More energy transferred to the arm means that less energy is converted to electrical signal by the cartridge.
Az a consequence, more bass boost would be necessary, the RIAA curve would not look look like the present one.
So this is simply not true, only in the immediate vicinity of the resonance, where because of the phase shift the signal also increases.
Only a very small amount of the energy that is transferred from the stylus to the arm is by the resistance to motion of the voice coil in the magnetic field. The vast majority is transferred by the suspension of the cartridge. Above the cartridge compliance/effective-mass resonant frequency the arm moves less relative to the motion of the stylus as frequency increases. The amount of movement decreases by 12dB per octave.
This works in exactly the same way as the suspension of your turntable (or car).
If you double the frequency but keep the amplitude the same the distance travelled by the headshell will be doubled and hence so will its average velocity. Likewise reducing the amplitude by 4 times, 12dB, will reduce the average velocity to a quarter. So doubling the frequency and quartering the amplitude will half the average velocity. As kinetic energy is proportional to velocity squared the energy transferred will be quartered. So the energy transferred to the arm will also reduce by 12dB per octave. This is assuming that the input is at constant amplitude which the RIAA curve basically is with bits of constant velocity at the frequency extremes.
The diagram shows the transfer function of a typical arm-cartridge combination tuned to 10hz and 5hz, blue and orange. It shows how much the cartridge body moves relative to how much the stylus is moving.
Hi Niffy,
The 1 K tone is a normal one without any equalization. In my opinion, if there is a small peak at 690 Hz as you mentioned before, but at a very low level, it shouldn't cause any concerns regarding the design of the air-bearing arm. I think the tolerance of the air-bearing is more important than the possible existence of resonant frequency of the air-bearing. The tight tolerance requires less airflow and makes the bearing even stiffer.
I doubt that their 4 points can sound better than the airline arm. For 4 points, it has a skating force. Skating is the worst nightmare for record playing back. I don't think rigidity is a problem for high-pressure air-bearing arms at all.
I won't be surprised if my air-bearing arms outperform Kuzma's airline. There are three things on my air-bearing arms, in my opinion, that are better than Kuzma's airline.
1. I use large air-bearing. One of my air-bearing arms uses 0.75" air-bearing which is compatible with Kuzma's 20 mm air-bearing. Although the lighter air-bearing enables me to use a medium compliance cartridge. Large air-bearing does perform better in the bass.
2. I use short arms. For a long arm such as Kuzma's, its lateral effective mass is not the same as its vertical effective mass. This may cause the lateral resonant frequency isn't equal to its vertical resonant frequency. On all my air-bearing arms, their lateral resonant frequencies are almost the same as their vertical resonant frequencies.
3. Wire and air tubing. It seems to me that the wires and the air tubings have less resistance than theirs. I understand that the airline is a commercial product and it needs to be foolproof. But my air-bearing arms don't have to.
Jim
Great to read what experienced men are posting and saying, I am enjoying this thread a lot.
Would you be kind enough to explain a bit more about coupling or point me in the direction of some good reading please?
What are we coupling to ultimately, I know, or think I do, that we are trying to get energy in the form of micro vibrations that have escaped the cartridge body to flow away as easily as possible, without resonance, hence the coupling across the bearings (of whatever type) is important. what happens down the chain from there and ultimately what does the arm need to be linked to before trying to dissipate the vibration energy in some way please?
M
How much vibration energy transfers between a metal and air will depend on the acoustic impedance (aZ) match between them. If the mismatch is large there will be high reflection and low transfer. Air at atmospheric has aZ of about 0.4Mrayl and brass 36Mrayl so reflected energy will be 96% and in phase. As air pressure increases so does aZ so it will depend on bearing pressure as to how much energy is transferred over the air gap.
You should be able to test this with a stethoscope on the air rail.
I've been toiling away with this issue in the ongoing development of my servo linear tracker. I am firmly in the rigidity and high mechanical grounding camp.
You should be able to test this with a stethoscope on the air rail.
I've been toiling away with this issue in the ongoing development of my servo linear tracker. I am firmly in the rigidity and high mechanical grounding camp.
I am always wondering why my air-bearing arms are so quiet.
This can be another reason. My table is SME 20. SME 20 has two plinths. The up plinth is suspended with rubber O rings.
I modified the table. The up plinth and the arms are floating on 5 round air bearings. These round bearings are supplied with 90 psi compressed air. The total weight of the top plinth with other structures and arms is about 30 lbs. So, the air films for these round air bearings are very stiff and must have a pretty high-frequency damping factor. The low plinth sits on 4 air pucks. These air pucks are supplied with 20 psi compressed air.
I am not saying the vibrations from the cartridge may transfer through the air film of air bearings. I guess the air film dampens the vibrations since one of the properties of air is damping. The stiffer the air film is, the higher frequency of the damping factor. Stiffer air film can be achieved by increasing the load or air pressure.
Again, rigidity isn't a problem for air-bearing arms. The most important property of air-bearing is frictionless. I can build a heavy-mass arm because of the frictionless air bearings. A heavy mass arm performs better than a low mass arm for linear arms. My 1" air-bearing arm is more than 100 grams if I remember correctly. It is not possible to use a heavy mass arm for mechanical linear arms due to its friction. Frictionless air-bearing also improves the tracking ability of linear arms greatly. I haven't seen a mechanical structure for linear arms that is to my satisfaction completely up to now. I said it before and would like to say it again. Friction is everything for linear arms.
This can be another reason. My table is SME 20. SME 20 has two plinths. The up plinth is suspended with rubber O rings.
I modified the table. The up plinth and the arms are floating on 5 round air bearings. These round bearings are supplied with 90 psi compressed air. The total weight of the top plinth with other structures and arms is about 30 lbs. So, the air films for these round air bearings are very stiff and must have a pretty high-frequency damping factor. The low plinth sits on 4 air pucks. These air pucks are supplied with 20 psi compressed air.
I am not saying the vibrations from the cartridge may transfer through the air film of air bearings. I guess the air film dampens the vibrations since one of the properties of air is damping. The stiffer the air film is, the higher frequency of the damping factor. Stiffer air film can be achieved by increasing the load or air pressure.
Again, rigidity isn't a problem for air-bearing arms. The most important property of air-bearing is frictionless. I can build a heavy-mass arm because of the frictionless air bearings. A heavy mass arm performs better than a low mass arm for linear arms. My 1" air-bearing arm is more than 100 grams if I remember correctly. It is not possible to use a heavy mass arm for mechanical linear arms due to its friction. Frictionless air-bearing also improves the tracking ability of linear arms greatly. I haven't seen a mechanical structure for linear arms that is to my satisfaction completely up to now. I said it before and would like to say it again. Friction is everything for linear arms.
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Hi Jim,
Are the air-pucks supporting the top plinth by themselves or do you still have the original o-rings in place? If you have removed the o-rings how do you keep the deck from sliding sideways?
One definite advantage of an air bearing is that its friction is not dependent on load so you can build a heavy arm suitable for very low compliance cartridges. I think that my jewelled bearings could be used for arms up to about 100g though I probably stick to 80g for safety. This would still allow for cartridges in the 10-12μm/mN range.
Low friction is important to a point. Once you get the dynamic friction below 1 or 2mN any cantilever defection will be completely inaudible.
Are the air-pucks supporting the top plinth by themselves or do you still have the original o-rings in place? If you have removed the o-rings how do you keep the deck from sliding sideways?
One definite advantage of an air bearing is that its friction is not dependent on load so you can build a heavy arm suitable for very low compliance cartridges. I think that my jewelled bearings could be used for arms up to about 100g though I probably stick to 80g for safety. This would still allow for cartridges in the 10-12μm/mN range.
Low friction is important to a point. Once you get the dynamic friction below 1 or 2mN any cantilever defection will be completely inaudible.
После перерыва я снова в деле
.Здесь в ветке много раз говорилось о бесконечных массах, т.е. об заземлении масс.
Это необходимо для «заземления» паразитных резонансов.
На практике борьба с резонансами решается двумя способами, первый - заземление, второй - обратный заземлению, пластина с диском и собственными резонансами подвешивается на резинках.
В этом случае резинками вы не даете внешним резонансам (например, проезжающих по улице поездов) проникнуть на диск поворотной платформы, но ни в коем случае не убираете резонансы самого подшипника, а также диска (колокола), они напрямую воздействуют на звук, а точнее модулируют его в полезный сигнал и окрашивают его.
То же самое происходит и с тонармом в воздухе, он отрывается от бесконечных масс и внешние резонансы не влияют на сам тонарм, но резонансы тонарма никуда не уходят, они резонируют тонарм с удвоенной силой и этот паразит непременно переходит в полезный звук.
Выложил здесь видео с поведением кантилевера при большом эксцентриситете, можете сделать подобное видео со своим тонармом?
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I am not in the same place as the arm for a while yet, so that will be done later!
After a break I'm back in businessПосле перерыва я снова в деле
Здесь в ветке много раз говорилось о бесконечных массах, т.е. об заземлении масс.
Это необходимо для «заземления» паразитных резонансов.
На практике борьба с резонансами решается двумя способами, первый - заземление, второй - обратный заземлению, пластина с диском и собственными резонансами подвешивается на резинках.
В этом случае резинками вы не даете внешним резонансам (например, проезжающих по улице поездов) проникнуть на диск поворотной платформы, но ни в коем случае не убираете резонансы самого подшипника, а также диска (колокола), они напрямую воздействуют на звук, а точнее модулируют его в полезный сигнал и окрашивают его.
То же самое происходит и с тонармом в воздухе, он отрывается от бесконечных масс и внешние резонансы не влияют на сам тонарм, но резонансы тонарма никуда не уходят, они резонируют тонарм с удвоенной силой и этот паразит непременно переходит в полезный звук.
Выложил здесь видео с поведением кантилевера при большом эксцентриситете, можете сделать подобное видео со своим тонармом?
.Here in the branch a lot of times talked about infinite masses, i.e. the grounding of the masses.
This is necessary to "ground" parasitic resonances.
In practice, the fight against resonances is solved in two ways, the first - grounding, the second - the reverse of grounding, the plate with the disk and its own resonances is suspended on rubber bands.
In this case you do not let the external resonances (e.g. trains passing through the street) penetrate the disk of the turntable, but by no means remove the resonances of the bearing itself, as well as the disk (bell), they directly affect the sound, or rather modulate it into a useful signal and color it.
The same thing happens to the tone arm in the air, it is detached from the infinite masses and the external resonances do not affect the tone arm itself, but the resonances of the tone arm do not go anywhere, they resonate the tone arm with double force and this parasite is bound to go into the useful sound.
I posted here a video of the cantilever behavior at high eccentricity, can you make a similar video with your tonearm?
Niffy,
I still use the original o rings. The o rings are mainly for holding the plinth in place. Otherwise, it will be sliding.
Jim
Hi gents, here is where I hope to be successfully different than some, from what i have learnt from others!
If we allow the vibrations to flow easily out down the chain of the tonearm to the plinth with minimal reflection or resistance then we can achieve something much better, we don't need reflections with double force so couple the individual parts and let the vibrations (micro) dissipate?
M
This is what I was meaning by mechanical grounding. An easy test is to place a stethoscope on the tonearm somewhere around the mount and if the arm is well grounded the music will be clearly audible. My resin/bentonite plinth the music is audible near the TA mount and becomes less audible the further away from the mount I place the stethoscope but it is NEVER totally inaudible.
My biggest concern with any passive (air bearing included) LTA once breakaway torque is minimized, is carriage overshoot tracking eccentricity. This is why I have been developing a pivoting arm on a linear carriage, horizontal EM can be tuned like any pivoting arm and overshoot can be minimized with viscous damping
Hi Warren,
The stethoscope test you describe is a great way to demonstrate mechanical grounding/coupling. That you can hear the music in the arm base means that energy has to be flowing from the arm to the base meaning that there has to be less energy left in the arm. That the music becomes less audible as you move further from the arm base shows that the plinth is successfully dissipating this energy. Get the energy out of the arm and deal with it out of harms way.
The "problem" with air bearings overshooting due to eccentricity is not actually a major problem and would be just as applicable to mechanical linear trackers. This overshoot is actually not unique to linear arms and is applicable to all arms, it applies to pivoted arms as well.
The best way of thinking about this is to look at how much the cantilever is deflected by this overshoot.
A typical cartridge fitted to a well matched pivoted tonearm tracking a typical level of eccentricity will have its cantilever deflected by maximums of less than 0.01°. This is the deflection due to just its effective mass and does not take into account any other factors such as bearing friction or anti-skate.
I think that we can agree that 0.01° is utterly insignificant.
If your linear tracking arms carriage has an effective mass (basically it's entire mass) 4 or 5 times that of the pivoted arm the deflection of the cantilever will also be 4 or 5 times greater. 0.04-0.05° is still utterly insignificant.
The deflection due to varying skating force in the pivoted arm will be much greater than this.
As you mention the level of overshoot can be slightly reduced by the addition of damping. With an air bearing this is via an external silicone damping trough and with a mechanical bearing it's via bearing friction. One advantage of an air bearing is that the level of damping is tunable where it isn't with the mechanical counterpart.
I wouldn't worry about "overshoot" as it's a problem that doesn't really exist.
Niffy