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Discussion Starter #1
Anybody ever do a sealed sub enclosure with two sections joined by a smaller connecting tube? In 20 years, I've never seen anybody do this.

Imagine two 0.5 cubic foot rectangular enclosures connected by a 3" or 4" diameter tube or duct between them. Sub mounted in one 0.5 cubic foot enclosure facing normally (cone out to the vehicle interior). Net internal volume of the entire assembly = 1 cubic foot minus sub displacement plus internal volume of duct.

I'm trying to wrap my mind around installing an 8W7 in a regular cab Ranger between a set of bucket seats. I dont want to be jamming my elbow backwards into the enclosure between the seats so I may have a problem attaining the 0.7 cubic feet of airspace recommended by JL for this sub. I already own it so don't really want to go a different route.

I'm willing to cut a 4" hole in the floor pan and fab up some sort of metal or PVC pipe extension to the enclosure to gain the required airspace outside, below the cab of the truck. Curious if the cross-sectional area of the connecting tube or 'tube portion' of the enclosure will have any influence on performance before I begin cutting anything. Is there a minimum cross section for the tubing in this case, and if yes, how is it determined?

I can fab up a test box, but it's easier to ask first. Have heard of double-tuned ported boxes sot of like this, but never a sealed variety.
 

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I can't imagine how your elbow would be touching a box behind your seats. Try making a mock-up box out of cardboard to see just how big this box really needs to be.
 
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I would imagine your situation would better be suited for a shallow subwoofer. That JL sub is way too deep. You will never make it fit.
Yes your elbow would be bangin against it. If you try the shallow subs you would beable to fit 2 eights. That w7 woudlnt come close to what 2 eights would offer.
 

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Anybody ever do a sealed sub enclosure with two sections joined by a smaller connecting tube? In 20 years, I've never seen anybody do this.

Imagine two 0.5 cubic foot rectangular enclosures connected by a 3" or 4" diameter tube or duct between them. Sub mounted in one 0.5 cubic foot enclosure facing normally (cone out to the vehicle interior). Net internal volume of the entire assembly = 1 cubic foot minus sub displacement plus internal volume of duct.

I'm trying to wrap my mind around installing an 8W7 in a regular cab Ranger between a set of bucket seats. I dont want to be jamming my elbow backwards into the enclosure between the seats so I may have a problem attaining the 0.7 cubic feet of airspace recommended by JL for this sub. I already own it so don't really want to go a different route.

I'm willing to cut a 4" hole in the floor pan and fab up some sort of metal or PVC pipe extension to the enclosure to gain the required airspace outside, below the cab of the truck. Curious if the cross-sectional area of the connecting tube or 'tube portion' of the enclosure will have any influence on performance before I begin cutting anything. Is there a minimum cross section for the tubing in this case, and if yes, how is it determined?

I can fab up a test box, but it's easier to ask first. Have heard of double-tuned ported boxes sot of like this, but never a sealed variety.
Yes, that would work but damn thats alot of work. Maybe you could do a custom console.
It doesnt matter what shape the box is as long as its got the correct amount of air or close to it your good.
A pic of what you have in mind would give me a better idea of alternatives before you cuting into your truck.
 

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I can't say as I've ever seen that either. I would be weary of sound waves not transitioning from side to side, or creating standing waves, trapped in the far end.

What kind of dimentions are you dealing with? Seatback to back of cab, width between seats, height between seats?

Wondering if you could make a "T" shaped enclosure. The short ends behind the seats and the long end, extending out between the seats. Even an internal volume of 12" high and 12" wide, with a depth of 2" will yield you .15 behind each seat. Even with sub displacement you should be able to sqeek .4 out of the center part.
Maybe fire the sub downward, if you have enough depth. (which I can't imagine you would) Or fire it forward and put a couple cup holders in the top.

Food for thought...
 

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What you describe smells like a sort of bandpass box. At least, if the linking port is small enough and long enough to behave like a port.

There has to be a better way to go. Amp power is cheap, so maybe look for a less efficient woofer that's happy in a smaller box. Does Kicker still make Solobarics? If you have a Woofer Tester or equivalent, you could mass-load a sub yourself and get the same effect.
 

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Discussion Starter #8
Thanks for all the replies!

Few things; I have plenty of space between the buckets to fit a box running front to back that will accomodate the 8W7's depth, along with enough width and height to have a baffle the sub will mount to. The truck has been converted to a T5 tranny, so the shifter handle sits quite far back. Hypothetical box measuring 8x8x18 internal is only good for 1152 cubic inches, or .66 cubes not including the substantial displacement of the sub. And I don't believe I've got 18" since the shifter handle is so far back (measurements and CAD drawings on an older computer not hooked up right now).

Don't really want to do fiberglass, it's cold this time of year. I could fab the box so that extra airspace is located between the vertical part of the buckets and angled back much like the seat itself. Since the T5 shifter sits much further back and lower than the stock one, my elbow may hit the part of the box between the seats when pulling for 2nd, 4th, or reverse.

There will not be a lot of leftover room in this truck; behind and under the seats is already spoken for. I need to stuff in a CDX-C90 deck, XDP-1000 Proc, a 3-way MB Quart component set, a Mobile ES 6-disk changer, and Helix HXA40 and Sony ES XM2100G amps. That's if I don't include the RF Omnifi. I'm 6'2" and this is a regular cab Ranger. Even with Prelude buckets, behind the seats is really only an option for the processor and changer. Amps will fit under the buckets since I fabbed metal frames to adapt them to the Ranger floor pan, there's some decent height under there now.

Not sure if my idea will act as a bandpass box since the woofer is radiating to open air instead of being in the box on a baffle between chambers. Threaded 4" PVC parts are pretty costly, it might be preferable to do four 2" tubes if I'm going to create airspace below the cab.

It's tempting to do one of the new Type R Alpine 8's but I'd really like to use the 8W7 if possible, I got it mint in the original box for less than an 8" Type R would cost from an authorized dealer.
 

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What you describe smells like a sort of bandpass box. At least, if the linking port is small enough and long enough to behave like a port.

There has to be a better way to go. Amp power is cheap, so maybe look for a less efficient woofer that's happy in a smaller box. Does Kicker still make Solobarics? If you have a Woofer Tester or equivalent, you could mass-load a sub yourself and get the same effect.
First of all the air inside the box will not be moving at all. THERES NO WHERE FOR IT TO GO. The air is acting as spring for the woofer the bigger the box the looser the spring.
Secondly he's not looking for subwoofer recemendations.
To the op the idea with the box being extended behind your seat sounds like a winner.
You could also make the box shorter towards your shifter so that your elbow has some to clear the top of it.
 

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I've also contemplated this idea before to increase airspace in an enclosure but I have never tried it. Honestly, without actually seeing what space you have a available, it's difficult to recommend an alternative route and since you have come to the conclusion of trying this method, I assume you've already thought about other things to do.

I say go for it and see how it works out.

If I had an 8w7, I would literally put it any place I could possibly fit it.
 

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Discussion Starter #11 (Edited)
Here's a screen cap of the CAD file. I designed this with a cardboard template and measurements of the sub before installing the T5, so I will have to check it now versus the shifter's actual location.



The area circled is where my elbow will likely hit. As drawn, the enclosure has an area of 211.87 square inches internal. Assuming I can eke out 8" of width internally, I'm at ~ 1695 cubic inches, slightly generous after subtracting the woofer displacement.

I know 0.1 or 0.2 cubes is not going to have a profound effect on the sub's performance, and I have PEQ with the XDP-1000, I'd just like to get as close as I can to start with.

Want to delete that circled area if I can. Wouldn't take much PVC under the truck to make up for 0.2 or 0.3 cubes lost there.
 

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Discussion Starter #12
I guess the question in a single sentence would be, "Does the frequency response of a subwoofer in a sealed box depend only on the compliance of the volume of air inside it, or can the internal enclosure size and/or shape introduce unforseen effects other than standing waves?"

It's 3 degrees outside, but I will drag a tape measure out to the truck in a bit to see if I can massage the design in the CAD file to solve the problem without adding PVC and cutting holes.
 

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Anybody ever do a sealed sub enclosure with two sections joined by a smaller connecting tube? In 20 years, I've never seen anybody do this.

Imagine two 0.5 cubic foot rectangular enclosures connected by a 3" or 4" diameter tube or duct between them. Sub mounted in one 0.5 cubic foot enclosure facing normally (cone out to the vehicle interior). Net internal volume of the entire assembly = 1 cubic foot minus sub displacement plus internal volume of duct.

I'm trying to wrap my mind around installing an 8W7 in a regular cab Ranger between a set of bucket seats. I dont want to be jamming my elbow backwards into the enclosure between the seats so I may have a problem attaining the 0.7 cubic feet of airspace recommended by JL for this sub. I already own it so don't really want to go a different route.

I'm willing to cut a 4" hole in the floor pan and fab up some sort of metal or PVC pipe extension to the enclosure to gain the required airspace outside, below the cab of the truck. Curious if the cross-sectional area of the connecting tube or 'tube portion' of the enclosure will have any influence on performance before I begin cutting anything. Is there a minimum cross section for the tubing in this case, and if yes, how is it determined?

I can fab up a test box, but it's easier to ask first. Have heard of double-tuned ported boxes sot of like this, but never a sealed variety.
Probably wouldn't work, the sub would see the area it's mounted in as a box, the other section would likely act as a helmholtz resonator, which could either work in your favour or against it. You can model this type of design, check diyaudio for more info and what programmes you'd need.

Joakim uses a helmholtz resonator in his SQ car in this thread, he may be willing to garnish you with more info:
http://www.diymobileaudio.com/forum/build-logs-project-install-gallery/76199-bmw-e34-touring-mosconi-odr-norwegian-sq-car.html


Alternatively you can do what I did and use cabin gain as a mechanical EQ in a linkwitz transform style enlcosure:
http://www.diymobileaudio.com/forum/diyma-sq-forum-technical-advanced/116923-cabin-gain.html
 
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