When a collaboration of like-minds, driven by a shared passion, combine their considerable knowledge, talents and resources with the desire to create something beyond the state-of-the-art, special things can happen.
The ordinary constraints that normally limit most endeavours can suddenly disappear. The AIM FOR PERFECTION becomes the driving force, the only constraint. The result of such a collaboration is Caliburn-Cobra-Castellon
Not happy at acheiving our goals we tasked our design team to better the design of our Caliburn-Cobra-Castellon while significantly reducing the cost to our customers, an impossible goal, but the end result is our new Criterion - Copperhead which may not quite scale the heights of our reference design but compared to the competition?
We will leave that for you to decide, but remember this Continuum owners smile to themselves alot!
Search for the perfect turntable material
Many people may consider building a turntable is not rocket science. Read on!
Turntable design has gone through some interesting developments over the years.
The Caliburn’s design process began with the analysis of existing high-end turntable designs to identify their strengths and weaknesses.
We took away the aesthetic considerations and concentrated on the physical properties of a material and it became apparent that the sonic signature of a turntable is greatly affected by the selection of materials.
In the search for the perfect turntable material, Continuum Audio Laboratories analysed many commonly used materials in existing turntables such as:
Wood based products -
We often see references to aeronautical alloys such as 2024-T3, 6061-T6 and 7075-T6 which have material properties that are well known and published.
So too are Stainless Steel alloys and the family of advanced metals and ceramics such as Titanium Magnesium and Tungsten, Amorphous Metals etc.
We also looked at a range of Magnesium Alloys and determined that commercially available Magnesium Alloys were not perfect for turntables either.
Challenging problems often require the creation of purpose specific materials
Caliburn advanced metallurgy
The Caliburn uses advanced metallurgy and composites engineering used in the aerospace industry, to create purpose specific materials to achieve a level of performance never before realized from analogue reproduction systems.
We sought the assistance of some of the finest metallurgists to discuss our unique needs.
In conjunction with materials engineer, John Vietz (see Design Team), these specialists worked out a formulation for a unique alloy specification, which has been tailored to address the needs of a turntable and tonearm combination.
We realised early on that to build stiffness and damping into a design required the use of metals which behaved differently to carbon fibre composites, wood based products, masonry (granite, marble etc) and plastics.
This led to the creation of a new alloy using Magnesium as the primary material with trace elements of other alloying materials to create the right mix of properties.
To verify our design we then prototyped the Caliburn turntable shape out of readily available aeronautical alloys and compared that to an identical prototype using our newly forged “Caliburn” Magnesium Alloy.
The result was a significant improvement in real world audiophile performance between the purpose built “Caliburn” Alloy and the commercial alloy.
Spatial information retrieval, timbre and tone accuracy, absence of high frequency distortion etc etc.
Of course you will need to judge the results for yourself.
Search for the Perfect Acoustic Shape
Once we had the material with the desired damping and stiffness, the next critical design stage was shape optimization.
To understand the impact a shape has on acoustic properties we turned to one of the most respected authorities in this field, Dr Neil McLachlan, creator of the Australia Bell.
The Australia Bell is a break-through design showcasing Neil’s talents - www.ausbell.com
He used a technique called Finite Element Analysis. Three dimensional, flexural vibrations of solid objects can be computer modelled using this technique.
The elastic flexing of each part can be described by a
simple equation (given the shape and material properties
such as density and elasticity) and the contribution of
all the parts is then summed.
Shape optimisation is a technology in which the computer calculates changes to the shape of a model based on a series of FEA analyses and some specific design objectives.
The Caliburn uses a technique known as gradient method optimisation, in which the computer analyses the direction and amount of change in the design variables due to a series of shape changes, and then calculates the direction and degree of the next shape change.
A variety of design targets and constraints may be applied to the task, such as, which acoustic property should change and which should remain unchanged, which parts of the model should be allowed to move and in which directions, and which parts should move in unison.
Interestingly, putting other highly respected commercially available designs through the same rigorous process highlighted that only a select number of designs showed any understanding of the forces at play.
Our ability to “see” where audiophile attributes, ie. darkness, muddiness, brightness, bloomy, strident, constrained etc, are situated in the physical domain allowed us to engineer these distortions out of the audible band. Using shape optimization we can move these distortions and their associated eigen values up or down the frequency spectrum.
The Caliburn’s design is fully optimized for analogue reproduction.
Lastly, the design process must address the features, which enhance performance and useability. Continuum Audio Laboratories was to develop solutions to the following:
• A vacuum hold-down mechanism that delivers silent vacuum pressure maintained within strict parameters.
• A 38-kilo platter mass where only one kilo pressure was exerted on the bearing.
• A user selectable speed control - 33, 45, 78 rpm.
• An easy set-up procedure that remains in calibration.
• An ability to mount both pivoted and linear tracking arms as well as provide room for mounting a secondary arm.
• An ability to run multiple types of belt - round, flat, rubber, cotton, mylar, pyrathane, hytrel, etc.
• A free standing, zero cogging motor that can kick-start a 38 kilo (83.6lbs) platter, yet drop into low-torque mode during playback that can be powered by choice of battery or ultra-low noise power supply.
• An armboard design that solves the problem of bearing vibration transmission.
• Design a tonearm with superior stiffness, damping and weight that provides user adjustable VTA, azimuth on the fly with the ability to be mounted on standard pitch circle diameter mounts, such as SME or Graham Engineering and accepts a wide range of cartridges.
A collaboration of like minds
The prior art in turntable design highlights some exceptional individuals who were able to make breakthroughs in certain aspects of turntable design.
To find a single individual who operates at master level in all the required disciplines and is also blessed with a set of “golden ears” would be an extreme rarity.
At Continuum Audio Laboratories we use a design methodology called “synectics”.
This principle brings masters of engineering together into a collaborative team and allows for a single vision to be maintained to achieve results hitherto unimagined.
Pushing the envelope
The Caliburn is the fruit of this collaboration and has pushed the envelope of what was imagined possible. We believe Caliburn sets a new benchmark against previous designs, designs that we hold in high regard.
Our team of design engineers used complex modelling tools such as Reshape™, NASTRAN, PATRAN, DYTRAN and other 3D FEM (Finite Element Modelling) tools.
These tools are used extensively by companies such as Boeing, NASA, Airbus and the automotive and defence industry to improve engineering designs.
We also used Shape Optimisation software, which allowed us to prototype several hundred thousand models to arrive at the optimum shape for our turntable and arm.
Our acoustical engineers who specialize in the control of resonance, vibration and energy propagation created the Caliburn’s unique noise-free platter.
Our materials engineers were briefed to find the elusive “unobtainium” with the required properties to address the problem frequencies the shape optimization process identified and shifted.
With reference to the acoustical engineers results, they blended materials and created our purpose-built alloys and composites used to manufacture the chassis and platter.
Our electrical engineers designed the required electrical mechanisms to support the turntables operational parameters.
Our vacuum engineers developed advanced vacuum generation and control mechanism to deliver noise-free vacuum hold-down.