Quiescent Apex 40 coupler and Peak Speaker module by Kevin Fiske for Hi-Fi+
Products that aim to mitigate the sonic damage being done to audio reproduction by electromagnetic and radio frequency interference are common. Not least because the latter is a higher frequency version of the former. However, there is a third corrupting influence that is less frequently addressed. It is microphony. Quiescent is one of the few brands attempting to reduce EMI, RFI and microphony.
If we leave aside micro-tremors from the earth’s crust and from traffic, microphony in our audio systems has the same primary source; the speakers. The acoustic energy from them modulates ambient air pressure against our eardrums, but it also vibrates our audio system too. Inside most speaker cabinets, the crossover is bombarded by energy from the rear of the speaker drivers. Meanwhile, circuit boards in system components such as amplifiers are effectively palpated by the modulated air in the room.
Those who paid attention at school will recall that physical energy applied to a conducting material is converted to electrical energy. During normal playback, our systems are processing not just the musical signal that we want to hear but, electrical artefacts that we don’t want to hear. These travel back down the speaker cables to the amplifier, and propagate from discrete components such as capacitors in system separates. They become particularly audible when contending fundamentals or harmonics beat against each other to produce intermodulation distortion, typically heard as ringing.