The Opus 99 is a hypercardioid dynamic microphone with a low-mass, large-diaphragm moving-coil element. The mic is intended for low-frequency instruments, especially including the bass drum.
The dynamic cartridge uses Neodymium magnets and a low-mass diaphragm made of Hostaphan (Mylar). It is Beyerdynamic’s TG-X 80 capsule; see the sidebar for links to other microphones that shared this capsule.
Its frequency response is pre-equalized or “tailored,” with peaks in the low frequencies (0dB at 100Hz) and highs (+7dB at 2500k, +8dB at 5kHz), and somewhat scooped mids (-4dB @ 400Hz).