Why will no other turntable beat the EMT 927?

I heard a clearly better and more believable presentation with the SME V-12 than I did with the SME V using the same cartridge and cable on the same turntable during a direct comparison over a two week period. In fact, it was not really close.

The effective mass of the V-12 is only 1g more than the V. Inertia may even be less because the counterweight ended up being considerably closer to the pivot on the V-12. The weight of the arm tube and counterweight is greater on the longer arm, so there is more weight on the knife edge bearing, so that may also help drain energy away from the cartridge and into the arm base.

The headshell angle is less on the longer arm, so there is less need for antiskate and I used two Mint LP custom arc protractors for each alignment, so I presume one was not better set up than the other. So it is reasonable to presume some of the better sonics I hear are a result of the lower tracking distortion of the longer arm. To Tony's point, SME did spend two years developing the longer version of the V arm. It is not simply a 3" longer arm tube like some other designs.

My only experience with arms in my system is with three different SME arms, so I can not make a general argument for 12" arms over 9" arms, but the points raised above by both Raul and Lewm do make sense.

But, Peter, Raul and I were at odds on the subject. Whilst out for my evening constitutional, I thought of an additional advantage of 12-inch arms vs 9-inch: The former makes it easier for the cantilever to work against bearing friction at the pivot, because the longer arm affords greater mechanical advantage in overcoming that force. Of course, the possible negative trade-off is the additional inertia associated with heavier tonearms.

Well, I think Raul points out potential problems with the longer arms and if they are not addressed, then the disadvantages are outweighed by a correctly implemented 9" arm. However, if the effective mass is low enough and the arm and cartridge are properly aligned, then the advantages of the lower tracking distortion of the longer arms can be realized.

Though I'm not sure, I think that longer arms can have the same or lower inertia than shorter arms. It is a function of where the counterweight is located in relation to the pivot. In my specific case, though the effective mass of the V-12 is 1g greater than that of the 9" V, the inertia may be less because the counterweight is considerably closer to the pivot allowing the arm to react quicker.

People who have compared the V to the V-12 have commented that the V is more dynamic and "quicker" sounding. I did not notice this. I did hear a clearer, more detailed and smoother sound with the V-12 though.

Perhaps John Gordon can add some comments about effective mass and inertia.

Don't worry about inertia. Just add the cartridge effective mass to the tonearm's effective mass and use the cartridge compliance to calculate the system natural frequency. As long as it is around 10Hz, it's fine.

Tony, I never worry about inertia, except my own.
Peter, I think the total inertia is the sum of the inertia of the tonearm in front of the pivot plus that of the stub and counterweight and anything else behind the pivot. I think what you are referring to is the counter-intuitive fact that the moi of the rear part of the tonearm is related to the square of the distance from the pivot to the center of mass of the counterweight and to only the first power of the mass of the counterweight. Thus, a heavier counterweight that can be moved closer to the pivot will result in lower moi.