VPI 3D tonearm

Thanks Stringreen. That makes sense. I completely agree that the counterweight should ideally be as close to the pivot as possible.

I heard a description of this VPI arm at the NYC show in April. Harry explained that there are some complex shapes and sectional changes in the arm tube interior that are not possible to produce by other methods. Apparently this arm tube is very good at controlling/damping vibrations. The lack of joints/seams also was discussed as an advantage.

I don't know how different the VPI 3D is from my SME V-12 arm tube, but the latter is also one piece with a varying cross section, and it is made of magnesium.

I was also told the 3D takes one day to make in the printer.

Why not just supply each new arm with all of the counterweights? That way, the owner would be covered for future cartridge changes.

I can't speak to the VPI 3D arm, but regarding the counterweight issue, I agree with Stringreen. At least on my 12" SME arm, the counterweight is very heavy and is as close to the pivot as is possible with the design. My AirTight Supreme cartridge weighs 12.5 g which is the ideal weight for this arm and allows the heaviest SME counterweight to slide very close to the pivot. The cartridge was developed in part on this arm.

I believe the relevant issue is moment of inertia. The closer the counterweight is to the pivot, the less inertia and the quicker the arm can respond to movement as the stylus tracks the groove. And I presume the less the cantilever has to work to overcome the inertia of the arm, lessoning distortion as the stylus remains more in the center of the groove.

There is also the issue of resonance within the structure that supports the counterweight. If the counterweight is far from the pivot, I think the support is more likely to resonate, all else being equal.

This does not address the issue of resonance in the main armtube that was discussed up the thread, which is perhaps the main design goal of the 3D arm. It will be very interesting to see how this arm performs.

Some companies do offer in-home trial periods. Reno HiFi does with Pass Labs electronics. No rental fee, just shipping costs. Some dealerships offer home trials on speakers for a fee. My friend is doing this now for an expensive, massive speaker system. I think this is a direction some companies will go as local dealerships dwindle in number. It does offer a high degree of confidence in the purchase decision when one can audition a component in his own system over a period of time.

It's interesting that VPI would offer this instead of or, in addition to, their dealer network. I like the idea of touring demo units. I would like to try one of the ultrasonic LP cleaners and compare it to the machine I have. All sorts of possibilities.

Stringreen, I can't seem to find that post you started the other day. What happened to it?

Nevermind, I see it now.