I gotta have tunes when I'm wheelin', camping, and DDing. Lately I've had a stack of engineering projects at school. This one is for Acoustics & Noise Control, a graduate level mechanical engineering course. As a final project, everyone uses what they've learned about acoustics to design a speaker. I decided to design a sealed enclosure for a 12" subwoofer.

The first step was using some data acquisition and laboratory equipment to do some free air tests on the driver itself. This gave me the Thiele Small parameters, which are used for designing the enclosure. These parameters are published by the speaker manufacturer, but in many cases (mine especially!) they differ widely for every speaker produced.

I will save you from future engineering jargon, but the end result is a box of almost twice the volume recommended by the manufacturer. After thinking through it, here's the design I came up with to fit in my '86 4Runner:



Below: Here are my layout tools. I used 3/4" MDF



Below: The first few cuts with a cheap skillsaw. A table saw is nice, but I don't think it's necessary for this kind of project.



Below: Here's where the speaker is designed to fit in my 4Runner. I had it follow the lines of the rear seats and made it narrow enough so I could put my toolbox and spare tire next to it.



Below: These clamps are really handy! I used wood glue along each joint with screwed spaced 4" apart maximum.





Below: Another trial fit to make sure things look right



Below: I got this quick release terminal from Radio Shack. I'm glad I measured it because the cutout they recommended was oversized by about a half inch! I think it was a typo...





Just for reference, don't buy these crappy RadioShack terminals. They come unsprung easily and basically suck. I wish I had known this before I made the cutout for 'em.



Below: I needed to make the hole for the driver, so I fashioned a compass out of some scrap. I used a screw in the center and drilled a 3/8" hole at the appropriate radius to fit a sharpie. Worked great!

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox11.jpg[/img]

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox12.jpg[/img]

Below: Lots of screws and glue in this project

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox13.jpg[/img]

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Below: Here's the nearly finished box in the truck.

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox15.jpg[/img]

Holy cow a little engineering makes a heck of a difference! I am really impressed with the response! I have had a few different speaker boxes in my truck of varying driver size and type (sealed, bandpass, ported, 8s through 12s) and this one blows them all away. The sound is incredible and I am discovering sounds in some songs that I had never heard before.

Below: The next step was sealing the inside corners with some caulk. I didn't hear any leakage, but it's standard practice to seal the insides. I suppose I should have done a better job of cleaning off the excess. Oh well.

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox16.jpg[/img]

Below: Next I rolled on a few coats of exterior grade latex. Add about $15 to this project for paint and supplies.

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox17.jpg[/img]

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox18.jpg[/img]

Below: Hmm... what's this?

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox19.jpg[/img]

Below: Arts and crafts on an offroad website? Holy smokes...

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox20.jpg[/img]

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox21.jpg[/img]

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[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox23.jpg[/img]

After putting the driver back in I stuck it in the truck again to see how it looked.

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox24.jpg[/img]

I've still got room for hacking my bed later down the road. I want to take about 12 inches out of it. Not sure where I'll put the spare tire at that point.

[img]http://thebandit.xtremefabricator.com/speakerbox/speakerbox25.jpg[/img]

There's still a bit of paint touch up to do as there are a few places that look kindergartenish, but what do ya think?

I've got a couple ideas for a speaker grill - we'll see how they pan out.

Pretty cool Bandit.
For a grill, a 12" cut out section from a rock crawler wheel would be kinda cool. Go with the paint job at least.

I was actually thinking of trying to construct 2 boxes that would run the length of the cargo area. Take out the stock plastic covers and compartments for the jack and run it from the back seat to the tailgate. Putting an 8" woofer in each. That way they could be bolted down and not 'walk' if the truck was broken into!

I have a buddy who designs boxes so I will see what I can do for material.

Regarding your design, I like it alot and dig the paint job! I just can't take up that much room in my Runner so I am going to try to work something else out.

John

that looks really good. i wish subs didnt take up so much room though. i even hate how much space my 6x9's take up. but w/ my amp they put out enough umph to satisfy me. almost everyone i know no longer has subs b/c they got stolen or b/c they didnt like how much room they took up lol. and believe me, all my friends had them.

luv24by, if you make a box that big and only have 8's subs they wont sound good b/c they have too much air to move. if you had even one 12" sub it would probably sound better. 8 inchers are kind of pointless.

if it were me, i would make internal bracing. esspecially the longest section...

a couple pieces of 2x4 would do...


also, you should know, having twice the internal volume is just... well a waste of materials and overall space in the cargo area...

looks awesome, let's here it for engineering! <img src="/forums/images/graemlins/kewl.gif" alt="" />

nice graphic too <img src="/forums/images/graemlins/smile.gif" alt="" />

nice to see someone doing audio the right way. audio is like 90% install and 10%equip. ive made sony p5 woofers sound and hit better than stuff twice the price. typically a larger sealed enclosure will provide a more linear response and transient sound. ive always wanted to do a real free air setup but im not walling off the back of my truck and doing sooo much sealing. this looks like all the other good work ive seen from you. keep it up man!

Well, I wasn't 100% on how long the actual box would be. If the actual sub enclosure would be less than the full length. I was entertaining 10"ers too, just wasn't sure of what the specifics were going to be. The only reason they would go all the way to the rear seat is so there was something to lock the rear seat to and not have to fab something else. It's just a thought and idea right now, I haven't even had time to get together with my buddy in town. The box may be shallow but I figured the length (enclosed accordingly to the sub) would be ok. I am not a guru on air volume needed for each size sub, so I was just trying to give the best example I could with the best information possible!

I'll let y'all know!

John

I remember back in the days when I used to install car audio systems in highschool, lots of fun but you should think about putting bar guard or a mesh guard to protect your subwoofer they sell them at crutchfield and a pluthra of other sources.