How much force can a tiny stylus and a fragile cantilever exert to deform a steel or aluminum arm tube. Maybe Marc needs to shed some light on what he means by deformation because I've never seen it in an average lowly aluminum or steel J pipe. This keeps the cartridge more stable on the “centre†of the groove and can track it more accurately than with an arm that deforms more under the forces exerted while playing a record.Since we brought up modern cartridges which are typically designed for 1.0-1.5g or 1.5- 2.0g VTF how much lighter are we talking about here? What's the sonic advantage of setting VTF lower than manufacturer's recommended force besides a change in character? The fact that we can track many cartridges with way lower VTF than the recommended, is due to the much higher rigidity of the arm structure. One can argue that choice of material will have equal or more of an effect on the overall sound than slight differences in rigidity, CF has certain resonant attributes as a medium which I personally always found questionable when used in audio, do you negate that with your process? How rigid/stiff does an arm tube have to be when dealing with such minuscule forces? There are plenty of arm tubes that don't deform as you mentioned below.
Better tracing certainly results in both higher resolution and faster transients too along with many other factors including design of the cartridge and turntable and materials used in each one's construction ultimate stiffness might now always be the best solution. Marc said, " Besides, a more rigid tube provides much more accurate and faster transients and higher resolution, as you could probably hear during your listening sessions". I can understand when you mention " much more rigidity" for a 9" arm tube vs 12" and keeping the same mass, how much more mass are we talking about if you kept the thickness of the tube the same? Why wouldn't there be the same overall improvements brought about by superior tracing to your design? Further there's a distinct benefit to the low frequency reproduction, better overall balance, tone, timbre, texture resolution and depth, while I have no way of measuring rigidity I can measure and hear the benefit of higher tracing ability and additional mass.
Better tracing means less distortion which means more musicality, higher tonal resolution, solidity and naturalness (if that's one of the goals). I guess you couldn’t hear tracing distortion compared to a 12†arm.- Of the better arms I've owned and tested there was always a lot more to the 12" version vs the 9" & 10" ones than tracking ability and dismissing it. Besides, a more rigid tube provides much more accurate and faster transients and higher resolution, as you could probably hear during your listening sessions. The decrease in distortion due to a much more rigid arm tube more than compensates the increase in distortion due to a shorter arm length. The decision to make the arm 9†long is based on the much higher rigidity that can be achieved for the same arm mass while just sacrificing a minuscule improvement in the tracing error. Some further comments from SAT arm designer Marc Gomez about what went into the design of his arm. Accessories including Stillpoint Aperture panels, Cathedral Sound panels, Furutech NCF Nano AC receptacles Silver Circle Tchaik 6 PLC, Symposium ISIS and SRA Craz 3 racks, Audiodharma Cable Cooker, Symposium Ultra and assorted SRA OHIO Class 2.1+ platforms. 6, Skogrand, Viero, Kubala-Sosna, Audience Au24SX, Genesis Advanced Technologies and Ensemble Power Cords Assorted cables including Transparent XL Gen. Technics RS1506 with Flux Magnetic heads, Doshi V3.0 tape stage (balanced)
2, vdh Colibri Master Signature, MutechHayabusa, MOFI Master Tracker, Sumiko Songbird cartridges VPI 12-inch 3D Fat Boy dual pivot tonearm, VPI 12-inch 3D Fat Boy gimballed and SAT LM-12 arm Goldmund Mimesis 37S Nextgen preamplifier