Discussion on what materials to build speakers out of - Page 82 - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

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 11th September 2011, 08:18 PM   #811
...truth seeker...
diyAudio Member
 
Ed LaFontaine's Avatar
 
Join Date: Feb 2004
Location: where the Appalachians rise from the Blue Grass
Default Category: For What Its Worth

Click the image to open in full size.

I triangulate my stiffeners. One is visible through each of the driver openings. These are made from hardwood, ~1' inch thick, about 2" crown in the center and tapered to each end. There are 14 distributed in each of those cabinets. There are mid-point cross braces front to back and side to side in the finished work.

They all cross the panel points most susceptible to vibration.
They use a minimum of material.
They are easy to install...glue and pin nails.
  Reply With Quote
Old 11th September 2011, 08:40 PM   #812
kaktus is offline kaktus  Sweden
diyAudio Member
 
Join Date: Nov 2004
Location: Stockholm
454: "Increase the wall thickness as high as you can afford"

Youre right in a bigger sense. The cost of housing makes the inner width of the walls to my Stockholm apartment the main limiting factor.

mondogenerator: "To me BOTH have their valid arguements, but i simply believe that SOME level of panel damping is always necessary, no matter how stiff a panel may be."

Perhaps there is some way damping that is easy to put in and take away to experiment? or I could do left speaker with and right speaker without damping.

For the sub the inner height will be 56cm (width: 34cm, depth: 43cm). With a 30cm speaker on top of front baffle it means only some 25cm height below the hole in the baffle. Is it any idea to squeeze in two horizontal shelfs there? perhaps instead one holey horizontal shelf just below the speakers hole and then another one above (which means it will not be full length since the basket is in the way and Planet 10 have strong opinions against it)?
  Reply With Quote
Old 11th September 2011, 09:12 PM   #813
kaktus is offline kaktus  Sweden
diyAudio Member
 
Join Date: Nov 2004
Location: Stockholm
Ed, that kind of stiffeners looks clever. And so very beautiful cabs!
  Reply With Quote
Old 11th September 2011, 10:46 PM   #814
diyAudio Member
 
mondogenerator's Avatar
 
Join Date: Sep 2009
Location: City Of Villans
Blog Entries: 1
i wouldnt like to say if you have enough room for the brace you describe, but i do think a vertical brace may be better, even if that means making a cutout for the woofer. Failing that any almost any bracing can help if done properly. It takes time adjusting damping material, but ive used brown bread damping sheet. Bitumen base with alu foil. I warm it slightly to apply, and it holds ok. Even so it can be removed relatively easily ie needed. Felt or wool lining is good for absorbing reflected sound, but does little to damp panel resonance.

I have a similar problem. I wanted to have a vertical brace in a different plane. Centre of baffle to rear panel, including a magnet brace. Fairly P10/Woden inspired i guess. If u can fit 2 or more horizontal braces in the right places, then the difference with a single vertical brace, i feel would be minimal.
__________________
Every new piece of knowledge pushes something else out of my brain - Homer.....................Simpson

Last edited by mondogenerator; 11th September 2011 at 10:56 PM.
  Reply With Quote
Old 11th September 2011, 11:44 PM   #815
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
Quote:
Originally Posted by kaktus View Post
454: "Increase the wall thickness as high as you can afford"

Youre right in a bigger sense. The cost of housing makes the inner width of the walls to my Stockholm apartment the main limiting factor.

mondogenerator: "To me BOTH have their valid arguements, but i simply believe that SOME level of panel damping is always necessary, no matter how stiff a panel may be."

Perhaps there is some way damping that is easy to put in and take away to experiment? or I could do left speaker with and right speaker without damping.

For the sub the inner height will be 56cm (width: 34cm, depth: 43cm). With a 30cm speaker on top of front baffle it means only some 25cm height below the hole in the baffle. Is it any idea to squeeze in two horizontal shelfs there? perhaps instead one holey horizontal shelf just below the speakers hole and then another one above (which means it will not be full length since the basket is in the way and Planet 10 have strong opinions against it)?
Does it matter if the damping goes on the inside or the outside? For a speaker test bed, aesthetics should be the least of your worries.
  Reply With Quote
Old 11th September 2011, 11:51 PM   #816
diyAudio Member
 
revboden's Avatar
 
Join Date: Feb 2011
huh... a brace is not really used as a panel stiffener, it does that but that is not why it works, it bisects the surface in the same way your finger does when you press down on a guitar fret board, put your finger half way down the string and you rase the pitch one octave. If the open panel primary resonance is say 500Hz and you bisect it once with a vertical brace you get two panels with primary resonance of 1kHz bisect those vertically and you get four panels with primary resonances of 2kHz.

technically two vertical braces on 3rd's will rase the panel resonance more than an X brace, as an X brace only moves the resonance one octave and the two vertical braces on 3rd's rase the panel resonance one octave + perfect 5th.

raising the resonances as much as possible then damping (impedience mismatch) the open areas with something heavy and flexible like pond liner glued down with silicone has worked well for me.
Attached Images
File Type: jpg 800px-Guitar_harmonic_nodes.jpg (52.6 KB, 216 views)
File Type: jpg Harmonic_motion4.jpg (16.5 KB, 212 views)
  Reply With Quote
Old 11th September 2011, 11:56 PM   #817
diyAudio Member
 
revboden's Avatar
 
Join Date: Feb 2011
although... an X brace will spread the first , second and third resonances over a larger frequency range so you will not get a box that goes nuts at one frequency but goes slightly mental over a larger frequency range
  Reply With Quote
Old 12th September 2011, 06:28 AM   #818
kaktus is offline kaktus  Sweden
diyAudio Member
 
Join Date: Nov 2004
Location: Stockholm
mondogenerator: "i wouldnt like to say if you have enough room for the brace you describe, but i do think a vertical brace may be better,"

Planet 10 said the same thing I think. But why shouldnt it be more effective to brace the bigger surface (the box will be higher than it is wide)?

revboden: " a brace is not really used as a panel stiffener, it does that but that is not why it works, it bisects the surface in the same way your finger does when you press down on a guitar fret board"

That was interesting. I thought the braces also weakened the vibrations some dB.
  Reply With Quote
Old 12th September 2011, 06:59 AM   #819
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by mondogenerator View Post
... the ideal for would be to raise the resonant frequency of the panel high enough that it is not excited by the loudspeaker.
A huge factor here is the energy available to feed a resonance, Physics says that the energy available decreases with the square of the frequency. There are further factors that one can use to argue that in a speaker it is actually decreasing by the 4th power of the frequency.

Discussion on what materials to build speakers out of

Quote:
expanding upon this and dividing the panel along the longest width say with 3 braces rather than a single, increases stiffness again. dividing this with horizontal braces will increase it further.
Actually the horizontal brace likely does not improve things significantly.

What bracing does is reduce the span across which the panel can resonant. The short dimension dominates. The relationship here is linear, halve the distance double the frequency. (edit: i see revboden beat me to that)

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 12th September 2011, 07:03 AM   #820
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by 454Casull View Post
I like the method where you increase the wall thickness as high as you can afford.
At the possible penalty of increased energy storage (and later release), particularily with homogeneous materials

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  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
Cone Materials Discussion J.R.Freeman Multi-Way 46 11th May 2009 01:22 AM
Other ESL build with simple materials available from local grocery stores Audio_idiot Planars & Exotics 69 7th September 2006 05:52 PM


New To Site? Need Help?

All times are GMT. The time now is 08:37 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