axial surround instead of radial surround - 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 26th June 2009, 02:19 PM   #1
Calvin is online now Calvin  Germany
diyAudio Member
 
Calvin's Avatar
 
Join Date: Nov 2004
Location: close to Basel
Default axial surround instead of radial surround

Hi,

I´d like to know if anyone has experimented with axial surrounds instead of radial surrounds. They should offer the advantage of larger membrane area with same basket size, and it´ll look cool
Does anybody know where to get such stuff for a 15" or 18" driver?

jauu
Calvin

Click the image to open in full size.
  Reply With Quote
Old 26th June 2009, 05:55 PM   #2
MaVo is offline MaVo  Germany
diyAudio Member
 
Join Date: Jan 2006
I doubt such a thing exists and i think its nonexistance has reasons.
  Reply With Quote
Old 26th June 2009, 07:11 PM   #3
GM is online now GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Yeah, seems like a bellows surround would add a 'pumping' noise overtone.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 26th June 2009, 09:51 PM   #4
Collo is offline Collo  Australia
diyAudio Member
 
Collo's Avatar
 
Join Date: Nov 2004
Location: Newcastle, Australia
Send a message via MSN to Collo
A normal surround adds sideways stability to the cone, helping to keep the voice coil centred within the magnet assembly. The design you are looking at appears to be less supportive in this direction.

Also, the amount of flex required from the surround would probably be more.

Keep those ideas coming though...
__________________
Ports rule!
  Reply With Quote
Old 27th June 2009, 06:08 AM   #5
Calvin is online now Calvin  Germany
diyAudio Member
 
Calvin's Avatar
 
Join Date: Nov 2004
Location: close to Basel
Hi,

thanks, the idea of the axial surround came, becuse of the well known disadvantages of radial surrounds. The stability issue could be coped with a double or even triple spider suspension. Another idea would be to use a radial surround simply because of availabilty, but mounted ´behind´ the diaphragm, so that the membran overlaps the surround. The membrane would need to be shaped appropriately so that the surround could be glued to the membrane lets say ´halfway´ between voicecoil and rim of the membrane.

jauu
Calvin
  Reply With Quote
Old 29th June 2009, 12:35 AM   #6
diyAudio Member
 
Join Date: May 2009
Location: Wellington
One of the functions of a surround is to provide an airtight join between the diaphragm and the edge of the enclosure. Mounting the surround inwards of the edge effectively reduces the diaphragm size at low frequencies, because the "sealed" area of the cone is reduced to that of the surround diameter. The cone outboard of the surround simply moves air around its edge, just like a driver in free air.

Some years ago I did see (but not hear) a pair of Japanese origin speakers (JVC? Sharp/Optonica?), part of a "mini system", which had the surround mounted behind the edge of the cone. The actual edge of the cone was very close to the edge of the driver basket, rather like a piston in a cylinder. This would have problems with the trapped air behind the cone edge being forced through the narrow gap as the cone moved in and out. Provided that this did not cause significant noise, it could be used to provide controlled damping to the cone movement, in the manner of a "dashpot".

I suspect the main reason for the half-round radial surround being the most common is simply that an axial surround would be more expensive but not provide enough performance increase to offset the cost. It's cheaper and more impressive to make the driver a little larger to allow for the radial surround's size. Who hasn't looked at a driver with a huge half-round surround and thought, "man, that baby must pump." In any case, a drive with an axial surround, even right on the diaphragm edge, would still need a gap between the diaphragm and the basket to prevent pumping noise.
  Reply With Quote
Old 29th June 2009, 05:57 AM   #7
Calvin is online now Calvin  Germany
diyAudio Member
 
Calvin's Avatar
 
Join Date: Nov 2004
Location: close to Basel
Hi,

I fully agree with You. One would have to have an eye on the points You mentioned (e.g. the compresion of trapped air volume etc.) and yes it would be more expensive since with the axial surround the driver would be more difficult to mount. It´s not even sure that the axial surrounds advantages would lead to a better behaviour of the driver, too. One of the main reasons for such a construction would be the nice optics. Our subs are globes with opposing cutoff sides. I´d fancy a driver with an outwards curved membrane which would ´complete´ the global looks without the need of a protective grid which You need with a driver of common style.

jauu
Calvin
  Reply With Quote
Old 30th June 2009, 03:07 AM   #8
diyAudio Member
 
Join Date: May 2009
Location: Wellington
A current fashion is to make driver cones look like a smooth concave "bowl" by adding a second diaphragm, rather like an enlarged and inverted dustcap. If you leave the domed dustcap/diaphragm facing outwards instead, you would end up with a driver that looks like a dome tweeter. You would need to fit a domed mesh grille to protect it, but this grille could match the curve of the enclosure to complete the sphere outline. Such a cone/dome might not work too well at mid frequencies, but as a sub it should work well.
  Reply With Quote
Old 30th June 2009, 03:42 AM   #9
diyAudio Member
 
Join Date: May 2009
Location: Wellington
Addendum to the above:
I think I misunderstood what you are trying to do. On reflection, it appears that you have already thought of a dome diaphragm profile. You are trying to hide the surround to give a cleaner line to such a driver mounted in a spherical enclosure.

But to look good you would need to have the cone edge flush with the basket / driver opening edge. When the cone moved out it would move freely, but when it moved inwards it would enter the cavity and be subject to resistance from the air trapped behind it. (Between the outside of the surround and the basket.) Not good for sound quality...

You could investigate a constrained surround to reduce the necessary gap. Imagine a surround that is much deeper than a half-round, a complete "U" shape. This is not a good shape in free space, as it can collapse under air pressure. But if you mount it so that the "U" is behind the diaphragm face (makes a "groove" betwen the diaphragm and the basket), then you can constrain the surround by having close-fitting cylindrical sides on the diaphragm and the basket.

A crude diagram:

|U| |U|
| | | |
\ ___/

As the cone moves, the surround "rolls" betwen the cylindrical sides of the cone and basket. You could make the cone from expanded foam and give it the desired dome profile to match the enclosure.
  Reply With Quote
Old 30th June 2009, 07:42 AM   #10
Calvin is online now Calvin  Germany
diyAudio Member
 
Calvin's Avatar
 
Join Date: Nov 2004
Location: close to Basel
Hi,

I thought of a ´hidden´ surround earlier, but preferred the axial surround, because of the fixation ring (Membrane to surround) that has to moulded into or to be glued to the membrane´s backside.
This adds mass where we wouldn´t want additional mass.
But since the membrane coluld be made very stiff using foam, the use of an easy to obtain radial surround could be the decicive design point.

jauu
Calvin

Click the image to open in full size.
  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
Kit surround jalejos Digital Line Level 0 18th January 2009 10:00 PM
One bar surround legendaryfrog Multi-Way 30 12th December 2006 11:19 AM
sub surround i_m_new9 Subwoofers 4 30th June 2005 02:57 PM
For those of us with $$$, DIY surround Tieftoener Digital Source 0 20th November 2003 06:06 PM
axial vs. radial caps A3rd.Zero Parts 0 17th November 2003 02:24 AM


New To Site? Need Help?

All times are GMT. The time now is 01:50 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