The MD 421 has been improved over the years with upgrades to the housing, output connector, basket, and capsule assembly. A limited-production MD 421 Special Edition that recaptured the full-bodied performance of the microphone's original design was introduced in 2003 to commemorate the ninetieth birthday of Sennheiser founder, Prof. Dr.-Ing. Fritz Sennheiser. The MD 421 II continues the tradition of the MD 421 while upgrading the original design in order to take advantage of improved production techniques and materials.
Significant upgrades incorporated into the MD 421 II include a metal inner chassis for better weight distribution and, with the contour-fitted bass roll-off control, a shorter, sleeker housing. The glass composite housing and hardened stainless steel basket afford improved durability. With the acoustic components now enclosed in the inner chassis the mic is less sensitive to dust and humidity. Servicing is also easier with the new design, since individual components can be more easily replaced and self-sealing acoustic connections mean that adhesives and sealing compounds are no longer required.
Like the original design, notable features of the MD 421 II include a highly directional cardioid pickup pattern that provides clear sound reproduction across a frequency range of 30 Hz – 17 kHz along with very effective feedback rejection, plus a hum-compensating coil. The five-position bass roll-off switch tailors the microphone's performance for diverse applications from radio voice broadcasting to solo and group vocals as well as high SPL instruments such as brass, amplified guitar and bass, Leslie cabinets, and drums, especially toms and kick drum.
The MD 421 II continues to be popular with touring sound engineers such as James Berry (Beyoncé, Solange Knowles) and Bryan Worthen (Foo Fighters, Limp Bizkit). Lady Antebellum's front-of-house engineer, Brett â€˜Scoop' Blanden, former manager of the Ocean Way Nashville recording studio, uses a pair of MD 421s on electric guitar. “Growing up in the studio as I did, you could never go wrong with 421s,” he says. Sugarland's FOH engineer and production manager, David Haskell, uses MD 421s on both the bass player's rigs and on Leslie, and is an avid fan of the model. “I've used those things for a hundred years on drums,” he professes. “I'd use a hundred of those things if I could find a spot to stick â€˜em!”