Thoughts on Turntable Design 2
My Secrets to Turntable design
By George Merrill
The Turntable system ( turntable/ arm/ cartridge) copes with 4 types of energy intrusion as stated in Thoughts on Turntable Design 1
In order to design the AR modifications and the Merrill Turntables I used two sets of tools: One - I designed and constructed a device I called the Vibration Intrusion Table along with a vibration pickup transducer. The operating frequency was from .1 HZ to 100 K HZ. The VIT allowed me to analyze important design points. Testing the ability of a turntable to effectively decrease the mechanical input from the platform supporting the turntable. The intrusion of airborne acoustic energy. Testing the different parts within the turntable for resonance frequency and top.
The other device I used is a simple set of tuning forks and a stethoscope.
As A side note the results from tests of mechanical intrusion lead to the design of the Stable Table support stands and the Energy Absorption Plate (EAP). These products were manufactured over 25 years ago.
This brings me to the first point of the paper. Which type of turntable 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 plus of a suspended turntable is the subchassis can be shrouded to help impede airborne intrusion. The springs allow good isolated from mechanical input vibrations. If properly designed the subchassis will act as a tuned low pass filter. In order for the filter to perform effectively the total mechanism resting on the springs must have a balance between weight and self resonance. For instance most effective suspended designs have a less bulky platter. This allowing for a more supple suspension, Lighter springs allow less energy intrusion into the subchassis. The suspended turntable can be designed to control energy to very good degree. This is the reason the old AR was such a good design and to this day still a highly regarded product.
Their are three major drawback to the suspended turntable.
One: The low resonant point of the system is subject to foot fall problems. A stable platform is necessary.
Two: The tonearm is energy connected to the platter bearing. This can be a major deterrent to energy management if not designed properly.
Three: The motor is decoupled from the platter and subchassis This can cause a torque recoil problem. To over come this problem I developed the constant resonant tuning system for the Merrill Heirloom subchassis. This allowed the subchassis to have the constant energy input band when using any tone arm. And help to stabilized the subchassis from torque recoil.
Most non suspended turntables rely on mass to lower the intrusion of energy. The problems are: Most of these non suspended turntables are manufactured using materials in the energy conduction path that conduct energy to a high degree (metal, glass and wood ). Energy moves freely within the mechanics of the turntable. There is not a filter within the turntable to act as a barrier to mechanical intrusion. Some try to achieve this with feet. The feet will help, but due to the stiffness necessary to support the total weight of the turntable they are not a totally effective filter.
The new era in turntable design.
The Merrill- Williams R.E.A.L. 101
The 101.2 utilizes a 14 lb rubber elastomer to isolate and absorb energy.
All of the parts motor, platter bearing, support feet and tonearm mounting are suspended in a rubber isolation barrier. These operating parts are totally isolated and completely energy damped. Their is NO metal, glass or wood in the energy conduction path. A outer skeleton is used to contain the elastomer.
The design is so radically new that a 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 listen to the other. Energy moves freely. Try it with rubber. No transmission.
The other problem that was eliminated by mounting the motor in the same rubber elastomer as the spindle bearing eliminating torque recoil.
The other advantage to the design is cost. This new design allows anyone to own the most advanced turntable possible.
Merrill- Williams Audio www.realturntable.com