The dynamic cardioid microphone is a common workhorse transducer, specially built to capture the sounds of a wide variety of musical instruments, voices, and ensembles. In particular, drums and percussion instruments are often best aurally translated via dynamic cardioids, thus their predominance on drums in studios and on stages around the world.
As a transducer — a tool that converts one form of energy to another — a microphone captures the sound of an instrument using its diaphragm, then converts it into electrical energy. In doing so, the most common dynamic, the moving coil microphone, utilizes a coil of wire attached to its diaphragm, both of which are suspended within a magnetic field. When vibrations occur, the coil moves and an electric signal is generated.
Well-designed, good-quality moving coil dynamics such as the ubiquitous Shure SM57 are both rugged and capable of handling high sound-pressure levels (SPL). That certainly makes them a no-brainer for drums. Drum sticks and microphones can easily collide, and drummers regularly pound out some hearty SPLs. Finally, moving coil dynamics operate without external power to create their magnetic fields, so they generally offer easy, trouble-free performance.
Cardioid microphones feature unidirectional pick-up patterns that reject off-axis sounds to the sides and the rear of the mike (see diagram above), providing superb sound-source isolation. Using a cardioid microphone in proximity to a sound source causes a low frequency boost called “proximity effect.” On a miked drum, proximity effect can often add desirable warmth and body to its sound.
Best of all? Dynamic cardioid microphones suited for use on drums are relatively inexpensive. The aforementioned Shure SM57 regularly costs under $100 and can be heard on popular recordings of every drum, cymbal, and percussion instrument imaginable. Purpose-built percussion microphones (sometimes excluding overhead cymbal microphones) are most always dynamic cardioid mikes if not dynamic supercardioid or hypercardioid — featuring 8.7dB and 12dB less pickup from the sides, respectively. The AKG D112, arguably the industry standard for bass drum, is usually priced around $200 — a price on the top half for almost all designated drum microphones.