ReMusic World Premiere | Some days ago, my friend and ReMusic Co-editor Roberto told me excited about his new Facebook friend Randolph, the brave Dr. Hedgebeth, Architect. We must be antennas for the news, so, detto fatto, here we are interviewing him, a brand new tonearm designer.
Question: Seems that there is not enough room for brand new tonearms nowadays…
Randolph D. Hedgebeth: The Sonority Tonearm design is a product born of my quest for reproducing very low frequencies in music reproduction using an LP playback system. LP's are rich in subsonic ambient information that I discovered greatly enhances the musical experience. Applying a rumble filter and/or tuning the system to attenuate these frequencies is, at best, a band-aid solution for an inadequate system since the recorded information in the grooves is going to affect the up-stream frequencies. The stylus will track these frequencies anyway. Better to design a non-resonant arm that will play the grooves cleanly and undistorted than to try and 'tune them out'.
Question: There were no other tonearms to accept the challenge?
Hedgebeth: I designed this arm driven out of desperation over tonearms that simply would not track recordings with these frequencies and/or remain stable while these frequencies are being played. The subsonic environment is simply hostile to the vast majority of tonearms old and new. Cartridge tracking is very arm dependent.
I tried out several very well known turntables and tonearms with my deep bass system and recordings I know that have deep recorded bass information. They all failed and one quite dramatically. While tracing the 12 Hz groove of the Liverpool Pipe Organ recording the sound was slightly distorted all the way up the frequency spectrum and with the 10 Hz groove it was very distorted at all frequencies. Miss-tracking was very apparent. When the stylus entered the 8 Hz groove the tonearm launched off the record groove. I had to catch the arm before it fell back down to prevent record damage. It was clear the traditional ‘tuned’ turntable and arm systems were inadequate to the task.
Question: You’re speaking about very low frequencies.
Hedgebeth: Yes. One other action that affects this situation are the many seismic tremors that are prevalent in most areas of the world. The big picture issue we must understand is the earths crust is constantly on the move, constantly vibrating. We are seldom aware of this because we are born into it. Our bodies adjust to these constant micro vibrations. Our newly built audio gear does not have built in sensors or controls to cope with this information. We are only aware of the larger quivers and quakes. Anyone living in active earthquake zones and near volcanoes will identify with this. The thing is that this is going on at a micro-quivering level constantly. The folks that read the Seismographs are not daily reporting this to the local TV news but they are constantly monitoring these micro-quivers for changes and indications of greater activity all over the world. In the study of earthquakes we can gain much knowledge of how the earths crust works in extreme situations as well as in the micro scale.
This is one form of 'distortion' we do want to ‘tune out' of our LP playback setup. These are much lower frequencies than the traditional ‘Effective Mass’ approach deals with and very different. I know this from direct observation having witnessed my LP setup play through a 4.2 earthquake in 2000. The epicenter was near my house. It did not falter due to the way I had suspended the entire assembly. There are the human generated low frequency noises as well, such as traffic, footsteps and other various thumping and banging that happens in our neighborhoods and buildings.
Question: We know, it is a never ending story…
Hedgebeth: In fact, the situation of a tonearm is contradictory. At the same instant on a record the arm needs to have both infinite mass and be massless with absolute stability. An impossible condition. I have made every effort to come as close to this situation as possible in as simple a way as possible.
Question: Notwithstanding, maybe you found an effective solution.
Hedgebeth: Finally I chose a 250 mm effective arm length as the longest practicable length before the Moment of Inertia issue becomes impractical with a medium mass cartridge in place.
A pivoted tracking arm design was chosen as the simplest approach to most simply solve the contradicting design goals and objectives after considerable time spent considering all the linear tracking options.
There is a geometric situation that most linear tracking arms create. The vertical pivot is well above the record surface where the stylus tracks. The slightest vertical warp will present an increasing angular VTA displacement and error far greater than even a less than perfect radial arm will present to the stylus VTA.
With this VTA situation, the complexities climb to an unacceptable level attempting a linear tracking solution for a functional device. It is doubtful a fully satisfactory solution can result. So far I have not heard one that I deem fully satisfactory. Linear trackers are acutely vulnerable to subsonic frequencies in addition to their fragility. Most are solutions I previously considered and rejected in principal or for the conflicting details.
Question: That was for the tracking, what about the tonearm rigidity?
Hedgebeth: It is another situation that I deem critical: the most direct coupling possible between stylus, the pivot bearing(s) and the turntable bearing. This needs to be as rigid and dimensionally unchanging as possible. Air bearings and magnetic levitation leaves much to be desired in this regard. Those kinds of suspensions and bearings belong outside this rigid system, levitating it from the outside world not separating the arm from the turntable bearing or the turntable platter from the plinth. Pneumatically floating the entire assembly would be a great solution for separating the assembly from outside forces.
The first objective was to produce the lightest and stiffest arm wand possible that would survive a subsonic environment without producing any resonances or sonic colorations in playback. After trying all the conventional and not so conventional approaches the three leg tapered truss design was chosen as the best solution. Most important is the dramatic reduction in the moment of inertia. It is my considered opinion that this is far more important than any single part of the arm design. Aside from basic geometry this more profoundly affects the stylus action in the groove and dramatically reducing the moment of inertia.
The second objective of having infinite mass was partly and practically achieved with the use of symmetrical fluid damping in a unique configuration as seen it the picture. This has the secondary benefit of providing the necessary anti-skating resistance; a further simplification. This is augmented by the adjustable Mass Blocks disposed close around the pivot post to adjust the total arm mass. The moment of inertia they contribute is reduced significantly by this location. The counterweight is configured in a similar manner. More than a pound of mass is possible without a significant increase of the moment of inertia. A range in mass of nearly 10:1 is possible.
The arm geometry produces the lowest overall tracking error which goes into a 60 mm radius. The arm pivot point and stylus tip are in a horizontal plane with the record surface for maximum stability and minimum error in any plane. This is the main failing of every linear tracker I've encountered. The bulk of the arm mass is below this plane creating a very stable and well damped arm system. There is no discernible resonant Q. Operation in a subsonic environment is a walk-in-the-park.
Question: Technically speaking, it is a big result. Since the very first sight, the geometry of your tonearm looks really innovative.
Hedgebeth: One of the more important geometric features is the stylus and pivot point being in the same plane. With my new turntable design this arm is designed so the systems primary suspension, in all planes, is in the plane of the record surface. The majority of the assemblies mass is well below this plane for maximum stability. Thus the arm pivot, stylus and record surface are undisturbed by most external vibrations. External vibrations are not translated into other vectors of arm disruption. Also any record warps are treated in a much more neutral way with negligible effect on the VTA. Warps have little effect on playback. The entire assembly is effectively isolated from external vibrations. The record is perfectly clamped to the platter with a single spindle clamp.
This situation makes the exercise and mathematics of ‘Effective Mass’ irrelevant. My question early on: ‘Why would you design an arm which would resonate at all?’
Question: Funny, I have to make you the same question…
Hedgebeth: The effect this approach has on the rest of the audio bandwidth is not inconsequential. The reduction and cancellation of resonances and micro-vibrations in the arm wand alone is profound for the maximum performance of any phono cartridge. This is further aided by the fluid damping. This is not to mention the enhanced subsonic capabilities.
Selection of the materials for the arm was first for their non-resonances then for any structural or other functional necessities. The truss configuration and selection of paper reinforced phenolic for the head shell has profound significance for all the desired characteristics. Magnesium is more than twice the mass and VERY resonant. The sonic differences in a side-by-side comparison was clear and unequivocal. This, along with Redwood as an arm wand material completes the most important assembly. Old Tech preferred with super High Tech specially tailored Epoxy adhesives.
Question: How is build the rest of the tonearm?
Hedgebeth: The uni-pivot concept is both super precise and super simple with the aid of a very high tech plastic cup seat and grade 10 mini ball pivot point. A dry system is used for maximum coupling of the stylus to arm to turntable bearing to platter to record surface to stylus tip loop. My new turntable design has a similar bearing system. The solid copper mass blocks of the tonearm assembly aids in a tight bearing coupling.
Though not a moving part the cast bronze base is what ties the whole thing together. It also has mass for base damping and facilitates other parts of the arm system such as the arm lift and optional phono preamplifier. This eliminates the usual long cable and the cartridge signal is more intimate with its processing electronics. A tube version is used for high output moving magnet and moving iron cartridges. A solid state Head Amp is used to couple moving coil cartridges in a current sourced configuration for best performance. Limo connectors are used for their high performance.
Overall arm stability is excellent with lateral and VTA adjustments made easy. When the total music system becomes available there will be remote controlled arm lift/lowering operations included.
Question: Could you give us some ‘listening impressions’? Obviously, from your manufacturer’s point of view.
Hedgebeth: I do have a London Reference I have not heard yet. I have had a Decca Gold, Garrott modified which demonstrated this is THE arm for Decca's.
My Takeda Labs Miyabi is totally phenomenal in this arm as well. I have had a Sonus Blue an ADC XLM Mk.II and a Denon 103D as well. All performed exceptionally well once I had ‘tuned’ them in with the arm.
Absolutely thunderous bass can be had with the Denon and Decca with a grip I've not heard with aany other arm. The other cartridges also did exceptionally well if not with the iron grip of the Denon or Decca. I think these are specifics of the cartridges that my arm allows to be revealed.
The startling thing was the ADC XLM. It was nearly as incredible in the bass as the Denon and Decca while presenting an astonishing musical experience that was extremely satisfying. Far beyond its price point as is often said but this really caught me by surprise. Not to say it would replace the Allaerts or Miyabi but not so much difference I would take the stylus from the groove.
Having my very deep Infra Bass allows me to analyze cartridges in their entirety. The Allaerts really does go very deep 10Hz as its specs imply. Not thunderous but it will shake the room with its depth and power. In comparison the sheer deep slam of the Decca is a unique audio experience.
It's very easy with my arm to get caught up in the fine points of cartridges' performances.
Question: Thank you, Randolph, ReMusic is ready to get your first production to reviewing it.
Hedgebeth: I promise, it will be a world premiere.
Official technical specifications
Arm geometry: 250mm Length, 16mm Overhang, 22 degrees Offset Angle, supplied with set up and alignment template.
Mass: Arm Wand 13.5g with cables, 12 g bare, Complete Arm 534g with 10 g Cartridge, pair of largest Mass Blocks and Counterweights for balance.
Fluid damping: Paddles have a 54mm radius from the Pivot Point. Viscous Silicone Damping Fluid. This also provides the Anti-Skating Force in the most neutral manner possible.
Adjustments: All adjustments are made either with ones fingers or simple hex wrenches and Allen wrenches. Counterbalance is by simple Counterweight(s) and a small Adjustment Nut. Azimuth is by small nut weights on the rods in the damping fluid.
VTA: The Pivot Post is vertically adjustable. A special locking wrench is provided. Damping and Anti-Skating are adjustable by raising or lowering the threaded rods. The Arm Assembly is completely removable without altering any adjustments. Different Cartridges can be mounted and adjusted on its own arm and exchanged.
For further information: email directly Dr. Randolph D. Hedgebeth