mounting a woofer by the magnet - 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 28th April 2005, 04:45 PM   #1
diyAudio Member
 
Join Date: Apr 2005
Location: Washington state
Send a message via Yahoo to barth2102
Default mounting a woofer by the magnet

I hope to get some feedback from some of the guys who having been building for a while. There is an article at the linkwitz.com website about how to mount a speaker. It is probably most common that a speaker is mounted to the baffle board in the traditional method using the bolts or screws outside the suspension. It seems that woofers and some midrange units that have a stamped steel basket are subject to some output losses due to some vibrations and or resonances in the basket itself. However, if the driver is mounted by the magnet inside the cabinet these losses and be almost eliminated.

My concern is that the wooden frame that holds the speaker by the magnet might hinder the sound waves coming from the rear of the cone and thus reduce the efficiency of the bass reflex design, ( or TL design for that matter ), resulting in less output.

Has anyone used this method of mounting the woofer at the magnet? And if so, do you really hear a positive sonic difference?

And what about woofers and midranges that have a cast aluminum frame? Perhaps they might also be better sounding if mounted at the magnet ?

Thank you.
  Reply With Quote
Old 28th April 2005, 04:54 PM   #2
hermanv is offline hermanv  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Northern California
A couple of opinions:

The speaker parameters that are published are most certainly derived from a test unit with a conventional mounting, you may need access to acoustic tools to confirm you haven't messed up the desired results.

The outer ring of the woofer must be connected by an air tight means to the front baffle thereby complicating your suggestion.

If you mount by way of the magnet structure IMHO the mountng should not protrude past the outside diameter of that structure. Cone drivers radiate pretty much identical signals off the front and back of the cones. You do not want the rear wave to bounce off the magnet mounting device and flow forward through the pretty acoustically transparent cone material to the listener. It will be time smeared and not all frequencies will reflect the same.

Other than that, most agree that greater woofer mounting stiffness has positive acoustic results.
  Reply With Quote
Old 30th April 2005, 05:44 PM   #3
diyAudio Member
 
Join Date: Apr 2005
Location: Washington state
Send a message via Yahoo to barth2102
First I want to correct an error, the website is linkwitzlab.com. There are some impressive graphs to back up the subject of the article, "how to mount a speaker".

Another idea was mentioned to me just recently. It is to have a "compression pole" mounted between the rear of the magnet and the back of the cabinet. I would assume that the pole would
attach to the center of the magnet and run straight back to the rear of the cabinet , where it would attach to a support that is already being used to hold the back panel more firmly in place. This too would help to reduce any resonance or vibrations because of the flex of the speaker basket.

If the magnet has a vented pole piece, then the compression pole could be drilled out so that it is hollow. This long, small diameter void could be stuffed with a dampening material to absorb the vibrations coming thru it from under the voice coil dust cap.

In any event, the compression pole and the magnet mounting frame could both be coated with a sound absorbtion material to reduce sound reflections that could hinder performance.

Also, I think that there could be a way to clamp the magnet mounting brace from the outside of the cabinet using long bolts.
This way, the speaker could first be clamped down using the standard screws or bolts located outside the suspension in the traditional method. And then the magnet clamp to secure the speaker internally could be tightened up with a socket wrench or cresant wrench.

It just seems to make sense that, if there are more attachment locations to secure the woofer in place solidly, that it will make for a more efficient set up, as long as the internal magnet mounting brace does not hinder any sound waves coming off the rear of the cone.

Comments ? Suggestions ? Ideas ?
  Reply With Quote
Old 1st May 2005, 05:47 AM   #4
diyAudio Member
 
Join Date: Jan 2004
Location: chico CA
Default it makes sense

Well I think its time to try it.
It makes alot of sense I have been thinking about using shims and glue and wedge the magnet against a crossbrace.
another way of doing it would be to use 9/16 inch bolts and Tnuts and have an expanding pole squeezing up against the magnet....
I guess its such a hassle that only freaks like us even consider it.
__________________
thanks for reading.
H.Honda Chico CA Land of the fooled
  Reply With Quote
Old 1st May 2005, 06:10 AM   #5
mac is offline mac  United States
diyAudio Member
 
mac's Avatar
 
Join Date: May 2003
Location: Puget Sound
I recently used Linkwitz' Phoenix style mounting for my dipole mid woofers.

Although I didn't conduct any measurements to verify improved performance, I can subjectively tell that there is less energy being transmitted into the baffle.

Btw, This is SL's article on alternative baffle mounting: http://www.linkwitzlab.com/frontiers_2.htm#N.

Click the image to open in full size.
  Reply With Quote
Old 1st May 2005, 05:10 PM   #6
diyAudio Member
 
Join Date: Mar 2002
Location: Toronto, Canada
You might want to take a look at my implementation, it works quite well (the speaker is NOT under compression, unlike the Phoenix).

http://www.htguide.com/forum/showpos...1&postcount=17

Mac, where did you source that profile that you use on the back of your drivers? A very clean and minimal implementation.

Ron
Attached Images
File Type: jpg img_3424.jpg (75.1 KB, 551 views)
  Reply With Quote
Old 1st May 2005, 05:25 PM   #7
mac is offline mac  United States
diyAudio Member
 
mac's Avatar
 
Join Date: May 2003
Location: Puget Sound
Nice work, Ron.

Quote:
Originally posted by transducer
Mac, where did you source that profile that you use on the back of your drivers? A very clean and minimal implementation.

Ron
I found the steel rib at a local home improvement store (Home Depot). Cheers, mac.
  Reply With Quote
Old 1st May 2005, 06:40 PM   #8
diyAudio Member
 
Join Date: Mar 2002
Location: Toronto, Canada
Thanks mac. What is interesting in my design is that there is a layer of Sorbothane between the MDF "donut" and the magnet itself. It's hard to see, it's the thin grey stuff. I was trying to minimize vibrations being transmitted back into the baffle.

Cheers,
Ron
  Reply With Quote
Old 4th May 2005, 03:59 AM   #9
diyAudio Member
 
Join Date: Apr 2005
Location: Washington state
Send a message via Yahoo to barth2102
Those are some nice cabinets ! You have creative minds to come
up with various methods of securing the woofers.

I have a question for transducer. Those are real nice woofers you have mounted in the cabinet. The magnets are quite large, but what interests me more is the cones. Do those woofers have metal cones ? What are the cones made out of ? What is the diameter ? Do you have thiel specs on them? And are they available to the general public?

I am quite interested in metal cone woofers and hope to gather more info as time permits.

Thanks
  Reply With Quote
Old 4th May 2005, 03:38 PM   #10
diyAudio Member
 
Join Date: Mar 2002
Location: Toronto, Canada
Quote:
Originally posted by barth2102


I have a question for transducer. Those are real nice woofers you have mounted in the cabinet. The magnets are quite large, but what interests me more is the cones. Do those woofers have metal cones ? What are the cones made out of ? What is the diameter ? Do you have thiel specs on them? And are they available to the general public?


Thanks
The woofers are HiVi M8A, 8" aluminium/magnesium cones. I don't have the t/s specs handy. I bought them from Solen in Quebec, but I believe that Parts Express also carries them.

Ron
  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
magnet design 101 - saturate iron with a ferrite magnet? capslock Multi-Way 18 28th April 2010 04:51 AM
Box-tuning magnet-to-magnet construction Mr_Oasis Full Range 21 2nd June 2009 12:51 AM
Mounting tweeters over the woofer in a line array. GuyPanico Multi-Way 8 28th June 2007 11:10 PM
modifying woofer with neodymium magnet _henry_ Multi-Way 0 4th November 2005 05:13 PM
In push/pull woofer mounting, Why Vas will be half that of single driver? haggy Multi-Way 7 10th December 2001 02:29 AM


New To Site? Need Help?

All times are GMT. The time now is 08:09 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