Just brainstorming a bit guys... Any advice is appreciated.

So, since my van isn't a delivery van anymore, I don't have to worry about how big a sub box is...

I could build a bigass box for the APX18, and bolt it down in the back... Copy the design of my Rob VO dual port box for my 12, and just make one BIGger...

But I'm thinking about free airing it. Stick up a complete wall, on the C pillars, not the B pillars. C pillers are halfway through the back of an Astro, where the left side of the sliding door meets. Right behind the middle/rear seat, the seatback would actually rest against a wall put there. Slap the sub way up high, facing front. Close the rear doors and that's the box... Ports or not, dunno, probably try no ports at first then cut some holes, guesstimate port length, and stick in some aeroports.

It would be for daily driveability, still able to seat five. I'll see what it does at competition, but it's not a competition setup.

Then, out at the lake when I open up the back doors and rock the beach all weekend, keep the front closed up and it'd be the box...

I dunno..... it's neat in theory, but I'm thinking the SPL in the back would rattle the rear doors all to hell and lose sealability... They're not great as it is...

Anybody ever seen a setup similar to this?

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95 Astro Cargo Van
KW KDC-X979
DVD, XBox, Sirius
RF Punch 55.2 - Orion Cobalt 5 1/4's
ALP V12 - KW KFCX698 6x9's
CLAR APX400.4 - KFC-X698
(2)Orion 1200D - (1)Orion H2 12.2
Roger Waters June 23rd Pengrowth Saddledome WooHOO!

I'm a big fan of free air because of the flatter, more natural response. I haven't seen it done in a van since the 80's.
Free air isn't usually for SPL. And, unless the subs are made and recommended specifically for free-air, you have to underpower them from the rating. With little or no back pressure to dampen thier movemnt, it will easily max out excursion.
I have 2 CVR15's. They're rated 500wrms, but they pump pretty good amped at 380wrms each mounted free-air. Kicker doesn't recommend freeair but thier specs show the response curve for it.
I've been told the surrounds will stretch with time/use, but so far i haven't maxed them out.

ooo Very interesting...

The sub is an Atomic Apocolyopse APX18, custom built with quad 1.4 ohm coils... Yes, it's a super-duper competition oriented sub, which I wish to use as a daily sub (I didn't buy it, I won it as a prize this summer). I don't know how well it'll like being a free air sub, but if I'm not happy after I do the job, I suppose I could "attach" a box to the back of the wall afterwards eh...

So I can hook it up to my two 1200d amps at 1.4 ohm final (for about 2000-2100 watts), or .7 ohms each (for about 1500w x 2), or even try .7 bridged (but that'd be just for burping, I don't think the 1200d's would like to see .35 of an ohm each)...

Either way, it's far less than the 5000w continuous, or 25,000w bursts that it's rated for.

Response curve though... I have no idea.

__________________

95 Astro Cargo Van
KW KDC-X979
DVD, XBox, Sirius
RF Punch 55.2 - Orion Cobalt 5 1/4's
ALP V12 - KW KFCX698 6x9's
CLAR APX400.4 - KFC-X698
(2)Orion 1200D - (1)Orion H2 12.2
Roger Waters June 23rd Pengrowth Saddledome WooHOO!

Your proposed set up is huge.
I had a free-air setup in my Toyota Tercel with a Pioneer TS w302F which is designed for free-air. That sub (on box building programs liked 5-8 cubic feet.

That's a sub which is designed to be run free-air.
Your Sub is not designed for that. And you're looking at 30 - 40 cubic feet for that enclosure.

I have a hunch it will sound like junk.

I like the idea of the wall and using the back of the van as the enclosure, but if you do it, get 8-10 subs.

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Nostalgia just isn't what it used to be.

free air suck in my opinion its just a lazzy way of makin bass theres no skill involved IMO..

lol, free air in a van would take some skill.

well depending on how you do it

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(GrizZz here, wife's PC)

Well this is why I'm debating it, I've never actually seen a free air setup at all, let alone one in a van.

30-40 cu ft is a little high, the back of the van would be roughly 20 to 25 cu ft. MY main concern is how bad it would treat the rear doors. Recommended box sizes are 6 cu ft..... People that have experience with these things have recommended at least double that, 12 to 15.

Lazy... nah. I was thinking of doing it from a "coolness" standpoint. Cool, that is, from all my non-stereo friends and relatives. From the front all you'd see is the sub cone in the wall. But open the back, and you have the back of the sub hangin' up there with EIGHT cables (daily, reduced to four for dBDrag) running to two amplifiers... That'd look insane!

But you're right, it could sound like caa-caa. We stuck the sub in a crappy ~10cu ft box this summer, with just a slot at one end for a port... The lower ohms made my amplifiers suck about 30% more power, so everything was workin' harder... But it was 10dB quieter than my 12" H2's best score (146.6).

So....... No decisions yet. I'm still debating!

Thanks for the advice guys... keep it comin'!

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This might be GrizZz, or this might be GrizZzled (Mrs. GrizZz). You figure it out

Lazy? I wouldn't go that far... Anyone can go buy a prefab box, or build one to manufacurer's specs, throw it in the trunk, and hook it up. trying to get good bass out of a sub that isn't designed to be run like that, in a van none the less, would be a lot more work...

Mark

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Free-Air setup done right is usually a lot more work than going with an MDF enclosure.

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