8 inch under dash sub - Pontiac Bonneville Forum - Official home of the Pontiac Bonneville Club.

phoenix_flame220 · 02-26-2008, 05:49 PM

I bought a Sony 8 inch sub for my gfs car, but luckily we broke up before i installed it (lol) so Ive had it collecting dust for a while. I tried so hard not to change the audo system in my buick as it is my beater and will be replaced by my bonneville as soon as I get the engine back in.
I had the ashtray out and realized that theres a bit of room under there, no center console. SO i had some spare time at work and built this box for it. All I had was a jig saw and every cut was angled to match the shape of the car, so I definately need to reseal it. But I finally got it in yesterday. Im going to tune the box and fiberglass it so keep in mind this is only temporary. Its a .25 cuft box. So it doesnt go very low, but I wanted it for midbass as I have a 12 in the trunk. Its pretty good for what it is. Let me know what you guys think.

Infinity tweeters I stole off a blown pair of 5 1/4s

Trunk EQ

psburtis · 05-12-2008, 10:21 PM

i love it!! what are the measurements for it? i am thinking about doing something like this to my car and would LOVE to know what the measurements are for it!

phoenix_flame220 · 05-13-2008, 01:43 AM

The front of the box is approximately 9 by 11, the rear of the box tapers down to 7 by 4. I fit the box to the contours of the dash and floor so exact measurements would be hard to give. I started wth a cardboard template, then started cutting the MDF, big at first then piecing and trimming it as I went along. I used 3/4 MDF so my box is extremely solid, but I lost quite a bit of volume. I would suggest using 5/8, or 1/2 inch but adding bracing to stiffen it up. Also If you make a small box like this you need to stuff it with insulation. The sub will play a bit ower and smoother.

psburtis · 05-13-2008, 01:52 PM

awesome. thanks a ton.

ten_gigahertz · 05-13-2008, 07:51 PM

Isn't that asking for a break in? Or will the finish product be blended in to look like it's just more dash below the deck?

I think it's a cool idea and looks good, I'm not trying to be pessimistic, but that seems the way the world is going lately...

bonnevillemac · 07-01-2008, 11:33 PM

Not bad I dig it. specially after the glass is on it and it is blended more to the interior.

Tim

**niceguy** · 07-01-2008, 11:39 PM

That enclosure could totally be made stealth and no one would know its there, unless you're bumping down the road

iluvmybonnie · 07-24-2008, 05:39 PM

what are the two metal circular objects on the box at the top of it?

how do you tune a box for midbass exactly? i'v never heard of it...

how will you send it only the midbass range frequencies?

what freq. range will you be using, that is for mibass only? and what octave slope?

also a sealed .25 cubed box should be fine for that sub and will not affect it low freq extension abilities.

what did you use to seal the box?

nice install i like it where it is. i'd make it so it looks stock myself which should be fairly simple.
oh and i like the blue lights and the type R floor mats! classy!

phoenix_flame220 · 08-15-2008, 02:55 PM

The 2 metal things are screws with washers on them. The box is sealed with silicone, but the front baffle is just bolted on with foam rubber sealing it. It was only temporary because I was making the fiberglass face for it. Unfortunately It wontbe getting finished because Im driving my bonne now, and the buick is getting scrapped. Ive got a whole bunch of new ideas for the bone though

But as far as tuning goes. You can tune a driver for midbass just like you can any other enclosure. In this case, the sub is getting an even smaller volume, more like .1cuft after the magnet and frame displacement. Therefore the sub has a natural f3 that is pretty high, like I said , it gives up around 40-45 hz, so it has a natural 40hz highpass due to the enclosure, and the sub was running off my sub channel that had a lowpass of 80hz. I believe the lowpass is a 12db/octave filter. Ide have to look up the specs. If I was finishing the project I would have set a 40hz 12db/oct lowpass filter on the 12 inch sub in the trunk to try to limit the overlap of the 12 and 8 playing the same frequencies. even with a small driver like this, you still need a good volume to get good low bass. If I had a better driver I would have build a linkwitz transform circuit and sacrificed the added excursion for a lower Q.

Its put to rest though and Im taking out the 8 inch. Ill find something to use it for. My next project is to fit 5 or 6 6.5 inch subwoofers into the rear deck of my bonne and have them aperiodically damped.

iluvmybonnie · 08-19-2008, 04:51 PM

infinite baffle FTL...