Greetings all on this post.
Here was where I first learned about the 15 second "bounce" or swing time needed for my TD150:viewtopic.php?p=94615
I will repost the points here mentioned:
1) Please be shure to use a belt of correct length (min. 255 mm)
2) for the following steps you must have the belt mounted.
3) In order to get the correct adjustment, please mount the platter and
put the original plattermat and of course a vinyl disc on it.
4) Dismount the three springs
5) Dismantel the springs from the foam material cases
6) Afterwards remount the three springs and have a look for the correct
mounting position. The lower end of the springs must point to the platter
7) Only for the older Thorens there is the need to mount an additional
swash plate between chassis and each spring.
Now screw everything together and adjust the three springs. Afterwards
the platter should float for about 6 mm in height parallel to the upper
edge of the chassis/ motorplate.
9) In case the platte is to high, please start the readjustment with the
spring on the motorside first.
10) In case you have the swash plates mounted it is possible to center
the spring by turning the swash plate.
11) Any time you correct the fitting or the preloading of the springs or by
turning the swash plates you have to readjust the height of the platter.
12) By pushing the platter on the spindle the platter must swing freely
and for about 15 seconds
I then posted the original thread almost 8 years ago about my findings on the 15 second "bounce" or oscillation time to aim for with certain Thorens suspended sub-chassis turntables: viewtopic.php?f=17&t=33519
Note what Joel stated on this thread:
"The exact justage is a garantie for an efficient mechanical filter and to get the Chassis resonance lower as possible."
For the TD320, for example, he gave this explanation as to the reason why exact suspension tuning is important (which I have Google translated from German):
"How important is the dimensioning of the resonance frequency (4.6 Hz) of the mechanical filter. This filter has a slope of 12 dB / octave."
"One octave higher, at 10 Hz +/- 3 Hz, you set the depth resonance of the tonearm.
A well working mechanical filter allows the tonearm to work "undisturbed" at its most critical point! Another octave higher, at 20 Hz, begins about the linear transmission range of the useful signal."
And so this was not hearsay or nonsense, it is true.
From what I understood about his explanation I then posted this:
"Hello Joel, thank you for your expert explanation. Thus now it is all very clear to me. Correct suspension tuning allows the suspension system to act as an effective mechanical filter. The suspension is designed to Help mechanically filter any resonances that may try to find their way to the stylus down to inaudible levels, i.e. well below 20 Hz, so that they do not interfere with the audible frequency range.
This will also explain why the bass frequencies in particular clear up with proper tuning, the stereo image widens, and extra space is heard around the instruments when the suspension is properly tuned. There will be less vibration coming up through the platter to hinder stylus to groove adhesion.
And so it is all about learning the laws of transformation of energy, and, when having a knowledge of these principles, knowing how to apply them through mechanical engineering."
Turntable design is all about understanding about the laws of transformation of energy, and how to damp unwanted ones, as many far more learned contributors on this forum constantly state in their posts.
All the best,