R&D Report 1962-41 : The Sennheiser Type MD 82 and Electrovoice Type 642 microphones. W.I. Manson The Sennheiser type MD 82 and Electrovoice type 642 are both directional microphones in which sound is received through openings along a narrow tube. Type MD 82, a number of which are in use in the Corporation, is no longer in regular production but is included in this report for comparison with the currently available type 642. Measured frequency characteristics and polar patterns are given.