A novel approach to turntables
The Platterless Secret
We didn't create a platterless turntable for the sake of the platterless design, but the creation of the platterless design was a side effect of creating a beautiful turntable.
The Atmo Sfera™ shape is not, however, primarily dictated by the designer's taste, but it is ruled by the technical and sonic features we had in mind.
The first design rule of a mechanical or electrical engineer should be: if it is made of an elastic material, it stores energy...
...and the second rule is: if it stores energy, it releases such energy, sooner or later.
The not controlled energy, stored and released, causes blurriness or ugliness of sound, in an average turntable.
The audiophiles use to chat about mass when they describe a turntable, but the concept of (huge) mass in a turntable is completely meaningless, unless you consider also how this mass is distributed.
The audiophiles also use to talk about damping; damping is a magic word, for the average audiophile, but damping actually means spreading the stored energy of the physical body all around the audio spectrum, with horrible results.
So, why Atmo Sfera™ is different: we are well aware of the elastic behaviour of every man-made turntable, so we choose to put all “resonances” (the effects of the energy release) in a part of the audio band in which they cannot be very harmful.
First thing first: we chose to made the entire Atmo Sfera™ body in Anticorodal® aluminium; aluminium is stiff and has a pretty isotropic structure; the behaviour of the aluminium is fully predictable. The secret of seasoned engineers is to work, as much as possible, in a linear and predictable environment.
Second, but very important, issue: the shape of the turntable base and of the LP disc support are designed to show a series of natural vibration modes very far from the audio band or from the vinyl resonances.
Take, for example, the small reverse cup that holds the vinyl record: the cup and the record press device form a hemisphere, that is a solid with controlled and predictable vibration modes.
We made a finite element simulation on the record support and the results are the following:
This is the first vibration mode simulation, with the displacement ratio of the body shown in colours
Please note, the first mode of vibration occurs (in our model) at more than 9,1 kHz; the resonance of an average vinyl occurs at about 4 kHz (estimated in an empirical mode), more than an octave lower, so few chances are than a vibration of the cup can trigger any dangerous vibration in vinyl.
Take now as an example the Atmo Sfera™ base:
The (greatly exaggerated) displacement (in the real word are fractions of a micron) show the first vibration mode at more than 18 kHz, at the upper limit of the audio band, in which the RIAA equalization has an attenuation of about 18 dB with respect to the centre frequency.
We can fix the turntable motor directly to the base, without the use of damping material and get no vibrations induced into the record.
Next step for a turntable design: how to guarantee a rotation free of wow & flutter, the annoying “meeow” that plagues some reputed turntables with a low platter mass.
The secret is simple and is the following: “To create a turntable in which the pair of Complex conjugate poles of the mechanical rotating system are as close as possible to the Real axis” This statement is meaningless for all the people, we bet, except for the few electrical or mechanical engineers that are reading this document, so we will do an example.
Imagine to have two different driving belts for your turntable : the first made of rectified silicone rubber, similar to those used in many British turntables, the second belt made by a rubberband used for closing small packets.
Should an audiophile choose one of them for his turntable, he will undoubtedly choose the rectified silicone rubber belt without any doubt. I chose, instead, the rubberband, because it helped the designer to get the “Complex conjugate poles closer to the Real axis”.
It's not a joke, we really tested the rectified silicone etc. against a rubberband and the rubberband performed better in our design, from a point of view of W&F ratio, according to the theory and to the step response analysis.
Using this kind of approach to the problem, no matter how low the turntable weight is (within reasonable limits); you will get excellent results with light rotating elements and no heavy mass. An heavy turntable mass doesn't guarantee at all high performances.
Put together the following issues:
- controlled modes of vibrations, well outside the audio frequencies more sensitive to the ear
- limited stored energy due to the low turntable mass
and you will have Atmo Sfera™ with its neutral and fulfilling sonic behaviour.