Micro-microphony – the sound of metals
Micro-microphony describes tiny, materialspecific processes inside the conductor itself. Every metal consists of a crystal lattice with its own modes of vibration; on the quantum level these are called phonons – you can picture them as “packets of sound” travelling through the lattice. The music signal flows as an electron current through this lattice and, via electron–phonon coupling, interacts with these lattice vibrations. The phonons themselves live in the terahertz range (10¹² Hz), far beyond audibility – but their coupled effects become audible in the audio band, in three ways that shape the character of a metal.
First: the 1/f sonic signature
A real metal is never perfectly homogeneous. There are grain boundaries (transitions between differently oriented crystal regions), dislocations (tiny lattice defects) and interfaces (for example to adhesion layers). At these points the flow of electrons stumbles ever so slightly: sometimes the path is a touch more conductive, sometimes a touch less – and this microrestlessness changes over time.
From many such minichanges a broadband base signature emerges whose noise density increases towards low frequencies – the 1/f signature.
In listening it appears as more or less “calm” in the sonic image: the more ordered the microstructure, the quieter this fine intrinsic jitter.
Second: the 2f components (thermoelastic overtones)
When current flows, Joule heat is generated – in step with the music. The lattice warms up microscopically and cools down again; it “breathes”. As a result, the resistance changes slightly with temperature, ΔR(T).
This breathing produces a tiny harmonic one octave above the fundamental (2f). How strong it is at which frequency depends on the material (how sensitively R reacts to T) and on how the heat can dissipate (its thermal environment).
You do not hear this as a separate “tone at 2f”, but as a subtle change in transients and microdynamics.
Third: local resonances from Lorentz forces
When a conductor is in a magnetic field, the Lorentz force (J × B) acts on the flowing current. If this excitation hits a mechanical mode of a locale micro- structur of conductor, a narrow, tonelike spectral line can appear – strongly dependent on geometry, mounting and field environment, and less on the element itself.
Without a mode match the effect remains small; with resonance it can become distinctly audible.
System effect in one sentence
The music signal modulates the conductor parameters (R, L, ESR, ESL) in time with itself; crossover frequency, Qfactor and phase all shift, and the system feeds these changes back into the music signal – audible as level, phase and time modulation (calm/restlessness, colour, transients) and as fine intermodulation.
What distinguishes metals (on the material level)
- Silver (Ag) – Long mean free path, high mobility: fewer active microcontacts, lower 1/f component → impression of luminous clarity and transparency.
- Copper (Cu) – Very conductive, robust; with comparable processing slightly higher interface activity than Ag → balanced precision with body.
- Gold (Au) (often as an ultrathin top layer or in small alloy fraction) – diffusion barrier and interface stabiliser: less temporal drift, smoother microspectrum → calm, smoothness, density.
- Silvergold (AgAu, low Au content) – Combines Ag transparency with Au stability: smooths the 1/f spectrum and reduces longterm drift → clear, relaxed presentation and increased service life.
- Mundorf patented Angelique® Silver Gold Cooper Alloys – Fine control of texture via conductivity, hardness and stress profile; can further balance the noise spectrum and mechanically calm the structure.
What’s behind it – microstructure in one picture
The larger the grains, the fewer grain boundaries – and the fewer spots where the electron flow can stumble on the micro scale. This lowers the 1/f signature and makes the sound clearer.
Relaxed lattices (e.g. after gentle annealing) have fewer mobile defects; temporal microchanges are reduced. Stable interfaces (e.g. through a small gold content in silver) calm the grain boundaries and slow drift – the sonic image feels more relaxed.
In short: Element = colour, microstructure = focus, process = stability.
To the point
- Material signature: silver transparent, copper fullbodied and precise, gold / AgAu stable and calm.
Our implementation in development & manufacturing
- Angelique® Copper and Angelique® SilverGold: Both lead to a sonically harmonious, coherent sound image – one with an emphasis on warmth + tone colour, the other with an emphasis on tone colour + warmth.
- Targeted material selection: We consider all conductors (wires, terminals, solders, alloys) from the perspective of Micro-microphony.
- Dielectrics & insulators: Are tested and selected for their micromicrophonic properties; they are characterised by carefully tuned electrostriction, internal damping and very low losses.
In this way – based on Micro-microphony – we lay the foundation for calm, richly coloured and authentic reproduction directly in the material itself.
Note on the insulator: In the insulator, the dielectric itself can deform slightly (electrostrictive / piezolike). These effects couple back subtly into the music signal – as an extremely fine, materialspecific intrinsic sound.
Application note: Depending on the application, the emphasis of the micro-microphonic mechanisms shifts. In crossovers (high currents), I²driven effects dominate – the 1/f signature under load, the 2f “breathing trace” (thermoelastic) and, when a mode is hit, Lorentz resonances. In amplifiers (high voltages, small currents), voltagedriven modulations prevail.
This leads to different capacitor constructions tailored to the use case, each minimising the relevant mechanisms. We have taken this insight into account in our new capacitor lines.
(For more on how these minimodulations add up in the crossover transition region – level + phase + lobing – see the chapter “Crossover transition region – why small modulations have a big effect”.)
