Unique box design

[Dustin_Kimble]

I've got an idea for a box, but maybe the reason I've never heard of someone doing it is that it's a bad idea. I've got a hatchback with 42" of width, 16" of height with preferably as little depth (as looking into the back of the hatch) taken up as possible. The rear seats recline and make the place where I'd want to position the box an acute angle relative to the floor.

I've been wanting a sealed down firing box to hold 2 pioneer 12's that'll be anchored down against the back of the seat with the subs completely sealed off from any debris in the boot. But I was thinking that would "smoother" the sound and thought about building the sides of the box a little deeper than the box itself would create space for air to move. Is this making a bandpass enclosure and messing with the needed box volume? Any thoughts?

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[Dustin_Kimble]

View attachment 26554544

Roughly what I'm talking about. Yea, i know, i definitely didn't graduate an art academy. Box is going to be roughly 4 inches off the floor and 3 inches away from the back of the rear seats with the sides and back being the support

I've got a few questions about the best way to design this.

Should I still be treating the volume of the box as a normal down firing sealed sub box?

The floor this will be sitting on is a carpeted foam trunk forms with MLV and sound deadener underneath. Keep the foam carpet bottom or make it wood?

The seat is a fold down 60/30 type, there's this crack where the seats separate. Does something need to be done about that?

All ears for any thoughts here.... I'd love to do this the right way the first time.

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[Dustin_Kimble]

Well since I can't get a solid opinion on this design and I don't feel like taking the risk of possibly making a mistake requiring me to redesign the box, what it looks like I'm essentially doing is creating a 4th order bandpass enclosure. I'm gonna continue this build treating it as so, not taking risks on a questionable design, but going with something I know will work. I got on a website, found my speaker specs, and this is what I've got so far.

1) Speaker Parameters Diameter:

12.00 (inches)

Qts: 0.59

Fs: 35.00 (Hz)

Vas: 1.22 (cubic feet) = 34.59 (liters)

S: 0.60 (response curve - .4 thru .7)

2) 4th Order Bandpass Cabinet Parameters Lower 3db Rolloff: 30.00 Hz (F3 Provided by user) High 3db Rolloff: 86.71 Hz (Calculated)

Sealed Box: 1.09 cubic feet = 1878.45 cubic inches = 30.79 liters

Ported Box: 0.61 cubic feet = 1057.94 cubic inches = 17.34 liters

Tuning Frequency: 51.00 Hz

3a) If using a Single Port User definable port size:

Port Diameter: 2.00 inches ( 50.80 mm)

Port Length: 3.84 inches ( 97.63 mm)

Suggested: (.3 X Speaker Diameter)

Port Diameter: 3.60 inches ( 91.44 mm)

Port Length: 14.56 inches (369.87 mm)

3b) If using Two (Dual) Ports User definable port size:

Port Diameter: 2.00 inches ( 50.80 mm)

Port Length: 9.15 inches (232.44 mm)

Suggested: (.3 X Speaker Diameter)

Port Diameter: 3.60 inches ( 91.44 mm)

Port Length: 31.76 inches (806.67 mm)

3c) If using Three Ports User definable port size:

Port Diameter: 2.00 inches ( 50.80 mm)

Port Length: 14.46 inches (367.26 mm)

Suggested: (.3 X Speaker Diameter)

Port Diameter: 3.60 inches ( 91.44 mm)

Port Length: 48.96 inches (1243.47 mm)

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[Jeffdachef 5,000+ posts]

actual pics of the car trunk might help along with max depth. Cant really get a good design without that last dimension man. When you say as little as possible with the depth, it could mean from 6 inches to 20 inches, we dont know.. If its an angle measure the bottom depth and the top depth where the seat ends and see what your max depths for both are.

Along with the specific model of subwoofers.

 

[Dustin_Kimble]

actual pics of the car trunk might help along with max depth. Cant really get a good design without that last dimension man. When you say as little as possible with the depth, it could mean from 6 inches to 20 inches, we dont know.. If its an angle measure the bottom depth and the top depth where the seat ends and see what your max depths for both are.
Along with the specific model of subwoofers.

Sure thing.

Pioneer champion pro 12's w3003d4

Box is going in a 2011 subaru outback against the rear seats.

Dimensions here....

http://tinyurl.com/h7tgqth

43" from wheel well to wheel well, 16" from the bottom of the floor to the top of the rear of the seats (can be adjusted, but that's the approximate height I'd like) and the depth is going to depend on the the volume calculations.

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[Jeffdachef 5,000+ posts]

Sure thing. Pioneer champion pro 12's w3003d4

Box is going in a 2011 subaru outback against the rear seats.

Dimensions here....

http://tinyurl.com/h7tgqth

43" from wheel well to wheel well, 16" from the bottom of the floor to the top of the rear of the seats (can be adjusted, but that's the approximate height I'd like) and the depth is going to depend on the the volume calculations.

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you can go for a 4th order but just know that if you are too far away from a solid wall to load off of, you'll start losing bass clarity and output. Downfire is not as good as it used to be vs firing towards the rear hatch being close to a solid wall as possible. You'll find downfire sounding muffled and muddy most of the times on the upper notes and just a tad weak with the lower notes with subwoofers nowadays.

 

[Dustin_Kimble]

you can go for a 4th order but just know that if you are too far away from a solid wall to load off of, you'll start losing bass clarity and output. Downfire is not as good as it used to be vs firing towards the rear hatch being close to a solid wall as possible. You'll find downfire sounding muffled and muddy most of the times on the upper notes and just a tad weak with the lower notes with subwoofers nowadays.

Any suggestions then? I'd love the subs protected against cargo, and im going to need a pretty decent wall to mount amps on (separate high and low amps)

I'm not a bass head and don't really need everything in the vehicle shaking. How would a sealed down firing box fare with its open end to the back of the seats? (opposite of this picture) View attachment 26554557

All the math is starting to deter me from going bandpass for worry about doing the wrong calculation in the wrong spot, not to mention my inexperience in the specifics. This will be my first box built to subwoofer specs (not first box built, but hopefully the first box built right).

I worry about smothering the cone side of the subs, but I suppose people do put them right up against the back of seats with little to no room to breathe.

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[Dustin_Kimble]

Looking at the picture on my last post and thinking.... The "port" (i know it's not a port, it's just the open end of the design) would be pointed to the rear of the vehicle. Is that important? You had said something about having a solid wall to load off of, is that what that's intended for?

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[Jeffdachef 5,000+ posts]

Any suggestions then? I'd love the subs protected against cargo, and im going to need a pretty decent wall to mount amps on (separate high and low amps)
I'm not a bass head and don't really need everything in the vehicle shaking. How would a sealed down firing box fare with its open end to the back of the seats? (opposite of this picture) View attachment 26554557

All the math is starting to deter me from going bandpass for worry about doing the wrong calculation in the wrong spot, not to mention my inexperience in the specifics. This will be my first box built to subwoofer specs (not first box built, but hopefully the first box built right).

I worry about smothering the cone side of the subs, but I suppose people do put them right up against the back of seats with little to no room to breathe.

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Keep in mind this is with sound quality emphasized, not spl. You want clear sounding bass not muddied bass, to have that you need proper phase alignment via subwoofer loading and positioning.

With the subs in the middle of the car firing forward towards the cabin/the back of the seats will have all your output and bass go to the trunk and you have zero output in front. Basically the front cabin will be a dead zone. Thats how loading works, you want the sub to fire towards the wall furthest from you and the bass reflects back. However if the subs are in the middle of the vehicle firing to the back, the waves will cancel each other out as well.

Read this please for visual help of what i'm trying to explain.

http://www.teamrocs.com/technical/pages/aiming.htm

What you can do is build a sealed box in the area between the wheel well and back trunk.

Sort of like this but one on each side. Your height will might need to be a bit higher and your width will take up some space and you'll need to use poly fill to make up for some cubic feet but this loading is way better than the subs in the middle of the car firing out of phase.

each side will be around 16 height(if you can do more, you can decrease width), 10 width 17 depth with 1 LB of poly fill.

 

[Dustin_Kimble]

Keep in mind this is with sound quality emphasized, not spl. You want clear sounding bass not muddied bass, to have that you need proper phase alignment via subwoofer loading and positioning.
With the subs in the middle of the car firing forward towards the cabin/the back of the seats will have all your output and bass go to the trunk and you have zero output in front. Basically the front cabin will be a dead zone. Thats how loading works, you want the sub to fire towards the wall furthest from you.

What you can do is build a sealed box in the area between the wheel well and back trunk.

Sort of like this but one on each side. Your hieght will might need to be a bit higher and your width will take up some spaceand you'll need to use polyfill to make up for some cubic feet but this loading is way better than the subs in the middle of the car firing out of phase.

each side will be around 16 height(if you can do more, you can decrease width), 10 width 17 depth.

Thanks for taking the time to reply. So I should abandon my effort to hide the subs (i still want to place the box as close to or near the back seats for space concerns) and focus on properly aiming them. Alright, sounds like I should get a box with the correct air space and play with the angle they should be mounted for this particular vehicle huh?

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[Jeffdachef 5,000+ posts]

Thanks for taking the time to reply. So I should abandon my effort to hide the subs (i still want to place the box as close to or near the back seats for space concerns) and focus on properly aiming them. Alright, sounds like I should get a box with the correct air space and play with the angle they should be mounted for this particular vehicle huh?
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yeah it always becomes convenience vs performance. Use your small cubby holes right after your wheel wells and they should be out of the way and you have your whole trunk space left. If you have them near the seats, you lose out on vast amounts of performance. Closer to the rear hatch the better.

 

[Jeffdachef 5,000+ posts]

I'm talking about these areas right here.... One 12 on each side

 

[Dustin_Kimble]

I'm talking about these areas right here.... One 12 on each side

****.... Looks at tho I may have some fiberglass in my future. Could they be pointed at each other?

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[Jeffdachef 5,000+ posts]

****.... Looks at tho I may have some fiberglass in my future. Could they be pointed at each other?
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up firing or angled towards at the hatch/slightly towards eachother. Fiberglass would be a great way for a mostly custom and out of the way setup that retains a lot of space while having the SQ of a sealed box. A squarish box around there would of worked as well but wont be a snug fit vs fiberglass.