Ported operation and mid-range leakage - 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 17th January 2009, 07:00 AM   #1
diyAudio Member
 
Join Date: Jan 2004
Default Ported operation and mid-range leakage

Hi there,

Just wanted to ask a few questions. Port operation is under a narrow band of frequencies and coupling between driver and port goes down as frequency increases (above Fb).

Now I had a discussion the other day where a guy said that the rear wave of the driver leaks through the port. We were discussing subwoofers. He explained that with a ported sub, the rear wave of the driver always escapes through the vent.

Now I explained port operation as best I could and that above Fb the port isn't really active (it is, but the strength of coupling goes down) and well above Fb the driver does most of the work.

Then he said that in a full range speaker that mid-range leaks through the port where does mean that sound in a ported speaker (the rear wave of the driver) does leak through the vent.

On one hand the resonating frequency of the vent won't actively do anything unless frequencies start to approach fB. What about the mid-range leak ?

Calling the experts. . .

Regards,
  Reply With Quote
Old 17th January 2009, 01:45 PM   #2
diyAudio Member
 
Join Date: Jan 2004
Sorry about the poor sentence structure but I was really in a rush when I typed the above.

Basically, it has been said that the cones rear wave energy will leak through the port but this is a misconception because the vent only operates under a limited bandwidth.

So if the vent isn't used well above Fb then how can mid-range info leak through the ports ?

Regards,
  Reply With Quote
Old 17th January 2009, 02:55 PM   #3
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
It comes right through the cone as well. You can talk through a piece of paper can't you?
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. Aldous Huxley
  Reply With Quote
Old 17th January 2009, 03:06 PM   #4
diyAudio Member
 
Join Date: Jan 2004
So are you saying that mid-range doesn't leak through the port (if tuning is low) but through the driver only ? Some claim to hear mid-range leaking through the port if they put their heads at the port but how does that gel with the fact that port operation (given that it's range is bandwidth limited by definition) shouldn't be operating much higher than Fb ?

What else would be causing the mid-range to be leaking through ?

Please explain. Thanks.

Regards,
  Reply With Quote
Old 17th January 2009, 03:22 PM   #5
HK26147 is offline HK26147  United States
diyAudio Member
 
Join Date: Jan 2008
The port is tuned to a frequency, but it doesn't mean the out of band frequencies don't get through. It a hole - That let's anything that comes off the back of the cone to escape.
Suppression of the mid & high radiation is part of the function of the internal damping applied.
In Stereophile mag J. Atkinson places a mic to measure the port output. Many times a listening test correlates to what is contributed by the port's upper freq output.
  Reply With Quote
Old 17th January 2009, 03:27 PM   #6
diyAudio Member
 
Join Date: Jan 2004
So are you saying that the mid-range leak is almost completely explained by the lack of damping in the box (like fiberglass lining) ?

It's it's reflective and not mechanical ?

Regards,
  Reply With Quote
Old 18th January 2009, 01:28 AM   #7
HK26147 is offline HK26147  United States
diyAudio Member
 
Join Date: Jan 2008
Yes
I'd say primarily reflective:
Diffraction of sound by an aperture is many wavelengths wide.
  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
Electrolytic leakage lndm Power Supplies 5 26th July 2006 07:17 AM
Woofer Towers, front-ported or rear-ported? Goldenboy Multi-Way 6 15th June 2004 06:44 PM
Transistor leakage? Solid Snake Solid State 1 1st October 2003 08:48 AM
leakage and Ql in ported systems tech.knockout Multi-Way 3 24th June 2003 05:20 PM


New To Site? Need Help?

All times are GMT. The time now is 02:56 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