Designing my first enclosure, want to bounce ideas off you guys

[philrab]

Here's my Sketchup. Wasn't too hard to figure the program out, just fiddly about some things. That port took me longer than anything else, and I dare not try to make an aeroport (like it matters, it's there for reference.)

Final specs will be:

Trapezoidal box 14H x 31L x 10 1/16 deep on top +15 deep on bottom. Gross airspace 2.347 less 0.16 sub displacement. The aeroport will also displace another 0.09 cu ft roughly, so I won't be horribly oversized. I'm adding some bracing inside and will glue down some 2x4 if need to to soak up a little more air space. going to target 2.0 net as close as possible.

4" dia aeroport, 13.25" long, tuned to 32 hz. I don't have a subsonic on my amp, so I figure I better tune low to keep from locking this woofer up. Also looking to get as flat a response as possible. I'd go sealed, but this gives me better low end extension, and tuned low it's still plenty flat.

3/4 view, with dimensions.

http://imgur.com/Y2KDi4A

[nickricciotti]

1. Do I need to worry about putting some dowel in the port itself to keep things stable, since the box is so long?

2. If I do the above, how does that play into port area? Any adjustments I need to make, or will it matter that much in the long run?

box as the conventional wisdom seams to work well in hatchbacks.

all i can really help with is never put bracing inside the port, it wont be good. seems like you got everything else pretty much figured out. alot of it is trial and error when it comes to your first box you can ask me lol

[philrab]

Back when I was thinking slot port, I was thinking I may need to route bracing through the port cause of how long the box would be. Now that I'm using an aero, I'll just brace above and below the port.

Hope the design looks good. Only tweak I could think of making at this point would be make it 1" shorter with a change to the port length to lose some airspace. We'll see.

[Ritch40]

i personally would add some extra bracing in there and add an additional driver board to help keep things rigid.

[Krakin]

Make sure you add a bracing for the the port.

The minimum I would do is one flush with the inside mouth, the middle along with the outside wall holding it.

If you rough it up and then fiberglass it as well it will be much stronger and flex less, all giving you a overall better port.

[philrab]

i personally would add some extra bracing in there and add an additional driver board to help keep things rigid.

I planned to double baffle/flush mount, just didn't account for that in Google Sketchup.

Make sure you add a bracing for the the port.

The minimum I would do is one flush with the inside mouth, the middle along with the outside wall holding it.

If you rough it up and then fiberglass it as well it will be much stronger and flex less, all giving you a overall better port.

Wasn't planning to fiberglass the port itself, but it's been recommended enough times I'll consider it. Was already planning some internal 1" dowel to keep the box rigid (especially along that 31" length) and it wouldn't be hard to add a few lengths of dowel at the end of the port to keep it form vibrating.

I"m just glad I finally got through the process of designing. I wouldn't characterize it as difficult, just lots of variables moving around until I finally made some decisions. I feel good about that 4" aeroport vs. a slot port, though I don't think a slot port would've hurt anything either. I also don't think it'll hurt much to be slightly greater than 2.0 ^3 ft. net even though OA rec's a max of 2.0 just because I'm running slightly less than max RMS on the sub. I guess we'll see when I crank this thing out finally.

[hispls]

I like sub up and port backward use the curve of the roof line for sound transmission of the bass wave.

Like I keep asking though; is there any quantifiable/mathematical reason for that, or just based on what everyone's ears like? I'm at that point in designing this where I can certainly about face and do that, but I'm wondering what the madness behind the method is.

You never learn if you don't question.

Most of what people do to get loud is trial and testing. Theory may come into some things that people test, but there's simply too many variables in every different install to simply plug it into a piece of software and make accurate predictions. It's not subjective but measured with RTA and SPL meter. Your best bet is to build with the flexibility to try different orientations or positions of everything to see which works best. Sub and port placement and position on the box and in the vehicle can have a dramatic and audible impact on your overall sound.

That all being said, sub up and port either back or to the side seems to be what people go with in hatchbacks, I'd start with whichever you like best. Odds are that between the two the difference in output would be barely audible so just go with what looks good to you. If you plan on chasing numbers you should buy a meter and be prepared to build 5 or 6 different boxes and test out many different port configurations.

[philrab]

I like sub up and port backward use the curve of the roof line for sound transmission of the bass wave.

Like I keep asking though; is there any quantifiable/mathematical reason for that, or just based on what everyone's ears like? I'm at that point in designing this where I can certainly about face and do that, but I'm wondering what the madness behind the method is.

You never learn if you don't question.

Most of what people do to get loud is trial and testing. Theory may come into some things that people test, but there's simply too many variables in every different install to simply plug it into a piece of software and make accurate predictions. It's not subjective but measured with RTA and SPL meter. Your best bet is to build with the flexibility to try different orientations or positions of everything to see which works best. Sub and port placement and position on the box and in the vehicle can have a dramatic and audible impact on your overall sound.

That all being said, sub up and port either back or to the side seems to be what people go with in hatchbacks, I'd start with whichever you like best. Odds are that between the two the difference in output would be barely audible so just go with what looks good to you. If you plan on chasing numbers you should buy a meter and be prepared to build 5 or 6 different boxes and test out many different port configurations.

Not chasing numbers, honestly couldn't care less. This is all for me, so if it perks my ears that's all I care. Nothing wrong with the guys that do, just not what I'm in this for.

The reason I disregarded sub up is because of the cardboard back package tray. Pointing the sub up will turn the whole thing into a rattle trap, and I really want to keep it in place. Likewise, the reason my box dimensions are what they are is to take up as much height and length as possible to keep the depth minimal, so I can keep as much hatch space as possible. Likewise, the way the box is built is to but up against the backs of the seats. May not be what the meter likes, but I'm planning ahead to try and keep my car as usable as possible baring in mind it's my daily driver.

This is also my first foray into ported enclosures. I enjoy a challenge, and learning something new. Thinking if this works out nicely, I might jump off the deep end and try to build a T-line for an 8" woofer I have lying around.

[philrab]

One more question for you guys.

OA recommends a single 4" or 6" port for their OA12, and I'm right at the top of their max net airspace for my enclosure. I keep hearing 12-16 inches of port area/cu ft of airspace, and a single 4" port in my 2 ft. enclosure is pretty small. A single 6" port would give me 28 square inches of port area, right at 14/cu ft, but a single 6" port is going to be a 27" long port (PSP only sells up to 17" long.) 27" is also going to get really close to my sub.

Should I worry about it, or go with their rec (even though it sounds small) and use a single 4" aeroport? If I double up and use a pair of 4" ports, PSP's calculator is calling for a pair of 25" ports, still long as Hell. Should I just ditch the aeroport altogether and go with a slot port, and round over every damned thing to kill port noise?

Looking for opinions here guys. I feel like I'm missing something.

[Joe X]

Definitely you are missing something, usually flared round ports are given 9-12 sq in/cube (Torres manual) instead of the 14-16 which is given to slot ports

Those are merely vague estimates though, if the manufacturer is saying you need a 4" to 6" round port in their tuning range just go by that. in that port area range you can also use 2 3", 3 3" or 2 4" ports.