I still stand by any isolation system that isolates the motors and the turntable in 2 separate domains (2 separate isolation devices) will in fact induce wow & flutter as the turntable & motor will vibrate independent of each other. This in itself must be considered. So, then we can postulate the best isolation will be a wall mounted stand with the motor suspended apart from the turntable. Unfortunately not a possibility for me and for most.
So back to basics, it is important in the design of any turntable that the motor has as little vibration as possible. This can be measured but in fact no currently published magazines in the US ever do such a measurement. Neither do they measure speed accuracy. But if I remember correctly there are some magazines in Europe which do such measurements. I wonder what motors measured best in terms of speed stability (at the platter, not motor) and in terms of vibration at the motor directly and finally how much vibration is transmitted to the platter/LP from the motor. All good questions. So now, I will also suggest a good isolation system or stand will in fact absorb vibration from the motor and also keep it away from the all important stylus/LP interface.
Now, on to the theory behind more motors. I have thought extensively about this. I am by no means an expert but put forward the following points.
Syncronizing multiple motors does have its challenges and might lead to the less is more philosophy from this perspective.
While a motor pulls the belt on one side of the pully, it in fact pushes the belt & creates slack on the other side of the pully
Using 3 motors will have a "take up motor" that will pull the belt and reduce the slack amount of belt being pushed.
Also 3 motors allows for less contact area between the platter and belt. This results in less surface resistance and less induced vibration from the motor through the belt to the platter. But also, this results in less realized torque at the platter, as there is less contact between the belt and platter. Again 2 items in conflict with each other. Ultimately you will need to let your ears be the judge. I know I have, and have spoken privately about my conclusions with my audio friends.
Back to isolation, I am in agreement that more weight on top of a stand will give you a lower resonant frequency but I think there must be some way to come to an ideal number. I forget my physics as it is over 20 years ago but for anything to isolate it must vibrate. If it is too stiff it won't work. Just think of the difference between a Cadillac suspension compared to a sports car or BMW/Audi for the Germans. One is softer on your but while the other wobbles more. Ultimately I find the stiff suspension of a car better, but ask my father and he would say to opposite.
I am using springs for my stand as many have seen. I wonder if reducing the # of springs will improve isolation. I know reducing the mass on top of the stand sounded worse as the resonant frequency rose too high. But then I might as well use less springs. I wish I remembered my spring constants etc.
