Rule 5 - Vibration Control
Isolate or mitigate components from harmful vibrations
“Mechanically isolating all equipment is so important to getting the attack and decay correctly for every note.”
Max Townshend.
Maintaining the integrity of the signal flow
Vibrations can take any of several forms of electrical, mechanical, or acoustical elements or combinations thereof. All solid, liquid, or gaseous substance are to some degree elastic in nature that has inherent mechanical energies. Vibration is the source of all mechanical energy that propagates through a body, is stored in a body, and must therefore be recovered. Vibrations tend to transmit or absorb mechanical energy which depends entirely on their density and molecular composition. That means vibration that is inherent in a component or is introduced by an external stimulus will cause the host component to develop a resonant condition. All solid objects, particularly irregularly shaped ones, vibrate through subtle flexing and twisting forces having several natural resonant frequencies. The vibration will excite the objects' natural resonant frequency, even after removing the external stimulus.
Problem
Resonance will cause the host component to collect this energy and impose it along with the audio signal thereby increasing harmonic distortion and affecting the integrity of the signal by adding ‘their frequencies’. This is because all electronic components within a circuit are deemed microphonic, which means, they are susceptible to vibrations that will cause them to alter their electrical properties. The effects, subtle or otherwise may cause undesirable artifacts that may change the listening experience. Electronic components such as capacitors, wires, resistors, and transistors are affected in varying degrees by vibrations, however, the effects are worse on cartridges, loudspeakers, and electron vacuum tubes. The resonant character of the room including its accessories affects the housing of other audio components and thereby affects their internal circuitry creating an undesirable phenomenon called hysteresis which negatively influences the audio signal. Therefore, an audio system that is not suitably isolated and supported mechanically will compromise the integrity of its signal transfer due to vibration-induced distortion.
Sources of vibrations
Airborne - loudspeakers, fans, air conditioners, low-flying airplanes, door opening and closing, strong bass from neighbor’s home theatre systems and strong winds outside the building, etc. These are vibrations of an infrasonic nature that may not be heard (except by loudspeakers) but are nevertheless transmitted to your components through the floor, walls, and air. This may also explain why they say it’s better to have listening sessions at night because most human activities are already settled after work hours. Therefore, less traffic and ambient noise would not affect the listening experience as much.
Structure-borne – loudspeakers, washing machines, moving vehicles, trains, trucks, drilling or piling machines, etc., The intensity of airborne vibration is not as forceful as structure-borne vibration. Structure-borne vibrations from beneath the component are transmitted sympathetically through the floor, room boundaries, and equipment racks. The problem is compounded when audio components are placed near the source of vibration. The intensity of structure or floor-borne vibration in some cases can seriously color the music. It is pertinent to note that, the lower frequencies from 5Hz to around 100Hz are generated either by external influence or by the loudspeakers.
Internally induced vibrations - loudspeakers, turntables, CD players, digital transport and transformers, etc., other front-end components that require attention are motor-driven components such as turntables and CD players whose spinning disc and motor bearings create harmonic noise and vibrations that can be induced into other electronic components. Power transformers are also a source as the alteration of the magnetic field from their core laminations causes the individual laminations within the power transformer to vibrate. This is why toroidal transformer designs are preferred because they vibrate less. The cooling fans from audio components if used are also a cause of vibrations and noise. Cooling fans have no place in a high-end audio system. While audio components need to be isolated from vibrations, it is equally important to block vibration-producing audio components and affected bodies from radiating out and continuing to influence others.
Loudspeaker vibrations
The irony is that loudspeakers are a primary source of vibrations, they propagate vibrations as part of their design function enabling sound waves that render the music as we hear it. Therefore, loudspeakers are a major contributor to airborne vibrations and the main culprit for structure-borne vibrations. They become their own worst enemy because the surfaces where the loudspeakers are placed will vibrate and reinforce certain resonance frequencies more than others. They produce airborne vibrations by creating high-and low-pressure areas (standing waves) within the room through the mechanical action of the woofers. The larger the woofer the more air it pumps pressurizing the room and exciting other physical objects into motion. This may explain why most audiophiles prefer mini-monitor and bookshelf loudspeaker designs.
Loudspeaker drivers cause mechanical energy to be stored in the enclosure through their mounting frames. In addition, energy is also created through the periodic fluctuations in atmospheric pressure that they produce inside the enclosure. These two energy sources (one being reactive and the other airborne) will propagate swiftly through the entire enclosure at a high velocity. The periodic stress they produce during each cycle causes panel vibration that migrates outwards by sympathetic means (surface-borne). Vibrations may be delayed in time relative to the direct output of the drivers, therefore the audible resonance from the cabinet will be slightly out-of-phase with the direct sound. Additionally, the amplitude of the enclosures’ resonance may either add or subtract from the amplitude of the direct signal, thereby altering the frequency response. The strong vibrational energy created by the woofer can also cause enough cabinet movement to affect the delicate information produced by the tweeters.
To combat enclosure vibrations, serious high-end loudspeaker manufacturers design panel or open baffle loudspeaker designs, or use special cabinet materials, thickness, braces, and factory-damped designs to control resonances. Therefore, it is imperative to first position loudspeakers appropriately (See loudspeaker placement) to mitigate standing waves that are airborne. Secondly, to suitably treat the room with devices against structure-borne vibrations thereby absorbing much of the remaining vibration to mitigate the transfer of energy.
Resonance mitigation strategies
There are ways to deal with resonances; you either move the resonances outside the audible frequency range or attenuate them below the threshold of audibility. Suffice it to say that whatever methods are used, controlling vibration in the mid-band and upwards is generally much easier to achieve than the lower frequencies. The following are relevant strategies that may be used to mitigate vibrations:
Isolate all sensitive audio components (e.g., turntable, phono stage) away from the listening room (the hostile environment) to a safe environment (resonant-free).
Providing the necessary mechanical ‘conduits’ to transfer excess vibration quickly to the ground – Also known as Coupling Devices e.g., Spikes, Cones, Tip-Toes, etc.
Dissipate mechanical energy into heat by absorption with the aid of a compliant foreign body – Also known as De-coupling Devices e.g., Footers or Pucks utilizing rubber, viscoelastic polymers, elastomers, neoprene, etc., or using ‘bass trap’ acoustic treatment devices.
Change the object’s resonant frequency to a more desirable one by using purposed build control devices or by expedient means – Also known as Damping Devices e.g., Mass loading and resonant blocking materials.
Isolation
This is a prevention strategy of physically isolating components and should be your first consideration. You should try to avoid the problem first - prevention is better than cure. Locate all front-end audio components away, where practical to another room or an area blocked by a barrier wall or a bass trap leaving only the power amplifier(s) and loudspeakers behind. The isolation method is perhaps the best method to guard against airborne-induced vibrations. You would only need a long high-quality double-shield RCA interconnect or an XLR balanced interconnect (preferred) from the preamplifier to the power amplifier(s). If you can't afford the space, try to position them in a place within the listening room where there are nulls at most bass frequencies. Otherwise, move the said components farther away from the source of vibration to attenuate resonances. A practicable way in this instance is to use an SPL meter together with a test disc to locate the null (low-pressure) areas.
The following illustration provides a guide to the best isolation placement possible for your front-end audio components.
Coupling Devices
To efficiently evacuate vibration, the connection between various elements of the mechanical structure must have ideal properties. Vibration can be 'transmitted' from one material to another if some specific characteristics of the materials are not respected. Vibration can also be reflected and not transmitted depending on the surface and kind of material. Vibration can be easily transmitted from a `slow’ material (soft, with slow propagation speed) i.e., lower mass to a `fast’ material (hard, fast propagation speed) i.e., higher mass.
Coupling devices, therefore, use the technique of mechanical grounding which employs hard metals in the form of cones, spikes, or tiptoes between the equipment and the Ground. These devices are available in many shapes and sizes, albeit they are all tapered (sharp) at one end. They may be made from a variety of materials such as steel and aluminum. Some are made of special plastic composition, special woods, ceramic, solid copper, and graphite; still, others are a combination of metals. They are designed to provide a low impedance path to efficiently channel (drain) vibration energy to the ground. This way, there will be maximum energy transfer and quick dissipation while restricting ground vibrations from migrating to the object component because of its tiny contact area at the tip. Co-incidental resonance is also kept to a minimum.
Metallic cones are known to ‘ring' in tandem when subjected to severe vibration because of their inherent resonant frequency if they are not also suitably damped in their middle cavity. The “points” of these couplers must be hard and durable to avoid rounding with time, which could be detrimental to the proper evacuation, and blocking processes, and also prone to movement. Once installed they should not cause the component to rock or slide.
Ideally, all components should have only 3 points that would ideally define a plane to prevent rocking. Cones should be sited under the target components at or near the motors and transformers with the sharpest side (cones) pointing toward the ground (resonant surface). The heavier parts of a component usually benefit most from these support devices. Three points also contribute to mass loading by increasing the component's contact force (pressure) to the surface. With such pressure, resonance is greatly reduced as the components are more solidly linked to the surface.
Generally, the more levels of coupling the better. Double coning components i.e., place a set of cones under the component that sit on a platform and another set of cones under the platform that sits either on the ground or a component shelf. In this situation, offsetting the cones may be advised as they allow maximum interjection of the platform and add their benefits to the isolation system. That means you should ensure that both sets of cones are not directly under one another but are instead directly opposed. See illustration.
The use of coupling devices will depend entirely on the quality of the furniture or floor on which the equipment is finally rested. A special mention to Steve McCormack from 'The Mod Squad Inc' who was said to have invented the first tiptoe for audio use which made him a pioneer of coupling devices. Steve to the best of my knowledge, was perhaps the first to recognize the importance of vibration control in audio equipment many moons ago, but I stand corrected on this.
De-Coupling Devices
De-coupling devices are available in many shapes and forms such as pucks, discs, bases, pods, footers, etc. designed to decouple the components from their surface. These devices utilize elastic materials that trap resonances within their structure so that they will not travel back to their source or into another component. Materials such as Sorbothane, Butyl rubber, Neoprene, Delrin, Silicon, viscoelastic (long-chain) polymers, or elastomers are used to absorb mechanical energy from the surface and airborne vibrations by converting them into heat.
They act as shock absorbers by minimizing both internal and external vibrations, simultaneously de-coupling the components from the floor or surfaces. These devices are very effective in suppressing resonance and cleaning up high-frequency ringing. They are quite effective in isolating moderate amplitudes of vibration ranging from the upper bass region and above. The use of De-coupling devices will depend entirely on the quality of the furniture or floor on which the equipment is finally rested. As a rule, you would want to use it for soft, flimsy, footfall types of surfaces or structures. It is also highly recommended for bookshelf loudspeakers that sit on stands or heavy-duty ones for floor standers. The late Max Townshend from Townshend Audio strongly advocates that loudspeakers should be de-coupled from the floor based on his research.
Damping Devices
Foreign objects are commonly used as tweaks to dampen a component by increasing its mass (mass loading) or decreasing its stiffness to lower the components’ resonant frequency to as low as possible. It is a process of the time it takes the natural frequency of resonance to build up to maximum intensity (another frequency) and then decay to a minimum thereby altering or reducing the mechanical Q (amplitude of the system's resonant condition) of the component (and sidebands of that resonance). This method is effective to guard against airborne pressure. The disadvantage of mass is that when you get it excited, it tends to give off its energy slowly. The damping application makes use of aftermarket materials known for their good damping properties. These are strategically placed on top of the component chassis or parts, directly against it or inside the chassis to reduce resonances.
Manufacturers may use stone, crystal, wood (e.g., Shun Mook), marble, lead, or granite slabs that are placed usually on the bottom and sometimes on top of a component where practical to act as a damper because of its mass. Another manufacturer makes a “Brick” (e.g., VPI) said to consist of layers of high-grade laminated steel packed tightly in a compact wood case. The Brick is supposed to be used directly above transformers to soak up stray magnetic fields generated by transformers and attenuate transformer vibration. The added mass also lowers the components' resonant frequency.
Also available are damping self-stick sheets, squares, tiles, pads or mats, etc. They are practically applied to any side of a component chassis for additional damping. Recommended for use on loudspeakers and motor-driven components. Damping sheets are popular in the car audio industry.
Damping sheets are usually used inside loudspeaker cabinets and for the hardened tweakers outside cabinet panels to further damped resonances. Among other loudspeakers, damping tweaks are special woofer gaskets, terminal washers, flanged bass ports, and magnetic damping sheets. Some aftermarket metal tuning devices (fins) were sold to be affixed at the rear of loudspeakers to control resonances.
Wooden sand-filled bases and top mounts for loudspeakers may be customized to dissipate vibrations further. Aftermarket, sheets, pucks, or other tuning objects designed to be placed on top of components (or affixed against the bodies of the host component) are best applied by identifying the susceptible resonant points along the length and breadth of the chassis. Other than the manufacturer’s instructions, this area may be identified by physically tapping the body parts of the component with a hard metal object to hear the `thud’. A ‘hollow’ sound identifies the problem area. There may be more than one point on a piece of equipment. Another method is to use a tuning fork. It is easier to hear exactly those spots on a product, where there is a change of resonant frequency (maximum vibration). The higher the pitch the worse the area that should have priority treatment.
Isolation platforms
Isolation platforms may be used in conjunction with multi-tier component racks or as a stand-alone. They are usually made of special non-resonant composite materials for further isolation and damping. The materials may range from either; MDF (medium-density fiberboard), plywood, glass, aluminum, acrylic, carbon fiber (Kevlar), marble, granite, steel, lead, slate, or Corian. They will normally incorporate some form of damping footers, mechanical spikes, or cones. Some have unique designs to mitigate vibrations by using materials with honeycomb designs for added stiffness or constrain layer properties for multi-tier de-coupling.
Others feature a labyrinth-like hollow grid structure (air suspension) with a wooden frame and blocks in each corner to act as an acoustic filter to manage acoustic feedback and attenuate low frequencies. Some are designed as a clamp to clamp the top and bottom of a component for mass-loading effects, and some platforms are designed to be extremely lightweight for quick transmission and dissipation of unwanted vibration. Platforms are necessary for amplifiers placed on the thick carpet to provide enough ventilation on the underside. They are also recommended as additional support on the equipment rack for multi-tier isolation if there is enough room.
Component Racks
The furniture that the front-end audio components are usually placed on may comprise a metal structure, a wooden rack, and/or a combination of metal columns and wooden shelves. The racks usually have multi-tier support stations for audio components (see illustration below).
The individual support shelves should be large enough to hold isolation platforms, spike and cone components, and other audio peripherals. More layers of isolation are always better than less. Low-resonant furniture (well-damped) designs should be preferred to mitigate vibrations. Component racks should also incorporate coupling or de-coupling techniques with the surface they are rested on. Springy, footfall (reacting on footsteps) or poorly suspended floorboards are to be avoided for rigid metal stands that are mechanically coupled to the ground. The audio components on mechanically coupled racks should ideally be de-coupled with compliant footers instead of coupling them to the respective shelves.
The ideal rack should be rigid, sturdy, and heavy in mass, with good damping properties. It must be resistant to vibration, which means that there should be less mechanical energy propagating within. Complete wooden racks lack rigidity, and their mass, stores energies that are released later in an uncontrolled manner into the component they support. Racks should ideally be a welded one-piece construction (or glued in the case of wood) for maximum rigidity. The stacking types that make up multiple shelves are not ideal.
Ensure racks are firm and do not rock when installed. The racks should ideally be adjustable at the feet to level the respective shelves. Open-frame metal racks are preferred over enclosed cabinet types which attract vibration because of their larger structural area.
Turntable Stand
The turntable apart from other audio components is most sensitive to vibration because its cartridge is indeed a vibration sensor. The turntable will not know if the vibration is correlated but sends what it detects to the preamplifier. Besides coping with vibration created by its motor, a turntable must deal with structure and airborne energy propagated by loudspeakers. Though vibration is generally dealt with by the turntables’ suspension system, it is pertinent to note that the stand on which the turntable sits becomes part of its suspension system. Therefore, it can have as much effect on the sound as the actual turntable design especially turntables without good suspension designs.
Ideally, you should isolate turntables in an area other than the listening space (resonant field). Therefore, turntables would benefit most by placing them away from loudspeakers and other resonant areas. They should sit on a good-purpose build rack and on isolation platforms, coupling or de-coupling them from their support. A dedicated purpose-built turntable stand is perhaps the most important performance upgrade you can have for your turntable. The platform that your turntable sits on must be as solid and heavy as possible. The resonant point of the platform top should have the lowest resonant frequency possible. Thick granite slabs, carbon fiber, or equally heavy inert material are recommended. Stay away from wall-mount turntable stands.
Lightly sprung suspension turntables (low center of gravity) will benefit from a rigid and low-mass turntable stand (wood or equivalent). Light rigid stands will have a high resonant frequency that can be filtered out by the sprung suspension. These types of turntables should also be decoupled from their surfaces. Heavy mass turntables on the other hand will benefit most by placing them on massive stands (heavy-duty) and mechanically coupling (energy sank) them to the ground. The underlying principle remains that, increasing mass or decreasing stiffness lowers the resonant frequency of a structure.
Loudspeaker stands
The performance of any loudspeaker depends largely on the quality of its support. The support should provide a direct and unrestricted path for maximum energy transfer to the ground and at the same time restrict ground vibrations from migrating to the stands. This means loudspeakers must be rigidly attached to the stand (if used) and the stands must be attached rigidly to the floor by coupling or decoupling techniques. Since the loudspeaker cone has the least mass, it should naturally be the only one moving. All loudspeaker stands should be filled with sand, lead shots, or special fillers to dampen vibration and increase their mass and stability. Some stand manufacturers have theirs pre-filled. Once sited, the stands must not rock and should be leveled. The interface between the stand and loudspeaker, loudspeaker, and floor will influence the behavior of the loudspeaker’s cabinet walls. Therefore, the choice of the stand itself will have a major influence on cabinet vibration, an effect, independent of the interface. Generally, rigid wooden stands will relatively lower the bass efficiency of the loudspeaker. Ideally, a loudspeaker should be bolted onto the underside of the stand to become `one'. This service is sometimes provided by serious manufacturers or you could have them customized. Alternatively, it could be de-coupled by damping sheets or even Blu-Tack to minimize loudspeaker rocking. There is no substitute for a dedicated, high-mass, low-resonance rigid metal support stand.
Bookshelf loudspeakers have no business being on the bookshelf or against the wall in high-end audio. Generally, the top plate of the stand should be sufficiently thick and the same size as the loudspeaker’s base. More pillar columns are stronger than lesser columns. The base of the stand must be larger than the top plate. The cones or spikes on the base plate should be adjustable for leveling purposes. The columns should ideally be fully welded instead of spot-welded.
Floor-standing loudspeakers may be coupled with spikes or cones directly to the ground, to improve performance, especially in the area of bass. Therefore, it is recommended that adjustable spikes or cones be used on three points to improve mass loading and for easy leveling. The loudspeakers should never be seated on the floor directly without some form of coupling. On thick carpets, you must ensure that the sharp mechanical point has pierced the carpet through - 'mechanically grounded,' i.e., directly in contact with the floor thereby reducing the loudspeaker’s reactive motion.
Vibration control devices for turntables
Record Clamps
Record clamps will absorb vibrations (vinyl resonance) from records that will otherwise feedback to the stylus as it tracks the groove. Record clamps are available in many design applications. The most common is the weighted ones that simply drop onto the spindle and rely on their mass-loading properties. There is a ‘clamp-on’ or the ‘threaded shaft’ that would firmly press the record against the platter and act as a vibration bridge for energy to exit to the platter, thereby freeing the cartridge–record-interface of distortion that would otherwise enter and associate with the signal. The clamp materials may be made of steel, heavy-duty plastics, special wood, etc.
Turntable Mats
Turntable mats are said to eliminate residual ringing reflected by platters by shunting them away from the records. They provide an ideal record-to-platter coupling by supporting and filling the voids between the grooves of record surfaces. The record mats are designed to allow stylus-generated energy to be dissipated into tiny amounts of heat rather than deflected back into the cartridge. Some mat designs incorporate constrained layer damping (different materials layered together), or embedded spheres, holes, and stabilizing rings. Mat material may be available in cork, felt, rubber, metal, acrylic, or special composite wood fibers.
The vacuum suck-down platters
Vacuum-ready platters are ideal to transfer vibrations into the platter more efficiently. They offer the best record for platter coupling (impedance). They are also designed to stabilize your imperfect or warped records thereby keeping your stylus from ‘surfing’ distortion.
Tonearm damping
All tonearms’ tubes vibrate at the arm cartridge resonant frequency from the energy derived from the record groove. There are various applications designed to mitigate vibrations such as the use of a plastic or fabric (low mass) ribbon used as a wrap. It is applied under tension in a continuous spiral fashion around the arm tube to constrain damp vibration. The stored 'memory' of the wrap will seek to return to its original length and will therefore create a longitudinal tension that will constrain the arm tube with a radial force. Another uses a constrained damping ring applied on specific areas of the tonearm. Another technique that comes as a part of the tonearm assembly uses a viscous damping trough located at the rear of the tonearm and is coupled directly to them. The trough is usually filled with silicone gel provided by the manufacturer. You may vary the damping factor of the tonearm by a plunger attached to the tonearm assembly (SME V) when lowered into the trough. These damping methods are extremely effective to dissipate micro-vibrations migrating on the arm tube. Another manufacturer provides an after-market version that may apply to specific tonearms types.
CD players or Digital Transports
The CD player or transport is also affected by inherent vibration from its transformers, motorized transports, out-of-balance discs, and bearing and servo movements that control the laser mechanism. The disc mechanism already has a difficult task getting information out of the disc. What it doesn't need is additional vibration to render hysteresis. Even if the presence of vibration in a digital player is of the smallest magnitude, it can be easily magnified through electronic amplification. This will cause response errors in the audio signal path and a deterioration of the player's performance. The crystal oscillator found in CD mechanisms is especially sensitive to vibration-induced errors. It is said that even very low levels of vibration may cause a slight shift in the crystal oscillator, resulting in excess jitter.
Coupling and decoupling techniques or a combination thereof in conjunction with damping objects on top of the component’s chassis will provide considerable improvements. Multi-layer isolation using an isolation platform is highly recommended. I found that putting two cones; one directly under the transport drive motor assembly and the other under the transformer and a de-coupling foot at a suitable location for balance works well.
Cable Isolators
It is believed that suspending cables away from the ground would result in better sound integrity because floor-borne vibrations can affect the performance of cables in much the same way as it does with other electronic components. Acoustic or mechanical vibration is said to stress the cable's dielectric, which will vary in capacitance, hence creating variations in the output signal. Long interconnects are also known to exhibit longitudinal mechanical resonance in the audible range. By suspending cables off floor surfaces, cables would be better isolated from ground-borne vibration.
Cables should not come into contact with one another to minimize or eliminate interference (crosstalk) when the two magnetic fields collide. Therefore, cables should be kept separated from one another and de-coupled from the surface that they are resting on, hence the least surface contact on a cable the better the integrity of the signal. Cable isolators may be designed in plastic, wood, metal, rubber, or other special materials.
Tube dampers
Tubes by design are susceptible to microphonics which may affect the integrity of the signal transfer. Vibration may originate around the tube glass or may be picked up from the equipment chassis. They travel into the thermionic base of the tube, then into the pins. The vibrations are time-dispersed and result in augmenting or canceling the effect of resonance which unites in the tube itself. By dumping the glass and its base, some of these resonances are reduced and the grid-plate relationship is better maintained in a static condition. This way, the discharge of electrons is held constant relative to the position of the principal tube elements. This is a desirable condition when we consider that the operation of a tube is electrostatic.
Tube dampers are available in many designs and materials that are recommended especially for tubes used in the phono stages. Some are designed in rings using Sorbothane or from viscoelastic polymers to convert any physical motion into heat. Others are made from a weave of Kevlar and copper wire strands designed as a ‘sock’ that is said to further provide shielding from EMI / RF interferences as well as being a vibration-absorbing device. Some come in a form of a radial fin arrangement looking very much like heat sinks to reduce the tube operating temperature of the glass envelope, thus extending tube life besides dissipating vibration. Yet others attempt to reduce vibration by hydraulic means, using a combination of metallic materials to tune and control resonance.
A dozen recommended tips and tweaks
Coupling cones or spikes should be threaded into the component chassis or cabinet for best impedance coupling. Otherwise, they could be super-glued or affixed with strong adhesives. Do not use the thick foam type double-stick because they tend to `rock’. Cones should never be placed on the underside of anything without being properly fastened or secured.
For vacuum tubes, use 2 rings; one on the upper 3/4 area and the other at the 1/3 area near the base for maximum effect.
You can dampen the resonance of your tonearm by using industrial rubber ‘O' rings (thicker version) that are slightly smaller in diameter and placed along the length of the tonearm. Fit onto 2 or 3 strategic positions (just after the head-shell, center arm, and the end before the pivot assembly).
The protective disc widely sold for the sharp points on spikes or cones to prevent floor scratching should be avoided as they will render the loudspeaker unstable during operation especially on carpets severely affecting imaging. The sharp point should contact to Ground (floor) to achieve a firm grip.
Coupling a bookshelf or mini-monitor loudspeakers with cones or spikes on top of its stand is not recommended instead, de-coupled them with good elastomers because of their lightweight. Only the bottom of the stand should be coupled with spikes.
All metal racks/stands have a natural resonance point that tends to `ring’ when excited by vibration. The hollow member structures should be filled with sand or lead shots #8 or #9 (ball bearings) to minimize ringing. A mixture of sand (60%) and lead shot (40%) is also said to provide excellent results. The filling will also increase its mass for maximum stability. Otherwise, fine sand or iron filings would suffice for the columns.
A three-column stand is better than a four-column stand for easy stabilization (leveling) and provides for a higher mass loading effect. Keep racks as short as possible to maximize their rigidity.
Sandboxes or pods may be used below or on top of components, especially loudspeakers where structural vibration is converted into heat by the sand bed. Airborne vibration is also absorbed by the sand bed, reducing its net effect. Vibration generated internally will also likewise be channeled to the sand bed and be dissipated as heat.
As a rule, mechanical coupling is recommended for hard rigid floor surfaces, and equipment that is sufficiently heavy such as amplifiers should be on cones and metal stands on spikes.
Sensitive components, such as turntables, CD players/transports, and tube equipment benefit most from platforms with added isolation properties.
Commercially available ‘Blu-Tack’ is a plaster-like putty that may be considered as an interface between cones and components or loudspeaker and stand. This will stop the component from moving and offers some measure of damping.
A cheap way of isolating cables off the floor is to use old school blackboard duster; the felt part on the floor and use blue tack on the wood top to hold the cables in place. Another tweak is to use solid rubber or foam balls and cut a slit just to snugly accommodate the cables.
Conclusion
The high-end audio industry had explored the effects of vibrations over the years and has incorporated medical and aerospace materials in their designs. They have also applied scientific and other ‘mystifying’ techniques to address the problem of vibrations. Nevertheless, there are sonic improvements when a component or an entire system is suitably protected from vibrations as the integrity of low-level signals is not compromised by hysteresis. Most people will perceive a slight rise in resolution, hence an increase in clarity. You will probably hear less high-frequency 'ring' or bass hangover. This I believe will clean up the midrange. I also feel a distinctive improvement would be a smooth frequency response, and an overall improvement in the area of dynamics, especially micro dynamics. The soundstage and imaging would also improve when phase and time are kept in relative check due to the reduction in resonances. High-end manufacturers will usually go to extremes in building and designing products to perform so and recording engineers will go to considerable lengths to help you enjoy every detail of the performance. You don't want to corrupt any element in the audio chain and lose the benefit of enjoying the full potential of a given recording.