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Unread 03-07-2013, 11:06 AM   #1
brianestep
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Spare tire well Sub Box

Hey friends... I know this is a common "desire" at least in the WJ community. I posted here since it is more of a "spec" question than a "will it fit" question. I am building a sub box for the spare tire well. I have one JL 10W0 (10", DUH!!).

Two questions: I find that mounting specs range from .50-.90 ft3, sealed. That is inside enclosure, correct? (and if someone could verify, that would be great!). I am trying to keep it on the smaller end. Is sound quality going to be noticeable at either end of that range?

So i come up with outside measurements of 14.5"L x 12"W x 8"H. Assuming 3/4" MDF (or beech plywood?) that makes inside measurements 13"L x 10.5"W x 6.5"H, for a total of 887 in3 or .51 ft3. Am I doing this right? Also, sub mounting depth is about 5.5". Is 1" behind the magnet enough room?
Thanks dudes!!

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-Brian- 2000 WJ Four liter, 4" RC springs; Bilstein 5100s; JKS trackbar w/KOR bushings; Stillen rotors; KOR (RC) 1.5" wheel spacers; 265/75/16 Treadwright Guard Dogs; Rusty AirTube, Amsoil Cone; Thule M.O.A.B.; Bumper delete; rear seat disco
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Unread 03-07-2013, 11:09 AM   #2
funkduck
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Quote:
Originally Posted by brianestep View Post
Hey freinds... I know this is a common "desire" at least in the WJ community. I posted here since it is more of a "spec" question than a "will it fit" question. I am building a sub box for the spare tire well. I have one JL 10W0 (10", DUH!!). Two questions:
I think you forgot the two questions.. ?
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Unread 03-07-2013, 11:12 AM   #3
brianestep
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Quote:
Originally Posted by funkduck View Post
I think you forgot the two questions.. ?
Haha I pressed enter on accident!!! I was hoping you'd be here! They are up now!!
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-Brian- 2000 WJ Four liter, 4" RC springs; Bilstein 5100s; JKS trackbar w/KOR bushings; Stillen rotors; KOR (RC) 1.5" wheel spacers; 265/75/16 Treadwright Guard Dogs; Rusty AirTube, Amsoil Cone; Thule M.O.A.B.; Bumper delete; rear seat disco
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Unread 03-07-2013, 11:36 AM   #4
funkduck
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There's nothing wrong with having very little room behind the magnet, actually if the magnet touches the back panel (or has a block of foam squeezed between it and the panel so it's under constant tension) your mechanical distortion levels go way down. This is "secret sauce" in some very high end home speakers.

0.51 cubic feet sealed is pretty small for a 10" W0 driver. Going to start having some coloration there with a "punch" in the mid-70's and drop sharply below 50hz with a F3 somewhere around 45hz. It takes a pretty huge enclosure (3 cubic feet) to get that driver in an ideal Q of 0.707

Are you talking about building a square box to shove into the round spare tire well, with a hole in the spare tire cover or something?
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Unread 03-07-2013, 11:43 AM   #5
brianestep
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Quote:
Originally Posted by funkduck View Post
Are you talking about building a square box to shove into the round spare tire well, with a hole in the spare tire cover or something?
Yes, square, since that's the easiest shape for me to build. (well, rectangular actually, but yes). I was trying to avoid cutting a hole in the cover, which is why I was keeping height at 8" or less. and the 12" width is what I have measured from front of well to the jack retaining mount, although I suppose I could cut that sucker off. If I chopped a hole in the cover, I suppose that would give me and extra 1.5-2" I think of extra height, and could line it up flush with the top of cover. Is this all a bad idea?
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Unread 03-07-2013, 11:48 AM   #6
brianestep
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Quote:
Originally Posted by funkduck View Post
There's nothing wrong with having very little room behind the magnet, actually if the magnet touches the back panel (or has a block of foam squeezed between it and the panel so it's under constant tension) your mechanical distortion levels go way down. This is "secret sauce" in some very high end home speakers.

0.51 cubic feet sealed is pretty small for a 10" W0 driver. Going to start having some coloration there with a "punch" in the mid-70's and drop sharply below 50hz with a F3 somewhere around 45hz. It takes a pretty huge enclosure (3 cubic feet) to get that driver in an ideal Q of 0.707

So a depth (height actually, assuming I downfire) of 6.5" would be good, and squeeze an approximately 1" foam in between magnet and back of box? And I don't think it will make a huge difference which direction I point the sub, does it? Besides up... don't want to do that really... and what is Q? Frequency measurement? So I am looking for the middle of the .5-.9 ft3 range?
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Unread 03-07-2013, 11:53 AM   #7
brianestep
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Oh and it is currently in a 14.5L x 9W x 13H, 1/2" mdf box. That comes out to 1296 in3 or about .75 ft3. It sounds pretty decent in there. Is there a huge difference between using 1/2" and 3/4" mdf? It would give me a little more leeway on my measurements...
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Unread 03-07-2013, 01:22 PM   #8
funkduck
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If you're sticking the sub in a box under the original spare tire cover, and then putting the spare tire cover over it.... remember that a speaker's job is to move air. Some bass will still escape from under the cover but really you'd be better off selling all that stuff and buying a bass shaker if you're just going to stick your box inside another box and only really experience the vibration from it, not the sound.

The other problem with a small box is as I said, you'll reach the driver's peak efficiency somewhere above 70hz in a 0.51ft box, and start really running out of output under 55hz even in a 0.75ft box - any decent set of 6x9's in the front doors will play 55hz so why waste your time with a subwoofer if it's not going to sub-woof?

Good 6x9's in the doors coupled to a decent amplifier and a meaningful investment in sound damping material will usually outperform a badly implemented subwoofer with no loss of cargo room. A well implemented sub is another story, but you run into the whole problem of
  • Easy
  • Inexpensive
  • Any Good At All
Pick any TWO.

I'm not trying to be negative or talk you out of this, just giving you realistic numbers and expectations to work with.
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Unread 03-07-2013, 01:48 PM   #9
brianestep
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Quote:
Originally Posted by funkduck View Post
If you're sticking the sub in a box under the original spare tire cover, and then putting the spare tire cover over it.... remember that a speaker's job is to move air. Some bass will still escape from under the cover but really you'd be better off selling all that stuff and buying a bass shaker if you're just going to stick your box inside another box and only really experience the vibration from it, not the sound.

The other problem with a small box is as I said, you'll reach the driver's peak efficiency somewhere above 70hz in a 0.51ft box, and start really running out of output under 55hz even in a 0.75ft box - any decent set of 6x9's in the front doors will play 55hz so why waste your time with a subwoofer if it's not going to sub-woof?

Good 6x9's in the doors coupled to a decent amplifier and a meaningful investment in sound damping material will usually outperform a badly implemented subwoofer with no loss of cargo room. A well implemented sub is another story, but you run into the whole problem of
  • Easy
  • Inexpensive
  • Any Good At All
Pick any TWO.

I'm not trying to be negative or talk you out of this, just giving you realistic numbers and expectations to work with.
No, I appreciate naysaying.. it keeps bad ideas from happening! I was thinking that the loose gaps around the cover would allow enough air to escape. Probably not though, eh? So the .9 ft3 end of the range would be most appropriate? How awful would an up-firing sub, through a hole in the cover, covered by a grate be? Terrible, I bet... Maybe I'll just build a longer, more slender box...
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Unread 03-07-2013, 02:39 PM   #10
Demp
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JL Recommends for the 10W0v3-4 to use a .65ft3 box for sealed, giving the external dimensions of 18"x11"x9" using 3/4 MDF. They list this giving a Fc of 43hz which is higher than I like. I would continue with funkdunk's thinking and go for a lower tuning through porting or bigger sealed. Most aim in the mid to low 30s for sound quality.

For MDF, 3/4" will give you better strength compared to 1/2". Lower strength will cause flexing which will distort your sound and rob you of output. Honestly, all I find for sale here is 3/4" anyway, so I don't have much choice :P
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Unread 03-07-2013, 03:03 PM   #11
funkduck
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Quote:
Originally Posted by brianestep View Post
No, I appreciate naysaying.. it keeps bad ideas from happening! I was thinking that the loose gaps around the cover would allow enough air to escape. Probably not though, eh? So the .9 ft3 end of the range would be most appropriate? How awful would an up-firing sub, through a hole in the cover, covered by a grate be? Terrible, I bet... Maybe I'll just build a longer, more slender box...
I wouldn't cut up the cover, that would just be a shame. The obvious problem here is if you mount a woofer right in the middle of your cargo area, then you can't use your cargo area either.... even with a grille over the speaker there will be crap getting down in it and ruin it before long.

If I were trying to mount a sub in the tire well, I'd probably make a circular disc to cover the whole well (under the factory cover) with a padded edge to offer a pretty good seal, then I'd line the well itself with sound deadener and mount the subwoofer directly in that disc - along with a hinged, flip-up leg on the top of the disc to prop up the factory cover when I want to rock out, and to fold flat when I want to carry cargo.

Alternately I'd make a whole new cover like this:
to keep mess/damage outta' the speaker while letting the sound escape.
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Unread 03-07-2013, 03:15 PM   #12
funkduck
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Quote:
Originally Posted by Demp View Post
JL Recommends for the 10W0v3-4 to use a .65ft3 box for sealed, giving the external dimensions of 18"x11"x9" using 3/4 MDF. They list this giving a Fc of 43hz which is higher than I like. I would continue with funkdunk's thinking and go for a lower tuning through porting or bigger sealed. Most aim in the mid to low 30s for sound quality.

For MDF, 3/4" will give you better strength compared to 1/2". Lower strength will cause flexing which will distort your sound and rob you of output. Honestly, all I find for sale here is 3/4" anyway, so I don't have much choice :P
Recommended is a funny thing... because "best" is a funny thing when we're talking about necessarily imperfect topics like reproduction of audio.

I can see why JL recommends 0.65ft in a sealed driver, to keep enclosure size realistic and to leverage the vehicle's cabin for those deep long waves (you can make a box smaller if you know it's going to live inside another box whose dimensions are shorter than the waves you're playing... but don't get me started on the math for that when the outer box happens to be a leaky, semi-plush car interior full of upholstery and human bodies....)

I modeled the current 10w0 in winISD using their published t/s parameters, and though ISD is sloppy and deals in halfspace it offers a pretty realistic view of a machine's performance without much effort. Here's how we look with 0.51, 0.75 and the "perfect" 2.959ft enclosure:



You can battle some of that with equalization... and honestly it's not awful even on the yellow line - but I would never accuse that driver of being sexy in a sealed or OB application.
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Unread 03-07-2013, 06:01 PM   #13
brianestep
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okay haha I guess this turned in to more of a "where do I put it, then?" thread than I imagined... Obviously a 3 ft3 enclosure is out of the question. Although I do like the design of your trap-door hinge with leg idea, I also value being able to slide large containers in and out of the back without impedance. I am now looking at removing the center console, rearward of the front cupholders, and maybe extending it most of the way towards the back seat. Initial measurements are about 14"H x 15" L x 9" W. =.75 ft3. I can probably go longer and taller than that. Thoughts? I am not looking for absolutle sound perfection. I mean it's just a W0 for pete's sake! Although I will add, it's a great sub IMHO and I have been bumping it for about 10 years, on and off.
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