The Reflector or Parabolic Dish Microphone

The reflector microphone is typically a conventional omni mounted in a parabolic sound reflector or dish, usually made of plastic. Reflectors range from 18 to 38 inches ( 50 cm to 1 metre) in diameter.

In addition to sound directly impinging on the microphone from the front, on-axis sound hitting the front of the dish is bounced back onto the microphone. The pickup pattern is therefore very narrow and the on-axis sound is amplified, albeit with some differential delays due to the extra length of the reflection path. Sound from behind the microphone is reflected away from the microphone as well as being to some extent masked by the body of the dish. Some people use a cardioid microphone in a reflector, but depending on the shape of the dish, a cardioid can perform much worse than an omni, as much of the reflected sound may reach a cardioid in the less sensitive regions of its pickup pattern. A deep dish is therefore needed for use with a cardioid, and these can be awkward to handle in the field as they are inherently front-heavy, so you need a very sturdy stand or a very strong wrist.

So much for the principle, but as well as its advantages, the reflector microphone has some defects and practical disadvantages. It can't amplify sounds with a wavelength longer than the dish diameter, so it has a low end cut-off around 300-600 Hz depending on its size. But it's also much less directional at low frequencies, so in the presence of background noise such as traffic rumble it's less effective. Within its optimum frequency range, its frequency response can also be very uneven, with large peaks and troughs of sensitivity that depend on the geometry of the dish and the precise positioning of the microphone in it more than on the specifications of the microphone itself.

Recently a number of very expensive parabolic microphones have come onto the market that make use of multiple mics. Some use a combination of an inward pointing narrow cardioid and an outward pointing omni, and some use integrated stereo mics. But it's not at all certain that these complex devices pay their way. Particularly, it's not really feasible to use a parabolic reflector for stereo. The pickup pattern of a reflector microphone is so narrow that there's little stereo information available anyway, and the multiple reflection paths within the dish result in sounds from many directions within the pickup angle impinging on all sides of the microphone array, confusing the little directional information that may be present. Attempting stereo by using two independent reflector microphones normally results in a stereo image with a "hole" in the middle due to the narrow pickup angle of the reflectors and the wide spacing between them constrained by their size. So mono recording using an omni microphone in a relatively flat dish is the best choice.

The reflector microphone is very susceptible to wind noise and, unless on a very sturdy stand, can also be blown over by the wind due to its large profile. So it's really best used hand-held unless you're very sure in advance of the position of your recording subjects and the weather. It's mainly used for recording individual animal vocalisations by pointing it directly at the source of the wanted sound at a distance of 10-50 feet (3-15 metres). An 18 inch flattish parabolic on a pistol grip is the traditional microphone used by field ecologists as its defects in sound reproduction and other disadvantages are outweighed by its narrow field and amplification for scientific recordings. But it's not a good choice for high sound quality, or for soundscapes, which present inherently wide sound fields.