MM

A moving magnet cartridge is an electromechanical transducer that converts the physical vibrations of a turntable stylus into electrical signals for amplification. The stylus rides in the groove of a vinyl record, and as it traces the undulations, it vibrates a cantilever armature. That armature is fitted with one or two small permanent magnets. As these magnets move, they oscillate within a fixed coil of wire, inducing a varying electrical current that carries the audio information.

Moving magnet cartridges dominate the budget and mid-range turntable market because they are robust and relatively inexpensive to manufacture. The magnet assembly is rugged enough to withstand the tracking force exerted by the stylus, typically between 1.5 and 3 grams for modern designs. Most MM cartridges have output levels around 4 to 6 millivolts at 1 kHz, which is high enough to work with a standard phono preamplifier without additional amplification stages. This practicality has made MM the de facto standard for consumer turntables over the past fifty years.

Common variants include single-magnet designs, which are simpler and cheaper, and dual-magnet or multi-magnet configurations, which can offer better stereo separation and lower distortion. The cantilever material, stylus shape, and compliance of the suspension all affect frequency response and tracking ability. Elliptical or conical styli are standard; nude sapphire or diamond tips are preferred for durability and minimal record wear.

Performance and limitations

Moving magnet cartridges typically produce acceptable frequency response from 20 Hz to 20 kHz, though the rise at high frequencies can contribute to sibilance if not carefully designed. The moving mass of the magnet assembly is heavier than that of a moving coil cartridge, which can affect transient response and tracking on damaged or warped records. Stylus pressure and azimuth alignment are critical; misalignment degrades separation and introduces crosstalk between channels.

The name distinguishes this design from moving coil cartridges, where the coil itself moves and the magnets are fixed. Moving magnet technology sacrifices some sonic refinement for reliability and affordability, a trade-off that has secured its place in consumer audio for decades. Enthusiasts seeking higher output impedance and lower distortion may opt for moving coil, but MM remains the practical choice for most listeners.