The designer's name is Aleks Bakman and I asked him a few questions via email. He declined to come to the forum but gave me permission to post his responses.
First my questions, followed by his responses, followed by more questions followed by Aleks's final set of answers.
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"2 issues were raised. One pertains to this claim of yours: "A first in the history of the audio turntables self-centering One Degree of Freedom or Onedof™ bearing eliminates the source of acoustic distortions associated with microscopic movements of all existing cylindrical shafts."
It was said (not by me), that "There are other TTs which provide same stableness and bearing technology. Look at the EMT 927 bearing - and this is proofed in professional business since 50 years. Look at the Continuum`s bearing and do experience it in real life. "
I was wondering about your comment on this.
Secondly, it is said on that thread that standalone arm towers suffer deficiencies due to 1. the tt and tonearm being subject to different resonances, which differences cause distortion at playback and 2. relative motion between tonearm and spindle due their not being rigidly coupled which motion causes geometry errors.
I was wondering if and how you took these considerations into account in your design.
regards,
Minh"
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"Thank you, dear Minh, wonderful questions!
1. All cylindrical bearings have inherent problem of whirl described here: http://www.onedof.com/sites/onedof.com/files/images/Slide1.JPG
Onedof bearing eliminates this problem. Onedof bearing centers itself in all directions: up-down and in all horizontal directions. Onedof bearing restricts all translational movements of the platter: upward downward and to all sides. It only leaves one rotational movement of the platter. http://www.onedof.com/about-turntable
EMT927 has cylindrical shaft and ball bearing at the bottom, providing stiff load path to the supporting stand and associated high frequency resonances. This design does not eliminate whirl.
http://www.stefanopasini.it/EMT927F-main%20shaft.htm
http://www.pinkfishmedia.net/forum/showthread.php?t=80621
Continuum has replaced ball bearing at the bottom of the shaft with the hydrodynamic thrust pad, but the shaft itself remains cylindrical and therefore it is whirling, i.e. wobbles and shifts side-to-side at the same time. It also is not restricted at the top, only at the bottom. These are microscopic movements, which are damaging to the sound.
Rotation shaft/platter assembly of the Onedof TT does not resonate at all, because the design of the bearing/suspension assumes non-linear stiffness, i.e. stiffness that constantly changes with any microscopic movement. Condition for the resonance, permanent stiffness of the suspension is eliminated by design of the Onedof bearing.
Tonearm needs very massive support, to prevent high frequency resonances. If I added this weight (~15 lb) to the suspended mass of 50 lb, the symmetry of suspension loading would be impossible. In any case tonearm and platter would never be resonating coherently because they are so different in shape and acoustic response. Besides, suspension works only when the platter spins. I cannot add tonearm support to the rotating mass. The task of the designer is to prevent all vibrations as much as possible. If it is not possible, one has to damp suspicion. Onedof does both: does not resonate and damps external vibes coming from environment.
However, this is all theory. I like the sound of Onedof, but I had never heard Continuum or EMT927.
Ask more questions, Minh.
If your co-bloggers need answers let them read my web site, using links, that I have given above. ...
I am sorry, Minh, I made a mistake. Tonearm tower weights only 8 LB"
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"Dear Aleks,
Thanks so much for taking the time to answer my questions.
Regarding the tonearm tower, several of us on that forum have taken to having our own towers fabricated by machinists we know. Two of our main concerns were weight and materials. Regarding weight, some of us were of the view that the heavier the better. Thus, many of our towers are 16-21lbs. The idea is that mass loading the tonearm would dissipate errant vibrations and also that increasing weight would prevent accidental movement of the entire tower (thus messing up tonearm geometry). Evidently, with your 8lb tower, you seem unconcerned with what troubled us. Are we just being neurotic? On another note, how do you ensure that external vibrations coming up from whatever platform the tower sits on doesn't make it into the tower and then into the tonearm? Is there a design feature that takes this into account. [You might have answered this already in your response below, but admittedly I couldn't follow all of it (I'm no scientist, that's for sure).]
Secondly, regarding materials. We have made towers ranging from brass to stainless steel to various combinations. What is your tower made from? And what main considerations went into choosing the material(s).
Do I have your permission to post our exchange on the forum site? I believe many others would find your answers useful.
FYI: links to your site have already been posted.
I should say, lastly, that I find your turntable extremely tasteful and beautiful. Congratulations and best wishes!
Regards,
Minh"
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"Dear Minh,
thank you for the compliment. Yes, what I wrote to you is in public domain.
I do have a scientific background, but I am practicing engineering for 35 years. I am always trying to make myself clear to anybody. I avoid acronyms and abbreviations, I avoid professional vernacular. Still, if you do not feel comfortable with my language, ask again.
I think, the heavier the tonearm support - the better, but after some point extra weight does not make any difference. What does make difference is the stiffness of the load path from the stand to the tonearm. That does not change with mass only, but also change with material stiffness. Aluminum is three times less stiff than steel and 2/3 as stiff as aluminum bronze. Combination of mass and stiffness of the load path creates acoustic response of the system, which is the set of characteristic frequencies at which the system generates resonances. One should be talking about particular frequencies and how to deal with resonant response, rather than in general terms. My tower is made out of aluminum 6061 T6. I did analyze its acoustic response using finite element model of the tower housing and optimized its design to avoid some modes of vibration ("mode" is a change of shape that structure takes, when it vibrates). Some modes of vibration propel distortion upward and therefore are more damaging.
I will take your questions, Minh very seriously, and I will post answers on my web site with some illustrations. It will happen after the show in Denver.
Thank you for your questions and for your compliments, Minh.
By the way, tell the guys, NASA does not build any flight hardware, corporations do. NASA is a government agency, like US Post Service. NASA delivers staff from down here to over there."
