Question: What are the differences between moving magnet and moving coil phono cartridges?
Answer: Both #movingmagnet (MM) and #movingcoil (MC) #cartridges are tiny electromagnetic generators, converting the mechanical movement (vibration) created by their stylus riding in a record’s groove into an electrical signal that will be amplified and processed by a sound system for us to enjoy. Both use magnets and coils of wire to generate the signal, with one or the other vibrating in unison with the stylus assembly to which they are attached, and each type has its advantages and disadvantages. To fully understand these advantages and disadvantages, let us first discuss how the “ideal” #phonocartridge would need to function.
The goal of most every audio transducer, whether it be a phono cartridge, microphone, loudspeaker or other device, is to convert one form of energy into another as accurately as possible so that the original sound of the performance is retained. The device should have little to no “sound” of its own and add little to no noise to the signal. It is important to note however that these devices can be designed to be either as transparent as possible, or tuned to have a certain degree of coloration. This coloration is typically intended to achieve a certain effect or to address a certain problem. A vacuum tube microphone can add a degree of warmth and depth to an otherwise thin-sounding vocal performance, for example. A microphone that has a rolled-off high-frequency response can help tame a vocalist with excessive sibilance. Overall, most phono cartridges are designed to be as transparent as possible with many achieving remarkably flat frequency response for accurate audio reproduction.
Navigating the rugged terrain of a record groove is no easy task. The rapidly changing amplitude of the signal that is cut into the groove requires a generator that can react very quickly to these hills and valleys, yet stay firmly planted in the groove at the same time. A stylus assembly needs to be light in weight, yet stiff, to perform this task. Light to respond quickly and to keep record wear to a minimum, and stiff to quickly and accurately transmit the vibrations from the stylus tip to the generator. The assembly should have very little resonance, and any resonance that it does have needs not only to be kept out of the audible band of frequencies (20 to 20,000 Hz) so it does not affect the quality of the sound it produces, but also be low enough in frequency that it does not emphasize any inherent low-frequency noise, such as turntable rumble. Emphasis of such frequencies can cause stylus tracking problems, affect sound quality and attribute to feedback problems between the speakers and cartridge.
Jay Hunt
Hunt Creative Inc.
hciasia@icloud.com
www.huntcreative.com
