STRAWS STUFFED IN THE PORTS??

Toolfan66

Never seen this before..



https://denver.craigslist.org/ele/d/longmont-north-creek-borealis-speakers/7435536964.html

msg

Isn't that a way to change the port length or something?

Toolfan66

msg wrote: »

Isn't that a way to change the port length or something?

I’m not sure, never seen it before, maybe there is bees and honey inside. LOL!,

Edit: you were correct… 😎

Toolfan66

It is a tweak..

https://techtalk.parts-express.com/forum/tech-talk-forum/1350165-straws-in-the-port

Toolfan66

I copied this from Audiogon..

Here is an exerpt from the Rhythm speaker building manual courtesy of North Creek's Web Site:

2) Cut the straws into 5" lengths. Insert the straws into the end of the tube with one inch sticking out.
The fit should be so tight that the straws begin to go out of round (65 straws for a 2" port, 125 straws for a
3" port).
3) Wrap the straw bunch sticking out of the port tube with tape. This secures the straws and makes it
easy to adjust the length emerging from the port.

One can adjust the length of straws emerging from the port to adjust the tuning frequency by ear. We
have found the optimum to be between 1" and 2½".
Once the "perfect" tuning is reached, the port can be fixed by dipping the entire assembly in clear shellac
or black paint.
For those that are curious about the origin of this procedure, to the best of my knowledge it was first
discussed in writing by Neville Theile himself. The earliest reference I know of was in an article by Dr.
Theile in an ASA journal from the mid '60's, on non-linear port behavior. Which article and year it was
precisely is now unknown to me. -GS

The method also involves inserting a straw sized wooden dowel into the mass of taped straws, dipping the taped straws and dowel into shellac and letting it dry for a couple days. You can use the inserted dowel (which should be longer than the straws) to tune your port. The dowel, now glued to the straw mass will move the straw in or out of the port effectively increasing or decreasing the length of the port and its output in hz and db. As the port gets longer the tuning reaches lower frequencies but the output in db's drops.

motorstereo

Cutting and bundling straws isn't for me so an easier method and one that I've used is a 7'' high nap paint roller. Push it in the port hole till it's flush. Now the port size diameter is instantly reduced and lengthened. If it doesn't sound good then simply pull it out and move on to doing something else much more important .

SeleniumFalcon

I believe it is a way to reduce turbulence in a port, similar to Polk's Power Port technology.

pitdogg2

SeleniumFalcon wrote: »

I believe it is a way to reduce turbulence in a port, similar to Polk's Power Port technology.

Only problem is the new resistance in 125 tiny ports.
I've only heard some port noise when the speaker was severely over driven, that to me was more of a driver noise escaping.

Ymmv

VR3

I was following along with how to do this until he mentioned black paint.

I don't see how this would help a properly designed speaker.

Toolfan66

VR3 wrote: »

I was following along with how to do this until he mentioned black paint.

I don't see how this would help a properly designed speaker.

I chuckled a little at that, because there is still no black paint to be had!! LOL

mhardy6647

msg wrote: »

Isn't that a way to change the port length or something?

Yes, it's an old trick to play with port tuning empirically.
In the old days, folks would use the formulae to calculate the optimal port tuning, build a tuned box and them tune by ear using tricks like straws (or stuffing socks in the ports for pseudo-aperiodic loading).

Of course, with today's environmental climate vis-a-vis plastic straws (not to mention old socks), it is a misdemeanor offense if one is caught doing it.



In all seriousness, the straw trick, besides making tuning 'easy' (much easier to change the length of a handful of straws with a knife or cutters than it is to re-do a regular port) -- also might offer some favorable aerodynamic properties (as it would relate to chuffing or other Portnoy's port noise complaints) compared to a big open, umm, blowhole

Jstas

Yeah, that's like over stuffing a box. It doesn't do what people think it does.

Changing the port length and, honestly, the cross-sectional area with all those straws changes the port tuning frequency which kills the efficiency of the port and moves it away from the driver resonance. It can push into the enclosure resonance range which will cause noises from the enclosure and the port.

It can also kill the efficiency of the enclosure and make your drivers work harder which means that the enclosure has a lower sensitivity rate because it takes more power to reach the same SPL as previously as the drivers have to fight harder against the air cushion in the enclosure.

So if you have farty ports because you are over-driving your speakers or your ports are improperly sized to begin with then stuffing them with straws will make it SEEM like you're improving performance but, you're not. You're just pushing the enclosure performance outside of it's designed spec and killing it's efficiency so your port is ineffective and your enclosure is hampering your drivers instead of complimenting them.

The only way I can see it being beneficial is to use it to help figure out how long your port needs to be in an enclosure you built yourself. But the problem is it's not accurate because a 2 inch port might need 65 straws but once you get the tuning right, your port isn't actually 2 inches. It's 1.5-1.75 inches when you compensate for all the walls of the straws. So if you stuff a 2 inch hole with 65 straws at 5 inches long each and then get a 2 inch port that's 5 inches long, you're going to miss your target port tuning by a lot and it will never sound right. It's better to do the math or, hell, use one of the many applications or calculators all over the internet to figure it out.

It's a stupid idea, don't do it.

audioluvr

I would think that would eliminate the intended amplitude of the designed port diameter.

Jstas

pitdogg2 wrote: »

SeleniumFalcon wrote: »

I believe it is a way to reduce turbulence in a port, similar to Polk's Power Port technology.

Only problem is the new resistance in 125 tiny ports.
I've only heard some port noise when the speaker was severely over driven, that to me was more of a driver noise escaping.

Ymmv

Not quite.

Port noise usually comes from the port. Well, actually, it all comes from the port. Driver distortion can cause port noise because port length and cross-sectional area matter a great deal as you need even pulse widths to create the proper flow in the port to keep it efficient. Driver distortion can cause lopsided pulse widths on the air flow which can evacuate the air column in the port to the point where the port is drawing a vacuum or at least negative pressure.

If the port is sucking in too much, you get the whooshing staccato like the sounds gas escaping from your aft regions makes.

If the the port is blowing out too much, you get the clicking pops that kinda thump.

Both are cavitation situations as the air in the port column tries to equalize but is overpowered by the drivers. The conditions can be caused by improperly sized ports and/or driver distortion. They can also because by over-driving the enclosure.

You need to make sure your ports are the proper length in relation to the width so that you're not emptying the port on every driver motion.

That doesn't mean a properly designed port won't be noisy. It can get noisy at higher SPL levels and that's where things like rolled lips and flared ports or even Polk's Power Port can help because they smooth out the laminar flow along the edges of the port. That keeps the port from forming high pressure eddies at the openings which can artificially reduce the size of the port as the high speed, high pressure air exiting the port interacts with the much less active atmosphere around it.

Those port tricks don't improve the efficiency, they just make it easier for the driver/enclosure to reach higher SPL levels before overwhelming the enclosure.

motorstereo

Or better yet get speakers that don't have ports to worry about.

F1nut

motorstereo wrote: »

Or better yet get speakers that don't have ports to worry about.

BINGO!!!

SeleniumFalcon

From what I remember Scott Orth saying the straws improve laminar flow in the port which improved bass efficiency. The difference between a crowd trying to get through one large gate and ten smaller gates.

jbreezy5

mhardy6647 wrote: »

msg wrote: »

Isn't that a way to change the port length or something?

Yes, it's an old trick to play with port tuning empirically.
In the old days, folks would use the formulae to calculate the optimal port tuning, build a tuned box and them tune by ear using tricks like straws (or stuffing socks in the ports for pseudo-aperiodic loading).

Of course, with today's environmental climate vis-a-vis plastic straws (not to mention old socks), it is a misdemeanor offense if one is caught doing it.



In all seriousness, the straw trick, besides making tuning 'easy' (much easier to change the length of a handful of straws with a knife or cutters than it is to re-do a regular port) -- also might offer some favorable aerodynamic properties (as it would relate to chuffing or other Portnoy's port noise complaints) compared to a big open, umm, blowhole

Love the Portnoy reference.

mhardy6647

I think it's the only bass reflex enclosure joke I know.

Jstas

SeleniumFalcon wrote: »

From what I remember Scott Orth saying the straws improve laminar flow in the port which improved bass efficiency. The difference between a crowd trying to get through one large gate and ten smaller gates.

Yeah, if you can adjust for it. But it doesn't improve the bass efficiency at the tuning resonance of the chamber. It changes that tuning point and it will cut efficiency of the chamber overall.

So if the chamber is tuned for, I dunno, 45 Hz and with a 2 inch by 5 inch port and you jam 65 straws that are 5.5 inches long in that 2 inch port, yeah, you improved bass efficiency but you tuned the port to something like 50 Hz now so it's improved response there but you've totally killed your "bass reflex" function of a tuned port enclosure. So you're going to get really peaky response on the low end which could lead to easier localization in the sound stage and create chamber resonances (rattles and buzzes) whether previously were none. Additionally, you're going to attenuate your crossover points which will change what kind of programming is coming from the speakers. At a low end frequency response curve, attenuated response at the crossover point can leave your speakers sounding kind of dull and empty with no life because you're missing the high end of your low end response which will affect mid-range response. Especially with male vocals or rock guitars.

And to be honest, if it was such a great idea, you'd see ports coming from the factory like this.

You don't, for a reason and not just cost of complexity.

SeleniumFalcon

I'm sure you're absolutely correct, John.
To quote my Uncle Ted, "Any port in a storm".