Discussion on what materials to build speakers out of - Page 41 - 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 10th June 2007, 11:20 PM   #401
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Quote:
Originally posted by planet10


Yes. Adding damping to the panels means the need for even more bracing...
Panel damping is something i've abandoned as counter-productive.
No, that's not what I mean. As you damp, you don't have to add more bracing, just use the correct amount to start with. As the resonance has been driven upwards, it will be easier to damp.

Surely, I'm not the only one who sees the logic in this.
  Reply With Quote
Old 11th June 2007, 01:00 AM   #402
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 MJL21193
No, that's not what I mean. As you damp, you don't have to add more bracing, just use the correct amount to start with. As the resonance has been driven upwards, it will be easier to damp.

Surely, I'm not the only one who sees the logic in this.
Add damping to the panels walls. Adds mass with no increase in stiffness... pushes panels resonant frequency down.... bracing needs to be closer to counter this .... hence more bracing...

If the panel resonances are high and not excited then there is no resonance to damp so why try to cure a problem that doesn't exist?

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 11th June 2007, 01:49 AM   #403
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Quote:
Originally posted by planet10


Add damping to the panels walls. Adds mass with no increase in stiffness... pushes panels resonant frequency down.... bracing needs to be closer to counter this .... hence more bracing...

If the panel resonances are high and not excited then there is no resonance to damp so why try to cure a problem that doesn't exist?

dave

Make a large bell - it rings at a low frequency, difficult to halt the ringing (damp) once started. Melt this bell down and make smaller bells - they ring at a higher frequency, easy to damp the ringing.
Damping is not adding mass for nothing, it's a system for absorbing vibration. No extra bracing needed.

How is that when you drive up the panels resonant frequency, that it won't be excited? What resonances are you trying to damp in a 4" driver? How is it that the driver basket can have its resonance excited when the box panel does not?

Going back to the bell analogy, how much damping material would it take to critcally damp the large bell? If we made 100 smaller bells from it, would thedamping material for each be 1/100 of what is needed for the large bell? Most likely not, as the frequency to be damped is higher, therfore easier to damp.
  Reply With Quote
Old 11th June 2007, 04:31 AM   #404
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 MJL21193
How is that when you drive up the panels resonant frequency, that it won't be excited? What resonances are you trying to damp in a 4" driver? How is it that the driver basket can have its resonance excited when the box panel does not?
You must have missed the part where i stated, and Svante showed a chart, that the exciting energy decreases as the square of the frequency. A panel will not resonate unless a critical quantity of energy at the panel resonance is input into the panel. And if the panel is made of an inherently well damped material like plywood, it have to reach that energy threshold while the panel is draining the energy. If you get the panel resonance high enuff, there is never enuff (close to) instantaneous energy to overload the inherent damping in the panel. It is like trying to fill a container to the top when there is a big leak at the bottom and your delivery tool is a straw. Not being excited, it as if the panel has no resonance at all... so again, why would i complicate things to fix a problem that doesn't exist, especially when that fix will actually make things worse?

John, after extensive discussion in theother thread, one could get the feeling that most of it went over your head...

A basket/motor is a very different beast than a wall panel. It is not inherently well damped like a plywood panel... and a small resonance has a much more profound affect on the sound then a small panel resonance since it is directly connected to the speaker (actually it is part of the speaker)...

... and did you also miss the part where you got 2 fixes for the price of 1 -- just as important, in some cases more important, is the shaping of the basket exit. Even if you have a basket that doesn't need any damping, it can benefit from careful shaping.

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 11th June 2007, 11:33 PM   #405
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Quote:
Originally posted by planet10


You must have missed the part where i stated, and Svante showed a chart, that the exciting energy decreases as the square of the frequency. A panel will not resonate unless a critical quantity of energy at the panel resonance is input into the panel. And if the panel is made of an inherently well damped material like plywood, it have to reach that energy threshold while the panel is draining the energy. If you get the panel resonance high enuff, there is never enuff (close to) instantaneous energy to overload the inherent damping in the panel. It is like trying to fill a container to the top when there is a big leak at the bottom and your delivery tool is a straw. Not being excited, it as if the panel has no resonance at all... so again, why would i complicate things to fix a problem that doesn't exist, especially when that fix will actually make things worse?

John, after extensive discussion in theother thread, one could get the feeling that most of it went over your head...

A basket/motor is a very different beast than a wall panel.

... and did you also miss the part where you got 2 fixes for the price of 1 --

Yes, right over my head.

I found it interesting that you would advocate basket damping but not panel damping. I already agreed that basket damping has some value, and as for the shaping to streamline airflow? Could have some merit.

You have finally put into clear words how it is that the system of speaker building that you have adopted works. Sounds good to hear it explained like that.

I (as usual) have a problem though. We have been refering to resonance a lot, and it seems to be a kind of benchmark for noise. What about in frequency spectrum above it, and below it? You yourself said it's the noise 40dB down that will ruin the way a speaker sounds.
I know that there >might< not be enough enery to excite the panels resonant frequency, but it will vibrate none-the-less. This I know from my own speakers built from BB plywood with no damping.
Using your own analogy, the container doesn't overflow, but we can still hear the water running.
  Reply With Quote
Old 11th June 2007, 11:47 PM   #406
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Dave;
linoleum glued to a plywood converts mechanical energy of vibrating walls into a heat. It is not about changing a frequency though it is very heavy, it is about reducing amplitude of vibrations. Also, wavelengths on surfaces of such different materials are very different, so...
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 12th June 2007, 01:06 AM   #407
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 MJL21193
I know that there >might< not be enough enery to excite the panels resonant frequency, but it will vibrate none-the-less. This I know from my own speakers built from BB plywood with no damping.
If the panels aren't resonanting, then the panels aren't vibrating (that is by definition) -- the energy being pumped into them is being damped...

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 June 2007, 01:08 AM   #408
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 MJL21193
You have finally put into clear words how it is that the system of speaker building that you have adopted works.
Sure seemed to me like i was repeating myself... i'll grab that snippet for future reference...

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 June 2007, 01:44 AM   #409
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Quote:
Originally posted by planet10


Sure seemed to me like i was repeating myself... i'll grab that snippet for future reference...

dave

Sorry Dave, but I finally understood that you believe noise only happens at resonance.
  Reply With Quote
Old 12th June 2007, 05:41 AM   #410
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 MJL21193
f the panels are not properly damped, they will vibrate below the resonant frequency.
If the panel is vibrating it is resonating. Plywood is inherently well damped, and it is stiff. If resonances aren't excited the panels aren't vibrating.

I use finese to keep my boxes from being a sound source, not brute force.

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 08:18 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