Granite slabs

I was thinking about putting some granite slabs under my speaker stands. As usual the audio market is expensive. I was wondering if anyone knows what size is the best to order from a granite supplier as im sure it will be cheaper. Any other idears for under speaker/stands.

GAZZ

 

Hi Gazz!

Here's the cheeky fookers way to get cheap granite. Works for me! hehehe

First, you need to get as close to source as possible. That really means you want to buy it straight from the guy at the quarry, cut to size and polished. Buy it from anyone else, and you're paying 1, 2 or maybe even 3 peoples mark ups on top.

If youre a mean tight fisted git like me, you'll even pretend its part of your work and ask for trade price!

hehehehe

NB

For under speakers I did what Technobear (chris) did - bought some big thick concrete slabs from B&Q and spray painted them a more acceptable jet black with a can of plasticote paint.

Total cost about a tenner.

You can always box round them and stick an inner tube under the slab, and hey presto instant seismic sink/voodoo plinth.

 

Thanks bottleneck,

I,ll try some concrete first. It always gets me how hifi Enthusiasts will pay daft prices when you can get them elsewhere cheaper.

GAZZ

 

Once under you stands you will not be able to see the Granitic phenocrystalic structure of the rock !

You could just as well use limestone of gritstone, The actual densities are fairly close. The attraction of using a softer more easily worked is that you can do something really rather clever.

By bolting the slab to the under side of your stands the mass becomes part of the system rather than something its sat on. The slab would then need to be drilled and have threaded inserts to take the spikes but thats no big deal. There is a company [or was] in Retford Notts. that made slabs to fit the base of floorstanders, lowering their centre of gravity and stiffening the cabinets. I'm reliablly informed they worked very well, but at a price !

 

I may disagree with you on some things, Zanash, but I'm with you here. For my speakers, I have blocks of basalt, very fine-grained black igneous rock, related to granite. I drilled four holes for the speaker spikes - and it took forever! A sedimentary rock such as limestone would be much easier and still have the necessary density.

 

What do you mean .....its healthy discussion.

As long as you don't get to fisty cuffs !

Hey I've a degree in Geology so at least I know what Basalt is !


Did you know that the earths magnetic field is imprinted on the magnetic particles within the rock [magnetite mostly] and if you knew the orientation of the rock before it was excavated you could tell if it was extruded during a magnetic reversal. This was used to help authenticate mid oceanic ridge spreading and hence Plate Techtonics.

 

Absolutely.

Yes, but (a) I didn't know you had a degree in geology, and (b) other people mightn't know what basalt is. I did geology as part of my chemistry course and still retain an interest. It's interesting in a place like Switzerland, where there is vertical geology all around.

Yes, I knew about the magnetic orientation of magnetite in igneous rocks and how they could use it to trace geological history.

 

Only been to switzerland to ski.... its normally difficult to get down to the rock then !
We used to go anually to Adelboden ...very nice but we've been introduced to Mirebel this year not nearly as nice a place but more scope and longer slopes.

 

What advantage is to be gained by using granite?

Steven

 

As far as I can make out, only that it's rock and therefore rather dense and heavy and it makes a good, firm platform. The fact that it's granite (as opposed to limestone, sandstone, gneiss, etc.), I suspect not at all. However, sooner or later, someone is going to say something along the lines that the presence of orthoclase and/or plagioclase feldspars in granite has an effect on the sound and that this makes granite superior - and that the very best is, say, Alisa Craig granite (a unique granite from a little Scottish island, once universally used for curling stones) - obtainable only from them at very reasonable cost, considering it has the effect of a major upgrade.

Come to think of it, why aren't I doing that?

 

Because you don't have the right kit to demagnetise the stone first?

 

Is there a(nother) sceptic in the house????

(Just think, I could become STones! (SToned?))

 

I think it's not so much what its made of more what you do with it. Never rally been fond of the slab under the speaker, rather make it part of the speaker and or stand unit.

Weight IMO it needs to be 15-20% of the mass of the speaker, so denser the better.
This will aid stability, if secured to the base of the speakers as previously mentioned. It also has a chance of damping the cabinets and lowering resonance modes.

Rock type well sandstones a bit soft but I've used Derbyshire grit stone [millstone grit] in the past. Many people use igneous rock granites, basalts etc but perhaps those with the higher mafic [darker/more alkaline] minerals mite be better as they are denser. Granites are actually rather light in comparison, Geologically that why land masses are made of granites, as the lighter minerals melt out and rise through the crust of denser material.

 

Granite is cheap if you know where to go.

I sourced three shelves for my hifi rack (two 460x370mm, one 495x330mm, all three 30mm thick) for a total of £15, and that's only because the two equal pieces had to be cut from one. The pieces were off-cuts, which the granite place basically want rid of. If I'd had them tidy and polish the edges then it would have cost over £100, but I have an angle grinder (whcih is what they use), so it can be done if it bothers me...

 

out of curiosity - my floorstanders are spiked, and my floor carpeted concrete, would concrete slabs be any use..?
daft question I guess, but I'm always up for a tweak...

 

My very understanding wife is tolerating these at the moment.
I have been using a granite composite structure, speaker plinths for quite some time now to stabilise my speakers on my springy, suspended wooden, floors. From the bottom up the ingredients are as follows:
Springy suspended wooden floor > Carpet > 3 x Michell Tenderfeet low cones > 1 x Granite floor tile > 1 x 14" cycle inner tube > 3 x Granite floor tiles, bonded together, using silicon based adhesive > 1 x Plywood sheet (5 ply) ,bonded to Granite using silicn based adhesive, (this was used when my speakers where still spiked to stop slipping and bouncing on the hard granite !) > 12 or 13 1 gram balls of Blu-tac sqished down good and hard > 1 x Mission 782 floorstanding speaker.
How does it look? Well see for yourselves, I kinda like em and I'm the one that lives with 'em.
How do they sound, better than the stock floorstanding speaker. Maybe a bit of constunctural fine tuning is still on the cards , but i'm getting a sound that me and my ears like VERY much .......

 

Yes, nice looking had you though about introducing other materials into the stack say a hard foam or a plastic, that would really upset the floor vibrations !

Did you bead the glue or squish the slabs together I've heard that running a bead of glue and letting it just about set then adding the next tile. This gives you multi layers of hard and soft densities, sort of poor mans different layers of material.

 

My theory, for which i have no scientific background whatsoever, was to bond the top three tiles together in such a way that they are close enough to give a very stong bond and give the structure as a whole very good structural integrity. the use of silicon adhesive was because it is an excellent bonder, and as long as the layer isn't too thick it is fairly rigid. the differing layers would hopefully break up any standing waves. When using the silicon you need to lay a bead around the front and two sides , leaving the back open, you then lay beads from front to back. all of the silicon needs to come into contact with air otherwise it will not set. if you use a two-pac chemical reaction type adhesive then contact with air is not essential.

Maybe a more complex mix of materials is something to try in the future, or for somebody else to have a go at. My little block has granite, silicon rubber, plywood, aluminium, air , laytex type rubber and Blu-Tac in the mix, theat'll do for me for the time being.

i am getting the effect i desired when i first started this little DIY project, so I can't see me taking it much further, at some point in the near future i will whip out the Tube just to see if i notice a huge difference. I think that sometimes i have been a bit too quick fire in my A-B comarison demo's in the past. Far better to live with something for a while and then make a change, that way you get more of a 'Where the hell did the second guitar go ?!' type effect or even better 'where the hell did that guitar come from !? . If you see what i mean.

 

Ah there'll come a time when you start to think, I wonder if I can squeeze a little more from..... and your off again to the shed with more bits. I know coz I've been there !

 

I can see the huge advantages of putting stone inside the speakers or on top of the base of a stand. This would seriously lower the centre of gravity and make the speaker more stable but as far as I can work out, putting stone beneath the stand is simply decoupling the speaker/stand from the floor.

I can see how this would change the sound of the music and in some circumstances improve the situation but is this the reason why people are doing this?

Steven