Rwd, 54db is a little low, but it will do. It will cause just a slightly higher noise floor, due to having to turn up the volume a little higher for the same SPL. But it should be about the same as with your Helikon.
Regarding the use of the Shelter in the JMW, just because it can be bolted in there and make sound come out, does not mean it is the optimal set up. The Shelter 501 or 901 will sound real good even if it is not in the optimal set up, but it will sound alot better if it is.
I guarantee you that the Shelter will microscopically "wiggle" that tonearm around, causing loss of dynamics and information. That's just what happens with low-compliance and unipivots. I'm sorry, but this is just simple fact. Just because an arm gets a good review and rating, and costs alot of money, does not mean that you can just go slapping any cartridge you want into it, and expect to get optimum results. The Helikon at 12cu, is on the lower edge of compliance compatibility with this arm. Any lower than 12cu, and you are asking for "tail wagging the dog" syndrome. Oh, it will work. But not the way it would work in the right arm. Even a good medium-mass gimbal bearing arm needs to have extra lateral stabilizing mass to properly handle it. A unipivot, damped or not, will get wiggled around enough to lose critical information. A Graham with the right armwand could do it because of the outrigger stabilizing weights, but it would be pushing the Graham to the max of it's capability. It is just a matter of matching the compliance to the arm design. It is not any kind of knock on the JMW arms.
