Designing/building an isolation platform

[indus]

Hello

I'd like to make an isolation platform for my SL1210. There are a multitude of threads on the internet about these and there are of course many approaches so it can get a bit confusing.

Isolation and coupling is also something I'm not sure I've quite grasped!

Anyway, here are a few basic design concepts that I have found on the net and need advice as to which path to follow

1) A strange design I've found that consists of the inner bladder of a cycle tyre inflated to 10psi with a wooden board sat on top.:scratch:

2) A single surface of some kind ( ie acrylic, mdf) etc with sorbothane feet.

3) Two surfaces with sorbothane feet in between them and then metal spikes at the bottom. Like this

http://www.ebay.co.uk/itm/ISOKINETIK-ISOdEK-IF-2-TURNTABLE-ISOLATION-PLATFORM-NEW-/170468628656

If I follow option 2 or 3 I'd prefer to use acrylic (if it is a suitable material) as I think aesthetically it would be much better. It can be bought cut to size with the edges polished and in any colour over the internet. So it could actually look quite funky.


Anyway, any advice appreciated.:)

[Ali Tait]

You could try this, it's cheap enough-

http://www.tnt-audio.com/clinica/sandblaster_e.html

[indus]

Thanks Ali.

I did read somewhere that heavy sand filled boxes are not the best way to go for turntables. Something about it raising the amount of resonating mass that will then need isolating.

Thanks

[wee tam]

i am going to attempt an isolation platform of sorts this coming week , i will post pics as i go , basically it will be basic , i have two units all my gear is housed in , and i will use a cut sheet of reformed / reclaimed rubber intended as shock absortion for horses in their stables and a sheet of good old ply on top , at the same time outriggers for the speakers using sandwhiches of the above and eight transfi feet ( the forty mm diameter ones) so here's hoping , the rubber is reformed kinda like polystyrene with air pockets as they are small pieces of rubber bonded together but not stiff and a little bit compressable with your fingers , will keep you up to speed , PS a six by four feet by ten mm is only 26 squid deliversed

[nat8808]

Thanks Ali.

I did read somewhere that heavy sand filled boxes are not the best way to go for turntables. Something about it raising the amount of resonating mass that will then need isolating.

Thanks

I'm not so sure about that - the heavier something is, the more energy is needed to move it so the magnitude of the vibration imparted to it are smaller in magnitude - the total energy is the same but the same energy is being asked to move a much more massive object.

There's nothing more massive you have than the house itself and using a wall shelf attached to the massive house definately isolates very well.

So the massive object will still take up some lower frequency vibrational energy and translate it into smaller movements but high frequencies need to be absorbed too.

A massive load of sand can kind of do both things - it being a load of small particles free to move about to some extent, they will convert some higher frequency vibrational energy into movement of all the small particles and friction between them etc, transforming vibrations into heat essentially - the higher frequency energy is effectively absorbed.

Basically it's a lot about knowing what frequency vibrations you want to guard against and where it's coming from.

It's also about masses and their resonant frequencies, it's about stopping vibrations moving from one material to another by mis-matching their impedances or placing something lossy between them (like a rubber or spring or trapped air like in a bike inner tube) and about stopping big shelves bending and bouncing about by supporting them in the right places.

I think a lot can be learned from physics labs and anything to do with precision optical experiments. Olden day optical tables used to be just massively heavy marble tables then they started using massive stands with some kind of super-stiff honeycomb material, then there are others with passive air suspension (like Townshend stands) and there are others with active, constantly adjsting suspension. Now, some of the best are all mechanical using complicated and precision movements internally to absorb vibration in the support - these have to be made specifically for each application, for a small range of mass (normally over a certain figure).

Something like the last example was looked at on 6moons.com I think.