Ported box depth

[SMS 10+ year member]

Im looking to put a ported 12" in my trunk. Would it be possible to use a 28"L-16"H-11"D box? I have been told that you need around 15" of depth in ported, but I have seen some JL wedge boxes that were around 10" deep at the bottom with a slot port.

Would it work If I did a 9.5"-1.5"-25.5" port on the bottom or top exiting the side, or maybe an L shaped exiting the top or bottom corner?

I dont have the 12 yet, I would try to find the best one for this application.

Thank you for any help, I am new to ported boxes.

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[RAM_Designs 5,000+ posts]

Just do sub and port firing towards the rear or firing forward(you can obviously test out both ways with the same box). Box depth isn't as issue so long as you have enough clearance behind the woofer(if needed). But with the dimensions you provided(28"x16"x11") you only have 2.11ft^3 of air space before sub and port displacements, which just isn't enough for a slot ported box.

 

[09civic 5,000+ posts]

what 12?

 

[SMS 10+ year member]

Im beginning to think my local guy is incompetent, maybe thats why he is the cheapest around.

So I would go with a 14.5"-2" and keep it about 2" from the back wall giving be about 8" of depth. That would be tuned ?Hz. I feel bad asking you since you posted a link for calculations, cant seem to figure it out-said my port length should be 254".

An educated guess would be more than enough, Thanks for your help.

 

[09civic 5,000+ posts]

what sub are you workin with op?

 

[SMS 10+ year member]

what 12?

In my post I said that I didnt have sub yet, I wanted to find a sub that would fit my box. What I am interested in is an SA12, typeR, been looking into MMats and ID. It really depends on my budget- I can get a type R for $130. I have either 600w or 950w to power it at 2ohms

 

[pro-rabbit 5,000+ posts]

What kind of car or truck do you have? Also generally you want 1.75-2.5 ft3 after displacements for a 12". If your box guy came up with the first design he does not need to build your enclosure, find someone else.

 

[SMS 10+ year member]

Just do sub and port firing towards the rear or firing forward(you can obviously test out both ways with the same box). Box depth isn't as issue so long as you have enough clearance behind the woofer(if needed). But with the dimensions you provided(28"x16"x11") you only have 2.11ft^3 of air space before sub and port displacements, which just isn't enough for a slot ported box.

As I said Im new to ported boxes. If my math is correct I will have 1.97 internal volume,-sub (+or-.13) -port(+or-.16) leaving my with 1.7cuft. I find that the "average" spec for a ported 12 is 1.75cuft, which means Im missing something, possibly there spec is calculated with a round tube port. I have seen "1.5cuft with a 3"x8" port from Logic. Figuring 3" dia tube 8" long?

Thank you again.

 

[SMS 10+ year member]

What kind of car or truck do you have? Also generally you want 1.75-2.5 ft3 after displacements for a 12". If your box guy came up with the first design he does not need to build your enclosure, find someone else.

I have a maxima, but I cant take up alot of room in the trunk.

I came up with the design, the guy from my local sound shop told me that I need 15" depth for ported boxes-of any size sub. I build my boxes myself, so far just sealed. I cant see paying someone to build a box when a 4x8 sht of mdf is $27 and I have all the tools. The design is my problem.

 

[SPL KID 10+ year member]

1) make it as wide as you can and still fit it in the trunk.

2) average 12 is 8 inches deep and you need a minimum of 3 inches off the rear of the sub so at minimum your box need to be 11 to 12 inches deep internally. So a 15 inch long box is actually correct as a starting point.

3) If you have skill you want to add some corner 45's inside the enclosure for better air flow and to optimize performance.

4) Figure your enclosure with the design program to 3.0 cu ft for average box for 12 with the 45's OR 2.25 with out the 45's. Then go to port calculating portion and figure in your port. 35-40 tune is good average for SPL and SQ. Do not put a 45 in the port corner without tapering the opposite corner to match angle degree and width.

 

[RAM_Designs 5,000+ posts]

As I said Im new to ported boxes. If my math is correct I will have 1.97 internal volume,-sub (+or-.13) -port(+or-.16) leaving my with 1.7cuft. I find that the "average" spec for a ported 12 is 1.75cuft, which means Im missing something, possibly there spec is calculated with a round tube port. I have seen "1.5cuft with a 3"x8" port from Logic. Figuring 3" dia tube 8" long?Thank you again.

The problem is that the port opening you're using is too small for a normal 12" sub, but round ports do help cut down on port displacement by quite a bit. However, I wouldn't go any smaller than a 4" port, and it better be an aeroport with flared ends to keep port noise at a minimum and efficiency high. The issue then becomes that you need a 14-15" long port that needs to have a few inches of clearance inside the box...so you either will have to make the box deeper than you'd like or buy some 90* angles and make the port bend inside the box. Although slot ports take up more space, they're generally easier to plan out because you can just make it turn however you need to with ease.

Oh, and the 15" deep box requirement for ported boxes is not true at all. There's no rule-of-thumb like that.

 

[RAM_Designs 5,000+ posts]

1) make it as wide as you can and still fit it in the trunk.
2) average 12 is 8 inches deep and you need a minimum of 3 inches off the rear of the sub so at minimum your box need to be 11 to 12 inches deep internally. So a 15 inch long box is actually correct as a starting point.

3) If you have skill you want to add some corner 45's inside the enclosure for better air flow and to optimize performance.

4) Figure your enclosure with the design program to 3.0 cu ft for average box for 12 with the 45's OR 2.25 with out the 45's. Then go to port calculating portion and figure in your port. 35-40 tune is good average for SPL and SQ. Do not put a 45 in the port corner without tapering the opposite corner to match angle degree and width.

What size 45's are you using? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif