.jpg)
Turntable Design
Unique Insights on Turntable Record Player Designs
Thoughts on Turntable Design by George Merrill
This paper covers the self-generation and internal coupling of energy. The turntable record player must cope with four types of energy:
One
Self-generation and internal coupling of energy produced by the motor, drive system, platter support bearing, and tonearm.
Three
Airborne energy is contained within the operating environment.
Two
Mechanically coupled energy enters the support feet.
Four
Energy is generated by the stylus to groove contact during tracing (playing of the record).
"Energy Management Design""Tonearm Release Energy" is one of the major determining factor of sonic performance.
What Is Tonearm Release Energy
The term "tonearm release energy" was coined during my development of the AR modifications in 1975. This release energy is generated by the tracing of the record groove, with the stylus moving only microns. Even a small amount of energy intrusion can lead to a reduction in low-level information and result in a clouding of sonic quality.
The energy chain begins within the cartridge body, where it is equal to and opposite of the stylus movement. This energy is then transferred from the cartridge to the tonearm. Nowadays, numerous cartridge and tonearm manufacturers design their products with materials and forms that aim to reduce the body-induced resonances caused by this energy. The ultimate stage occurs when the energy is released into the arm-mounting platform, which serves as the critical test of the design. At this point, it is crucial for the energy to be dissipated rather than reflected into the tonearm. The Energy Management design principles are incorporated into all Merrill product designs. In the creation of the AR sub-chassis and Heirloom, the arm-mounting platform is seamlessly integrated as a non-removable part of the sub-chassis, facilitating effective coupling of the released energy to a sizable and uniform dissipating area. This area significantly surpasses the dimensions of any turntable record player manufactured during that era and likely even exceeds most present-day models. This is one of the main reasons for the sonic integrity and cult status of these products. The PolyTable utilizes the same principle.
The energy chain begins within the cartridge body, where it is equal to and opposite of the stylus movement. This energy is then transferred from the cartridge to the tonearm. Nowadays, numerous cartridge and tonearm manufacturers design their products with materials and forms that aim to reduce the body-induced resonances caused by this energy. The ultimate stage occurs when the energy is released into the arm-mounting platform, which serves as the critical test of the design. At this point, it is crucial for the energy to be dissipated rather than reflected into the tonearm. The Energy Management design principles are incorporated into all Merrill product designs. In the creation of the AR sub-chassis and Heirloom, the arm-mounting platform is seamlessly integrated as a non-removable part of the sub-chassis, facilitating effective coupling of the released energy to a sizable and uniform dissipating area. This area significantly surpasses the dimensions of any turntable record player manufactured during that era and likely even exceeds most present-day models. This is one of the main reasons for the sonic integrity and cult status of these products. The PolyTable utilizes the same principle.
The Spindle Bearing
The design of a high-quality spindle bearing for the best turntable record players is very simple. The lowest noise is achieved from an Oil Well design. You may test it with a stethoscope. The oil creates a dead quiet isolation film between the shaft and the bearing. Belt tension load on a properly designed oil well turntable spindle bearing is of no consequence.
A 7000-horsepower dragster engine uses an oil film to separate the connecting rods from the crankshaft. This surface is about one inch wide, smaller in width than the length of a typical turntable record player bearing, which is placed under a few pounds of load.
A 7000-horsepower dragster engine uses an oil film to separate the connecting rods from the crankshaft. This surface is about one inch wide, smaller in width than the length of a typical turntable record player bearing, which is placed under a few pounds of load.
The Drive System
The only drive system that will ensure low noise intrusion for premium audio equipment uses a single elastic belt and a single isolated motor (the more motors or idler pulley bearings, the more noise intrusion). A properly chosen belt for size, type, elasticity, and free air length becomes a low-pass filter. This filtering effect assists in eliminating higher-frequency information from infiltrating the platter and smoothing out the motor impulses. Remember, it only takes a very small amount of energy to cloud the input from the stylus to the cartridge signal generator.
Synchronous Motor: Synchronous motors are frequency-locked, not feedback-locked. With just enough torque, small motors equal low noise; large motors add more noise, which is my choice. Some say much torque is necessary to overcome groove loading. Groove loading will, to a minuscule degree, reduce the speed. Most quality turntable record players with a heavy platter will have enough inertia to keep the micro speed change invoked by signal modulation groove loading to a level completely undetectable.
Direct-Drive Motor: The name indicates the absence of isolation from the motor to the platter. Direct-drive turntable motors can show cogging. The amount of this cogging is determined by the pole number and the inertia (weight) of the platter. Hunting can be a problem if the feedback servo lacks definition. These motors do not use an oil well bearing.
Rim Drive (Idler): The rim drive (idler) is plagued with problems. Its emergence can be traced back to the necessity of using induction-type motors, which operated at high speeds (1800 rpm) and had enough torque to rotate the platter. The idler drive allowed enough speed reduction (16-33-45-78 rpm platter speed) and made for a compact design. More bearings and a hard drive wheel that generates and transmits noise are a real detriment to sound quality.
Early turntable record player manufacturers added a belt to the equation (Thorens TD124) to tame the motor noise presented to the platter. However, this did not eliminate the noise from the rolling wheel and second shaft bearing.
The test to verify if motor-induced noise plays a role is simple. The motor is first powered directly by the AC supply line. After listening, the direct AC supply line is substituted with a motor drive supply (DMD) that generates an internal sign wave, thus isolating the motor from the AC line noise. The noticeable difference is striking, as removing any noise transmitted from the motor through the belt and into the record support platter consistently enhances the sound quality.
My Secrets to Turntable Design by George Merrill
As stated in Thoughts on Turntable Design, the turntable system (turntable/arm/cartridge) copes with four types of energy intrusion.
To create the AR modifications and the Merrill Turntables, I designed and constructed a device called the Vibration Intrusion Table, along with a vibration pickup transducer. The operating frequency is from 0.1 HZ to 100 K HZ. The VIT allowed me to analyze important design points. Testing the turntable's capability to minimize mechanical input from its supporting platform and to reduce airborne acoustic energy intrusion involves examining the different parts within the turntable record player for resonance frequency and top.
As a side note, the results from the tests of mechanical intrusion led to the design of the Stable Table support stands and the Energy Absorption Plate (EAP). These were manufactured over 35 years ago.
This brings me to the first point of the paper: which type of turntable record player, suspended or non-suspended, is better at isolating energy from both airborne and mechanical intrusion from the support platform?
The tests prove a conventional suspended turntable is generally better. The Rubber Elastomer by Merrill-Williams, Springs Heirloom, and Sorbothane Isolation Pucks PolyTable Signature allow good isolation from mechanical input vibrations. If properly designed, the sub-chassis will act as a tuned low-pass filter. The total mechanism resting on the suspension must have a balance between weight and self-resonance in order for the filter to perform effectively.
For instance, the most effective suspended designs have a less bulky platter, thus allowing for a more supple suspension. Lighter springs allow less energy intrusion into the sub-chassis. The suspended turntable record player can be designed to control energy to a good degree. This is why the old AR was such a good design and, to this day, still a well-regarded product. There are three major drawbacks to the spring-suspended turntable.
To create the AR modifications and the Merrill Turntables, I designed and constructed a device called the Vibration Intrusion Table, along with a vibration pickup transducer. The operating frequency is from 0.1 HZ to 100 K HZ. The VIT allowed me to analyze important design points. Testing the turntable's capability to minimize mechanical input from its supporting platform and to reduce airborne acoustic energy intrusion involves examining the different parts within the turntable record player for resonance frequency and top.
As a side note, the results from the tests of mechanical intrusion led to the design of the Stable Table support stands and the Energy Absorption Plate (EAP). These were manufactured over 35 years ago.
This brings me to the first point of the paper: which type of turntable record player, suspended or non-suspended, is better at isolating energy from both airborne and mechanical intrusion from the support platform?
The tests prove a conventional suspended turntable is generally better. The Rubber Elastomer by Merrill-Williams, Springs Heirloom, and Sorbothane Isolation Pucks PolyTable Signature allow good isolation from mechanical input vibrations. If properly designed, the sub-chassis will act as a tuned low-pass filter. The total mechanism resting on the suspension must have a balance between weight and self-resonance in order for the filter to perform effectively.
For instance, the most effective suspended designs have a less bulky platter, thus allowing for a more supple suspension. Lighter springs allow less energy intrusion into the sub-chassis. The suspended turntable record player can be designed to control energy to a good degree. This is why the old AR was such a good design and, to this day, still a well-regarded product. There are three major drawbacks to the spring-suspended turntable.
One
The system's low resonant point (3-6 HZ) is subject to footfall problems, which require a stable platform. However, this is not a major problem with the M-W or PolyTable Signature.
Two
The tonearm is energy connected to the platter bearing. If not designed properly, this can be a major deterrent to energy management.
Three
The motor is decoupled from the platter and sub-chassis. This can cause a torque recoil problem (not a problem with Merrill-Williams or the PolyTable). To overcome this problem with the design of the Merrill Heirloom, I developed the constant resonant tuning system for the Heirloom sub-chassis. This innovative approach enables the sub-chassis to maintain a consistent energy input band when utilizing any type of tonearm, offering the necessary stability to counteract torque recoil.
Non-suspended turntable record players often rely on mass to minimize energy intrusion. However, these turntables are often made of materials that conduct energy to a high degree, such as metal, glass, and wood, causing energy to move freely within the turntable's mechanics. Unfortunately, there is no filter built within the turntable to act as a barrier against mechanical intrusion. While some turntable models incorporate feet to filter excessive energy, they fall short because they must be sufficiently stiff to support the turntable's overall weight and do not offer complete effectiveness.
The Merrill-Williams R.E.A.L.
The M-W utilizes a 14 lb. rubber elastomer to isolate and absorb energy. All of the parts, including the platter bearing, motor, support feet, and tonearm mounting, are suspended in a rubber isolation barrier. These operating parts are totally isolated and completely energy-damped. There is NO metal, wood, or glass in the energy conduction path. An outer skeleton is used to contain the elastomer. The design is so radically new that an 18-point USA patent #8,406,112B2 was granted.
To understand why it works so well, try this experiment: use a bar of metal and a stethoscope. Strike one end while listening to the other. Energy moves freely. Try it with rubber. There is no transmission. Mounting the motor in the same rubber elastomer as the spindle bearing eliminated the other problem, eliminating torque recoil.
Keep Your Turntables Running
We understand how difficult it is to maintain professional audio equipment. That is why Analog Emporium, GEM Dandy, is here to provide all the services you need for your turntable record player. Contact us to learn more about our turntable set-up and repair services.