port question

[phillfyspoon]

Do ports need clearence from each other?

I know ports need to be the diameter away from side walls etc but what about each other? as I have 2

 

[Iron-Wizard]

No not really, i prefer ports on the back, keeps the distortion they make away from my ears.

 

[Rademakers]

Ports don't need to be at least the diameter away from all sidewalls, they can even incoorperated one or more sidewalls into there own sides. Only if it's a wall that could obstruct the airflow or act as bend and thus increasing length at least one diameter distance is advised.
Two ports real close together essentially become one..

keeps the distortion they make away from my ears

With distortion from ports you mean chuffing or something else?

Wkr Johan

 

[Iron-Wizard]

With distortion from ports you mean chuffing or something else?

Wkr Johan [/B]

Yes, chuffing, is that the technical name or a general name for the distortion?

Some ports are trumpeted or dimpled and this reduces the sound but some times below the tunning frequency of the port you can hear it, not a fan of that at all.

 

[Rademakers]

General i guess..English isn't my first language.

If a port is making noise like that it's either designed wrong or has been part of a compromise. By increasing the port diameter/area the air speed in the port is reduced. As a rule of thumb 17 m/sec is the maximum air speed for home usage.
As the port area increases, so does the length for the same tuning. Taking up more space or becoming to long can be reason enough for restricting port size.

A trumpeted port gives smoother airflow, as do round ports over square, thus decreasing the distortion. Lower applied power means less excursion meaning lower air speed. A lowcut (highpass) can have great beneficial effects as well.



Wkr Johan

 

[Iron-Wizard]

General i guess..English isn't my first language.

As a rule of thumb 17 m/sec is the maximum air speed for home usage.

Wkr Johan

English is my 2rd language as well, ebonics is my first

why is 17m/sec the fastest speed of air in a port? is it because after this speed it creates the chuffing sound on the baffle?

Ports are hit and miss for me, on some woofers and enclosures they work when they should not and they dont work when they should, i always thought it was something to do with air pressure close to the coast? thats something i can't control.

 

[Glowbug]

http://www.harmonicdiscord.com/forums/viewtopic.php?t=9785&sid=dce4f26955763506705ce723c8822523

A 2sec Google search found this thread, another mention of the 17m/sec number...

If a port is making noise like that it's either designed wrong or has been part of a compromise.

Exactly. A well-designed port makes no noise.

 

[Iron-Wizard]

Thanks for that, i never thought about in those terms, i always though if the pressure was too high in the enclosure this put to much pressure on the mass of air inside the port and made it fart, so is there some kind of device than can measure port speed? like a weather vain or something or is it all math based work?

You have to fogive all my questions but this www information is new to me, i am having a great time trying to absorb it all

 

[kingdaddy]

Port velocity

Yea, 17 M/sec is absolute for any port noise using sine waves, but this isn’t really indicative of music content, you could probably push it to 22 M/sec if you really needed to. I posted this speed a few years ago from direct experience, strange someone came up with the exact same figure. I had to make several different mock up enclosures and several different port configurations and test each to come up with the number, a 20Hz sine wave did the best for finding chuffing, and yes it’s a horrid sound to the ears.