Foam core construction for subwoofers - Page 2 - 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 20th August 2005, 09:28 PM   #11
agent.5 is offline agent.5  United States
diyAudio Member
 
Join Date: Aug 2003
Location: San Francisco, CA
Just to clarify: are you guys talking about pvc foam core here? i assume the high density version. Something like this (no affilation with seller):

http://www.boatbuildercentral.com/pr...0Plain%20Sheet

what do you guys think about honeycomb core? for example,

http://www.boatbuildercentral.com/pr...id=30&NIDACORE
  Reply With Quote
Old 20th August 2005, 11:10 PM   #12
morbo is offline morbo  Canada
diyAudio Member
 
Join Date: Sep 2004
Location: Guelph, Ontario
Thanks for the interesting discussion everyone! Lots of good points here...

Its interesting that the composite material is stronger if curved, I presume this is because it is easier to start compressing/tensioning than to push something already compressed/tensed further?

Also, I just want to be clear, in this type of application, are we talking a stiff foam, like the pink type that is sold for wall insulation? This type of foam is like a stiffer version of styrofoam, and will snap if bent far enough. Or, are we talking about a flexible foam like carpet underlayment or regular grey closed cell foam, the type of foam you could roll up?
  Reply With Quote
Old 21st August 2005, 01:49 AM   #13
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
Smile It's Not just a bunch of HOT AIR

THe foam should be a high density closed cell foam. Like the stuff used to sheath buildings. Or if you have a source the kind used in boat building. But between the types there is not a huge difference in structural properties.

Concerning the kerf cut bending scheme. I would stay away from this if I could. A cut in a panel seriously compromises the strength that is available. But a thinner in tact panel when bonded to the foam core and the other panel on the opposite side will be very strong. It will bend farther without snapping in to little pieces. Mostly because it will be much more springy. Higher modulus of elastisity. ( Or lower? Heck I can't really remember it's getting late. )

Honeycomb panels are really good to. They are harder to make into a curve but it can be done with flats as in a conventional box. I've used cardboard honeycomb in larger cabinet projects to save weight. It is quite stiff. Just check out the doors in you home and you most likely have a good example of a honeycomb panel in everyday use.

The curved shape is better to work with. Just think about how many square pressure tanks you can come up with! Round rules!

Mark
__________________
Mark
  Reply With Quote
Old 21st August 2005, 03:13 AM   #14
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
If you are going to use a curved panel, there is no need for foam core, you can just use a sonotube and dispense with all the expense and trouble. If one really wants a composite curved structure, why not use two different diameter sonotubes and fill the middle with low expansion foam?
__________________
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 21st August 2005, 03:32 AM   #15
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
Default It's hard to argue with you when you make sense!

Quote:
If you are going to use a curved panel, there is no need for foam core, you can just use a sonotube and dispense with all the expense and trouble. If one really wants a composite curved structure, why not use two different diameter sonotubes and fill the middle with low expansion foam?
Yep!

Mark
__________________
Mark
  Reply With Quote
Old 22nd August 2005, 11:10 PM   #16
justinc is offline justinc  United States
diyAudio Member
 
Join Date: Jan 2005
Location: boston
If you were to cut the sonotube in half, to make a half round, and maybe attatch it somehow to a backless rectangular cabinet, would the sonotube be strong enough then alone? or would you need to use the two different sizes filled with foam inbetween as suggested above. say for subwoofer use
  Reply With Quote
Old 23rd August 2005, 12:04 AM   #17
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
You can use aluminum honeycomb instead of foam.
  Reply With Quote
Old 25th August 2005, 01:44 AM   #18
agent.5 is offline agent.5  United States
diyAudio Member
 
Join Date: Aug 2003
Location: San Francisco, CA
Will these foam work? The 1" is priced pretty good.

http://knoxfoam.com/cgi-bin/SoftCart...402+1124955649
  Reply With Quote
Old 25th August 2005, 11:49 AM   #19
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
Talking It would be great for a padded room

That type of foam is not rigid. It's designed for upholstery. The types of foam that have been discussed are all rigid foams. They are used in the construction industry for various things. Some of them are very rigid such as the urethane foams used in boat building. The house sheeting is also quite rigid and considerable cheaper.

Mark
__________________
Mark
  Reply With Quote
Old 30th August 2005, 08:09 PM   #20
morbo is offline morbo  Canada
diyAudio Member
 
Join Date: Sep 2004
Location: Guelph, Ontario
After pricing the foam and thinner plywood sheets, I've come to the conclusion that in my particular application, this would be no cheaper, and be significantly more labour intensive than just using standard BB ply. I will definately be investigating it in the future though, for curved enclosures and maybe together with CLD techniques in a full range speaker. Thanks for all the good ideas here!
  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 damping: Foam or expanding foam akunec Multi-Way 4 11th February 2014 01:14 AM
Foam, thicker foam or Open Cell qguy Subwoofers 4 11th March 2007 07:06 PM
Solen Air core inductors, Hammond Iron core. gnomus Swap Meet 0 30th July 2004 01:28 AM
Any website reference for diy choke ,siliver R-core, C-core, EI and power transformer bmpa Parts 2 22nd April 2004 04:15 AM
AIR-Core Vs Ferrite-Core Inductor in Class-D amplifiers Workhorse Solid State 13 23rd January 2004 09:14 AM


New To Site? Need Help?

All times are GMT. The time now is 01:33 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