The new HMD 27-series invites the Broadcast Commentators and Audio Engineers to experience the highest level of wearing comfort. HMD 27 are a closed and circumaural earcup design to provide a high passive attenuation but nevertheless unusually lightweight and comfortable over long working hours. Soft circumaural earpads endure a comfortable fit. The headset is similar to the HMS 26series equipped with the automatically opening two-piece headband, hence no pressure on the sensitive fontanelle. For those users who still prefer a conventional headband, a wide headband padding is included that converts the two-piece headband into a compact single piece.
Highest wearing comfort due to the lightweight circumaural design and the splitted headband (no pressure on the sensitive fontanelle)
Accurate and linear sound reproduction for very demanding monitoring
Dynamic Microphone, which stands out due to a strong and powerful sound pattern for an audio transmission in highest broadcast quality even in noisy environments
ActiveGard© (on/off switch) for protected hearing against noise peaks > 110dB
Modular concept of different cables and boom arms to offer highest flexibility
Cables of the cable 26-II series are compatible
Swiveling ear cap for single sided listening
Microphone can be worn either on right or left hand side
Wide headband padding is included that converts the two-piece headband into a compact single piece
The NoiseGard on/off switch is the switch that allows you to turn the active noise compensation circuitry on or off. It comes with a two colors LED for-power on and low battery-on headsets using a battery pack.
NOTE: If you should turn off the NoiseGard system there is no loss of, or reduction of, the received audio and you still retain the passive capabilities of the headset. You may have to increase the receiver volume to compensate for the increase of ambient noise due to the loss of the NoiseGard feature. The LED is located on the control-unit respective to the battery pack of the headsets. The control unit is included in-line on the models HMEC 45/46 series, HMEC 25/26 series, and HMEC 460 series. An optional battery pack is available for the HMEC 350 series.
It is a common saying that dynamic microphones just have no maximum SPL.
This saying is not technically exactly correct but for every day use use of dynamic microphones you will not find gain limitations. At SPL levels above 160 dB some mechanical problems might occur (for example the voice coil might crash onto the magnet) but these SPL levels are very hard to find in real world.
Here at Sennheiser we use dynamic microphones for distortion measurements on loudspeakers at very high sound pressure levels. At Sennheiser we have measured the SPL and THD inside a large 2" driver/horn combination with a MD 421. The max SPL this combination was able to produce was 150 dB and the THD level recorded by a MD 421 was below 1% (produced by the driver not by the mic)
So as a conclusion we can state the MD 421 has no maximum SPL limitations for practical use. However if using dynamic microphones at high SPL levels a user should be aware that the very high voltage (up to several volts) delivered by the microphone might cause problems when connected to mic preamps.