Subwoofer Box Dilemma - port or no port.

[Revelle]

So I currently have some shallow mount 12in pioneer subs that according to their specs, have a recommended enclosure size of .76cf for a sealed or ported box. Which is odd as I've never seen a sub with recommended volumes being the same for ported and sealed.
So if that is true, and I can basically do either ported or sealed, would it be possible to have a box that can go back and forth between being sealed or ported?
I currently have an under seat box that has an internal volume of .86cf per sub and with the restrictions I have the maximum port length I could achieve, round port, would be 12 in. Looking at a port calculator it looks like I could do a 2in diameter port that would be about 8in long, which would have me tuned to about 32hz.

My main question is, would a 2in port for a 12 in sub be possible? aka sound good. Or would I be better off just leaving this as a sealed box?

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[1aespinoza 10+ year member]

My main question is, would a 2in port for a 12 in sub be possible? aka sound good. Or would I be better off just leaving this as a sealed box?

If the subs call for 3.14 square inches of port area, you will be good.

 

[Revelle]

If the subs call for 3.14 square inches of port area, you will be good.

Ok, so after checking the specs again they actually recommend a port that's 3" in diameter and 5 7/8" long. Guess I could learn to read lol.
So would I be best using that size port or should I do any adjustment since this box is slightly bigger than recommended?
I just don't understand box tuning and how to relate that to what I need for my subs. btw I'm using pioneer TS-A3000LS4.

 

[Jimi77 5,000+ posts]

.75 cuft seams awfully small for porting that sub. OTOH, I don't think you'll get much output without porting. But I'd shoot for ~1.5cuft ported if you have the space.

 

[Revelle]

.75 cuft seams awfully small for porting that sub. OTOH, I don't think you'll get much output without porting. But I'd shoot for ~1.5cuft ported if you have the space.

This is going under the rear seat in an F150 so I'm already as big as I can get with the .86cuft per chamber as it is.

 

[Jimi77 5,000+ posts]

This is going under the rear seat in an F150 so I'm already as big as I can get with the .86cuft per chamber as it is.

In that case, I'd port and you can try it ported and then seal the port and see which you like better.

 

[1aespinoza 10+ year member]

I just don't understand box tuning and how to relate that to what I need for my subs. btw I'm using pioneer TS-A3000LS4.

So would I be best using that size port or should I do any adjustment since this box is slightly bigger than recommended

Do the ported specs say 0.75 cubic feet? If yes, then my calculations say your box is 116.26 cubic inches bigger. That can be solved by stuffing some wood in there.

 

[deez283 10+ year member]

Model it in WinISD seems strange the ported and sealed enclosure would be the same size.

 

[SlugButter]

They only recommend such a small ported box because people are normally buying these to fit in places that are super small. They aren’t recommending that small ported box because thats optimal for sound. They would probably work better in 1.5 cubes ported, but if you have 1.5 cubes to begin with you likely don’t even need a shallow mount sub. Also, .75 cubes ported would work fine and be louder than the sealed option, but that’s .75 cubes after port displacement. If you stuff a port into a sealed box that’s .75, now the box is only .65 (or less) after the port displacement, and the tuning you thought was going to be 32 is now 37 or 38.

 

[Revelle]

They only recommend such a small ported box because people are normally buying these to fit in places that are super small. They aren’t recommending that small ported box because thats optimal for sound. They would probably work better in 1.5 cubes ported, but if you have 1.5 cubes to begin with you likely don’t even need a shallow mount sub. Also, .75 cubes ported would work fine and be louder than the sealed option, but that’s .75 cubes after port displacement. If you stuff a port into a sealed box that’s .75, now the box is only .65 (or less) after the port displacement, and the tuning you thought was going to be 32 is now 37 or 38.

Yea that makes sense. I actually mistyped the recommended volume, it's .79 not .75. So I think I'm gonna try out the recommended port size of 3x5.875 with some PVC pipe. So after subtracting the sub displacement, .04cuft, and the port displacement, .03, volume of port inside the box since part of it will be going through 2 sheets of .75mdf, I'll actually be right at .79cuft.
I'll give this a shot and will be able to easily seal up the hole if need be. Will likely make port removable with screws and make a plate out of mdf to seal the hole with those same screws.

 

[Jimi77 5,000+ posts]

Yea that makes sense. I actually mistyped the recommended volume, it's .79 not .75. So I think I'm gonna try out the recommended port size of 3x5.875 with some PVC pipe. So after subtracting the sub displacement, .04cuft, and the port displacement, .03, volume of port inside the box since part of it will be going through 2 sheets of .75mdf, I'll actually be right at .79cuft.
I'll give this a shot and will be able to easily seal up the hole if need be. Will likely make port removable with screws and make a plate out of mdf to seal the hole with those same screws.

That's exactly what I would do. Good luck.

 

[2RZ-FE 10+ year member]

Some RF subs back in the day had the same specs for sealed and ported.

My guess is being a shallow mount it has low excursion and would bottom out in too big of a box

 

[deez283 10+ year member]

Yea that makes sense. I actually mistyped the recommended volume, it's .79 not .75. So I think I'm gonna try out the recommended port size of 3x5.875 with some PVC pipe. So after subtracting the sub displacement, .04cuft, and the port displacement, .03, volume of port inside the box since part of it will be going through 2 sheets of .75mdf, I'll actually be right at .79cuft.
I'll give this a shot and will be able to easily seal up the hole if need be. Will likely make port removable with screws and make a plate out of mdf to seal the hole with those same screws.

So you want to tune your box to over 50hz? That port is tiny.. 3" PVC x 6" long in a .79 enclosure would need to be 17.5" long just to reach a 36hz tune..

Unless i'm missing something here..

 

[Revelle]

So you want to tune your box to over 50hz? That port is tiny.. 3" PVC x 6" long in a .79 enclosure would need to be 17.5" long just to reach a 36hz tune..

Unless i'm missing something here..

That is the recommended size from Pioneer. I would assume they should have some kind of logic behind those numbers but, I see what you're saying. I'm also not too knowledgeable on what the difference would be in having a box tuned at 50hz vs 36hz.

 

[Jimi77 5,000+ posts]

That is the recommended size from Pioneer. I would assume they should have some kind of logic behind those numbers but, I see what you're saying. I'm also not too knowledgeable on what the difference would be in having a box tuned at 50hz vs 36hz.

50hz means you'll have a peak in response around 55hz, but a sever drop off in response below ~45hz. 36hz will be less peaky and play lower.