No, I think it is a matter of reason that an LP12 won't smoothly(!) wow over a period of seconds in response to stylus drag. The subchassis wobbling around under all sorts of stimuli is another matter altogether.Maybe, but can you deduce that from these 'steady state' recordings?
I'll post images tomorrow but the spectrum of the tone looks the same as phix's, two separated peaks. I think a query to Analogue Productions might be in order.Analogue Productions test record.
The polar plot represents a small number of revolutions of the platter, the further the line gets from the notional centre the faster the speed. The shape you see has to be interpreted. I think your original plot had 6 corners, and the idler rotates 6 times to turn the platter once. I don't know what the regular kink on the current plot represents, perhaps it is just tolerance on the platter drive surface.I meant how do you make difference on the polar plot between record eccentricity, idler beat and motor shaft eccentricity? How do you recognize those factors on the plot?
Undoubtedly some are, after all the test record captures the errors inherent in the lathe. But as a basis for investigating turntables I think there's potential, on a comparative basis as you upgrade or modify.I do wonder how much of these measured artifacts are down to the test record.
It would be interesting to know more about the mechanical arrangement of the turntable, to see whether any of the modest peaks can be explained
The plot is the spectrum of the speed variations, from 0 - 20Hz. So the peaks on the left are the eccentricity of the record at 0.55Hz and 1.1Hz. On my Linn I have an obvious peak at 4.2Hz which is the motor rpm. If I repeat the test at 45rpm using a Lingo this peak moves up to 5.6Hz.Could do, but I'm not sure what the modest peaks represent?
I'm not sure it is very useful except with obvious problems with, say, an idler. OTOH the potential of this form of display definitely warrants more investigation. If a complete loop were timed for a complete cycle of the belt then belt flaws might be revealed, for example.The Polar plot is quite a good result it seems to me, or is it? It does seem quite even and round.
I wonder if the jaggediness is the notorious suspension wobble?