Vibration Isolators - Air, Magnets or other materials - Page 2 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 November 2002, 07:03 PM   #11
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default DECOUPLING

Hi,

Quote:
A cheap Frugal-phile(tm) trick is to use squash or tennis balls cut in half under your kit.
If I'm not mistaken squash balls are made of sorbothane.
An elastomer with outstanding properties.
Since these don't contain air they seem the perfect candidate for this application.

One can easily make something like a Mission Isoplat just using a bit of imagination.
The component sitting on it should be of sufficient weight though,or weighted down for it to work effectively.

Some places will also sell sorbothane sheets which are very effictive for damping LS cabinet resonances as well.

See also:

Tube Dampers

And:

DIY Turntable Stand

Cheers,
__________________
Frank
  Reply With Quote
Old 10th November 2002, 08:10 PM   #12
claudio is offline claudio  Italy
diyAudio Member
 
claudio's Avatar
 
Join Date: Feb 2002
Location: Italy
More than one year ago, the italian SAP come out with magnet isolator.Test and info here: http://www.tnt-audio.com/accessories/relaxa1_e.html
  Reply With Quote
Old 10th November 2002, 08:13 PM   #13
GaryB is offline GaryB  United States
diyAudio Member
 
Join Date: Sep 2002
Location: Silicon Valley
I've been experimenting with vibration damping under various pieces of equipment and the results are very worthwhile. A friend helped make some isolation platforms using small inner tubes along with other damping and it made a dramatic improvement when placed under a solid state pream and a HK Citation II power amp. The only problem is that the power amp is quite heavy (75lbs or 34kg) and the weight is not evenly distributed. The power transformer and output transformers are all in a line at the rear of the amp. When put on the inner tube isolator, the back of the amp sags noticeably with tube being compressed more in the back then the front.

I didn't like the way this looked and also worried if it was good for the inner tube, so I substituted squash balls. Squash balls are not made of sorbothane, but they are quite effective. I was able to correct for the weight imbalance by using 3 balls in the back of the amp and only 1 in the front. Under the weight of the amp, the squash balls compress nicely so there is no tendency for them to roll. A quick push of the top of the amp gives a small displacement followed by a quick return to the original height with no low frequency wobble.

I'm not sure its as good as the damped inner tube, but its much cheaper and easier to set up.

Anyone have some ideas on how to deal with nonuniform loads on isolation platforms? I guess I could put some weights on the front of the amp, but theres not really room.

---Gary
  Reply With Quote
Old 10th November 2002, 08:30 PM   #14
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default WEIGHTDISTRIBUTION.

Hi Gary,

Short of putting your amp on a diet,here's something you can try out:

Have a Y-shaped support made out of U-shaped steel upon which you put the amp with the heavy part sitting on the two pronged part so the weight gets distributed there.

If that Y shape is longer then the amp itself you will gain even more stability.
For further isolation you can even provide for tapped inserts at the ends of the Y-shape and insert spikes there.

This can then be put on a slab of MDF wood and you can be put on the squash ball halves in a mirror to the Y legs to diperse vibration even more.
Always use an odd number of contact points/squash balls.

Obviously all materials have to be of sufficient strenght so they don't flex.

Cheers,
__________________
Frank
  Reply With Quote
Old 11th November 2002, 12:03 AM   #15
dice45 is offline dice45  Germany
diyAudio Member
 
Join Date: Jan 2002
Location: Munich, Bavaria
supermodel,
personally i feel fine if i get the natural frequency below 1 Hz.

Overcritical (is it called super-critical?) damping is based on the transfer function of an oscillator stimulated from outside. Below the oscillator's natural frequency the transfer funcion has practically unity gain. Stimulus frequency approaching the NF from below lets the gain rise and rise. If the oscillator's damping is low, gain raises high, if damping is zero, gain reaches infinity. Above the NF the gain falls and falls and falls into the abyss. The lower the oscillator's damping is, the steeper the fall of the gain, of the transfer function. Usually more than 24dB per octave, the slope can reach or exceed 48dB per octave.

If the NF is 1Hz or below with very low damping, then 8Hz (let's call that lowest permissible vertical tonearm resonance) is 3 octaves above and overcritical damping has a nice value at this frequency already. You walk around on a gooey floor beneath your TT and no tonearm is hopping from groove2groove. Not even trying. Not even messing up the soundstage. Call that paranoia, but i listened to such low-NF suspension TTs, high mass on TT and on platter. That's what i want, that is impact out of calmness sonically. 1Hz or lower, is fine, 2Hz, like Pink Triangle etc. is ok.
4Hz is no real suspension. It is a fake.

Dave,
cheap stone plates and bicycle tubes are also frugalphile (tm).
__________________
Greets,
Bernhard
  Reply With Quote
Old 11th November 2002, 12:21 AM   #16
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default THE FOUR LEGGED SUPPORT.

Claudio,

Thx for the link.

Having heard about that particular design before,it represents the disadvantages the reporter mentions.

One aspect of unevenly distributed load can be elegantly overcome if Mr.Puppin had considered what I mentioned in the reply to Gary.
It allows for much better distribution of weight and since I still have to find an audio apparatus that represents well distributed mass it is the best sollution I can put forward right now.

As it stands these platforms represent too many flaws,especially when you consider the high asking price.

Regards,
__________________
Frank
  Reply With Quote
Old 11th November 2002, 07:59 AM   #17
diyAudio Member
 
Join Date: Oct 2002
Location: English midlands
Default vibration isolators

dice 45

Thanks for the very helpful response.
I am trying to get below 1 hz, can`t see how to do it with rubber
Possible with air,but it is becoming complicated and bulky-
large reservoirs needed.
__________________
Richard
  Reply With Quote
Old 11th November 2002, 10:09 PM   #18
diyAudio Member
 
Join Date: Nov 2002
Location: Texas
Send a message via AIM to Danny
Default Levitator

Just a few notes on the Levitator.

I assisted Gary Dodd some with the design aspects and was used as a sounding board for ideas, and I came up with the name. I do not own any part of the company and I do not produce them. I do assist Dodd Audio with marketing their products and the Levitator can be purchased from our web site. I am officially a distributor as are several retail stores and Bolder Cable Company.

Gary did build a unit the was completed supported by magnetic fields. It used some attracting magnets to maintain alignment.

There were two problems with that.

The first was that if you bumped it hard enough to get it to twist to where attracting magnets would pull towards each other it would slam shut with finger braking force. This was seen as a huge liability problem.

Secondly, the attracting magnets created a really strong magnetic field that could effect a lot of other things.

The opposing magnets cancel each others fields just like adding a bucking magnet to a woofer or tweeter for shielding. Hopefully this just answered one of those other questions.

The two pin system works great and does not lock the top plate to the bottom plate. The clearance used in the top plate allows some float in the horizontal plane as well. So it actually does dampen in more than one axis.

The other magnetically levitating platform mentioned from SAP locks the top plate rigidly at the corners and does not allow any dampening in the horizontal plane. I believe that unit is about $150. more expensive too.

The free air resonance of the top plate is in the low to middle teens so it also isolates it from direct air born vibrations that hit it directly.

How well does it work and can you hear a difference are the most asked questions.

Yes is does work and yes you can hear a difference.

Some differences are greater than others depending on the rack system used, the room, the volume level of the music typically listen to, etc.

My CD player sets on top of a Lovan Sovereign rack system. Each level is Isolated with three spiked feet.

In this system it makes a marginally noticed difference.

If I were to set my CD player on top of my big screen TV, then add a Levitator it makes a very noticeable difference.

The whole thing acts as a really low pass filter. The higher the frequency the more effective it is. The lower the frequency the less effect. With this design though even the lowest frequencies are filter very well.

Plus, it looks really cool right?

Wayne did a really nice review and comparison to another insolation unit that he posted in his forum. I don't know if I can post a reference to it or not. Some forums freak out and reprimanded me for posting links to other forums. You guys can let me know.
  Reply With Quote
Old 11th November 2002, 10:13 PM   #19
halojoy is offline halojoy  Sweden
On Hiatus
 
Join Date: Nov 2002
Some forums freak out and reprimanded me for posting links to other forums. You guys can let me know.

I have seen a lot of refering links to other forums.
no problem, I think.
  Reply With Quote
Old 11th November 2002, 10:32 PM   #20
diyAudio Member
 
Pjotr's Avatar
 
Join Date: Nov 2002
Location: Netherlands
Quote:
The whole thing acts as a really low pass filter. The higher the frequency the more effective it is. The lower the frequency the less effect. With this design though even the lowest frequencies are filter very well.
Indeed

Two magnets that are repelling each other in close proximity are simply acting as a spring. However they do not act as a normal spring. The force is inverse proportional to the square of the distance: F = k/(d^2). This means that if d goes to zero, the force goes to infinity. In practice this is not true, because of large leakage fluxes not going trough both magnets.

On the matter of damping, here is some basic mechanics. Most of you already know of course. If we want to isolate vibrations, we have basically to do with a mass–spring system. As seen from the viewpoint of the mass to be isolated, such a system acts like a 2nd order low pass filter with a resonance frequency f [Hz] and a Q-factor Q. (Q is the inverse of damping factor b). The spring has a compliance c [m/N]. Further we have usually loss: r [Ns/m] and of course a mass m [kg].

The resonance frequency fs of the system can be calculated as follows:

fs = 1 / ( 2 * pi * sqrt( m * c ) )

Below fs vibrations are transmitted and above fs they are attenuated at a rate of 12dB/oct. The time and amount the mass stays swinging depends on the Q factor:

Q = 2 * pi * fs * m / r

or

Q = (sqrt( m / c )) / r

So if you want to go for a pretty low fs of 1 Hz or 2 Hz, you will need a fairly high mass and a fairly high compliance. The loss also does matter a lot. A Q-factor between 0.5 and 0.7 is optimal. Below 0.5 the damping will be less effective and above 0.7 the system stays swinging too much after an excitation (a bump for instance).

A large mass will not be the problem but a large enough compliance that can hold the mass, is rather difficult. Systems with a low fs are available at industrial level. But beware, they are bulky and usually use active pneumatic or magnetic control systems.

The idea of using an inner tyre, of a small trailer for instance, for the spring is not such a bad idea. The butyl rubber they are made of has a high loss factor r also.
  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
audio isolators how to mhtplsh Solid State 0 24th May 2008 01:56 AM
Liquid silicone filled vibration isolators? rickmack Parts 5 27th October 2004 12:19 PM
Liquid silicone filled vibration isolators? rickmack Car Audio 0 26th October 2004 07:01 PM
Pneumatic isolators Prune Everything Else 2 18th February 2004 08:55 PM


New To Site? Need Help?

All times are GMT. The time now is 02:56 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