Need help with box for two SA-8's.

[Nubster 1]

These will be going in the back of a Grand Cherokee. I was originally thinking a single SA-12 but I think I like the idea of less box so I can keep more cargo area and my goal is a daily driver SQ setup so I think the 8's will be just fine for my goals and it stays within my pretty small budget.

I have never built a ported box before so the design, tuning, and porting all are things I don't have a grasp on. I want to do a box that is wedge shaped to maximize the space available while leaving as much cargo area as I can. One thing I am not sure about is whether or not to go rear firing or top firing. The rear firing will allow for a slimmer box but I want to make sure I am also getting the most out of the box too. Also, I have no idea where the port(s) should be and in a box like this for these subs, should it be on large chamber or two separate chambers each with their own porting?

I did a couple very elementary drawings using Paint (don't laugh...lol) that gives the very basic idea of what I was thinking. I really appreciate the help. I have not been around car audio for more then 12 years so I am re-learning everything.

The subs I am planning (I am up for suggestions if this amp/sub combo is not a good one) to power with an Audiopipe AP-1000D at 2 ohms (700w RMS) if that matters in the box design. Also, the area that I have to work with that I would like to stay within are:

Width - 41"

Height - 16"

Base depth - 15"

Top depth - 7" but I realize this will have to be increased for a top firing box which is fine if this is the best box design for my purpose.

So here are my sad, sad drawings:

Edited October 19, 2010 by Nubster

[stevemead08 752]

Maybe a 2nd grade drawing but its better then just saying...someone build me a box.

Atleast you know your dimensions and how you want it. thats a good start.

I am no box builder so i cant help you

[ssh 924]

Considering the distance from the back of the rear seat to the tail gate, your not going to get as much of a unloading effect gain from the hatch as other rear firing setups do, so I vote upfiring

Plus if your upfire, you can have stuff stored in the back and don't have to worry about it getting too close to the drivers, or get big ugly grills

[Nubster 1]

Maybe a 2nd grade drawing but its better then just saying...someone build me a box.

Atleast you know your dimensions and how you want it. thats a good start.

I am no box builder so i cant help you

haha...thanks...I was worried...I hate starting threads asking people to do things for me but I have been reading for hours over the past couple days and just can't come up with the answers to what I need to know. Plus there is so much conflicting info out there it makes it even more difficult. Like the airspace needs of these subs. I read one place not to exceed .60cf ported but then I read people throwing these things in boxes with 1.5cf of space.

[Nubster 1]

Considering the distance from the back of the rear seat to the tail gate, your not going to get as much of a unloading effect gain from the hatch as other rear firing setups do, so I vote upfiring

Plus if your upfire, you can have stuff stored in the back and don't have to worry about it getting too close to the drivers, or get big ugly grills

Right...the safety of the subs was one concern I did have. I don't know anything about unloading so that was never a consideration. I'll look that up so I know what it is. And just an FYI...using a base depth of 15" there would be a gap of 26" between the sub and the hatch...just in case anyone wanted to know.

Edited October 19, 2010 by Nubster

[Duran 387]

Sub up port back typically does best

[ssh 924]

Considering the distance from the back of the rear seat to the tail gate, your not going to get as much of a unloading effect gain from the hatch as other rear firing setups do, so I vote upfiring

Plus if your upfire, you can have stuff stored in the back and don't have to worry about it getting too close to the drivers, or get big ugly grills

Right...the safety of the subs was one concern I did have. I don't know anything about unloading so that was never a consideration. I'll look that up so I know what it is.

In simple terms, unloading is when the sound waves have something to hit and reflect off of. Certain vehicles can make use of the shape of their rear window *cough* hatchbacks *cough* and gain a fair amount of output.

Generally in suv type vehicles, up firing works well if not best. There are exceptions, but those you can only find by trial and error, or a lot of math and physics knowledge

I would do a single chamber and single port for the enclosure.

[Nubster 1]

Sub up port back typically does best

Ok...thanks. How about ports, location, size? Also to keep the box as slim as I can...what is the minimum distance I should have between the edge of the basket and the edge of the box? The O.D. of the sub is listed as 8.25, so would I be able to make the top depth of the box somewhere between 8.5" and 9"?

[Nubster 1]

Generally in suv type vehicles, up firing works well if not best. There are exceptions, but those you can only find by trial and error, or a lot of math and physics knowledge

I would do a single chamber and single port for the enclosure.

Ok...thanks for the port info. I was typing as you were posting my last post. As far as math and physics knowledge...yeah...pretty lacking in both.

[ssh 924]

Sub up port back typically does best

Ok...thanks. How about ports, location, size? Also to keep the box as slim as I can...what is the minimum distance I should have between the edge of the basket and the edge of the box? The O.D. of the sub is listed as 8.25, so would I be able to make the top depth of the box somewhere between 8.5" and 9"?

Try port back, you can either do a simple slot port or use an aero port.

I think 8.5" or 9" would work fine, considering there's a few boxes I've seen built that had a width of 15" and had a 15" driver mounted, just had the ends on the box sanded down and the driver gasket was kept flush with the wood.

[Nubster 1]

Thanks again. I figure for now a aeroport will probably be easiest. Maybe after I get this first box together I can mess around with some different types of ports.

One question about the aeroport...does it matter if I use a shorter 2" port or a longer 3" port as long as the length is correct for the tuning?

Edited October 19, 2010 by Nubster

[ssh 924]

Thanks again. I figure for now a aeroport will probably be easiest. Maybe after I get this first box together I can mess around with some different types of ports.

One question about the aeroport...does it matter if I use a shorter 2" port or a longer 3" port as long as the length is correct for the tuning?

Depending on the enclosure volume and port diameter, you can have port noise issues (turbulence), but I'm not sure how much port area and diameter to volume you need.

Any box builder will know

[antonmiller 8]

use a 4 inch aero port around 16 inches long flare to flare and like 1.5 cubes, port up subs up works well int he 2007+ models that ive played with. not sure on the yearof yours, but in other years, sub up port to the side for low power applications worked well.

[Nubster 1]

It's a 2002 Grand Cherokee so it would be pretty similar to a 2007. So in a 1.5cf box a 4" port 16" long would tune the box to around 35Hz.

Edited October 20, 2010 by Nubster

[Nubster 1]

Ok...I have the subs and I want to start the box this week. I am not set on the aeroport yet so I was wondering if someone can someone help with dimensions for a slot port tuned to 40hz? Subs will be seeing about 700w RMS. Or at least tell me if this looks right for the slot port....height: 13.5"

width: 1"

length: 21"

tuning: 39.90Hz

Granted I am only using 8" subs but from all the pics of all the boxes I have been looking at....a 1" wide slot port just seems tiny. Any help would be greatly appreciated.