Quote Originally Posted by Ammonite Acoustics View Post
If anyone with a Jelco arm is a bit puzzled why placing a weight on top of the arm structure can possibly be a Good Thing, my advice is to try it. In the first instance, just use a spare counterweight (usually the heavy one that comes with the arm), and place it carefully on top of the damping knob. Adding mass in this way, to my ears, greatly enhances the depth of sound and musical flow. It's free to try in the first instance and you can always get Steve to make you a nice shiny one that sits more securely on top of the arm if you like the effect.

There's nothing pseudo-scientific or foo about why this works - one of the best ways of damping a resonant structure is to apply mass. That's all!

This tweak also works with my FR64S and I will get Steve to make me another weight to sit securely over the top of that arm

Interesting.

I noticed a while back that there was a Microseiki base weight on offer, that screwed in under the arm board - rather than the usual nut, this was a very chunky 5-6cm deep heavy weight, that screwed in to 'stabilise' the armbase (into which the arm is secured by two grub screws). What would be the physics of that? Any damping effect from adding mass there rather than on top?

My Ikeda armbase is exactly the same screw thread as the FR64S, also I guess the size means it could be done up quite tightly just by hand pressure. The Ortofon works a bit differently as the base is a sliding SME-type into a collar (the base secured to the armboard by four bolts, SME-style) so no potential for similar really. Neither are really amenable to adding mass from above ... the Ikeda has a round top over the bearing, so a bit harder to put a weight on top while the Ortofon has quite a narrow retaining ring for the bearing assembly.