Air Bearing Stiffness
Richard - thanks for providing this info - the part that hits home with me.
“This is explained by the design of the bearing (it's self centering characteristics) and its extremely high resonant frequency. Many times higher than the audio spectrum. Although the bearing uses air which we know to be compliant, at the frequencies of interest, the bearing medium is stiff.”
I usually hear only about audio designers trying to come below the audio spectrum – especially with a TT setup ?
That is what the conversations have been based on here as well ? 2hz – 6 or 7 hz.
This is truly outside of the box. Dover mentioned somewhere on this thread a while back that testing of the resonances with the ET2 seems to just pass through it ?
Dover - was this the same study? Maybe the test gear was not good enough to capture this info. I mean - its parameters setup for human hearing.
"Many times higher than the audio spectrum" I guess this explains why my dog does not start howling when I play music. Its beyond him as well. ...
Regarding leading note edge performance. My reference in my room are master tape dubs. No issues here with the air bearing.
Richardkrebs
Stiffness
Many years ago I remember reading an audio magazine which tested the rigidity of the ET2 bearing. It may have been Martin Colloms, but I can't be sure. This was done, again from memory, where accelerometrs were used and a sweep frequency was applied to the spindle. The result showed a bearing that was stiff at audio frequencies.
This is explained by the design of the bearing (it's self centering characteristics) and its extremely high resonant frequency. Many times higher than the audio spectrum. Although the bearing uses air which we know to be compliant, at the frequencies of interest, the bearing medium is stiff.
I also show here a quote from an industrial air bearing manufacturer. While these a big load bearing devices, their design is virtually identical to the ET2
"Outstanding stiffness for small deflections Most engineers visualize an air bearing as being like a hovercraft, and they erroneously conclude that a bearing which floats on air cannot be very stiff. Actually these gas bearings are many times stiffer than a ball or roller bearing. Sapphire orifices within the bearing gap control the pressure in a film of air which is only 0.0003 inches thick. As a load is applied to displace the bearing rotor or slider, the gap decreases very slightly on one side, reducing the flow of air through the adjacent sapphire orifice. This results in a pressure increase in the gap on this side which pushes the rotor back to its original position. In essence, the air bearing is a servomechanism with closed loop control, and maintains a uniform gap in spite of external forces that may be applied. This results in bearing stiffness of millions of pounds per inch for small deflections. Stiffness is linear and does not change with temperature. In contrast, ball or roller bearings have almost no stiffness unless heavily preloaded. The stiffness of a ball bearing is not linear, and varies considerably with temperature."
Richard - thanks for providing this info - the part that hits home with me.
“This is explained by the design of the bearing (it's self centering characteristics) and its extremely high resonant frequency. Many times higher than the audio spectrum. Although the bearing uses air which we know to be compliant, at the frequencies of interest, the bearing medium is stiff.”
I usually hear only about audio designers trying to come below the audio spectrum – especially with a TT setup ?
That is what the conversations have been based on here as well ? 2hz – 6 or 7 hz.
This is truly outside of the box. Dover mentioned somewhere on this thread a while back that testing of the resonances with the ET2 seems to just pass through it ?
Dover - was this the same study? Maybe the test gear was not good enough to capture this info. I mean - its parameters setup for human hearing.
"Many times higher than the audio spectrum" I guess this explains why my dog does not start howling when I play music. Its beyond him as well. ...
Regarding leading note edge performance. My reference in my room are master tape dubs. No issues here with the air bearing.