Direct Drive vs. Idler Drive vs. Belt drive

Ralph, One of the virtues of a coreless motor as originally designed by Dual and used by Pioneer, Yamaha, and Kenwood, and even now Brinkmann, is that the field it generates is in the horizontal plane, mainly. The engineers who designed for these companies and those who designed for the iron core motors in the Denons and Technics turntables, were not ignorant of this potential problem.  They took care to provide shielding.  In the case of my Kenwood L07D, in addition to the motor being encased in a metal that adds shielding (the motor in its case looks like a metal discus, sealed all around top and bottom), the platter uses a thick heavy sheet of stainless steel for a "mat".  Kenwood call it a "platter sheet".  Nevertheless, L07D owners are known to add even more shielding by various methods.  In my case, I had a machinist (Colby Lamb in Oregon) make me a new platter sheet out of pure copper.  It mimics the original in shape and weight to within a few centigrams.  I've been meaning to buy a cheap field strength meter to see whether I can detect a difference in radiated EMI, comparing the original stainless steel sheet to the new copper sheet, but I have not done it yet.  Although I like to think my copper platter sheet makes a big difference, because I paid Colby $700 to make it, I really cannot say the difference is huge, because I heard no problem before, and I hear no problem after, maybe a very very subtle difference.  Anyway, I don't care because the copper is beautiful to behold.  With my SP10 Mk3, the platter is simply enormous and thick, made of brass and aluminum.  It's dead silent.  With my SP10 Mk2, when I owned one, there I may have heard a faint grayish coloration to the sound, only when comparing it to the former two turntables named above.  Belt-drivers like to claim that the faint coloration they say they hear with the Mk2 is due to the servo "hunting" to maintain constant speed.  I think it's more likely due to EMI which could easily be ameliorated by either using a metal mat (which many do use with the M2 and others) or by simply adding shielding under the platter.  Perhaps the reason people like metal mats on some DDs has to do more with blocking EMI than with the inherent goodness of metal as a mat.  One reason I sold the M2 and kept my Denon DP80 is because the DP80 lacks that faint coloration I thought I heard from the Mk2.  (This is before I was lucky enough to find my Mk3 and the L07D.)

Atmasphere, I never thought it was a noise issue and I have to admit it is an intellectual bias without a shred of evidence that I know of. But magnets and magnetic fields have interesting ways of interacting with each other physically as well as electrically. My theory is that it is a distortion or tracking problem. All I can say for certain is that when these tables hit the market we were all enamored with them but quickly decided there was something wrong with the way they sounded. This is not just me but but all the audio big wigs in Miami circa 1980. The drive behind these tables was that they were cheaper, easier to assemble, much lighter (less expensive to ship) and could be pumped out in large numbers which they were. Since the Japs are capable of turning out an extremely polished device and the marketing hype was good they sold in droves until the digitally mandated vinyl crash. There are some newer DD tables I find intriguing and would like to hear but given my own experience I would never buy one sight unheard. 
One other problem is that I have never seen a DD table properly suspended. A drive be it belt, DD or Idler is entirely dependent on it's plinth for isolation. Cartridges being the very sensitive devices they are will pick up any vibration transferred from the environment to the drive. This is best and most reliably done (IMHO) by having a very inert sub chassis suspended by a system with a resonant frequency around 3 Hz.
SME and Basis tables are examples of external sub chassis. The SOTA and Linn are examples of internal sub chassis. The Walker and Air Force 1 use air springs. Other types of plinths rely almost entirely on the structure they sit on down to the foundation of the house. 

Al EMT DD are good suspended.
Two my friends -
One sold Linn LP12 for EMT 948 and other one sold Sota for EMT 950.
Other my friend prefer EMT 948 over Kenwood L07d and Technics SP10mk2, but he likes Yamaha GT-2000 as much as EMT.

I think than EMT 950 is the most unic DD. It was introduced in 1976.
It weighs ~80Kg and has ultra light rubber plate and powerful coreless motor. Even some EMT and vintage TT collectors prefer EMT 950 over idler drive EMT 927 and 930.

https://en.wikipedia.org/wiki/Elektro-Mess-Technik

Mijo, blah-blah-blah.
what could be cheaper to make than a typical modern belt drive in the under $3K price range? They multiply like rabbits. THAT is why belts became dominant. You can build one in your basement. ( I have respect for some expensive belts, starting with Dohmann Helix.) And most suspended turntables are not properly suspended. Or do you still want to ignore the placement of the motor, on or off the suspension. Either way is a compromise. If you’re obsessed with suspensions, Minus K or Herzan or possibly Vibraplane are ways to go. And each of those can be used with any drive system.

@lewm

If you’re obsessed with suspensions, Minus K or Herzan or possibly Vibraplane are ways to go. And each of those can be used with any drive system.

the Herzan active type systems can only be used when the gear has zero sensed self noise. any self noise will set up a feedback loop and burn out the device, or at least compromise the benefit. which is why it can’t be used on many turntables.

for instance it works perfectly with my dd Wave Kinetics NVS as it zero self noise. but my Saskia model two idler has considerable self noise so it’s not a candidate. most belt drives and idlers are not candidates. i could use a passive air device such as a Stacore with the Saskia and may try it.