What to do with a 35kg sandstone plinth?

[Wakefield Turntables]

My old front door step is now being made into a plinth for my 301, at long last. But, is it better to use spikes or isolation feet?

A

[Macca]

You are mounting your 301 in sandstone? Is that a new idea,? don't recall ever hearing about sandstone as a material for plinths. Not to say it won't work, I really have no idea about these things.

[YNWaN]

It depends what kind of isolation feet you envisage using? To really isolate, the compliance of the feet has to be matched to the mass of the plinth.

[Mike]

How heavy is this thing going to be? You might have to stand it on bricks! :D

[walpurgis]

If it is really heavy, maybe industrial isolating blocks would do the job, The type used under big electric motors and the like.

[The Grand Wazoo]

35kg + a Garrard chassis isn't that heavy - I've a lightly built Sound Org stand with two big power amps (one of which is 36kg alone), a weighty Accuphase tuner and the G99 + a wide six layered ply plinth on it. Nothing's bending yet!

[WOStantonCS100]

My old front door step is now being made into a plinth for my 301, at long last. But, is it better to use spikes or isolation feet?

A

Certifiable indeed! :lol: Gotta luv it!

Hope it does the job.

Extreme hi-fi should be an Olympic sport. :thumbsup: :D

[Wakefield Turntables]

Thanks for the replies. The reason I'm using sandstone is because its free. The doorstep has been living in my garage for over a year ever since I built my extension. I dont really fancy buying an expensive granite plinth. So, sandstone it is. Looks like I need to do a little more researching.

[The Grand Wazoo]

I don't see any reason why it shouldn't be great. It's a sedimentary rock, in the same way as the much touted slate is, although the particles it's made from are bigger. If you want to sink energy into something, then 35kg of sandstone would seem to me to be perfectly reasonable.
If it's going to be thick, I can't see much energy from the tt mechanism making it's way down into whatever you stand it on (or vice versa), so I'd just stick some practical feet that look good under it & not worry too much.

[YNWaN]

Industrial isolating bushings aren't really the right thing in this case; they assume the supporting weight will be at least 250kg and even then are only effective over quite a narrow frequency range.

[Lodgesound]

My entire house is built from sandstone and I can personally vouch for it's incredible isolation properties. With the studio monitors on at high levels you can barely hear them in the next room. The down side is that wifi won't get through it well at all.

[Moko]

Vic over at Trans Fi does some great feet for decks which he uses on his heavy weight Salvation decks which can be seen here http://www.trans-fi.com/salvation.htm

I have used them on my 70Kg slate deck and they make getting everything level so easy as to isolation etc they seem to do the job.

[YNWaN]

Yes, those feet are nicely made. However, being rigid they offer more in the way of coupling than isolation.

[nat8808]

I've some EVA (Ethyl Vinyl Acetate) foam blocks that were from a sprung dance floor that was being pulled appart which I stuck under a large bit of 50kg granite and they've almost kept their thickness and springiness with a further 20 odd kg on top. Used about 8 of them and they're 2" square, 1/2" thick. I was only really using them to protect a sideboard but with an unscientific nod to isolation.

As YNWaN says, you would need to factor in the weight of the complete deck/plinth and then also work out what frequency they should resonate at to isolate properly.

Alternatively, use some bike inner tubes as you can change their resonance by inflating or deflating and do it by ear (and find you prefer it when a big resonant hump comes through :) )

[Mike]

35kg + a Garrard chassis isn't that heavy

Drop it on yer foot and say that! :lol:

[bobbasrah]

Although it will oundoudtedly look good (love the look of stone), one element would trouble me Andrew, that is sandstone's relatively weak structure. Take too much out of it in terms of cross section (and it is very easy to work), and it may break under it's own weight. Sandstone lintels tend to be very deep beasts to combat this, and they are fully supported in walls.
Perhaps a stiff frame or similar with shock absorber between frame and plinth might give the feet a lesser point load on the plinth.
Just my 2c.

[Wakefield Turntables]

Right, I'm still at work so I will post some pics of said piece of sandstone and put some of my own thoughts forward when I get back home

[walpurgis]

Industrial isolating bushings aren't really the right thing in this case; they assume the supporting weight will be at least 250kg and even then are only effective over quite a narrow frequency range.

There are many weight ratings and types available with varying specs.

[YNWaN]

Yes, I appreciate that. Nevertheless, I have researched their use before and not found anything I felt was appropriate in this context.

[Wakefield Turntables]

hmmm. I have a couple of ideas

1. how about mounting the whole thing of 4 massive springs, to decouple the
plinth?

2. I have access to EVA in whatever thickness I choose, I could in theory have a piece of EVA made up to whatever thickness and size and then stick it under the plinth to couple the plinth?

Any ideas of either??

[nat8808]

hmmm. I have a couple of ideas

1. how about mounting the whole thing of 4 massive springs, to decouple the
plinth?

2. I have access to EVA in whatever thickness I choose, I could in theory have a piece of EVA made up to whatever thickness and size and then stick it under the plinth to couple the plinth?

Any ideas of either??

Err... I might be wrong about EVA. Is EVA that fine-bubbled, compact stuff they use in say home-wares packaging?

What I have has a kind of sealed top and bottom but a larger bubbled internal. Certainly I can stand on four between two bits of thick granite and it still wobbles a little.

Depends where you put the springs if there is concern over it supporting its own weight reliably around the narrower bits where the cut-out will be.

[Wakefield Turntables]

I've just had word back from the stone mason, turns out my 35kg plinth is actually a little over 100kg in weight! So looks like i need some serious supports to house this beast!

[The Grand Wazoo]

Bloody hell! Did you not notice the other 65 kilos?!

[Wakefield Turntables]

I only intended using half of it, hence the low kilo value. I'm now gunning for a 2-tier plinth on spikes. To hell if it dosent work, it sure will look pretty. :lol: