I made careful measurements of low frequency spectra for wet play versus dry play. Using a test disc with pink noise to 30Hz. Measured 3 samples for each of dry and wet play, with the test disc clamped in place for all measurements. Ortofon 2M Red in Pro-ject 8.6C arm.
From which it seems reasonable to conclude there is a tangible lf effect from playing wet.
Now it needs explaining !
Peak f of the lf response perhaps has shifted down a bit. Q has increased (?). Does wet play effectively provide damping (excuse the pun), fluid drag proportional to velocity ? Can't get my head around it yet, but the reaction force to any drag force would be effected through the cantilever.
How interesting !
Thread link is here : viewtopic.php?f=19&t=22360&start=235
The above post has remained an enigma as to how/why playing wet would significantly improve lf stability. But I think the answer may be as follows :
Normal stylus-groove friction seems to follow a flicker law, as set out in this thread here :viewtopic.php?f=19&t=41978&start=66
In the follow up discussion, it's suggested that friction has a steady state part and a random element which follows a 1/f flicker noise law, being based on stick-slip friction.
Consider a silent groove. Tonearm drag from friction would then have a random element, potentially with a strong low frequency element - as flicker law noise characteristically has. Then skate force would have a random noise element due to friction, with a strong LF spectrum. This would then be a stimulus, and would show up in the cart/arm frequency response plots, modified by the response of that system.
Wet playback significantly reduces measured stylus-groove friction, as demonstrated on this thread. If it significantly reduces the random element, eg by eliminating stick-slip, then LF noise stimulus from skate force might be significantly reduced too. This would explain the significant improvement in LF spectrum, and apparent stability, observed in wet playback.
Then, wet playback might well reduce/eliminate a significant instability stimulus. And there's no need to try to explain any changes to the spring-mass-damper system of the cart/arm, the phenomenum can be explained without that. Just by changes to groove-stylus friction.
But the stability gain from wet playback is significant here. A corollary is that high friction records can stimulate instability. Interesting ?