slot port angle box question

[jpmo]

So I looking to build a box for 2 8's sundown probably E's or SA's. Box is 9H 40W - 9D (top) 11D (bottom) the rear slant will face seat subs will be on flat surface facing rear with port in middle .75 port will this port once it reaches the back and makes a turn will this need to be slanted with the back or how do I calculate this? Thanks. Also another question is with port at 7.5 H and .75w this gies my ratio 1:10 is this ok also I can go shorter port legth with .5w but this leaves me at 1:15. Thanks for the help. If I dont get any answers I might just go tube port.

[Triticum Agricolam]

That's nowhere near enough port area for those subs, and the 10:1 aspect ratio is very inefficient. I try to stay under 5:1

[jpmo]

I dont have enough room to get close to 5:1 maybe I have to go tube port

[jpmo]

I can go 1 port at 3"D in 12L inches to reach 33hz

[Triticum Agricolam]

Are you planning on using one port per sub or one port total?

[jpmo]

1 total port maybe 3 inch or so 12" or longer 1 total space 2 subs side port I guess round I was going to run slotted but wont have enough efficient space and cant get it to work correctly.

[Triticum Agricolam]

One 3" port is going to be a recipe for poor performance. Sundown recommend 8-12 sq in of port are per sub for E-8s. A single 3" port is only 7 sq in so that's not even half. If you go with SA-8s you would need even more.

If you stick with E-8s I would use three 3" ports, if you got for SA-8s I'd go up to two 4" ports. It's going to be tough to fit that amount of port in your box, but that's just the nature of the beast.

[philrab]

So I looking to build a box for 2 8's sundown probably E's or SA's. Box is 9H 40W - 9D (top) 11D (bottom) the rear slant will face seat subs will be on flat surface facing rear with port in middle .75 port will this port once it reaches the back and makes a turn will this need to be slanted with the back or how do I calculate this? Thanks. Also another question is with port at 7.5 H and .75w this gies my ratio 1:10 is this ok also I can go shorter port legth with .5w but this leaves me at 1:15. Thanks for the help. If I dont get any answers I might just go tube port.

A. My box is larger, but laid out somewhat similarly. It sounds as if you're trying to point the sub and port the same direction, hence you're contending with that slanted wall. Don't. I thought about doing the same thing, and ended up deciding even if I had the port slant with the wall (have to maintain the same cross sectional area of the port all the way through) the air coming through that port is going to be turning that corner at a different time from top to bottom of the port. That's a recipe for turbulence.

I ended up doing sub back, port to the side. This way, the port is straight (more efficient than making a 90 degree turn in my opinion) and I dodged the issue with the slanted back wall.

My final dimensions changed slightly, but the design is the same, this is what I wound up with.

B. I NEVER make a slot port less than a 1:4 ratio height vs. width (or vice versa). 1:5 as recommended earlier is probably still perfectly fine. At a certain point, even if you have all the port area in the world, the port is just too damned narrow to breath properly. Think about trying to breath through a round tube, or a long narrow slot, I can promise you the long narrow slot is going to be much more restrictive. Port efficiency goes down fairly quickly as that slot gets longer and narrower, requiring more port area than if you'd made is square or near square to begin with.

C. If I read your dimensions correctly, you have a terrifically small gross area to try and make a ported enclosure for those two subs. Sundown says 0.5-0.75 per sub NET on those E8's, you've got about 1.25 Gross. Take out 0.2 cubes for sub displacement, and you're already at the minimum without any port displacement.

If you're open to suggestion, I say your best optoins are:

1. Ditch one sub, run the other ported, 0.75 cubes net like SA recommends with generous port area and port length. A single 8 ported on good power in the right box will sound better than two subs crammed into too small an area with too little port every day of the week.

2. Run two E8's you have sealed. You'd need to lose some box width to get the net area down closer to 0.6, but two 8's on decent power sealed would probably trump 1 8" sub ported Twice the motor force and cone area in play, you'll lose the boost from the port but double everything should make up for it, and it'll have a much wider playable bandwidth than a typical ported box (generally.)

3. Make the box bigger. If you're dead set on 2 8" subs ported, you're just trying to cram ten pounds in a five pound bag. Get a bigger bag.

[jpmo]

Maybe just go 4 SD's for same air space and say screw the ports. I can fit 4 SD's in over 1 cube as they take .25 to .40 cubes per.