I'm no expert at this, but I'd think that as long as the cross section doesn't change and you get the full length top and bottom it would be ok. Any reason you're not using the bottom for the slot?

Josh

 

Bottom port would be firing into my false floor. I can get away with modding part of my false floor having the port vertical on the face.

 

Any "paint" renderings so we can get the idea...

 

Not mine, found this when searching. Only diff would be my on top.

 

I would thing that as long as you use the absolute center line of the port as the length then you will get the best average for the length of the port to figure out the tuning frequency.

I would however make all corners of the enclosure smooth by using rounded over corners.

There might be a little more perceived surface area in the corner too.

You could just build a test enclosure with your planned specs and test it to figure out if the actual tuning frequency matches the planned specs. If it is a little off then you can make the needed adjustments for building the inal enclosure.

 

You need to measure the impedance with woofer inside the box. Only way to determine the exact tuning when building vented boxes with "odd" designs. The design the OP posted works but it might be hard to calculate properly.

Sent from my Samsung Galaxy S5 using Tapatalk

 

I'm just going to run round port to make it simple now.

 

Are you limited on the height?
Could do like the JL Wedge's and run the port the width of the front panel, above the sub, and down the angled rear panel.
Easier to calculate the length that way.

 

Trying to keep height limited. Been doing a lot of designs. I might go rectangle box. Wondering if a 13.5" x 2" port is too narrow. It hits the right in2 I need. This is or a single Sundown SA-12.

This is what I came up with in Torres. SA-12 calls for 1.5-2.0ft3 ported.

 

You could just use a 4 inch pvc pipe and a 90 degree elbow and use a router on both ends or sand the hell out of it. I doubt you would have much port noise. Or you could have the slot port firing out the front of the box on the right with the sub on top on the far left. To take the back angle out of the calculation you could make a rear port wall that goes straight up and down not angled. So the port opening would be on the right and would use the right side panel of the box as a port wall then the port would go straight back and run into the vertical mdf port back that you would build then turn left and come straight back towards the front of the box and the furthest left port wall would be inside the box like the rear wall. The disadvantage would be that you would have more port displacement due to the extra two boards that are in the box so you would need to widen the box accordingly. You would still be using the top panel and the bottom panel and the right panel as part of the port the only extra internal walls would be the back port panel and the far left port panel. To picture it you would have the slanted rear panel behind the rear port wall, you would have a little cubby hole space between the rear port wall and the back slanted panel.

 

+1 on going to an internal tube with a 90. I'm looking for similar design with back side slanted. Basically it strikes me to depend on the dimensions of the space you can place the box and how you can enviro orate the box and tune for the internal volume you're after. I'm after .7cf tuned to 30hz.

For what it's worth, sketchup is your friend. And the12volt site has some slick volume and port calculators on the same page.

 

There are some videos out there on how to flare a PVC pipe with a heat gun fyi.....but I usually do the following.... On the inside of the box where the port ends I usually cut a square piece of 6 by 6 piece of mdf and then take the 4 inch pvc pipe and trace around it and cut a hole in the mdf to mount the end of the pvc through so the end of the pvc is flush withe the mdf "baffle" and use wood glue with sawdust in it or Bondo to secure it and let it dry then I run a router with a 90 degree roundover bit to give where the pvc and the mdf end together to create a flare and then sand it smooth. It is not a long or wide flare but enough to reduce most port noise plus it gives the end of the port stability and brings it off of the bottom of the box. I do the same thing on the front of the box where the port starts but I just use the front of the box and do not cut a 6 by 6 piece like the end of the port. It sort of makes the port look like a pipeline above the ground and if needed you can do one in the middle of the port for support without the flare of course.

 

Just don't tell anyone it's a toilet flange.
Seriously though.. This thing is already flared a bit, and countersunk holes for mounting.

Shop Oatey Fits Pipe Size 4-in Dia PVC Flange at Lowes.com

 

13.5" x 2" is just fine for a net 1.75cf enclosure. You usually want to stick between 12-16 inches of port area per cubic foot, so you're right there, and that isn't too narrow.

As far as the angled design, the issue is that the port height changes once it's angled. It may not be by a ton, but you're going from the height of the straight portion to an increased height of the angled portion. This changes your port area and overall port volume in that section. Picture it like running a 13" x 2" port to the back, then making the port 15" x 2" for the back section. There wouldn't be an accurate way to tune that, and while it might not drastically change things, it's less than ideal. The rounded vent with a 90 sounds like a better option, or just don't do an angled enclosure or find somewhere else to place the slot port so it doesn't catch the angle.