Encapsulation in a housing with visco-elastic sealing compound

When encapsulated in the housing, the capacitor coil in a sturdy housing is completely surrounded by a visco-elastic, acoustically optimized sealing compound. The aim of this structure is not only to dampen mechanical vibrations “from the outside”, but to calm down the wrap so that it is also stimulated to move as little as possible from the music signal. This is because not only housing vibrations or structure-borne noise act in audio capacitors, but also signal-dependent forces: The alternating current in the capacitor creates electric field forces and current distributions, which can lead to movement pulses microscopically and macroscopically in the wrap. When this causes the winding to vibrate, macro-microphony occurs – the capacitor winding vibrates along with the signal and modulates the music signal with its natural resonances.

This is exactly where potting comes in. The wrap is mechanically tight and can no longer rock up freely, even at high levels and large impulses. Coupled energy — whether from the signal itself, from vibrations in the device or from structure-borne noise — is converted into heat in the visco-elastic layer. This reduces the tendency for extensive wrapping movements and effectively suppresses “sounding” eigenmodes. This turns the capacitor from a potential player back into a silent component that processes energy confidently without becoming a sound source itself.

The combination of housing material and sealing compound is decisive here. It is only through interaction that the overall damping and vibration behavior of the component is achieved. The natural resonance frequency of the coil decreases, coupled energy is absorbed, and natural resonances are not only spread across a wider frequency range but also significantly reduced in amplitude as a result. This means that resonances no longer appear as narrow, conspicuous peaks, but are both distributed over frequency and reduced in amplitude — disruptive resonance peaks are effectively eliminated. As a result, the mechanical stimulation of the coil due to the music signal, housing vibrations and structure-borne noise is significantly reduced, and the tendency towards macro microphony decreases noticeably.

Which combination of housing material and sealing compound is therefore not a standard decision, but the result of intensive research and years of experience. In practice, several parameters intertwine: hardness and internal damping of the casting compound, its coupling to the housing and coil, the mechanical stiffness of the housing and the desired resonance behavior as a whole package. Here, the right coordination determines the overall result — and thus the difference between “technically quiet” and “audibly confident.”

Tonal effects

• The stage remains stable and calm even at high levels because the capacitor itself virtually no longer resonates as an additional sound source.
• Voices and instruments stand clearly and firmly in the room; they do not lose their contours, even if the system is heavily controlled.
• Housing ringing, structure-borne noise and other mechanical background noises largely disappear — the sound image appears sorted and focused.
• Fine details are easier to perceive because signal-dependent winding movements and resonance modulations are less likely to superimpose the signal; decay processes, quiet room information and microtextures emerge from a quieter background.
• Overall, playback appears more controlled and more suitable for long-term use: Even complex musical passages remain organized, without nervousness or harshness, because the mechanical basis of the component remains stable.