Do drivers shake their mounting boards? - 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 30th December 2010, 07:38 PM   #11
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Quote:
Originally Posted by planet10 View Post
Hi, I should of thought about it more, that is as described, rgds, sreten.

Reversing one driver and reversing its phase will still give force cancelling and 2nd
harmonic cancellation, but it wouldn't fix driver "DC" position issues, the above does.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 30th December 2010 at 07:44 PM.
  Reply With Quote
Old 30th December 2010, 07:57 PM   #12
49 - for the 18th time
diyAudio Member
 
c2cthomas's Avatar
 
Join Date: Oct 2006
Location: Near "Music City" (Nashville Tennessee)
Quote:
Originally Posted by planet10 View Post
That concept looks verrrrrrrrry interesting Dave - me like it!!!

If I can ever put together a couple of $$$ I think I slap one of those together for a try. Of course I will need to work out a bit of the math (hmmmmmm - haven't done that stuff inawhile) about the size of the baffles etc. Ah heck - who needs that math stuff anyway - just go fer it and throw sum stuff together! (Just joking kids - I though I heard several folks grabbing their chest while they spit their beverage of choice out their nose).
__________________
DIY audio can be expensive but getting to see things go up in smoke - that's priceless!!!! ..... "whatever - call it brainfart of Mighty ZM"
  Reply With Quote
Old 30th December 2010, 08:05 PM   #13
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Dave,
Quote:
Push-push on the other hand actively cancels most of the reactive forces, dramatically reducing energy machanically passed to the box.
I'm sorry, but I can only see how this may affect the overall moment if you look at the box as a single solid mass. What is happening is that each wall experiences twice the force it would normally experience due to air pressure. If the drivers are not bonded together, then the moving mass of the driver system still affects each side independently until where each side is coupled where you can hope for some cancellation. It depends on how much energy was lost along the way.

It is a cool idea, and it does address the bass cancellation issues of open baffles. However, it does not qualify as an open baffle does it? It looks like a sealed or ported enclosure with drivers firing out each side.

Hi sreten, martin,
Yes, agree. A collection of moving masses coupled by compliances. Even a single box does not act as a solid block. Each panel will resonate at it's own resonance that may couple somewhere else in your system. I don't want to figure it all out.

If you place bright coloured adhesive dots in the middle of various panels and objects, then illuminate it all with fluorescent light (or similar), you'll be able get an idea of what is moving and by how much depending on signal levels. If you use an oscillator, you can identify each resonant frequency. Could be fun in fact.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 30th December 2010, 08:51 PM   #14
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 anatech View Post
I'm sorry, but I can only see how this may affect the overall moment if you look at the box as a single solid mass. What is happening is that each wall experiences twice the force it would normally experience due to air pressure. If the drivers are not bonded together, then the moving mass of the driver system still affects each side independently until where each side is coupled where you can hope for some cancellation.
The interior walls see no greater pressure than 2 drivers in the box (or even a single driver in an appropriatly smaller box -- force/unit area).

The more effectively the 2 drivers can be coupled the greater the force cancelation. Just usung the box walls is not all that effective.

Here is an illustration of an xtreme approach:

Click the image to open in full size.

You get a significant portion of what is possible with just a good driver brace (avoid MDF).

An example (for a very specific woofer -- this would not be considered generic): woofer magnet plugs into, and is supported by, the vertical braces. Minimal baffle and tightly fitting horzontal brace provide good coupling.

Click the image to open in full size.

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 30th December 2010, 08:53 PM   #15
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 anatech View Post
It is a cool idea, and it does address the bass cancellation issues of open baffles. However, it does not qualify as an open baffle does it?
Both examples before your post are OB. The 2nd image is a simplified view of the render on the webpage.

It does not address bass cancelation. You end up with a compound driver with all the same OB cancelation as a single driver.

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 30th December 2010, 09:03 PM   #16
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 sreten View Post
Reversing one driver and reversing its phase will still give force cancelling and 2nd harmonic cancellation, but it wouldn't fix driver "DC" position issues, the above does.
Take the concept a bit further. PushPush pair of PushPull drivers (not much use in an OB).

Click the image to open in full size.

Something similar could be done on an OB, but wouldn't be as tightly coupled (and not isobarik).

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 30th December 2010, 09:25 PM   #17
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
I dont think you can entirely get rid of shake, just reduce it using practical materials.

3/4 inch Thick plywood with 2inch*2inch bracing works best for me.
I can still feel a little vibration through the panels.
I dont think it is enough to worry about tho.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 30th December 2010, 09:27 PM   #18
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

I agree Isobaric stuff for open baffles means you don't understand Isobaric.

But to get back to the OP question, I think the cause is driver assymetry.

rgds, sreten.

The push-push arrangements would have some resonances higher up,
in fact you might as well fold back the side wings as far as I see it,
making it effectively a compound push-push folded W baffle.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 30th December 2010 at 09:40 PM.
  Reply With Quote
Old 30th December 2010, 09:52 PM   #19
diyAudio Member
 
Join Date: Feb 2006
Location: usa
Blog Entries: 1
I don't think push-push will work on open baffle. There will be no bass at all.
Both drivers must move synchronously in the same direction, push-pull.
  Reply With Quote
Old 30th December 2010, 10:00 PM   #20
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Dave,
Quote:
The interior walls see no greater pressure than 2 drivers in the box
Yes,and the bracing is everything at those working pressures.
Quote:
The more effectively the 2 drivers can be coupled the greater the force cancelation. Just usung the box walls is not all that effective.
Yup. That's why I asked.
Quote:
Here is an illustration of an xtreme approach:
It's not that extreme. I've seen this in commercial production, same as the idea where you have internal bracing to hold / support the magnet structure.
Quote:
Both examples before your post are OB
Are they open to the sides Dave? Top and bottom also? Because you have a pair of baffles so close together, I'm not sure it acts the same way as the classic open baffle design. You have some acoustical passages there.

I'm not criticizing the design at all. It looks interesting and shows the lengths it can take to avoid cabinet participation in the acoustic output (yuk, yuk, yuk). That goes to the original poster's concerns. I am curious as to how close you are getting to some type of enclosure in an acoustic sense. A simple OB it ain't.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  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
Do open baffles shake? bentoronto Full Range 16 2nd October 2010 07:09 PM
just to shake things up moray james Planars & Exotics 17 5th June 2005 02:00 AM
Need Help Mounting Drivers aggielaw Multi-Way 1 10th February 2005 02:08 AM
Flexible mounting of drivers? Jonathan Bright Multi-Way 13 19th April 2004 11:02 PM
Mounting Drivers GeniX Multi-Way 4 20th September 2002 05:24 PM


New To Site? Need Help?

All times are GMT. The time now is 05:50 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