Spikes versus wall coupling

Hi Newbee,

You are quite correct. Coupling one of the main sources of vibration (the speaker) to the floor will allow that unwanted energy to travel towards the components. If they are also coupled to the floor (by rigid points, rigid spikes, a slab of rigid stone or rigid wood) the vibration will travel up into the bottom of the component. Any rigid device allows vibration to travel in BOTH directions - down out of the component AND up into the component.

In the case of speakers, if you rigidly couple them to the floor they will also be subjected to external sources of displacement (vibration) such as exterior traffic (trucks, autos, busses, airplanes, trains, freeways) and natural geological seismic activity. That will negatively affect their performance.

Best Regards,

Barry Kohan

I am a manufacturer of vibration control products.

Hi All,

Even though there may be asymmetrical mechanical impedence between the point interface and the opposite interface of the spike there is still significant mechanical transfer occurring in BOTH directions. This pathway does not provide isolation. It allows vibration to flow up the rigid point or spike into the component that is placed on top of it. This problem is quite significant when components are placed on a rigid mounting but is still an important issue when speakers are placed on a rigid point.

Points have been a relatively popular method of mounting a speaker. Is it the best method for mounting a speaker? No. It does provide sonic improvements as compared to having a speaker sitting directly on carpet because the carpet does not support the cabinet effectively and allows it to deflect in reaction to the drivers’ movements. This creates Doppler shift as well as allowing some of the drivers’ energy to be diverted from the main task of making sound to making the cabinet move. A speaker resting directly on a hard floor does not usually sit as flat as we assume it will. Both the floor and the bottom of the speaker cabinet are not truly flat and “chatter” between the two does occur. Again, wasted energy. Placing three points under the cabinet does help the speaker become much more rigid and that is the main reason for their relative popularity. Three points does define a plane and that will naturally make the mounting more stable than without the points in place. Unfortunately, the spikes are not nearly as effective as other methods of transferring vibration out of the cabinet and they also do not support the rear two corners of the cabinet which allows them to be much more susceptible to internal resonance. The rigid mounting for the speaker also allows external sources of vibration to enter into the cabinet from the floor which causes a different source of Doppler shift contamination. This vibration is not sourced from the speaker and therefore has no relation to the music signal in the recording – it is exhibited as a general displacement of the speaker cabinet which lowers the overall dynamic range and interferes with pace and rhythm.

The fact that the support and interface we place under a speaker perceptively changes the sound clearly illustrates the insidious nature of vibration as it relates to an audio system. Almost every aspect of sound reproduction - tonality, spatiality, dynamics, coherence, etc. - is compromised by unwanted vibrational energy. That is the result of a disturbance in the relationship between frequency, amplitude and phase of the original signal that the audio system is reproducing.

As the speaker drivers are radiating acoustic energy into the room (the energy that we want - music) they are also sending energy into the speaker cabinet because of air pressure from the inward motion of the cone and by conducted energy through the frame and mounting flange which becomes unwanted stored energy (USE). This USE causes the cabinet walls, the crossover components, the connected speaker cable, etc. to vibrate (the drivers are also subject to compromise by their own vibrational energy that they've sent into the cabinet that is then reflected back towards them after a delay in time). The cabinet vibration has the most consequence towards corrupting the speaker's performance. If we were able to quiet the driver's acoustic output into the room and just hear the result of the cabinet walls vibrating I think we would be shocked as to just how much audible acoustic energy the cabinet would be radiating! THIS version of the audio signal would have a different frequency balance than the driver's output (it would sound muffled being dominated by the primary and secondary resonance frequencies of the cabinet) it would be lower in amplitude (but not uniformly lower because of the non-linear nature of the cabinet materials) and would be delayed in time (the amount of time it would take for the energy to leave the drivers, be absorbed by the cabinet and then be released into the air) thus affecting phase integrity. If we think about this 'smeared' version of the signal (which contains corrupted frequency, amplitude and phase) being mixed back into the original signal it is no wonder that USE significantly affects the reproduction and that altering the USE has an audible effect!

Now, just imagine if we make a significant reduction of USE in the speaker cabinet. The amount of audible difference would be profound. Placing high mass on top of the speaker cabinet will significantly increase the resonance frequency (a good thing) and decrease the amplitude (also a good thing) of the top panel. The weight load will then be translated onto the side panels with a related change in their resonance frequencies. Furthermore, the added mass will more effectively couple the speaker bottom to the top plate of the speaker support, the floor or more suitably to a high-mass high-absorption platform so the USE can be drained from the speaker cabinet.

If we used laser infrarometry to measure the displacement of the speaker panel we would see a noticeable reduction in displacement (vibration) when high mass is set on top. In addition, if a high-mass high-absorption platform is placed under the speaker, this multi-stage vibration control system forces the speaker to be more effective in its main task of reproducing music - the drivers do not waste their energy in making the cabinet or internal parts vibrate because the cabinet is far more resistant to displacement. The drivers have no choice but to use their energy more efficiently in creating music.

The most effective method for supporting a speaker would be a high mass element on top of the cabinet, a high-mass high-absorption platform directly under the speaker (on top of a rigid and strong stand for a mini-monitor) and a pneumatic base on the floor to decouple the speaker's energy from entering the floor and being transmitted to the equipment rack (the pneumatic mount must be designed in the correct manner so that it does support the speaker without allowing Doppler shift to occur). This configuration is highly successful in eliciting the peak performance from the speaker without a redesign of the cabinet or the component parts.

The other components in an audio system will also benefit by a reduction of USE in their chassis. Besides speakers, turntables exhibit the largest degree of improvement by proper vibration control. Since they are electro-mechanical devices it is almost intuitive to us that this be so but the purely electronic devices also benefit: tubes are microphonic, the master and sub-clocks (which are based on oscillating crystals) in digital devices are affected, a spinning disc inside a digital player will exhibit non-linear movement, all component parts (transistors, ICs, capacitors, resistors, wire, diodes, etc.) that process the signal become microphonic, motors, fans and buzzing transformers induce vibration into surrounding parts, and the list goes on.

What are the sonic results of vibration contamination? As we discussed, frequency, amplitude and phase are corrupted. Frequency balance is skewed: one portion of the spectrum is highlighted or diminished as compared with another. Brightness may increase, midrange may become too forward, and bass may bloat and become ill defined. Amplitude of the signal is changed: the dynamic range of an instrument and indeed the dynamic relationships between the instruments are altered. Phase integrity of the signal is deteriorated: the spatial relationship of the instrument with its environment and the spatial relationships between the instruments are altered. In fact, frequency, amplitude and phase are interrelated and changing any one affects the other two. If all three are affected at the same time (by the presence of unwanted vibration) the resulting cacophony significantly reduces the ability of the system to convey what is actually contained in the recording - and that's what audio is all about. Not just what sounds pleasing because it makes someone feel fuzzy all over but what is musically and emotionally fulfilling because it reflects the actual sound of the instruments as they have been captured in the recording.

When we eliminate the sonic results of vibration contamination we more accurately hear what the individual components in a system are doing. It is possible that these results might be misinterpreted by some individuals. For example: if a speaker is providing excess out-of-phase elements the size of the soundfield might INCREASE beyond what is actually in the recording. Bigger is not always. This individual will have adjusted speaker placement and acoustic room treatment based on this exaggerated sonic view of the soundfield. Once the out-of-phase elements are properly controlled by reducing vibration the size of the soundfield may become smaller in this incorrect set-up and the listener may say, "Oh, this is not as good as it was before because things are not as large." What they should be doing is reevaluating speaker position and room treatment to optimize the now correctly operating speaker. Once that is accomplished they will find that not only is the soundfield as large, if not larger than before, but the instruments are in proper relationship with one another and ambience is cohesive instead of exaggerated. Frequency changes can also be misinterpreted: in a vibration plagued system a too forward midrange during transients is a typical symptom. Some people might misinterpret this as the system exhibiting "good presence" or a forward brightness region is often described erroneously by some listeners as "good detail". The removal of the vibration will eliminate these effects. Some may feel at first, that the removal of these exaggerated artifacts is a step backward in reproduction, but what they are hearing in the now vibration free system are the possible cumulative effects of previous tweaking and/or component choices made with a vibration drenched palette. Once the problems caused by unwanted stored energy are removed some system choices may need to be reevaluated.

Best Regards,

Barry Kohan
President
Bright Star Audio

Disclaimer: I am a manufacturer of vibration control products.

Text correction:

In my last parapgraph the line should read: "Bigger is not always better."

Best,

Barry

Hi Joe,

Optimally, the speaker will be place on the Plinth (top plate) of our Big Rock platform. The special coating on our products is not only non-resonant, it is slightly textured. This textured surface has the ability to contour to the bottom of a speaker allowing a significant increase in contact area compared to placing the speaker on a standard hard surface. We do not want a compliant material between the speaker (or other audio or video component) and the Plinth of the Big Rock. The Plinth is the conduit which directly routes the unwanted stored energy out of the component and down into the bed of sand where it is effectively dissipated as thermal energy (heat). It is critical that the vibration (mechanical energy) be dissipated as quickly as possible and placing the absorptive element as close to the component as possible is best for maximum efficiency. Attempting to route that energy through a multitude of materials and down into the floor (as most spike or cone manufactures describe) is not nearly as efficient or effective.

Best,

Barry

Hi Newbee,

I can empathize with people who may feel overwhelmed with the numerous (seemingly) conflicting theories and the multitude of products on the market.

The most important aspect to vibration control is understanding the nature of the problem. Without that, it will not be possible to design the most effective means to deal with contaminating vibration. Most manufacturers only seem to consider floor-borne vibration that is sourced from the loudspeaker and do not address other sources and forms of floor-borne vibration let alone internally generated or air-borne vibration. It is also critical that the designer be very familiar with a wide range of materials and how they interact with each other as well as having the appropriate measurement equipment to assess how well the devices address the problem.

Best,

Barry

Hi Tom,

Thank you for your comments. It seems that I must have not been as clear as I intended. Please allow to explain again in more detail.

The vibration control system which I designed and described utilizes a high-mass, high-absorption platform directly under the speaker cabinet. The best implementation of this type of platform is the Big Rock which I created in 1985 and for which I was granted a patent in 1993. The Big Rock uses a quantity of sand to absorb and dissipate vibration from the component’s chassis or speaker cabinet that is placed on top of it. Virtually all “sandbox” type platforms which are discussed on the internet are copies of my original design. When used under a loudspeaker the entire bottom panel of the speaker cabinet is in intimate contact with the Plinth (top plate) of the Big Rock for maximum transfer of unwanted energy. Sand has the ability to absorb a huge amount of mechanical energy (vibration) by quickly and efficiently converting this destructive energy into more benign form – thermal energy (heat). As we know from the laws of physics; ENERGY CAN NEVER BE DESTROYED – IT CAN ONLY CHANGE FORM. I have used bold type because of the importance of this concept in our endeavor to control vibration. It encompasses every aspect of how vibration enters and contaminates the signal which flows through our audio and home theater systems and must be at the forefront of our thoughts as we design a vibration control system to most effectively address this problem.

There are multiple sources and multiple forms of vibration. The sources of vibration are:

1) Floor-borne vibration which includes; Vibration that is directly-coupled from the loudspeaker which transfers through the floor and up through the component stand into the feet of the component. Air conditioning and heating systems which send low frequency vibration through the building’s structure. Exterior traffic (trucks, busses, cars, freeways!, subways, trains, airplanes, etc.) which sends very low frequency energy up through the floor and into the system’s components. Natural geological seismic activity which sends extremely low frequency energy up through the entire building which contaminates the system’s components.

2) Air-borne vibration sent directly from the loudspeaker drivers through the air towards the chassis of the component (this also includes energy reflected off the walls, ceiling and floor).

3) Internally-generated vibration that is created within the chassis of the component by spinning motors, humming transformers and cooling fans.

Not all of these sources produce the same type of vibration. The vibration from the speakers as well as air-borne vibration are related to musical signal flowing through the system. Their sonic degradation to the system will be similar to a “ghost” image on a television. It will be vaguely similar but different in spectral content and have out of sync timing as compared to the original signal. The primary sonic symptoms of this type of vibration are a shift in tonal balance (typically excessive brightness and bloated bass), diminished transparency (detail and clarity) as well as degraded pace and rhythm. The secondary sonic symptoms include exaggerated dynamics for certain frequency groups and diminished dynamics for other frequency groups plus an alteration of imaging and soundstaging (either smaller than what is contained in the recording or an exaggerated version of what is contained in the recording).

The vibration from the other sources is not related to the musical signal which is playing through the audio system. The sonic symptoms of this type of vibration are diminished dynamics due to an increase in the noise floor and a general lack of coherence of the musical spectrum of each individual instrument and diminished coherence of the musical ensemble.

Mechanical vibration is a displacement of a physical body from its “at rest” position in reaction to the energy wave presented from the vibrating source. Some of these waves are vertically oriented (floor-borne vibration sourced from the loudspeakers and air conditioning/heating systems plus sympathetic vibration of the shelf directly under the component as it is excited by air-borne vibration) and some of the waves are horizontally oriented (air-borne vibration and the majority of the vibration sourced from exterior traffic and geological seismic activity). Furthermore, some of these waves are a combination of both. In addition, the horizontally oriented waves do not only come from one direction – they enter the system from a number of different vectors.

Clearly, comprehensively addressing vibration will take much more than simply placing a few feet or a single slab of material under a component. Any vibration control product that does not take into account all of the above sources and forms of vibration will not adequately address the problem. In addition, it is critical that the vibration control device does not add any new problems that will affect the signal flowing through the component.

The beauty of the Big Rock as a vibration control device is in its elegance and straightforward effectiveness. When the Big Rock is implemented as I recommend it has very high mass and is extremely absorptive yet is not significantly compliant. A speaker cabinet placed on the Big Rock’s Plinth will not rock back and forth in reaction to the speaker’s drivers while a significant amount of unwanted stored energy will transfer out of the speaker cabinet and be dissipated in the sand bed – the “exit strategy” if you will. In addition, a Little Rock pod (a very high mass damping and absorption pod) placed on top of the cabinet will damp excessive resonance in the speaker cabinet, absorb unwanted stored energy as well as causing the speaker to be planted more firmly to the top of the Big Rock making the transfer of unwanted energy even more efficient. Our upper model Little Rocks also incorporate EMI (electro-magnetic interference) shielding which is important when they are used with electronic components.

For ultimate effectiveness the Big Rock / speaker/ Little Rock should be placed atop one of our multi-cell Air Mass pneumatic mounts which will effectively decouple all of the above from the floor. This will stop the speaker’s mechanical energy from entering the floor and traveling towards the system’s components. The speaker is also protected from the other floor-borne sources of vibration which can compromise its performance. When an electronic component is placed within an Air Mass / Big Rock / Little Rock combination it too is protected from floor-borne vibration as well as being critically damped from above and below while it is simultaneously in intimate contact with high absorption reservoirs from above and below which significantly minimizes the effects of air-borne and internally generated vibration.

This vibration control system places the highly absorptive energy reservoirs in direct and intimate contact with the speaker or component. The transfer of energy from the component and its conversion to benign thermal energy is immediate and very efficient without any intermediate structures.

Another virtue of the Air Mass / Big Rock / Little Rock combination is that it is very resistant to horizontal displacement because of its extremely high mass. Is also has a resonant frequency in the horizontal plane as low as 2.5 Hz and 1.5 Hz in the vertical plane.

Vibration control devices that employ rigid coupling as the principal method of execution require the mechanical energy to go through a number of structures before it can leave the locale of the components. They typically claim to route the energy into the floor but unfortunately the floor does not readily dissipate mechanical vibration. If it did, the vibration would not be entering the component’s feet in the first place and we wouldn't even be discussing the need for vibration control. Moreover, the floor is one of the primary SOURCES of the destructive vibration!

Merely placing a vibration control device under a component does not address air-borne or internally generated vibration. Even if the device below the component does route some unwanted energy out of the component it can only do so AFTER the vibration and resonance have had time to degrade the signal flowing through the component. How far does the horse have to be out of the barn before the door is closed? No amount of “draining” after the fact will restore the signal to its original, pristine state.

It is also extremely critical that the vibration control device not add any of its own degradations to the signal flowing through the component. Employing materials that ring (metal, glass, stone, etc.) or materials that are resonant (wood, acrylic, etc.) will virtually guarantee that they will affect the signal and restrict the ability of the system to faithfully reproduce what is contained in the recording.

The fact is that making ANY change to a system will result in a change in the way that system reproduces sound. Even moving the location of the equipment rack by just a few inches in any direction will alter how the various pressure zones in the room will interact with the various resonance frequencies and resonance characteristics of the equipment resulting in change in the sound of the system. Moreover, changing the support under a component will usually cause a significant change in performance. Most audiophiles simply listen to the difference and try to decide if it is "better" or not. There is some merit in that method but I believe that controlling vibration should have the goal of allowing the system to more faithfully reproduce the sound of the original musical instrument as it has been captured in the recording. That can only be accomplished when contaminating vibration is minimized as much as possible in the audio or home theater system.

In many cases, simply adding or changing a vibration control device will not give the full indication of whether the change brings the system closer to my stated goal or not. Trying to “balance off” or “tune” resonances within a system may be an interesting pursuit, it will not allow that system to faithfully reproduce the sound of the instrument as it has been captured in the recording. In some cases when contaminating vibration is eliminated it will more clearly expose the true nature of the system by letting one hear all of the previous choices of components, set up and applied accessories. If those choices were made while the system was being plagued by destructive vibration (which describes virtually all systems until a comprehensively designed vibration control system is employed) the devices and set up already in place may no longer be appropriate once the problem of vibration eliminated. If the change is simply compensating for a deficiency or problem elsewhere in the system the listener may reach an erroneous conclusion about the efficacy of the change.

Tom, please let me know if you have any questions.

Best Regards,

Barry

Hi Tom,

Tom asks: "Are there no losses in conversion?"

Converting to what?

If you are asking about the conversion from mechanical energy to thermal energy in the vibration control system I described the answer is yes, there is a great deal of loss which is the objective.

"If you let it vibrate, like it will do anyway, no matter what and you provide a efficient path way for vibration to exit would there not be be less loss than high mass dampening?"

You are right. There is LESS loss of mechanical energy when coupling is employed. What we want is MORE loss of energy so that it will have less effect on the signal that is flowing thorough the component.

"Some coupling devices have a geometric bandpass at 4hz and below to reject the incoming at the point tip"

Which coupling products manufactured for audio systems have resonant frequency and bandpass at 4Hz and below? Are there measurements to show this?

Please let me know if I had understood your questions correctly.

Best Regards,

Barry

Hi All,

Anyone interested can see laboratory measurements of a speaker system with and without the vibration control system I described.

Here is the link:
http://www.brightstaraudio.com/new_page_6.htm

or

link

Figure 1 shows the frequency response of a speaker without the vibration control system (red line) and the same speaker with the vibration control system I described (black line). You will notice a significant increase in response with the vibration control system.

Figure 2 shows a Cumulative Spectral Decay (waterfall) response of the speaker that is not placed in the vibration control system. Note the significant amount of vibration residue the speaker exhibits. This is vibration and resonance that is absorbed and released by the cabinet walls after the drivers have stopped producing the original signal. The extra "ghost" signal not only significantly colors the music it also produces random out-of-phase elements which affect imaging, soundstage abilities and transient response.

Figure 3 shows the same speaker that has been placed within the vibration control system. You will note that there is far less extra residue present in the speaker system and the graph looks much "cleaner". The extra energy that had been wasted making the cabinet vibrate is now being used to create more music - increasing efficiency and performance in all areas.

Figure 4 shows the same two waterfall graphs together
so you can more easily see the differences.

Please let me know if you have any questions.

Best Regards,

Barry

As long as the evaluation includes the complete vibration control system I described above I would also welcome a comparison.

I would also like to say that I have nothing against Tom, either personally or professionally. I do not know him and I do not believe we have ever met in person. He seems like a very nice guy and I know he has been helpful to many Audiogon members in a number of different areas which makes him an asset to the audiophile community.

I do feel, however, that there is a general lack of thorough discussion on the internet and in many audiophile publications on the subject of vibration control. Typically, there is a trial and error methodology that is used by most audiophiles and is also sometimes recommended by manufacturers and dealers – add the device to your system and see if you like it or not. We live in free society so no one can tell another person what they like or don’t like (and, of course, people should like how their systems sound), but this haphazard manner of evaluation is fraught with difficulty and many times leads to erroneous conclusions.

I think that we would all be well served by the introduction of more science and more stringent evaluation to the category of vibration control. This will advance the state of the art of audio reproduction. The most important issue is to understand the nature of vibration, how it affects the components within our systems and ultimately, how well the devices, materials and methods that are used address those issues.

Best Regards,

Barry Kohan