Ingress Audio Engineering

When granite or bluestone or whatever is placed on springs it’s isolated right along with the component. Also, when the slabs are two or three inches thick they will not ring unless you strike them with a hammer. Even then they go thunk!  Also, don’t strike them with a hammer whilst music is playing. The great advantages of such materials is their stiffness and mass.

Slate actually appears to have much in common with bluestone. To whit,

Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Wikipedia

bdp245,265 posts05-21-2019 2:07amDamn, 3" thick?! What's one weigh?

>>>>A lot.

I used to buy bluestone 18”x18”x3” slabs at Home Depot for around $20 each. Dunno about availability in other locations. 

Everything you never wanted to know about bluestone, 

Bluestone is quarried in western New Jersey, Pennsylvania and eastern New York.[15] It is also quarried in the Canadian Appalachians near Deer Lake in Western Newfoundland.[16]The Pennsylvania Bluestone Association has 105 members, the vast majority of them quarriers.[17] Bluestone from Pennsylvania and New York is sandstone defined as feldspathicgreywacke. The sand-sized grains from which bluestone is constituted were deposited in the Catskill Delta during the Middle to Upper Devonian Period of the Paleozoic Era, approximately 370 to 345 million years ago. The Catskill Delta was created from runoff from the Acadian Mountains ("Ancestral Appalachians").[18] This delta ran in a narrow band from southwest to northeast and today provides the bluestone quarried from the Catskill Mountains and Northeast Pennsylvania. The term "bluestone" is derived from a deep-blue-colored sandstone first found in Ulster County, New York.[citation needed] It can, however, appear in many other hues, mostly shades of grays and browns. Bluestone quarrying is of particular value to the economy of Susquehanna County, Pennsylvania. The Starrucca Viaduct, finished in 1848, is an example of Pennsylvania bluestone as a building material.[17]

Starrucca Viaduct, Pennsylvania, U.S.

The other, lesser known, type of American 'bluestone' is a blue-tinted limestone abundant in the Shenandoah Valley of Virginia. It is a limestone formed during the Ordovician Period approximately 450 to 500 million years ago, at the bottom of a relatively shallow ocean that covered what is today Rockingham County, Virginia. The limestone that accumulated there was darker in color than most other limestone deposits because it was in deeper waters exposed to less light. The darker blue color resulted in limestone from this region being dubbed bluestone and with two sequences measuring about 10,000 ft thick, it gives the area one of the largest limestone deposits in the world.[19] The stone eventually fades from a deep blue to a light grey after prolonged exposure to sun and rain. Given the abundance of the stone in the Rockingham County area, the first settlers used it as foundations and chimneys for their houses. When James Madison University was built, the local bluestone was used to construct the buildings because of its high quality and cultural heritage.[20]

It’s easier to get better “action” for the set-up with four springs, all things being equal. By “action” I mean how easy it is to put the top plate and component into smooth vertical up and down motion by bouncing the top plate manually. For moderately light components I would preload the springs with granite or bluestone. My Cryo Baby Prometheans are rated at around 40-50 lb for four springs. Add a spring for every ten pounds over 50 lb. My Super Stiff Springs are rated at around 80-120 lb for four springs.

My springs are designed to achieve better performance (circa 2-3 Hz) than almost any pneumatic device. And there is no leakage issue, no guessing at the air pressure, and no friction or damping issues, either, with my springs as there are with pneumatic designs. When you think about it it’s kind of a no brainer. 😳

Uneven loads are handled by moving one or more spring slightly so the load is equally distributed among the springs. 

My springs are more cost effective than the pods. Besides, I don’t advertise or recommend my springs for speakers, anyway, except medium-size speakers and subwoofers (low center of gravity). My springs are primarily for amps, turntables, CD players and subwoofers. I suspect most of the cost of the Townshend pods is the attached framework that allows the pods to be widely spaced underneath speakers with a high center of gravity,

Even when speakers ARE isolated, front end components are still subject to low frequency vibration from the floor. My springs allow someone to *cost effectively* isolate everything -except big tall heavy speakers. Actually, a large 2’x2’ maple board under the speakers will solve the problem using my springs for speakers with a high center of gravity. The 2’x2’ board allows a wide pattern for my springs, thus building up the lateral support needed for stability. Problem solved!

If I told you they wouldn’t be secrets, would they?

I wouldn’t be quite so loose with how to employ my springs, no offense.

Somebody hasn’t been paying very close attention. I’ve already shared the secrets for the springs I use. Wake up and smell the coffee! ☕️

I would imagine damping would be more appropriate as well as less expensive for dipoles since speaker isolation is primarily used to prevent mechanical feedback. And dipoles don’t transmit much energy directly to the floor. It would probably be much more cost effective to isolate the front end.

bdp24
The V.2 plus a set of Geoff’s springs would make a great budget isolation system. @geoffkait, how do you recommend your springs be partnered with roller bearings? I may just use my Symposium Jr’s, double cup style, therefore not having to be concerned about the LFT’s rolling off the bearings!

My “budget” springs having been outperforming high priced isolation systems for more than 20 years, and have been used in some of the most outstanding systems at CES including Mapleshade, the big Tenor Rockport system and two John Curl Bob Crump systems. My springs have gotten less expensive over the years as I learned how to simplify and evolve the design. Anybody can over-engineer spring-based isolation system. It’s not rocket science. 🚀 My springs have isolated Verdier turntables, 200 lb Flagship Classe amps, $30K high power BSW Consulting tube amps, Lamm tube amps, great big VPI turntables, Raven turntables, and many other high end systems. By going to a smaller high-performance spring I could dispense with everything else - the two plates, the dampers -and use only the spring. Make sense? Wasn’t it Einstein who said a thing should be made as simple as possible?

redlenses0
@geoffkait
am aware of the challenges of inner tube in both setup and performance as you eluded to - has to be just right and thus my reference to trying wave springs etc..just not sure what and where to get them yet, ideas?

>>>>I design high carbon heat tempered, cryo’d compression springs for moderate loads 25 to 70 lb and Super Stiff Springs for heavy loads, 75-200 lb. Both types of springs are suitable for placing directly under a component. Performance circa 2-3 Hz.

geoff kait
machina dynamica
vibration isolation and resonance control

bdp24
redlenses03, if you want pneumatic isolation, and don’t mind spending a little money and time, you can keep your eyes open for the old Townshend Audio Seismic Sink platforms that were made in the 90’s-00’s. There were a few different versions, but they all shared the same basic design: an inner tube inside a top and bottom steel plate structure. The inner tube is inflated just enough to keep the top and bottom plates from touching; the lower the P.S.I., the lower the resonant frequency and the greater the isolation. A set of roller bearing on top of a Seismic Sink provides isolation is all planes.

>>>>>Actually there is what we call a design pressure for pneumatic iso stands, as it turns out the *ideal pressure psi* is not (rpt not) the minimum pressure psi, but something in between very low pressure and very high pressure. Otherwise the inner tube is too floppy and won’t act like a spring. You have to hunt for the ideal psi by ear. On my original single airspring Nimbus sub Hertz platform with 0.5 Hz performance the ideal pressure was around 30 psi for a load of 30 lb. For higher loads, the ideal pressure would go up, 🔝depends on the load. Also, inner tubes can’t provide effective isolation in the horizontal plane 🔛 or in any of the rotational directions. 🚁 since the inner tube is quite stiff in those directions. 

Inner tubes also have too much internal friction/damping for my taste and there’s the leaking problem as well.

It’s probably not that obvious but worth pointing out since inner tubes were just mentioned. The smoother and harder the surfaces are made for the roller bearing assemblies the more critical balance and level become, even if cups are used top and bottom, as I pointed out a couple posts down. Therefore, I humbly submit inner tubes are not (rpt not) a good choice for vertical isolation with roller bearings, or even used alone. Steel springs like you know who’s are a much better choice, not only because of the leakage issue but because inner tubes have a very non-ideal geometry for pneumatic isolation - the ideal geometry being tall and slender. I.e., large volume of air v per surface area in2. As I also just got through mentioning, there is some degree of vertical isolation with ONLY roller bearings and cups. Which reminds me, the reason some components can be mounted directly on bearings with no cups is probably because the hard roller bearings make slight depressions in the metal of the chassis base.

The physics of roller bearings, pt 2.

If the base of the roller bearing assembly is flat there can be only rotational isolation in the twist direction. 🕺🏻 Plus isolation in the horizontal x-z plane. You lose the isolation in the roll and rock directions. It is the rotational seismic forces that try to rotate the building and everything inside. If the base is concave the component is isolated in those two rotational directions. The smoother and harder the surfaces of the bass and base the easier the component will move when acted on by any external forces. Which means the whole roller bearing set up can easily get “stuck” when the balls roll to the edge of the base if the set up is not perfectly level and balanced. That condition limits the iso device’s isolation, since it cannot move further in that direction. Isolation effectiveness in a given direction is proportional to how easily the component can move in that direction.

Another advantage of a concave surface for the base is that when the component rotates slightly due to rotational forces, there is some degree of vertical isolation since the component moves up and down vertically 🔝 as it rocks and rolls, no? Up and down as it rotates around its centerline axis. Recall wave passing under boat analogy.

You can buy miniature 2” shallow ceramic bowls on line that might work very well and a glass marble of the appropriate size, one bowl on top and one on the bottom. Total cost for set of three roller bearing assemblies $30.

glupson

"Pop quiz

Can anyone think of a reason roller bearings might not be a good idea under a turntable?"

It would roll of the shelf.

>>>>>>>There’s one in every crowd.

Pop quiz

Can anyone think of a reason roller bearings might not be a good idea under a turntable?

The physics of roller bearings, pt. 1

The reason vibration isolation is important is that low frequency vibration and forces related to that vibration affects the audio signal, including but not limited to the wiring in the wall, the wall outlets, the wall plates and the wall itself, wire in cables and power cords, internal wiring and electronic elements in the components and speakers. The audio signal itself is not (rpt not) a vibration per se or at least it SHOULD NOT BE but is affected by forces F of external vibration. Like magnetic field lines on a magnet are affected by rapidly moving the magnet manually.

The entire building is subjected to continuous seismic waves that are produced by many things including Earth crust motion, wave action on shore lines, trucks, buses, subways, cars, construction, footfall, wind. The entire building is forced to move in many directions. Seismic waves have six directions of motion, including three rotational directions. The horizontal plane x-z represents the other two directions 🔛, vertical y is the sixth direction 🔝. The three rotational directions are around the x, y and z axes. 

The analogy to seismic waves and its influence on a building and everything inside the building is a boat ⛵️on the ocean when a waves in one direction passes under it. The boat moves vertically, sideways and also rotates back and forth as the wave passes under it. Waves in other directions affect the boat similarly but the boat moves in different directions according to the direction of the other waves. In order to reduce or eliminate forces F that seismic waves produce on the audio signal the entire audio system should be isolated, decoupled from the building. An object will remain at rest unless acted on by an external force. I’m disregarding acoustic waves in the room for this part of the explanation.

Roller bearings are interesting because they are capable of isolating the component in several directions of motion, low in cost, depending on how the roller bearings are designed. The most simple design is a cup with a flat bottom that has small diameter base so the ball can not move very far. Three of these roller bearing assemblies will provide good isolation in the horizontal plane and in the twist rotational direction around the vertical y axis. If the cup is concave the component can be isolated against forces in the other two rotational directions. The roller bearings are not effective in the vertical direction, well, perhaps a bit, never say never. The vertical direction can be easily handled by springs, very effective in the vertical.

Materials for the cup and bearing should be chosen with the goal of keeping friction very low, I.e., smooth very hard surfaces.

There are many ways to skin a cat. I use those heavy one inch high glass candle holders for the base and either Super Balls or some appropriately sized ball made of glass, maybe a glass marble, or other very hard material for the balls. Super Balls are 1” diameter type sold in bubble gum machines. I Even if the surface of the base is not concave roller bearings will work for the horizontal plane. Hardness and smoothness of surfaces, I.e. low friction, are the critical factors. The best isolation is when there is great ease of motion. By the way cryo’d, heat tempered high-carbon steel is much harder than the best aluminum. Like my springs.