I find this somewhat interesting so I thought I'd share....
I've been working on upgrading the sound system in my NSX and was careful about what I chose for equipment. One of my primary goals was not to lose any room in the car, while still installing all the gear into the cabin itself.
The largest problem is finding a decent subwoofer that doesn't require a lot of enclosure volume (not too hard to find) but also has a very shallow mounting depth (almost non-existant). The #1 driver for this has always been a sub by Illusion Audio, which unfortunately are no longer sold in the US. However I found one on ebay.
So, Illusion says the ideal sealed enclosure volume for this 10" sub is 0.8 cu ft. Doesn't sound like much, and as far as speaker enclosures go, it's not, but that volume is equivalent to six gallons of liquid. That sounds like a LOT more, and certainly much more volume than the original stock enclosure. Great.
So, for the past week while I've been waiting for the sub to arrive, I've been trying to come up with different ideas while keeping it simple (ie, no fiberglass). For the hell of it last night, I threw the ND10 driver parameters into an enclosure design program and was pretty surprised at what I saw.
The second graph shows frequency response based on a box with the ideal 0.8 cu ft volume. Not great but not bad. As it's a sub, we're going to use a crossover with about an 80 Hz cutoff, so already this box is rolling off from that point, but the slope isn't bad (and generally a car interior will provide some compensation for that). At 30Hz we're only 10dB down.
Now if anything went and I could use any driver in the world, it would not be this one, but for what this speaker's requirements are, it's a really good choice. Well made, minimal space impact, really decent sound quality, and freq. response is pretty decent.
So, back to six gallons of milk..... for the hell of it, I decide to fill up the stock enclosure with water to figure out the volume. It's around 0.1 cu ft... tiny! I throw it into my program........ huh???
The freq response is very very similar even in this tiny enclosure space! Ok so we're down 10dB at 25 Hz instead of 20, small price to pay. Down to 50Hz, they are identical.
So while it's not yet complete, I've taken the back of the stock enclosure, cut off the raised plastic protrusions so the top is flat, taken 2 pieces of 3/4" MDF and cut to shape, mounted the sub to the MDF and the MDF to the stock plastic enclosure. Now I just need to get some sort of filler to fill in the small holes left because the driver was just a tad too large to fit within the back of the plastic piece.
The big test comes soon... listening! But it looks damned good on paper and will lose virtually no leg room and will use stock mounting screws and points.
[This message has been edited by robr (edited 19 July 2002).]
