Is this a viable port flare alternative? (1 Viewer)

[Dustin B]

http://www.polkaudio.com/home/techno...ry=3&speaker=2
Would this really work? What about the other end of the port?
I'd think a large cone would be easier to make than a large flare if this would actually work. And I guess a little bit of ingenuity would allow one to be mounted on the other end of the port as well.

 

[Joe Tilley]

The port is still flared on the side with the cone,but the inside of the port is not. I have always kinda wondered why Polk did not do the same to the other end of the port. I would think that the flared side would work very well,but that you would still get some noise from the non flared side. I have all an all Polk set up & all of them have the power port. I have never really noticed any port noise out of them,but at the same time I don't think they really move enough air to be noticed,like a sub would.

 

[Shawn Solar]

I always wondered why would you go to all the trouble. I mean how much turbulence be generated from 2-8" drivers? I think a 3"-4" port would suffice. probably be overkill

 

[Chris Carswell]

I agree with what Shawn said. For example, the Xmax on those woofers is not super conducive to moving vas amounts of air thus creating turbulence, so you can't really tell if the "power port" works or not. A true test of design would incorporate this "power port" on something like a Tempest (or something that can move large amounts of air) then comparing it to a standard port then to a flared port as well. A 3 part test. I think the best design out is by B&W, where they put dimples (like on a golf ball) on a flared port. It makes sense. The air can move faster over the dimples. A proven fact. I read an article where they measured baseball bat speeds of regular wooden bats compared to ones that had dimples drilled on them. The result was the dimpled bats had an increase of speed from 3%-6% if I remember correctly. Of course this was only done to illustrate a scientific point in a real world concept, so don't expect Sosa to come to the plate with this new "Super Bat." Also, for all you golfers out there, remember a long time ago when Taylor Made put dimples on the heads of there Burner Metal Woods? Same concept.

 

[Dustin B]

I should have specifically mentioned I was bringing this up as an alternative for use with high output subs. I would think it would be easier to make a reverse flared cone than a flare for an 8" port.

But the other thing that bothers me, is the starter of a thread over on AVS that lead me to this concept claims it also reduces the length of the port required for a particular tuning. He even went as far as to say that inches of straight port would just about equate to cm if this power port design is properly used.

He also said that for a while Polk had an Excel spread sheet available on their site that calculated the appropriate dimensions for this cone.

 

[Chris Carswell]

Find it and post so I can get to experimenting

 

[Dustin B]

http://www.avsforum.com/avs-vb/showt...hreadid=154825
Well here is the thread on AVS. You can see if the Hangman guy actually has it or not.
And then please experiment, I'd be interested in your results.

 

[Bryan Michael]

polk used the power port on ther 1200 sub with was 2 12 i herd it was prety good i have polks but i just dident like their subs that much went with a velo

 

[Bryan Michael]

http://www.polkaudio.com/home/produc...r=110&recent=1
link to pws 1200 with power port it is a sub

 

[Dustin B]

Well I think I've figured out the port length reduction. Typical advertising style claims.

200L enclosure with a 12" port tuned to 20hz would result in a 250cm port length. 200L enclosure with an 8" port tuned to 20hz would result in a 100cm port length. Since we are claiming that a 8" port with the power port cones has an effective port diameter of 12", we'll also claim this reduces the port length by 2.5 times as well.


Edit: Well the guy tells me this isn't the case. The 100cm 8" striaght port could be almost 2.5 times shorter with this power port cone. This makes no sense to me.

 

[Rory Buszka]

Polk even uses Power Port on the speakers they bundle with Hewlett-Packard Pavilions.

 

[Michael R Price]

This is intriguing, although I don't entirely understand how it works. Is this still a "Helmholtz resonator" like the ports we are used to? If so, then how can the port compression/turbulence be reduced by having a cone at the end of the port? The air still is moving back and forth through the tube. I'm not getting it yet.

 

[Nathan Bower]

I think the best design out is by B&W, where they put dimples (like on a golf ball) on a flared port. It makes sense. The air can move faster over the dimples. A proven fact. I read an article where they measured baseball bat speeds of regular wooden bats compared to ones that had dimples drilled on them. The result was the dimpled bats had an increase of speed from 3%-6% if I remember correctly.
I had an argument about this a while ago, and I was on your side - untill I got real indepth, then I had to agree with what was lain in front of me.
It turns out that the laminar flow enhancing methods such as roughening, or dimpling, only work in continuous airflow streams. As we all know the port acts as a resonater; the air is an AC flow, stopping every xth of a second and slamming back into itself. Essentially text book hydro-dynamics dont apply.
If anyone is interested ill try to dig out the backup materials for this arguement!
B&W are just as succeptable to 'inventing' fancy technologies as any other loudspeaker manufacturer or so it seems :frowning:
I dont know if these little inverted cone things have any plus or not. My best guess is that it actually alters the ports tuning frequency (by restricting the airflow - bit like those airvent things that dynaudio used to sell) and because the resonant frequency is higher, the air mach number is lower, hence no chuffy chuffy.
Just a guess tho. My sub dosent have ports otherwise I'd do a quick test for us.

 

[Chris Tsutsui]

Nathans idea explains why ports arn't designed with a tornado/vortex in mind. So what we need is teflon coated flared ports that are stiff and sturdy.

Lets see, 4" RCP plus teflon insulation would be about $50 LF?

I think I'll stick to $10 precision flared ports. That is until drivers are capable of creating noticeable port noise with those.

 

[Rob Lloyd]

What about using wax or a teflon spray?

Just an early morning thought....

 

[Brian Bunge]

Rob,
Early morning? I've been at work for 2 hours now!