DIY Speaker Project: Vent location? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 12th January 2009, 03:05 AM   #1
JBCon is offline JBCon  United States
diyAudio Member
 
Join Date: Dec 2008
Default DIY Speaker Project: Vent location?

I'm building a set of LCR speakrs for a hometheater, using a pair of Dayton Audio RS125-04 and an M&K Tweeter in each cabinet, the box design using Winspeakerz indicates a ported design works best. For such a speaker where is a good place to mount the port?

Front baffle, or rear? If I mount it on the front I will loose the symetrical layout I have, thus would prefer to have a rear firing vent or port, but am curious as to the pit falls

The center speaker will be on the top shelf of a big A/V cabinet and the L/R 's will be on the top of the whole cabinet, thus the center will basically be have another shelf above it, the L/R will be out in the open.

Thanks
  Reply With Quote
Old 12th January 2009, 08:13 PM   #2
diyAudio Member
 
Join Date: Jan 2008
Ports can be split into 2 or 4 triangle shaped units (or smaller ducts) that can be placed around the cone, so can still be symetrical.

A rear loaded port tuning may be affected by placement close to the wall or other surfaces.

In the end, it does not make much difference, the frequencies reinforced by the port are low enough to be virtually omni.

As long as the cabinets are not too close to the wall the position is pretty arbitrary, except in the case of large shallow ports where reflected mid-high frequencies may be heard through the port.
  Reply With Quote
Old 12th January 2009, 08:38 PM   #3
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
The general feeling is that port location doesn't matter and yet, I have always found that it does. The closer to the woofer the better they seem to work. And make sure that you don't undersize the port. Make it as big as you can.
  Reply With Quote
Old 12th January 2009, 10:14 PM   #4
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
The location I'd think to be best (this is of particular interest since I'm designing the venting for some cabs right now) would be downfiring. This allows a lowpass filter effect for port resonance and other higher frequency components. Earl's approach would seem to have an advantage at frequencies where the integration requires some cross-cancellation, and reduce any localization effects (listener hearing the port separately from the woofer) at port resonances.

Earl, would you like to comment from a theoretical perspective? I've heard some speakers with the ports 'surrounding' the driver and they seemed to integrate well.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 13th January 2009, 12:13 AM   #5
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Leaving any subjective discussions aside, I have measured results that indicate that closer is better. Mind you it's very difficult to get good data at these low frequencies. I think that far too much importance is given to all of these effects. from what I can tell the details of any LF design are not even a close second to the rooms dominance. And since the room dominates the number of subs and location is far more important than any detail like where the port is.
  Reply With Quote
Old 13th January 2009, 02:20 AM   #6
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Default C'mon doc

Spill the beans fella. I don't need to see graphs, just tell me what "measured results" indicate that right next to the driver is preferable. And if you want to throw some theory around that it'd be cool too. I like downfiring for aesthetic and lowpass reasons as mentioned, natch.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 13th January 2009, 02:43 AM   #7
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
It would be too difficult to dig up the data, I just remember that I started the Summa with a rear port but did not get the performance that I was looking for. I moved the ports to the front and it worked better. Don't recal much more than that, sorry. Theoretically it shouldn't make any difference - I never sorted that out, mostly because I don't use ports anymore.

I should really bow out of this discussion because I don't use ported enclosures in anything anymore. I do use them in the bandpass subs that I like, but that's not ported in the standard sense. As I said, when I found multiple subs all else fell by the wayside and I don't really care what the LF configuration is anymore as long as there are several subs supporting the mains.
  Reply With Quote
Old 13th January 2009, 03:22 AM   #8
diyAudio Member
 
LineSource's Avatar
 
Join Date: Sep 2003
Location: SiliconValley
Quote:
Originally posted by badman
The location I'd think to be best would be downfiring. This allows a lowpass filter effect for port resonance and other higher frequency components.

badman and B&W agree that raising the BASS cabinet on legs and putting a large diameter, large radius(inside and outside) port on the bottom of the cabinet has several advantages.

1) Takes full advantage of uniform floor gain. B&W adds a bottom floor board in case of carpeting, and includes a back board to block just the rear path.
2) Filters any midrange rear cone sounds from directly reaching the ear
3) allows longest straight port tube... ML TL favor this

Rear ports can sometimes rattle normal drywall construction and windows.

I only port deep bass alignments, never midbass, and also favor a downfiring port when possible. I put front bass ports near the floor for ground gain.
  Reply With Quote
Old 13th January 2009, 03:43 AM   #9
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
Default Re: C'mon doc

Quote:
Originally posted by JBCon
I'm building a set of LCR speakrs for a hometheater, using a pair of Dayton Audio RS125-04 and an M&K Tweeter in each cabinet, the box design using Winspeakerz indicates a ported design works best. For such a speaker where is a good place to mount the port?

Front baffle, or rear? If I mount it on the front I will loose the symetrical layout I have, thus would prefer to have a rear firing vent or port, but am curious as to the pit falls

The center speaker will be on the top shelf of a big A/V cabinet and the L/R 's will be on the top of the whole cabinet, thus the center will basically be have another shelf above it, the L/R will be out in the open.

Thanks
Rearward firing is best , but will make the speaker sensitive to wall proximity ...

Forward firing port is best located as close to woofer as possible ..

Close proximity makes for better coupling of port and woofer ....
forward firing will also be sensitive to speaker location and works best in near field application .....

DO not make the port more than 50% of effective cone area .........................



Quote:
Originally posted by badman
Spill the beans fella. I don't need to see graphs, just tell me what "measured results" indicate that right next to the driver is preferable. And if you want to throw some theory around that it'd be cool too. I like downfiring for aesthetic and lowpass reasons as mentioned, natch.

Downward firing works good in subwoofer application , i would not do so for a bass/mid driver .

2nd and 3rd harmonic distortion and time domain measurements tends to favor the port being of closer proximity when forward firing with bass/mid drivers ..

When forward firing in an subwoofer application this is not so critical due to the wavelengths involved ....
  Reply With Quote
Old 13th January 2009, 01:21 PM   #10
JBCon is offline JBCon  United States
diyAudio Member
 
Join Date: Dec 2008
Will keep both suggestions in mind.

I have done a bit of reading and as stated, the general consensus seems to be it doesn't matter, but my own preceived feeling (based on hours after hours of listening to various speaker designs over the years), is that it works better inline with the drivers, however what I don't know (or don't recall off hand), is there a "preceived difference" when using a small coned midrange, versus system susing larger 6" and above midwoofers.

My design with a pair of RS125's in a .27 cu ft box calls for two 1.5 inch ports of about 4 " each for a tuned frequency of 94 or so hertz. That is a 4.87 sq in. recommended port volume. I guess I could go with a larger port diamter, but I already have the prefab port tubs on hand and would prefer to use them.

What are the rules of having one port on the front baffle and the second on the back, as long as they are not on same ends of enclosure?
  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
Speaker & vent orientation zafira1981 Multi-Way 2 5th August 2009 02:07 AM
Controlling Vent Anomalies in Single-Driver Speaker Enclosures Taterworks Full Range 0 1st June 2008 10:47 PM
speaker vent with focal kevlars gasstronamicle Multi-Way 0 27th December 2007 06:53 PM
vent by the speaker wall, or in a corner jmiyake Subwoofers 3 19th September 2006 11:57 PM
old speaker question, bullet midrange question & link to speaker project wallijonn Multi-Way 10 5th November 2002 06:03 AM


New To Site? Need Help?

All times are GMT. The time now is 05:52 PM.


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