Grand Prix Audio Monaco Turntable

when both speed accuracy and stability is achieved to a high degree the music attains a solidity and tonal integrity which must be heard to be appreciated. my Rockport System III Sirius direct drive motor......"yields speed accuracies on the order of 10 parts per million with absolutely zero torque ripple".

it also has a servo which totally corrects groove modulation on musical peaks. this aspect of speed stability cannot be stated too strongly. every belt driven tt and many direct drive tt's will be effected by groove modulation (kickback from the additional friction) and most listeners assume the effect of groove modulation is in the recording. it is only when you hear the recording played back without any groove modulation that it's affect is recognized. on musical peaks you might assume it's your amp or speakers are distorting.....but it's only the slight speed hesitation which causes the distortion and momentary loss of musical flow and cohesivness.

hearing a concert grand piano Lp played back at high volume on the Rockport is revelatory. lots of dynamics and overtones.....any non-linearities jump right out. then on anything else.....not the same.

Peter Montcrief's article summarizes the advantages nicely.

i have played CD's along with Lps on the Rockport....and the timing is perfect.....the problem becomes the space between cuts.....which do not always match.

there is more to tt performance than speed correctness; but music is mostly a matter of timing.....getting it right is much of the challenge.

while belt driven tt's have theoretical limitations in speed stability as always it's the execution of a design that is paramount. there are some great belt driven tt's that do speed very well. it's just that the very best direct drive tt's do it better to my ears.

regarding the Rockport Sirius III; there is a very good reason it is no longer made......it simply costs too much to build. so it's particular approach to the speed issue has a level of execution that is unique.

it combines the special pure induction motor with an optical speed controller and servo which regulates the speed. it also uses an air bearing and 55 pound platter combined with vacuum holdown. then throw in an air suspension and multiple layers of mass and isolation and the speed control is allowed to work in an totally isolated environment.

other direct drive tt's might have a cog-less motor and speed correction but no servo to eliminate groove modulation; or a conventional if excellent bearing but not an air bearing, or a great passive suspension but not an active air suspension, or a more modest platter and clamping system but not the heavy platter and vacuum of the Rockport.

OTOH you can buy those other DD tt's as they are still being built.