Modeling Triangular Ports in WinISD? . . .

Steve_Lee

Would it be best to model a square/rectangular port 1st, then actually create two triangular ports of 1/2 the area of the model?
What about decreased air flow [wall friction] how would one account for that? (Maybe make the triangular port with 20% more open area?

Thoughts?

tktran

It's a good thought Steve. Whilst I agree that for the same length of the port, if you HALF the cross sectional area eg. turn a rectangular/square slotted port into a triangular slotted port, then all you need is DOUBLE the number of ports.

In theory this will maintain the same air velocity in the port, but as flow increases, it becomes less laminar and more turbulent.

I'd like to see some empirical testing to see what kind of End correction (fudge factor) is required. And whether twin triangular ports will allow a shorter port than that calculated, or result in lower air velocity (and thus port noise).
Or whether it reduces the typical pipe resonances seen in a circular port.

Let me ask someone who may have done some testing and get back to you...

jr@mac

I reached out to Scott Hinson to see if he has done any work in this area.

DrewsBrews

I've had previous interest in such triangle ports, but never tried it. Just add a block with 45deg miters to the corner of the enclosure. Not unlike a slot port in construction, and I suspect the tuning would be similar to a slot port.

jr@mac

https://www.facebook.com/DIYRM/posts/1212863525554986

jr@mac

Basically his conclusion is that triangular ports are pretty bad from a distortion perspective.

jr@mac

So don't bother.

tktran

Scott's study is a very interesting read. But I must say I'm a bit surprised he didn't go further with the triangular ports. If a flanged port beats an un-flanged port, then it's possible that a triangular port that is placed at the corners of the box is better than the centrally mounted one.

After all, two of the sides are fixed, as they are made from the walls of the cabinet.

Does Scott hang out here?

My guess was it probably wasn't worth exploring, since the triangular one lagged so far behind the circular port.

PS. Augerpro has done the most testing on ports I've ever seen:

https://www.somasonus.net/box-construction-methods

jr@mac

No, he admins a fairly busy FB group though.

I think his conclusion re. distortion is from when the exchange from port to outside world occurs. A radius might help with that, but the overall geometry doesn't really change whether corner loaded or not. I think the PA speakers install them in corners on the front to be able to set bass bins against a wall or stage. It also allows them to use some of the cabinet wall as part of the port length.

It is easy enough to cut a round hole and install a tube with a radius, I suppose. I won't be going through the complexity of building triangle or rectangle ports, myself.

hifiside

I did these many years ago because there was just no more surface area for ports and it braced the corners. With 2-6k crowns and 3/4 volume I can’t hear distortion. 😊

jr@mac

That's a lot of surface area, though. Probably keeps velocity down quite a bit, even at high volumes.

That must be insane inside that room.

DrewsBrews

It sounds like this was already a big endeavor for him so he had to draw the line somewhere.

To me, biggest difference between the others compared to the triangle is 45deg corners So I imagine that is where alot of the issue arises. Possibly filling in those corners would help, such as apply caulking to round out those sharp corners. But that sound like quite the PITA to accomplish in a small awkward shaped port.

I would be surprised if the internal sections of the triangle ports in those studio monitors (in the other thread) was not more smooth/rounded rather than sharp.