Direct drive vs belt vs rim vs idler arm

In_shore -
The centre disc method you outlined is flawed. It assumes the record is round, which often is not true. Therefore the diameters are not consistant. The groove is what is round, not the edge of the record.
The file method I suggested in the speed accuracy thread was trialled by Tonywinsc.

11-26-11: Tonywinsc
I filed the hole in my stereo test record. I improved the runout a bit. According to the iPhone app, I now have the raw Wow down to +/-0.16%. The filtered didn't change, -0.01%/+0.02%. The total spread within the published specs for my tt. With a little more filing of the center hole and more work/patient effort to center the record on the platter, I could improve the raw values even more.

Richardkrebs
Re Your post on the 24/1

I have alluded to another problem with speed stability in DD TTs that is unrelated to stylus drag or cogging...
It occurs at much higher frequencies...
Taking it away however is dramatic.
It also shows that we can perceive timing problems well below the threshold of measuring instruments.

Thanks for your illuminating post. The jitter you are referring to is one of the fundamental shortcomings of the Technics SP10 that other manufacturers have taken pains to design out. It is all too obvious for those of us with a quality turntable that the Technics possesses jitter that would make its purchase unacceptable. I am all too aware of the Technics jitter because my Final simply does not have it. Your attempts to remove the jitter from the Technics is laudable.

Thespier and Thuchan, I agree: posts should not be reviewed for censorship. Let the members have a free conversation.

Richard,

Great post about the arrival time difference between our ears of a sound 15 degrees away from straight ahead. It really made me think about how sensitive our ears and brains are. I'm kind of surprised that I never thought about this. I wonder if this has something to do with components that soundstage and image very well. It could just be that the component processes or amplifies (whatever the component is doing whether it be an DAC or an amplifier) all frequencies and gets them to the output terminals in exactly the same amount of time. The component would also have to have the same exact, non-wavering processing time for the right and left channels.

I checked the math (twice) and got a time difference of 0.00008 seconds between the left and right ears, though, not 0.0000053 seconds as you calculated. I may have made the same error twice or maybe not. It still doesn't change the fact that the time difference is extremely small for a sound that is 15 degrees away from straight ahead.

For those who didn't do the math, at a distance of 4 meters, 15 degrees is equal to the sound source being about 1 meter away from straight ahead. 1 meter is a reasonable distance to use for this calculation. I think anyone could tell if something is straight ahead or 1 meter to the right with their eyes closed. We are probably capable of hearing even smaller changes in distance.

We can tell the direction of a sound source by the arrival time difference between our ears.

A sound source 15 degrees to the right of straight ahead at a distance of 4 meters will reach the right ear slightly sooner, but this is not all that clues us into where the sound is coming from. The sound will also be louder in the right ear because there is a more direct path into the right ear. It's more than likely both things that help us determine where sounds are coming from- time differences and volume differences.