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A Short Theory of Isolation Feet
I always do not believe tweaking. Of all kinds of tweaking out there, I hate feet the most. Metal feet may squeeze the high out causing a temporal sensation of enhanced high frequency but it always compromises naturalness. In fact, the mid-high always starts to ring wherever there are metal feet underneath any components. If you are using ceramic drivers, this ringing always hurts the music.
Even in the case of tube electronics, the use of metal spikes underneath them may not always work. In another extreme end of the argument, it may be good for the wrong reasons. It is true that the insertion of any kind of spikes underneath tube electronics will help reduce the degree of mechanical vibration. When it translates into sonic vocabularies, this often results in better imaging, more energy, more speed and better bass resolution. Even though all of the above can be achieved easily, it does not necessarily mean equal movement in harmonic decaying dynamics, high frequency overtone, and the subjective airy feel in the bass section.
I suspect the aforementioned improvement does not come entirely from reduced mechanical vibrations but the elimination of the all-too-common PLASTIC FEETS on our expensive electronics. These feet usually absorbs energy, undermines focus, and attenuates the lower-mid bass, which ironically are often viewed as an improvement (including myself in the early years of this journey.)
Let me share one example. A friend of mine locates the Orpheus zero player and the Karan integrated amplifier on a plane of glass surface. The zero has the plastic feet underneath it, whereas the Karan as three metal balls bearing under her chassis. In the past, I would simply try different kind of feet in search of my preference. No more trial and error this time. The plastic feet of the Orpheus player are fine on the glass because the plastic helps absorbing the resonances from the glass. The direct contact of the metal ball bearing of Karan to the glass, on the other hand, is a problem because the vibration of the glass reinforces the metal ringing of the ball bearings made of steel. As a result, I put three wooden blocks (called interlaces) underneath the Karan. The result is reduced stress on high frequency.
Should I have the classic feet or the reference feet by Acoustic System Int'l, I would certainly use the feet but I will most likely unscrew the metal spikes from the feet if the surface is made of glasses or any kind of metals. If the surface is made of wood, I may or may not take away the steel spike. There is no fixed formula. You just got to listen carefully. Generally speaking, I dislike all kind of spikes made of steel now. This is very subjective.
Another example. A good friend of mine once placed the Heritage dac on the glass surface. Heritage is a serious machine. You cannot find any plastic feet in both the main and power supply unit. The feet are all milled by high quality steel possibly in the grade of 316L. When you have steel feet pressing against glass surface, what will happen? (1) Ringing in the mid-high. (2) Bass becomes one-note bass (3) Mid-range harmonic reduces and render a feeling of "dry". Later on, my friend found out the problem in the middle of the night. He then started relocating the Hertiage dac away from the glass surface to a wooden platform. Bingo! Problems disappeared.
When should I apply the feet? If the perceived system balance is correct in my mind, I will start searching for those plastic feet underneath our expensive electronics. If the insertion of wooden feet does not tilt the tonal balance of the system, I will then experiment with different configuration. One can try to apply 3 feet with two in front and one at the back first. This config usually produces a more distinct image but the soundstage may become a bit forward especially in the case of solid state electronics. In the case of tube electronics, I find this config is quite good to my subjective liking. If one finds a more layback soundstage, place one foot in the front and two feet at the back usually increases depth of the soundstage. The size of the equilateral triangle formed by 3 points often determines the size of the soundstage too. If the room is small and your system produces too much energy, you could try to reduce the size of the triangle formed by these 3 points. Again, the degree of change may be marginal from case to case. After-all, I would call it a fine-tuning section.
Does it mean we have to replace all plastic feet with wooden feet? Not necessarily so. There is no universal formula. Your ears should be the judge. My personal experience is always (1). Do not use metal or steel spikes (including carbon). (2) Try to use wood whenever possible. (3) Not to put any electronics on glass surface. (4) Try to tackle where resonances are the most first.
Point 2 may not be conclusive because different kind of wood exhibits different resonance characteristics by nature. For example, ebony has a tendency to damp the lower-mid-bass, sometimes too much, and in some cases when bass is excessive, it may work magic. Maple may sound fast but I personally find them to be starving the mid-range too much. There are endless examples that I cannot share so much here. You just have to keep trying.
Regarding point 4, it is usually the speakers that generate the most resonances due to cabinet as well as the unnoticed metallic spike plate that comes with the speakers. If you add some kind of metal spike metal underneath them to protect your floor (which I perfectly understand), I suspect one would kill harmonic information too much. Well said, who can really afford spiking the speakers underneath the floor? Don’t forget we still got to care the feeling of woman. These steel plates are often the culprit of bad sound. In the case of Kharma speakers, that steel plate is channeling the ringing sound of steel back to the ceramic drivers via the big metal spikes. They look cool but they sound bad. Take them out, there should be less ringing coming out from the ceramic drivers.
In conclusion, I think the mere and only function of the spike is to bolt the speaker in place. It may be functional for speaker the moves a lot of low frequencies, for example the subwoofer in physical separation. The use of spike spikes underneath will help alleviating the resonances of the low frequency without channeling vibration to the mid-range driver or the tweeters.
Let’s take the case of a full-range speaker as an example (also applies to multi driver), the use of spikes would transfer low frequency resonating energy VERTICALLY to the high frequency band, crossing and polluting the important mid-range. There are so much sound and energy there that makes or kills the performance of a whole system. What if we channel the vibration away in a HORIZONTAL manner? What if we let the speakers move horizontally as freely as possible? We may loose some mid-range details but this approach dose not transfers any MOTION energy into higher frequencies. The result is a dramatic increase of ambience information, transparency and hence more revelation of true musical color.
Franck’s wooden feet allows resonances to move away horizontally in steps because there are ventilation holes in different layers of his feet. I believe the scientific reasons behind it are well built. They are not voodoo, trial-and-error, but with real reasoning behind. Another extreme option is to use wooden balls underneath the speakers. Of course the challenge is how to fixate the speakers securely on the floor with the use wooden balls that have NO edges at all. I don’t know but I will have the closest solution to the extreme theoretical ideal next week.
Piano Tuner
Even in the case of tube electronics, the use of metal spikes underneath them may not always work. In another extreme end of the argument, it may be good for the wrong reasons. It is true that the insertion of any kind of spikes underneath tube electronics will help reduce the degree of mechanical vibration. When it translates into sonic vocabularies, this often results in better imaging, more energy, more speed and better bass resolution. Even though all of the above can be achieved easily, it does not necessarily mean equal movement in harmonic decaying dynamics, high frequency overtone, and the subjective airy feel in the bass section.
I suspect the aforementioned improvement does not come entirely from reduced mechanical vibrations but the elimination of the all-too-common PLASTIC FEETS on our expensive electronics. These feet usually absorbs energy, undermines focus, and attenuates the lower-mid bass, which ironically are often viewed as an improvement (including myself in the early years of this journey.)
Let me share one example. A friend of mine locates the Orpheus zero player and the Karan integrated amplifier on a plane of glass surface. The zero has the plastic feet underneath it, whereas the Karan as three metal balls bearing under her chassis. In the past, I would simply try different kind of feet in search of my preference. No more trial and error this time. The plastic feet of the Orpheus player are fine on the glass because the plastic helps absorbing the resonances from the glass. The direct contact of the metal ball bearing of Karan to the glass, on the other hand, is a problem because the vibration of the glass reinforces the metal ringing of the ball bearings made of steel. As a result, I put three wooden blocks (called interlaces) underneath the Karan. The result is reduced stress on high frequency.
Should I have the classic feet or the reference feet by Acoustic System Int'l, I would certainly use the feet but I will most likely unscrew the metal spikes from the feet if the surface is made of glasses or any kind of metals. If the surface is made of wood, I may or may not take away the steel spike. There is no fixed formula. You just got to listen carefully. Generally speaking, I dislike all kind of spikes made of steel now. This is very subjective.
Another example. A good friend of mine once placed the Heritage dac on the glass surface. Heritage is a serious machine. You cannot find any plastic feet in both the main and power supply unit. The feet are all milled by high quality steel possibly in the grade of 316L. When you have steel feet pressing against glass surface, what will happen? (1) Ringing in the mid-high. (2) Bass becomes one-note bass (3) Mid-range harmonic reduces and render a feeling of "dry". Later on, my friend found out the problem in the middle of the night. He then started relocating the Hertiage dac away from the glass surface to a wooden platform. Bingo! Problems disappeared.
When should I apply the feet? If the perceived system balance is correct in my mind, I will start searching for those plastic feet underneath our expensive electronics. If the insertion of wooden feet does not tilt the tonal balance of the system, I will then experiment with different configuration. One can try to apply 3 feet with two in front and one at the back first. This config usually produces a more distinct image but the soundstage may become a bit forward especially in the case of solid state electronics. In the case of tube electronics, I find this config is quite good to my subjective liking. If one finds a more layback soundstage, place one foot in the front and two feet at the back usually increases depth of the soundstage. The size of the equilateral triangle formed by 3 points often determines the size of the soundstage too. If the room is small and your system produces too much energy, you could try to reduce the size of the triangle formed by these 3 points. Again, the degree of change may be marginal from case to case. After-all, I would call it a fine-tuning section.
Does it mean we have to replace all plastic feet with wooden feet? Not necessarily so. There is no universal formula. Your ears should be the judge. My personal experience is always (1). Do not use metal or steel spikes (including carbon). (2) Try to use wood whenever possible. (3) Not to put any electronics on glass surface. (4) Try to tackle where resonances are the most first.
Point 2 may not be conclusive because different kind of wood exhibits different resonance characteristics by nature. For example, ebony has a tendency to damp the lower-mid-bass, sometimes too much, and in some cases when bass is excessive, it may work magic. Maple may sound fast but I personally find them to be starving the mid-range too much. There are endless examples that I cannot share so much here. You just have to keep trying.
Regarding point 4, it is usually the speakers that generate the most resonances due to cabinet as well as the unnoticed metallic spike plate that comes with the speakers. If you add some kind of metal spike metal underneath them to protect your floor (which I perfectly understand), I suspect one would kill harmonic information too much. Well said, who can really afford spiking the speakers underneath the floor? Don’t forget we still got to care the feeling of woman. These steel plates are often the culprit of bad sound. In the case of Kharma speakers, that steel plate is channeling the ringing sound of steel back to the ceramic drivers via the big metal spikes. They look cool but they sound bad. Take them out, there should be less ringing coming out from the ceramic drivers.
In conclusion, I think the mere and only function of the spike is to bolt the speaker in place. It may be functional for speaker the moves a lot of low frequencies, for example the subwoofer in physical separation. The use of spike spikes underneath will help alleviating the resonances of the low frequency without channeling vibration to the mid-range driver or the tweeters.
Let’s take the case of a full-range speaker as an example (also applies to multi driver), the use of spikes would transfer low frequency resonating energy VERTICALLY to the high frequency band, crossing and polluting the important mid-range. There are so much sound and energy there that makes or kills the performance of a whole system. What if we channel the vibration away in a HORIZONTAL manner? What if we let the speakers move horizontally as freely as possible? We may loose some mid-range details but this approach dose not transfers any MOTION energy into higher frequencies. The result is a dramatic increase of ambience information, transparency and hence more revelation of true musical color.
Franck’s wooden feet allows resonances to move away horizontally in steps because there are ventilation holes in different layers of his feet. I believe the scientific reasons behind it are well built. They are not voodoo, trial-and-error, but with real reasoning behind. Another extreme option is to use wooden balls underneath the speakers. Of course the challenge is how to fixate the speakers securely on the floor with the use wooden balls that have NO edges at all. I don’t know but I will have the closest solution to the extreme theoretical ideal next week.
Piano Tuner
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Comments
Not until recently I found the graet importance of these feet.
Mine is already a fairly good example to illustrate the problems of the feet coming together with original manufacturers. Almost every gear running from CD transport to the speakers has the feet problem. They hinder the maximal peformance of different gears.
The reference spikes from Acoustic System is excellant in the sense that they makes the sounds liner in performance without any distortion and compression. The harmonic decays sounds natural and rich. The only drawback of them is .............Expansive......
KAN
Kan, I question why designer of our expensive electronics use cheap plastic feet then?
William
Ha.....I have nothing to say....about your study. Damn ! always one step faster ! Excellent PT.
The Orpheus 0 and 1SE I am using came with rubber feet, I am now placing them on a wood platform. I welcome input from anybody here about the wisdom of using isolation feet on them. Thanks in advance!
Robert
Dan