port question - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th February 2006, 04:12 PM   #1
diyAudio Member
 
Join Date: Jul 2005
Location: England
Default port question

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
  Reply With Quote
Old 28th February 2006, 04:46 PM   #2
diyAudio Member
 
Iron-Wizard's Avatar
 
Join Date: Feb 2006
Location: Compton
No not really, i prefer ports on the back, keeps the distortion they make away from my ears.
__________________
Tap or Snap, it's up to you.
  Reply With Quote
Old 28th February 2006, 05:03 PM   #3
diyAudio Member
 
Join Date: Jan 2005
Location: Rotterdam, NL
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..

Quote:
keeps the distortion they make away from my ears
With distortion from ports you mean chuffing or something else?

Wkr Johan
__________________
Impossibilities we do immediatly, miracles take slightly longer.
  Reply With Quote
Old 28th February 2006, 05:12 PM   #4
diyAudio Member
 
Iron-Wizard's Avatar
 
Join Date: Feb 2006
Location: Compton
Quote:
Originally posted by Rademakers

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.
__________________
Tap or Snap, it's up to you.
  Reply With Quote
Old 2nd March 2006, 12:04 AM   #5
diyAudio Member
 
Join Date: Jan 2005
Location: Rotterdam, NL
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
__________________
Impossibilities we do immediatly, miracles take slightly longer.
  Reply With Quote
Old 2nd March 2006, 10:56 AM   #6
diyAudio Member
 
Iron-Wizard's Avatar
 
Join Date: Feb 2006
Location: Compton
Quote:
Originally posted by Rademakers
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.
__________________
Tap or Snap, it's up to you.
  Reply With Quote
Old 2nd March 2006, 11:04 AM   #7
Glowbug is offline Glowbug  United States
diyAudio Member
 
Glowbug's Avatar
 
Join Date: Feb 2006
Location: Hillsborough, NC/McLean, VA
http://www.harmonicdiscord.com/forum...5ce723c8822523

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

Quote:
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.
__________________
Jim J.
  Reply With Quote
Old 2nd March 2006, 11:10 AM   #8
diyAudio Member
 
Iron-Wizard's Avatar
 
Join Date: Feb 2006
Location: Compton
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
__________________
Tap or Snap, it's up to you.
  Reply With Quote
Old 3rd March 2006, 04:39 PM   #9
diyAudio Member
 
kingdaddy's Avatar
 
Join Date: Mar 2002
Location: Fort Worth, Texas
Default Port velocity

Yea, 17 M/sec is absolute for any port noise using sine waves, but this isnít 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 itís a horrid sound to the ears.
__________________
http://kingdaddy.linaeum.com/
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Have Question about Measurement on Port first_1st Multi-Way 1 18th May 2009 02:38 PM
fonken port question thiolperoxidase Full Range 5 25th July 2006 02:55 PM
Question about port tuning ostie01 Subwoofers 3 26th September 2005 01:30 AM
Port question? mace Subwoofers 6 10th December 2004 12:21 AM
Question on port placement??? Javaman Multi-Way 0 16th October 2003 01:34 PM


New To Site? Need Help?

All times are GMT. The time now is 01:54 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2