Sennheiser 2015 - Manual (Page 47)

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HDX noise reduction system
You can hear the difference:
This product is equipped with HDX , the Sennheiser noise reduction system that reduces RF interference. It
increases the signal-to-noise ratio in wireless audio transmission. HDX is a wideband compander system
which compresses the audio signal in the transmitter in a 2:1 ratio (related to dB) to lift it above the inher-
ent noise floor of the RF link. A 110 dB dynamic range signal is thus transmitted with an effective dynamic
range of only 55 dB, which is above the 60 dB noise floor of the RF link. In the receiver the signal is expanded
in an identical and opposite way in a 1:2 ratio to restore the original signal, at the same time reducing the
RF noise to below the noise floor of the receiver.
HDX has been specially developed for high quality RF microphone systems.
Note:
Only transmitters and receivers that are equipped with HDX can work correctly with each other. If non
HDX equipment was mixed with HDX , the dynamic range would be drastically reduced and the trans-
mission would sound blunt and flat. HDX is permanently active and cannot be switched off.
RF link
Transmitter Receiver
Inherent
of the
noise
RF link