bastlnut wrote:how you calculate ratios etc. makes a large difference in the results.
All parameters and ratios have classical, standard definitions. Units are always specified.
bastlnut wrote:you may want to calculate the stability factor of a tonearm that uses a different headshell and CW other than the original and factor that into the spreadsheet.
is the CW off axis or underslung? is the headshell higher or lower than the original?
where is the center of gravity of the tonearm? in which plane?
ALL of those factors get wrapped up into the standard 'tonearm effective mass' definition. That's what 'tonearm effective mass' is all about, it's whole reason to be. At these low frequencies, the arm can be modelled as though it is rigid, and all the various parts of the arm contribute their inertia. It all gets wrapped up into one single entity. Tonearm effective mass is all it's necessary to know. Really !
Of course, each factor has its own contribution to effective mass. Some add, some subtract. You can use the tonearm effective mass calculator to evaluate changes.
NB this only applies to consideration of lf stability. Tonearm effective mass, the topic of this thread, is entirely
concerned with lf stability. That is, the behaviour of the suspension spring/damping and the tonearm inertia. Not the vibration of the tonearm itself, whose typical lowest self-resonant frequency is far above the range at issue.
bastlnut wrote:i will have to look at the damping calculator.
When matching cartridges and arms for lf stability, you can see it's crucial to consider cartridge damping. So long as you know any two of the following three you can use loafer to work out the other one. Then it will report damping for you. You need to know any two of :
spec VTF range
bastlnut wrote:what about bearing drag?
There are two sorts of bearing friction : stiction (bad) and friction (good). According to Leigh Phoenix, typical bearing friction comprises a damping ratio of c 0.08. If you don't know the actual value, suggest use this. My own experience is modern arms can have far smaller values, perhaps 0.04 or less. For small values like this, it can just be added to cartridge damping ratio.
One comes to realise that a little bit of bearing friction can be a good thing. If its the right type in the right place and the right amount.
bastlnut wrote:and the affect of VTA?
Virtually none on lf stability. Virtually no interaction with tonearm effective mass.
bastlnut wrote:suspended chassis or solid plinth?
plinth/sub-chassis resonances are vibration sources
. To evaluate the effect in warpengine, change the frequency and amplitude to match the source. You'll see how much VTF gets eaten by such sources.
bastlnut wrote:the electrical aspects of an overstressed suspension and closer proximity to the magnets?
in all my various tests, I've never found evidence of mechanical loading via the electrical interface. Pity, because suspension damping could then be manipulated. But no.
bastlnut wrote:how about the room temp?
No idea ! Suspension elastomers probably are quite temperature sensitive as to spring/damping behaviour.