Could one not build a reasonably low friction bearing tube assembly
and then just adjust it angularely (sic) to overcome any remaining friction. i.e. give the cartridge arm a slight bias towards falling to the centre of the record The cartridge compliance would then only have to keep it centered so to speak.
and then just adjust it angularely (sic) to overcome any remaining friction. i.e. give the cartridge arm a slight bias towards falling to the centre of the record The cartridge compliance would then only have to keep it centered so to speak.
moving mass
There seems to be a little confusion about the moving mass and how the ideal arm should be. The criterias for Poul Ladegaard are among other things, that you should be able to control the mass independently vertically and horizotally so that:
- the vertical resonance is just under what we want to reproduce, typically 15 to 20 Hz. It should by all means be over 5-7 Hz as the pressing errors (warp) have a maximum there. This means practically a very short arm, which thus has to be tangential.
- the horizontal frequency should for best bass transients be very low, it should only be considerably over half a Hertz as an eccentric record has that frequency. He proposes 3 Hz as a good beginning and that means adding some mass, very depending on the cardrigde. The advantage of the Ladegaard arm is outsides its extreme simplicity that it is very easy to adjust for individual cardrigdes.
He finds himself, that the biggest problem with it is that he has not found a good way of damping it, limiting the air flow is too dangerous, but I can see, that some of you thought as me, that it should be made by some kind of liquid damping.
I have discussed these and other problems with him, we both wrote for the same danish audio magazine, and personally I think that the reason that these airborne arms are sounding so good also is due to the phenomen that when the wave runs down the arm tube itself, then it will not meet a mechanical mirror in form of a bearing, which will send the wave back. This is a medium/treble problem. Ladegaard agrees that it could be an important part of the explanation. Thus the interest in the damping of the tube and counterweight suspension.
Søren
There seems to be a little confusion about the moving mass and how the ideal arm should be. The criterias for Poul Ladegaard are among other things, that you should be able to control the mass independently vertically and horizotally so that:
- the vertical resonance is just under what we want to reproduce, typically 15 to 20 Hz. It should by all means be over 5-7 Hz as the pressing errors (warp) have a maximum there. This means practically a very short arm, which thus has to be tangential.
- the horizontal frequency should for best bass transients be very low, it should only be considerably over half a Hertz as an eccentric record has that frequency. He proposes 3 Hz as a good beginning and that means adding some mass, very depending on the cardrigde. The advantage of the Ladegaard arm is outsides its extreme simplicity that it is very easy to adjust for individual cardrigdes.
He finds himself, that the biggest problem with it is that he has not found a good way of damping it, limiting the air flow is too dangerous, but I can see, that some of you thought as me, that it should be made by some kind of liquid damping.
I have discussed these and other problems with him, we both wrote for the same danish audio magazine, and personally I think that the reason that these airborne arms are sounding so good also is due to the phenomen that when the wave runs down the arm tube itself, then it will not meet a mechanical mirror in form of a bearing, which will send the wave back. This is a medium/treble problem. Ladegaard agrees that it could be an important part of the explanation. Thus the interest in the damping of the tube and counterweight suspension.
Søren
Sound waves reflection and arm damping
The Schreder style arm has similar problem, that's why herr Schreder pays so much attention to the armtube material choise. I believe hardwood has some important advantage here, call it "sonic signature", which means the whole stylus-induced vibrations frequency band is being absorbed/reflected more evenly, causing less severe resonant peaks and cancellations.
Do not get me wrong, I think the air bearing tangential arm (and the Ladegaard design specifically) is a brilliant idea, and I like my Ladegaard clone very much. But it is important to clearly understand its weak point to address it. I'm going to try some sort of oil impregnated hardwood armtube and see how it helps to improve (or or not) the sonic. Will report back.
When the sound wave propagading through certain media, meets the boundary surface of the material, it is partly reflected back, and the reflected wave amplitude and phase shift is depending on properties of two contacted materials , like density, boundary shape and damping factors. Generally, the more dissimilar the contacted materials are, the more LF energy is bounced back (to stylus!), causing muddy bass. That's why the metal bearing arm usually have better bass resolution, comparing to air bearings. The metal bearing arms require less armtube damping, because direct metal-to-metal contact provides good path for LF vibrations to be absorbed "downstream".
The Schreder style arm has similar problem, that's why herr Schreder pays so much attention to the armtube material choise. I believe hardwood has some important advantage here, call it "sonic signature", which means the whole stylus-induced vibrations frequency band is being absorbed/reflected more evenly, causing less severe resonant peaks and cancellations.
Do not get me wrong, I think the air bearing tangential arm (and the Ladegaard design specifically) is a brilliant idea, and I like my Ladegaard clone very much. But it is important to clearly understand its weak point to address it. I'm going to try some sort of oil impregnated hardwood armtube and see how it helps to improve (or or not) the sonic. Will report back.
One way to impregnate some timber with oil....
Submerge the piece of wood in a vacuum chamber, cover with oil and pull a vacuum. Leave overnight. Air/moisture gets sucked out of the wood and cavities are filled by the oil. Best to use an oil which will harden like danish oil.... otherwise you will have oil leaching back out of the timber with changes in temperature.
Fran
Submerge the piece of wood in a vacuum chamber, cover with oil and pull a vacuum. Leave overnight. Air/moisture gets sucked out of the wood and cavities are filled by the oil. Best to use an oil which will harden like danish oil.... otherwise you will have oil leaching back out of the timber with changes in temperature.
Fran
Some years ago I used a similar homemade tangential airsupported tonearm
Only real problem was noisy and "pumping" airsupply
Should I make one today I would consider some form of small compressor with a tank big anough to supply air without any motor running
You then can adjust a precise amount of pressure and get a fluid supply of air without noise and "pumping"
Maybe you couold use a compressor from a old refrigerator
Anyway there should some form of "buffer"
Only real problem was noisy and "pumping" airsupply
Should I make one today I would consider some form of small compressor with a tank big anough to supply air without any motor running
You then can adjust a precise amount of pressure and get a fluid supply of air without noise and "pumping"
Maybe you couold use a compressor from a old refrigerator
Anyway there should some form of "buffer"
To livemusic: If you are following the guidelines I described, you will end up with 100 to 200g of mass in the horizontal plane with typical good MC cartrigdes in order to get the resonance frequency down to about 6Hz. The best place to have that mass is in my mind between the arm tube and the knives. Most people are not doing so and consequenly they do not obtain the full bass potential. However, the whole thing is being more critical, horizontal alignment and damping, but it works really well.
To tinitus: If you are using an aquarium pump, then an expansion chamber with a volume of 1 liter is overkill to obtain a stable airflow. A vario transformer is a good help to find the minimum airflow which can do the job. The pump with the expansion chamber as close as possible should of course be in another room or at least heavily damped.
Søren
To tinitus: If you are using an aquarium pump, then an expansion chamber with a volume of 1 liter is overkill to obtain a stable airflow. A vario transformer is a good help to find the minimum airflow which can do the job. The pump with the expansion chamber as close as possible should of course be in another room or at least heavily damped.
Søren
Ladegaard's Air Bearing Tangential Tonearm
Hi!
Her is a link for Ladegaard's Air Bearing Tangential Tonearm
http://www.aiko.com/airbearingarm.html
goggen
Hi!
Her is a link for Ladegaard's Air Bearing Tangential Tonearm
http://www.aiko.com/airbearingarm.html
goggen
Yes, i am curious about it too, so searched, and found this picture of it: http://www.tnt-audio.com/jpeg/opusarm.jpg
Now i know how it works, 2 ball bearings running in a C-shaped glass (or acrylate) tube. Thats all.
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