Port Velocity

[Soapbox 7]

I don't fully understand Port Velocity. Using BBP I can figure the velocity but at what are the acceptable limits prior to encountering negative effects?

[///M5 2,833]

Depends on what you would subjectively define as negative effects.

I have to ask, you design T-lines but don't understand port velocity??

[Soapbox 7]

Dude where have you ever read that I design t-lines to my recollection I have said I have a t-line designs for 2 sa-8. And that is about it. There aren't but a couple of people I disdain and it seems your one of them. Now if you would like to share some of your knowledge I'll gladly read it for what it's worth. I am pretty active in reading on this forum and it seems 90% of your remarks are prideful or haughty. Only a fool thinks he knows everything.

[Jay-C76 333]

Here's what TermPak has to say about it:

"When designing a vent, you should try to keep the vent air velocity

value as low as possible. Otherwise, vent turbulence and other

audible artifacts may be heard.

Ideally, you would use a vent with a very large surface area to

keep the vent air velocity low. This would work because vent air

velocity is directly related to the area of the vent being used.

Unfortunately, the larger the vent area, the longer the vent length

needs to be for a given tuning frequency. In reality, large area

vents usually need to be so long that they’re just not practical.

Because of this, many designers are forced to trade-off vent air

velocity for vent length.

Typically, audiophiles recommend keeping the vent air velocity

below 5% of the speed of sound. This is not very realistic in

autosound installations where enclosure volumes are usually

pretty small. At Wayne Harris Enterprises, we have determined

that a vent air velocity as high as 12% is acceptable for most

installations. With an Aeroport, the vent air velocity can be as high

as 20% without running into significant problems."

I hope this may help to explain it.

[antonmiller 8]

Here's what TermPak has to say about it:

"When designing a vent, you should try to keep the vent air velocity

value as low as possible. Otherwise, vent turbulence and other

audible artifacts may be heard.

Ideally, you would use a vent with a very large surface area to

keep the vent air velocity low. This would work because vent air

velocity is directly related to the area of the vent being used.

Unfortunately, the larger the vent area, the longer the vent length

needs to be for a given tuning frequency. In reality, large area

vents usually need to be so long that they’re just not practical.

Because of this, many designers are forced to trade-off vent air

velocity for vent length.

Typically, audiophiles recommend keeping the vent air velocity

below 5% of the speed of sound. This is not very realistic in

autosound installations where enclosure volumes are usually

pretty small. At Wayne Harris Enterprises, we have determined

that a vent air velocity as high as 12% is acceptable for most

installations. With an Aeroport, the vent air velocity can be as high

as 20% without running into significant problems."

I hope this may help to explain it.

a good bit of information here!!! +1 for the find.

[Soapbox 7]

Thanks Jay. Exactly what I wanted to know.

[///M5 2,833]

Dude where have you ever read that I design t-lines to my recollection I have said I have a t-line designs for 2 sa-8. And that is about it. There aren't but a couple of people I disdain and it seems your one of them. Now if you would like to share some of your knowledge I'll gladly read it for what it's worth. I am pretty active in reading on this forum and it seems 90% of your remarks are prideful or haughty. Only a fool thinks he knows everything.

Unless my memory is off, which I don't think it is you were pushing them on chop.

If you want my knowledge ask a good question, show that you tried, and stop being a baby about it. Amusing that you would bring up a definition of a fool considering I will always tell everyone I learn new stuff everyday, definitely never claimed that I already know everything. Not even close.

You've been on here long enough to know what makes a good thread and what doesn't, you've also read the T&C's well enough to know that this surely didn't match the requirements. If you are lazy in your thread, you'll get lazy answers. If you put in energy, then the response might be what you are looking for. If your inadequacy in posting makes you disdain me perhaps a quick look in a mirror will enlighten you. If not, oh well, I guess we can't help then anyways.

[KU40 173]

I think in the beta version of winISD it wants you to keep it under 14 m/s, which is around 5% of the speed of sound. So a bit low perhaps. But I haven't tested various port designs and velocities to determine where a cutoff point might be. I'd say up to 10% or 30 m/s for a round number may be acceptable.