So something approximately 4 inches thick that compresses down to 3 inches thick. Easy enough to test, thank you!
For reasons stated in my immediately-previous post, which I won't repeat, I believe these statement to be false.
Let us know how you get on - theory and some practice is all well and good, but the proof of the pudding and all that.
It appears that the boards are placed directly on the floor, so my immediate thought was inner tube and a straw, cost around £5, too cheap not to try. Whilst this is hardly hi-tech I think it mimics much more expensive products out there. Alternatively you could try some of the other DIY options that have been mentioned. I'm also a bit confused by the speaker stand, it appears, to have no spikes and be directly coupled to the floor?
I use isolation blocks on the stands and the speaker stands are spiked. The carpet hides them somewhat. So all good there
Interestingly enough, I just toured one of our vendor’s shops (they make large rotating industrial equipment to very tight tolerances) and they use granite in all vibration-sensitive areas. MASSIVE slabs in some cases, but also even as frame/chassis material for some of their highest precision machines. I wasn’t allowed to take photos, but suffice to say it was impressive.
The approach that these guys take makes the most sense to me: Granite Isolator | Home This would be a very simple DIY job if you have access to some offcuts from granite countertops.
Where did you get this malarkey? Because I've been a Quality Engineer for almost 30 years and I see precision instruments (i.e. sensitive to vibration) mounted on granite isolation tables all the time. I'm assuming that some pretty smart people seem to think it works. Are you versed in the properties of various materials?
Any suggestions for foam? Generic foam? EVA? I'm assuming some form of closed cell polyethylene. Certainly 2" layers are easy to find and I suppose I could stack two together to make 4" but if you can think of anything off the top of your head let me know. My turntable weighs 61 lbs and the chopping block probably adds a few more.
On the basis that it is cheap enough, buy a selection and see how much compression you get underneath your slab. You will probably not be able to measure the resonance frequency, because the mechanical losses in the foam will damp any resonance peak. Which is a good thing. Just measure the compression - one inch means 1Hz. But remember it goes as a square root. So half an inch will be 1.4Hz. Quarter inch will be 2Hz. All of which is pretty good - so don't get too hung up about the inch compression. Even a tenth inch give 3Hz - still a good result.
And then one must consider that "granite" covers a range of roughly similar rocks, containing different groupings of constituent minerals, in differing proportions, with differing crystalline structures and sizes. Let alone that some of the rock sold for kitchens and bathrooms as "granite" isn't granite at all (see also "marble").
Here is my experience as I recently went through the exercise of isolating my turntable . I have been avoiding commenting as these convos have a tendency to get derailed. But here goes.....I have a wood shop and made my own table out of ipe as it is the heaviest wood available locally. It is extremely high on the janka chart and will literally sink in water. I believe the table needs some mass to aid in minimizing any transference. I have readily available several types of foam and so added a type of closed cell foam on the underside a half inch thick. This actually helped but did not accomplish my goal as transference still occurred. The problem with most foams is that over time many will compress. The compression in itself is not an issue but because the turntable is heavier on one side the compression is not equal throwing the table out of level. The tire tube was the next step that worked perfectly as far as transference but did deflate over a long period of time. It had to be placed off center again due to the weight distribution of the turntable and may not be the most attractive. I then cut and laminated the tire tube rubber in to 4 squares, 2X3 inches by 0.5 inch thick, and placed under each corner of the ipe platform. This accomplished my task as far as transference and will not compress.
I did research on the net because I'm not versed in the properties of everything. Dense hard materials conduct vibrations more than soft less dense materials according to the articles I read. I'm not saying granite is not useful in the lab but for audio purposes there are better materials.
Well, maybe. I've used slate and granite under my turntables for a seriously long time (well over 20 years) and they've worked great. I'm gonna try the bamboo thing now to see what happens. Either way, it's just a turntable, so I'm not gonna get too wrapped around the axle about it. As long as it sounds good, and not skipping and feeding back when I crank the system, I'm ok with it.
Were these dense, hard materials of a uniform structure? Or were they of some variety of somewhat heterogeneous structures of different components having different properties, which granite has? The stuff is full of crystalline boundaries. ETA I have no strong views, horses in the race, axes to grind or whatever, I'm just curious that a group of materials, like granite, is being considered as some sort of uniform whole because of a couple of characteristics relative to some other materials.
That's one of my concerns about foam, the center of mass for my table is not really "centered" with respect to the dimensions. I'm wondering if I may need to get four pieces of differing density and arrange them to balance out the overall mass (tends to lean to the back if placed on springs...likely due to the PSU).
A simple example of dense materials transmitting vibrations more readily than less dense materials: Whale calls. Why can whale calls be heard over many many miles, a hundred or so from what I read, while no land based animal can be heard over the same distance, even the mighty roar of a lion or bellowing of an elephant? Because water is denser and transmits bass and other frequencies more readily. Different materials have different resonances depending on many factors. Look at speaker cabinets, even the over the top CNCd aluminum ones - it's just the Hz frequency they vibrate at that changes and by how much. Hey, use what you want to use as a base. I just thought I'd present a different view than using mass as an isolation device. My recently built bases using different materials than I used before are 'sounding' awesome with an increase in stage width and clarity. I'll post photos and materials used in a separate thread that may or may not appeal to you.
I bought 1" thick foam sheets at Michaels that have yet to sag after more than a year of use under my Kenwood KD 500 and under my Kenwood 750 which is even heavier. You'd be surprised at how strong foam can be when used under a decent sized base. I tried to compress it but couldn't.
Nice table! I think my load is going to be about 65 lbs so I'm going to look for some really firm stuff with a 4 inch thickness.
