# sealed box, downward firing sub, how far off the ground should it be?



## brainneeded (Aug 18, 2008)

well i have a jl 8w1v2 and i'm designing an underseat box for it. i'm pretty much 99% set on this design because of a) stealth and b) it's under my butt (mmmm rumbly, who needs factory massage seats when you've got this?). so i'm just wondering what the minimum clearance off the ground should it be?

so far the external measurements are as such, 14" deep, 14.5" wide, and 5.5" high, giving me just the right internal volume (with 3/4" mdf, 650 cu. in. vs. jl's rec. 648) and only .5" off the ground.

should i just make a switch to 5/8 mdf?

thanks for your help in advance!


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## bfowler (Nov 25, 2009)

so 5.5 is your total height? 

that might not be enough. the subs mounting depth is 3.8, plus 3/4 for the mounting outside the box, plus the excursion, plus that sub has a pole vent in the back too which ideally should have some clearance behind it too inside the box. 

thats puts you at over 5.5 even before you factor in how far it should be off the floor


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## Austin (Mar 12, 2009)

bfowler said:


> so 5.5 is your total height?
> 
> that might not be enough. the subs mounting depth is 3.8, plus 3/4 for the mounting outside the box, plus the excursion, plus that sub has a pole vent in the back too which ideally should have some clearance behind it too inside the box.
> 
> thats puts you at over 5.5 even before you factor in how far it should be off the floor


X2 It would be extremely close. You should have at least 3/4" -1" off the ground. Plus min .5" for the pole vent. Either find a different sub, or find a different spot to put it.


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## Oliver (Jun 25, 2007)

If it hits the floor ... raise it up a lil


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## brainneeded (Aug 18, 2008)

bfowler said:


> so 5.5 is your total height?
> 
> that might not be enough. the subs mounting depth is 3.8, plus 3/4 for the mounting outside the box, plus the excursion, plus that sub has a pole vent in the back too which ideally should have some clearance behind it too inside the box.
> 
> thats puts you at over 5.5 even before you factor in how far it should be off the floor





Austin said:


> X2 It would be extremely close. You should have at least 3/4" -1" off the ground. Plus min .5" for the pole vent. Either find a different sub, or find a different spot to put it.


hey thanks for the quick and detailed responses guys!

this is a w1v2, i don't think there is a pole vent, i think only the w6 and w3 have pole vents, at least this is what i've been brought to believe.

that being said, i've revamped my box design and i have JUST enough clearance. 

if this doesn't work i'll just but it in the hatch of my car, but i'd much much rather it under my seat.

anyways thanks again for the help!


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## el_chupo_ (May 27, 2007)

At only 14x14 your could probably get away with 1/2" MDF for the back, but may need add bracing.

I doubt it, that sub wont be flexing a box too much.


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## brainneeded (Aug 18, 2008)

lol wrd, i wasn't going for big bass, but something to compliment the bottom end of my car. i was thinking about 3/4 for the sides, and 5/8 or 1/2 with bracing for the top and bottom.

we'll i'll try it out and see what happens. i guess worse comes to worst i i can do a false floor in the hatch.


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## subwoofery (Nov 9, 2008)

Most people would say a minimum of 4" of clearance. 

Also read that you need half of the subwoofer diameter: 
8" subwoofer = 4" of clearance 
10" subwoofer = 5" of clearance 
12" = 6" 
And so on... 

Hope that helps, 
Kelvin


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## badmotorscooter (May 22, 2009)

I would build the box with 1/2" mdf and add some bracing. Whatever space you end up with is what it is. As long as there is some room beyond excursion limits it will be fine.


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## el_chupo_ (May 27, 2007)

subwoofery said:


> Most people would say a minimum of 4" of clearance.
> 
> Also read that you need half of the subwoofer diameter:
> 8" subwoofer = 4" of clearance
> ...


I have never heard of this, where did you find it?

I dont even see people using this in home audio, where there is some room...


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## tplaya07 (Mar 6, 2010)

I've always heard that the general rule is 3-4" as well. Haven't heard of the half the sub diameter theory before. 

I think bfowler is correct though in that you will likely be cutting things too close. I've always heard that at least 1-2" beneath the magnet/pole vent is recommended, depending on the wattage of the sub (higher wattage=more heat dissapation needed)...correct me if I'm wrong.

You could always use some spacers to raise your seat a few inches though...although it might make the ergonomics of the seat/position a little out of whack.


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## Greg S (Oct 21, 2009)

I've got about 3/4" clearence under one of my downfiring eights and it sounds great. I have lifted the box off the floor a couple inches to compare the difference in sound and it doesn't change at all so I don't think you'll have much of a problem as long as you fit it all under there.


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## PorkCereal (Nov 24, 2009)

Im doing a downfire box in my f150 behind my seats and Eric at ID said min of 3in for an IDQ12 4+ would be best.


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## bsvrs (May 4, 2009)

I used to run my old sub downfiring in my F150 with about 1.25" of clearance between the floor. It sounded good; there was no noticeable difference in sound between down vs. upfiring. The only "problem" was the vibrations throughout the rest of the cab, but you will get those with any downfiring setup.


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## brainneeded (Aug 18, 2008)

i figured all the truck guys would chime in. usually not a ton of space and truck enclosures usually don't have space to have clearances like ya'll were telling me about.

oh well everything will be here by the end of the month and phase one will be done.


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## divvide (Apr 4, 2009)

This is where the shallow design subwoofers come to play.


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## Austin (Mar 12, 2009)

divvide said:


> This is where the shallow design subwoofers come to play.


X2 if it ends up not working out check into the new daytons and give us all a review


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## deesz (Feb 1, 2010)

94 ford f250 8" infinity reference with about 300 watts raised the center console up and had it down firing with about 2" space it sounded amazing....


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## Knobby Digital (Aug 17, 2008)

Don't forget this:

http://www.adireaudio.com/Files/DriverOrientation.pdf


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## brainneeded (Aug 18, 2008)

Knobby Digital said:


> Don't forget this:
> 
> http://www.adireaudio.com/Files/DriverOrientation.pdf


did it already, i've well within the sag limits. thanks though!


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## 2fnloud (Sep 30, 2007)

Knobby Digital said:


> Don't forget this:
> 
> http://www.adireaudio.com/Files/DriverOrientation.pdf


New info to me, and I am planning on a down firing sub. I am making an excel formula now for this, who is interested?


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## Knobby Digital (Aug 17, 2008)

brainneeded said:


> did it already, i've well within the sag limits. thanks though!


Anything for a Houstonian!!! 

Driver sag was mentioned in another thread a couple days ago, so I figured I'd post that here as well.


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## ajw2685 (Feb 14, 2010)

Knobby Digital said:


> Don't forget this:
> 
> http://www.adireaudio.com/Files/DriverOrientation.pdf


I have an excel file with this built into it, but no place to host it.


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## sqshoestring (Jun 19, 2007)

Distance: Sonosub FAQ

What you can do is cut a small hole that just fits the magnet of the sub. Then get a piece of say 1/8 aluminum plate and cover the hole. Works great on truck boxes to give the thickness of the wood more clearance.

Yeah I'd save those subs and get some shallows, but let us know how it works.


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