Tannoy MD-422

The BBC tested the MD-422 and gave the following summary:

"The axial frequency response, apart from the main rise which can easily be corrected electrically, is quite good. The ratio of front to back response is well maintained over a wide range, but the response characteristics at right angles to the axis are very irregular and fall at high frequencies.

The signal-to-noise ratio of the microphone is 16 db worse than that of the type AXBT, and is unacceptable for normal studio use. Interference by magnetic fields is moderate, and should give no trouble unless the microphone is used near apparatus radiating a strong field.

From a BBC R&D report:

The instrument is a ribbon microphone with a nominal cardioid polar characteristic; no provision is made for altering the directional properties.

The acoustic labyrinth, which forms part of the delay network used for producing the cardioid polar characteristic, occupies the rear part of the case, in an approximately elliptical cylinder.

The ribbon and magnet assembly is housed in the upper part of the remaining space, with the ribbon-to-line transformer beneath it. The ribbon is of aluminium foil, 1.5 inches (3.81 cm.) long and approximately 0.1" (0.25 cm.) wide and is mounted between pole pieces 1/8" (0.32 cm) apart.

Tho standard model has a nominal impedance of 600 ohms, and a ribbon of 0.0001" (2.5 x 10-4cm.) thickness.

The front is covered with expanded metal over a wire gauze screen, and the back is acoustically opaque. Rubber grommets separate the body of the microphone from its supporting stirrup, thus providing a measure of protection from vibration transmitted through the stand. The length of wire connecting the microphone to the plug is sufficient to allow an adjustment of the tilt of about ±90 degrees from the centre position.

The microphone, without the 20-foot (6.1 metres) lead supplied with it, weighs approximately 1.9 Ibs. (860 grams.).

A BBC R&D report on the MD-422 cardioid ribbon microphone.