My Findings...

[Krakin]

Would only be beneficial for the lanes though?

Having more control over the driver below tuning, to an extent. Would that not also be helpful for lets say home theater, when you you have infra sonic frequencies come about quite often?

[Krakin]

Precision port has a 4" dimpled port for sale on parts express.

The dimples however don't appear to go that far into the flare. Would a deeper dimple be more beneficial, or perhaps a higher quantity?

[bbeljefe]

Okay so then with regard to your post above the flare port, I have to go back to t-line theory. In my understanding, the back wave isn't far from being in phase with the front wave... 90° out, maybe? And I know that t-lines have excellent low end extension with no negative effects on the upper end of bandwidth. Plus, I've never needed to filter anything below tuning and have never had a sub unload in a line.

But with that said, I've seen a lot of lines built with perfectly curved and smoothed bends and in the end, most of the time those boxes require some sort of stuffing in order to make them perform. Or at least, the people who built them said it was needed. But I've never built a line with perfect curves and, I've never needed stuffing. I've played with it but to be sure, it has never been an improvement in a line I've built.

I don't want to fall into the trap of confirmation bias with this thought but from what I've learned in this thread it would seem to me that spending two months building the "perfect" transmission line may just be an effort in re-creating the phenomenon of free air cancellation. Because why the fuck do you need to slow down the speed of sound (with stuffing) in a box that's designed to slow down the speed of sound just right?

And that leads me to the topic of re-entry horns. Those things, when properly designed, are stupid efficient. So how is it that interrupting air flow somewhere in the wave guide makes things sound better?

I'm sure those questions have been answered by acoustical engineers and I've probably read some of those answers and didn't understand them. Matter of fact, I'd bet that Amar Bose has the answers to all of those questions but he's a greedy patent troll who would rather sell fifty cent full range drivers in cheap boxes to yuppies who don't know any better for thousands of dollars rather than contributing to the collective knowledge base of humanity... so fuck him and everyone who acts like him.

As for the Precision Port you linked, I think we can take their cue and conclude that dimpling is only beneficial in the radius of the port. Not that I wouldn't like to see some testing of it from OP but, that should at least be a benchmark.

But who knows... would deeper dimples be better? Would reverse dimples be worse?

I love this thread.

[ParDeus]

My guessnis those dimples are way to big. I've never had success with a texture like that. However, bedliner is very close to what I consider an ideal texture. I try to use anywhere from 20-40 grit finishes on cylinder heads.

Btw, you are kinda right about dimples creating less friction overall, but it increases boundry layer adhesion, hence boundry layer friction. That is not a bad thing though. The boundry layer represents an extremely small portion of the airflow, and it depends on texture size.

On a golf ball, it has the effect of lower overall friction due to flow becoming less turbulent above the BL, allowing for more energy from the spin of the ball to be used for lift.

[ParDeus]

That makes me wonder something... we know the effect of divots but divots aren't easy to create in a wood shop. So... all of us box builder who finish with bedliner have been masking ports and keeping them slick.

I wonder what effect bumps would have relative to divots and if positive, where do they need to be?

OP... GIT IN HERE! Please.

Bumps and dimples have the same effect, for all intents and purposes.

[bbeljefe]

Would you mind explaining the term "boundary layer adhesion"?

[ParDeus]

Basically, when the boundry layer is turbulent, there is increased friction there. Increased friction in the BL prevents seperation and eddy currents. It's when seperation occurs that you get into turbulent mass flow.

[bkolfo4]

Anyone ever put drinking straws in a port? My home speakers have 3" aeros with drinking straws in them.

http://www.audioasylum.com/audio/tweaks/messages/5370.html

[Krakin]

That's very interesting.

[oldsoundguy]

When I ported my chevy BB stock heads it was the intake runner that you didn't want smooth so to cause better atomization of the fuel. Now on the exhaust side you want it as smooth as possible for getting exhaust gasses out as fast as possible. I also did work to my aluminum heads on my 427 BBC Brodix RR . I cleaned up the intake port, did a little work to the short side radius and blended the bowls a little better. The heads are stock exhaust port location so it was important to get them nice and smooth as they won't flow as well as the intake side. I run my solid flat tappet cam with a tighter exhaust lash to make up for it.

So after all that post would you call the port on the box the exhaust side or intake side in comparison? So what part would you want smooth and what part would you want rough?