Hiello Marco, with over 40 years of intimite familiarity with wireless systems and Sennheiser in particular, please permit me to chime in here. Due to audio processing in the analog wireless link (pre-emphasis plus dynamics compression in the transmitter wth complimentary de-emphasis and dynamic expansion in the receiver) some effects on the high frequency response are inevitable. Some of this has been attempted to be compensated for by a slightly (+4 dB) larger high frequency peak around 10 kHz for the KK105 when compared to the KMS105. In the SKM 5000-N version the compressor has already been optimized to complement the KK 104/105 capsules. Unless you are intimitely familiar with the Sennheiser HiDyn compander details, I strongly advise against any attempts at further modification. Also, there is no reasonable prospect for achieving positive results through any simple modification of the circuit board in the microphone module, as this constitutes not much more than the necessary impedance converter and buffer stage for the capacitive transducer. May I suggest that any desired alteration of the audio signal should be done after the receiver?