E-350 down-fire sub box
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Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
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From: NE Tennessee
E-350 down-fire sub box
Putting a couple of subs in my '92 E-350 15 pass. van. I was thinking of down-fire under the passenger seats so the kids don't put a foot through a sub. Anyone ever done this or built a box for this? I've been calculating and for a 1.25 c.f. box per sub I'll have to do 2 individual boxes. 8"h 14"d 20"w then have 1-2 inch spacers under the corners of the box.
I'd just take out the rear seat and build a big box but I sometimes have to haul enough kids to fill it up and I like the stealth of the underseat down-fire.
I'd just take out the rear seat and build a big box but I sometimes have to haul enough kids to fill it up and I like the stealth of the underseat down-fire.
Elder User
Joined: Mar 2013
Posts: 847
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From: In my house..
Not all subwoofers are compatible with downfiring, there is a formula to use so you can determine if the subwoofer is compatible or not..
You need to know the Xmax (amount of excursion or how far the cone moves from a resting position to fully extended) and the Fs which is the resonant frequency in free air, once you know those two factors you can use this formula to determine if the subwoofer can be downfired.. Percentage of Sag = 24,849 / ( Xmax * Fs²).
If the amount of sag exceeds 5% of the Drivers Xmax then it is not compatible..
You need to know the Xmax (amount of excursion or how far the cone moves from a resting position to fully extended) and the Fs which is the resonant frequency in free air, once you know those two factors you can use this formula to determine if the subwoofer can be downfired.. Percentage of Sag = 24,849 / ( Xmax * Fs²).
If the amount of sag exceeds 5% of the Drivers Xmax then it is not compatible..
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Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
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From: NE Tennessee
Thanks for the formula. I'll check the stats and see if I can figure it out. I don't wanna point em up cause it will be under a back seat and don't wanna have a passenger have issues with a brown note :O. If I have to point em up maybe put a 3 inch spacer with a piece of plexiglass to push the bass to the sides.
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Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
Likes: 7
From: NE Tennessee
TS-W2502D4 pioneer 10" pro
Using the formula I think I'm getting 20percent if my numbers are correct. So it would be a no go. So thinking up-fire with something up top to push the bass out instead of up into the seat.
Using the formula I think I'm getting 20percent if my numbers are correct. So it would be a no go. So thinking up-fire with something up top to push the bass out instead of up into the seat.
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