DIY audiophile rack

[suri]

Hi Suri,

I love the idea of a suspended rack. And I must say it's very very finely crafted. However this is the first time I'm seeing springs on a rack. Any particular reason why you opted for this instead of damping the two shelves with something like cork or bitumen?

Also, do you like the difference in sound produced by the granite? Do let me know!

hi SHAHRUKH,
i am caught up with the idea that - more than isolating electronics and transport mechanisms from incident energy and resonant vibrations (which is, of course, important), the audio rack must be able to dissipate incident airborne vibrations and energy (especially if the electronic components and transport are in the same room as the loudspeakers) as quickly and as effectively as possible.
the inertia of the granite mass coupled with the ability of steel springs under tension to dissipate energy as heat, was what led me to this method of construction
Certainly, the sound is better than when the equipment is placed on the usual wooden racks which i used earlier, and that is evident even to the casual listener
cheers suri

 

[Shahrukh]

Interesting. I wonder if metallic springs will ring at higher frequencies. Do take a close-up shot of the actual spring assembly between the shelves if possible.

 

[gobble]

Hi Suri

Granite has some interesting acoustical properties. Apparently it is a quartz bearing rock with reverberation enhancing qualities.

THE SINGING PYRAMID - Gardiner's World

Pyramid of Secrets: The Architecture ... - Google Book Search

The Hindu : Karnataka / Bangalore News : The keyboards of antiquity?

Did you factor it in when choosing granite as a medium or did you go for its weight?

In the case of your rack, I think the choice of granite will induce even more vibrations than usual making the spring loading absolutely essential. So maybe choosing another heavy material might result in more benefits with the the same design implemented?

PS: How do you judge the reactivity of springs to mild "invisible" vibrations? Is there an engineering measurement like tensile strength that can be used for judgment?

Regards

 

[suri]

Hi gobble,
massively interesting article - singing pyramid!
No absolutely, i had no idea
i used granite entirely on the premise that granite is very dense and heavy and does not resonate easily - but perhaps people talk of it like that because it resonates at lower frequencies and not so much at higher frequencies?
All along, in all of the articles in the audio world, and specifically in articles about vibration damping and isolation of audio components, I was led to believe that granite possessed sterling qualities, and I have seen many of the more expensive isolation platforms are made of granite!
This is certainly an eye-opener and I have to research this in depth
will keep you posted about what i discover

 

[suri]

Hi gobbel,
found this- essentially says what you say-

Optical Tables : FormelTM Granite-Honeycomb Structures Technology

FormelTM Granite-Honeycomb Structures Technology





* Combines the vibration control performance of honeycomb construction with the flatness of granite
* Air-bearing compatible
* 50% to 70% lighter than solid granite blocks
* Custom sizes, shapes and mounting holes available

FormelTM Granite-Honeycomb Structures combine the vibration control performance and light weight of steel-core honeycomb construction with the unparalleled flatness of granite. The result is the finest table tops and breadboards ever offered. The granite work surface maintains flatness over the entire tapped working surface within 15 microns over one square meter.Formel structures can be fabricated with or without tuned damping.

Standard construction is without mounting holes. Sealed mounting holes on 1 inch or 2 inch centers are available, in addition to metric and custom hole patterns. Class 100 cleanroom-compatible Formel structures are also available.

Granite-honeycomb hybrids also offer the following advantages over solid granite structures:

*

Higher dynamic rigidity

Because granite-honeycomb hybrid structures are much stiffer and 50% to 70% lighter than solid granite blocks, they offer much higher dynamic rigidity for unsurpassed performance in applications requiring immunity from vibrations.
*

Tuned damping eliminates "ringing"

Solid granite is particularly notorious for its "ringing." This structural vibration reduces the accuracy of precision measurement and positioning systems. Damped Formel structures include multiple tuned dampers, each individually tuned by a skilled engineer to minimize motion at resonance modes.
*

Less chance of "hot spot" formation

The lower thermal inertia and higher thermal conductivity of Formel structures aids in preventing formation of "hot spots" on the work surface which can degrade the performance of instruments in applications that are sensitive to thermal variation.
*

Reduced weight

Because a Formel structure weighs 50% to 70% less than a solid granite block of the same size, you benefit from reduced shipping costs, easier installation, less demanding floor construction requirements, and more convenient transportation.
*

Easy customization

Formel structures can be easily fabricated in almost any shape for special or OEM applications. Some commonly requested custom capabilities include special thicknesses, mounting hole patterns, honeycomb core materials, special flatness specifications, and tight hole-to-hole tolerances.

To learn more about how a Formel structure can solve your vibration control problem, contact your local Newport representative.



FormelTM Structure with Tuned Damping (Left), Solid Granite (Right)

 

[gobble]

Kewl. Maybe now you can tune each granite slab in your rack to resonate at different frequencies to create a more "musical" setup

Cheers

 

[suri]

No gobble,
I think I better use the rack to store my cds and vinyl and books! and build a better rack without "ringing" granite!

 

[suri]

Hi shahrukh and gobble,
i am going to try an experiment - (one of these (late) nights when there is no highway traffic and ambient noise, )
place a container of water on each of the granite shelves and fix a cupola with contained water to each of the springs.
with bright light falling on water and close up lens focussed on the water surface, and music played at loud volume, I should be able to see disturbance of the water surface if the granite is resonating and cannot dissipate energy, and also should be able to see if the steel springs "ring".
I will repeat the experiment in the daytime with all the ambient noises and without the music playing.
I will take a close up shot of the springs between the shelves and post it tonight
Will keep you posted about results

 

[Shahrukh]

Try your experiment. Also, while you're at it, you could try damping your two granite slabs with a sheet of cork. It should help matters a lot.

Lovely articles Gobble.

 

[suri]

Try your experiment. Also, while you're at it, you could try damping your two granite slabs with a sheet of cork. It should help matters a lot.

Lovely articles Gobble.

shahrukh, where does the cork go? same size as the granite slab?

 

[suri]

gobble,
on a contrary note i found this

To simplify: black granite comprises three primary minerals, each with differing crystalline and therefore resonance characteristics. Resonance does not transfer readily between respective mineral structures and, happily, the three minerals are randomly oriented within granite. This makes it comparatively inert and therefore a good isolator.

 

[gobble]

Hi shahrukh and gobble,
i am going to try an experiment - (one of these (late) nights when there is no highway traffic and ambient noise, )
place a container of water on each of the granite shelves and fix a cupola with contained water to each of the springs.
with bright light falling on water and close up lens focussed on the water surface, and music played at loud volume, I should be able to see disturbance of the water surface if the granite is resonating and cannot dissipate energy, and also should be able to see if the steel springs "ring".
I will repeat the experiment in the daytime with all the ambient noises and without the music playing.
I will take a close up shot of the springs between the shelves and post it tonight
Will keep you posted about results

Great!! But you need to do the experiment with springs and without springs to understand how much difference the spring loading makes. Do you have an extra slab not attached to the rack? Checking with a good quality stethoscope might also be interesting.

Regards

 

[gobble]

Try your experiment. Also, while you're at it, you could try damping your two granite slabs with a sheet of cork. It should help matters a lot.

Lovely articles Gobble.

Hmm since it is the internal crystalline structures at the molecular level that resonate, I dunno how much an external piece of cork stuck to the surface will help as the granite may not vibrate visibly.

But I'm not an engineer, so I may be wrong.

Just my chaar-annas.

Cheers

 

[gobble]

gobble,
on a contrary note i found this

To simplify: black granite comprises three primary minerals, each with differing crystalline and therefore resonance characteristics. Resonance does not transfer readily between respective mineral structures and, happily, the three minerals are randomly oriented within granite. This makes it comparatively inert and therefore a good isolator.

Hmm ... then the pillars at Hampi would not play musical notes or the Pyramid would not sing

Maybe its only black granite that has these properties?

Regards

 

[gobble]

Hmm since it is the internal crystalline structures at the molecular level that resonate, I dunno how much an external piece of cork stuck to the surface will help as the granite may not vibrate visibly.

But I'm not an engineer, so I may be wrong.

Just my chaar-annas.

Cheers

Ah you mean the cork will absorb and attenuate low frequencies 125/250hz before they hit the granite. I suppose that might work.

Cheers

 

[Shahrukh]

Try the cork on top of the granite or sandwich the sheet of cork between two slabs. Listen and compare.

 

[suri]

Great!! But you need to do the experiment with springs and without springs to understand how much difference the spring loading makes. Do you have an extra slab not attached to the rack? Checking with a good quality stethoscope might also be interesting.

Regards

gobble,
I do know one thing for sure - Granite slabs should not be used just as slabs on which audio components are placed. The slabs will couple readily to the surface on which they are placed and transmit all sorts of vibrations and resonances directly to the audio component. granite slabs should be coupled to something that can "Jiggle" - a ready example would be lead shot or sand or sorbothane (never seen this myself). - this allows the incident energy to be dissipated as heat and therefore damping is achieved.
so, if at all the rack is to work to it's intended purpose, it will have to be with springs.
just placing the granite slabs on stoppers inside the wooden frame would not serve the purpose
Use of steth is a good idea, will try

 

[gobble]

gobble,
I do know one thing for sure - Granite slabs should not be used just as slabs on which audio components are placed. The slabs will couple readily to the surface on which they are placed and transmit all sorts of vibrations and resonances directly to the audio component. granite slabs should be coupled to something that can "Jiggle" - a ready example would be lead shot or sand or sorbothane (never seen this myself). - this allows the incident energy to be dissipated as heat and therefore damping is achieved.
so, if at all the rack is to work to it's intended purpose, it will have to be with springs.
just placing the granite slabs on stoppers inside the wooden frame would not serve the purpose
Use of steth is a good idea, will try

Yeah the idea was to estimate how much difference the springs really make. Good luck with your experiments, awaiting the results.

Cheers

 

[suri]

HI SHAHRUKH AND GOBBLE,
I HAVE DRAWN A DIAGRAM OF THE CONSTRUCTION
HAVE A LOOK AND TELL ME WHAT YOU THINK
in the diagram blue is granite, coils are springs, brown is wood.
the wooden legs of the rack are not represented
only the granite and spring are shown
the three lower shelves are suspended from the uppermost composite shelf
the springs between the granite slabs (top and bottom) are 3/4 inch compression springs
and the long ones are elongating springs

 

[smedhavi]

I use Isonodes and Vibrapods for my equipment. I have a feeling that cork would also work to some extent.
-------------

I would be concerned about the stability of the above spring design. It would swing too much and topple the equipment at the top. The shelf hanging via springs from a stable frame would be better. I think you are going a bit too far with the springs, the shelf platforms in the rack should be allowed to move just a bit and not really swing. Check out the kind of movement allowed in spring loaded treadmills.

Thanks,
Sharad