Is this a functional ported box?

[Umbra]

I would go with a wood port....utilizing the front baffle as part of the port area. Tricky part is figuring out how much port area those need and then a design from there. Rectangle skinny port might work....then the bends with the wood.

The manual had a design that utilized a 3" aero. I plugged the x-max, cone area, and desired frequency into an equation and it recommended using at least 3.6" ports to prevent port noise. That's 10 sq. inches of area in aeros, but I don't know what that converts to slot port wise. I know people tend to use like 50-100% less area with aeros.

having elbows on the port kinda defeats the purpose of having aeroports. Either go side ported or go slot ported.

That's what I thought, but from what I've read about people doing it it seems like so long as the bend isn't too sharp and there's enough straight port before the outside it's okay. Not better than straight, but not problematic at lower velocities. Port Flares talks about it, but I can't begin to pretend to understand velocities at this point in the night, so I'll try tomorrow.

The box is going behind the third row in a minivan. If I do a side port it has to fire into the side of the vehicle. I tried facing a sealed sub to the side, but it didn't sound nearly as good as against the trunk lid. I do like the idea, though.

I like the idea of the aeros, especially since I had most of the hardware on hand (I bought the rest today), but if it's not a good idea in this situation (I can handle not ideal, but acceptable) I can go back to the drawing board and try slotted.

 

[T3mpest 10+ year member]

what dimension are you working with? Port side vs sub side usually isn't the same thing. The port will mostly be doing lower bass, so the direction it faces usually isnt' as important. Odds are the bass from 40hz and up is what got better with the sub rear firing.

Other than that, if you have lots of width, which in a van you should, I'd do side firing areos so you don't have to bend them. That being said, you could also do a slot port and make everything rear firing you wanted as well. Since space isn't at a premium, that's honestly the route I'd take. It's easier to get the right amount of port area with a slot port and it's cheaper to make overall s 1 sheet will make a whole box usually, including port walls.

 

[Umbra]

what dimension are you working with? Port side vs sub side usually isn't the same thing. The port will mostly be doing lower bass, so the direction it faces usually isnt' as important. Odds are the bass from 40hz and up is what got better with the sub rear firing.
Other than that, if you have lots of width, which in a van you should, I'd do side firing areos so you don't have to bend them. That being said, you could also do a slot port and make everything rear firing you wanted as well. Since space isn't at a premium, that's honestly the route I'd take. It's easier to get the right amount of port area with a slot port and it's cheaper to make overall s 1 sheet will make a whole box usually, including port walls.

I hadn't thought of that, but you raise a great point. It never occurred to me the ports won't play all the same frequencies as the subs with the same authority. If that's the case, which is probably is, then side firing is definitely doable.
Currently the box is 32"x15.5"x14" (WxHxD). Behind the last seat there's only about 4 or 5 extra inches of depth (less at the edges because the lid tapers) and I wanted a bit of room so the subs and ports could breathe. I can go up, I'm not sure how much without checking, but probably a foot before it gets to the top of the seat. The width is about 50". If I redo the box in either a side-firing straight port style or slot ported I'll probably keep it about the same height and depth (so I can fold down the seats and load large items like 4'x8' boards without the box impeding) and just go wider.

I say redo because I went ahead and frankenstein'd a new box against everyone's advice. I had enough MDF on hand to extend it (but not start fresh), 4" PVC, screws, wood glue, caulk, all that stuff. I just needed the elbows. It's certainly not ideal, but I believe I can make it work. If I don't like the outcome I'll just sell it on Craigslist and start from scratch.

I have two more inquiries, but this time I have an actual picture to work with:

Would it be better to have the ports diagonal like this or horizontal? If they're diagonal they're farther away from all the walls and less in the way of the subs, but they're also diagonal. I don't know if it makes and difference, but most designs I've seen have the ports running parallel/perpendicular to walls. Then again custom shaped fiberglass enclosures don't always have flat walls and people still make ported boxes out of them.

Also, any recommendations for supporting the pipes? I was going to build a MDF column and put them through, but I knew it'd take away a bit of space I hadn't accounted for and I didn't know if such a column behind the the sub affected anything else. Right now I plan on just using wire ties since they take up so little room. I've heard of people using duct tape too.

 

[T3mpest 10+ year member]

Port orientation wont' matter too much. Closer to the walls might lower tuning a bit and isn't likely to choke the port. Do the subwoofer baskets clear the port like that? Seems like subs with larger mounting depth wouldnt' fit in that. Also you don't want the subs firing directly into the port. You want the subs to pressurize the box and the airmass of the box to pressurize the port. Having the subs inside the port can lead to them unloading and weird pressure issues, sometimes resulting in ripped cones, torn surrounds, or at least greatly reduced mechanical powerhandling.

I prefer subs back in most vehicles to port up. Only time I go sub up is when I'm trying to maximize cone area for a daily beater spl/demo style car. I find it often doesn't sound as musical as sub back as response usually gets pretty bad on higher bass notes. In loud 150+ cars it's easier to make a roof support that kind of pressure as opposed to a hatch though. Basically under 150db and if SQ is of any priority, I usually go rear firing. If maximizing cone area is the goal, SPL is primary concern, then I go sub up.

edit: Sub up works great in hatches and pretty well in most extended cabs trucks too. SUV'sis where I follow the guideline above.