTeam's WinISD software for my box-planning, and came up with a design that was originally tuned to 32 hz.


That's WinISD...a really nice program available for free.
http://www.linearteam.dk/default.aspx?pageid=winisd


Then I cut the hole where I planned for my vent to be. I used a sawzall, which was no easy task due to the large size of the sawzall and the small working dimensions inside the trunk and cabin of the car.


I then built the box out of .75" MDF...no pics of the build process, but you can see it above inside the trunk, un-carpeted, and held in by a tow-strap for testing purposes. That battery mount and cable setup is temporary as well, for testing purposes.


There it is from the inside of the car. I chose to point the sub towards the backseats, because it protects the sub from stuff flying around in my trunk.

"But Coomer, subs always sound bad when they're firing towards the backseats in Celica coupes."

They often do in a sealed box, but this isn't a sealed box. Due to the nature of a vented box, most of the air is moved by the vent, rather than the outside surface of the sub, so although the sub moves some, it doesn't produce enough output going forward to rattle the thin metal behind the backseat and make it sound bad.


Bad pic, but you can see the vent in the box pointing through the hole in the rear deck. The vent is simply 3"(inner diameter) PVC pipe, 14" long. I had to cut the pipe down 2"(from 16") in order to get it to fit in the car, so it raised the tuning frequency to 34 hz. Note that the number of inches removed from a port does not equal the number of hz raised in most cases...it just happens to in my case.


While I was at it, I figured I'd relocate the JBL BP300.1 that provides an estimated 225 watts to the 10W6. I know, it's a bad choice of a box for this amp, because the amp has no subsonic filter. I'll just be careful, and if the sub blows, at least I'm only out the $30 that I paid for the sub. Anyway, the amp used to sit on top of my old sealed box, but now it'll be hidden away behind that side panel. On the other side of the car, my amp for my front stage sits behind the other side panel.

Sound Impressions
As far as SQ goes, the box actually does not sound as good as I'd hoped it would. The bass is sloppy, and I think that my box is tuned too high. Lots of rock songs don't sound near as good as they did with my 1 ft^3 sealed box and the same sub and amp, though most rap songs sounded pretty good with the vented setup.

As far as SPL though, this box setup blows away the SPL performance of the former sealed setup(Even when I had the seats down with the sealed box.) No longer is the bass absorbed and blocked by the trunk, but instead, it shoots right through the rear deck and off of the rear window, making the setup louder. Not only does it make it louder, but immensely reduces the rattles in the trunk. My trunk didn't rattle much at all before because of all my sound-deadening, but the plate would sometimes rattle. Now there are NO rattles outside the car at all, even with the windows up, trunk closed, and the volume up pretty loud.

Also, vented boxes will provide three extra decibels of output over a sealed box with the same power, so that makes the setup even louder.

Overall, I couldn't live with this setup on a daily basis. It's just too sloppy for me, but it's a good start. My plan is to build another vented box, but use a square L-shaped port instead, and tune the box to 29 hz or so. Maybe I'll mess with the box airspace as well to get better SQ.

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