As a key electromagnetic component, the speaker short-circuit ring's core function is to counteract the nonlinear distortion caused by the alternating magnetic field of the voice coil through the eddy current effect. Speaker short-circuit rings made of stretched copper are the mainstream choice due to their high conductivity and good ductility. However, the work hardening caused by the stretching process generates numerous dislocations and lattice distortions within the copper, significantly reducing its conductivity. Annealing, as a crucial step in optimizing material properties, eliminates internal defects through heat treatment, quantifying its impact on the conductivity of the speaker short-circuit ring stretched copper.
The core mechanism of the annealing process lies in restoring the crystal integrity of the copper. During stretching, the copper grains are elongated to form a fibrous structure, and the high-density dislocations accumulated at the grain boundaries become the main source of electron scattering, leading to an increase in resistivity. During annealing, the copper undergoes recovery and recrystallization at appropriate temperatures: the recovery stage reduces residual stress through dislocation rearrangement, while the recrystallization stage forms equiaxed new grains, eliminating the work hardening effect. This process increases the mean free path of electrons, thereby improving conductivity. It is worth noting that precise control of annealing temperature and time is crucial—too low a temperature leads to incomplete recrystallization, while too high a temperature may cause grain coarsening, thus reducing conductivity.
From a quantitative perspective, the annealing process exhibits a significant regularity in improving conductivity. Experiments show that the conductivity of speaker short-circuit ring stretched copper material after optimized annealing can be restored to levels close to the theoretical limit of copper. Specifically, the increase in conductivity after annealing is closely related to the degree of work hardening: for speaker short-circuit ring stretched copper material with high deformation, the conductivity improvement brought about by annealing is more significant. This quantitative improvement is directly reflected in speaker performance—increased conductivity means reduced eddy current losses in the short-circuit ring, more efficient cancellation of the alternating magnetic field of the voice coil, thereby significantly reducing harmonic distortion in the speaker.
The impact of the annealing process on conductivity is also reflected in the optimization of the material's microstructure. Observation using electron backscattering diffraction technology revealed that the grain size uniformity of the annealed copper material is significantly improved, and the distribution of grain boundary orientation differences is more concentrated. This structural feature reduces the scattering probability of electrons during cross-grain boundary transport, further improving conductivity. Simultaneously, the annealed twin structure formed during annealing also contributes to the conductivity improvement—twin boundaries, as low-energy interfaces, impede electron transport less than ordinary grain boundaries; this microstructural optimization is a crucial intrinsic mechanism for improved conductivity.
In practical applications, the quantification effect of the annealing process must also consider the specific design requirements of the speaker short-circuit ring. For example, short-circuit rings with symmetrical structures require uniform conductivity in both the radial and axial directions, necessitating that the annealing process restores the isotropic properties of the copper material. Furthermore, for thin-walled short-circuit rings, oxidation control during annealing is particularly critical, as the surface oxide layer creates additional resistance, offsetting the conductivity improvement effect of annealing.
The quantification effect of the annealing process on the conductivity of speaker short-circuit ring stretched copper has multi-dimensional characteristics. From a macroscopic performance perspective, the significant improvement in conductivity directly optimizes the speaker's electromagnetic conversion efficiency. From a microscopic structural perspective, grain refinement and twinning create more efficient electron transport channels. From a manufacturing process perspective, precise control of annealing parameters is key to balancing conductivity and mechanical properties. These quantitative effects collectively support the speaker's lower distortion and higher sensitivity in the high-frequency range, highlighting the core value of annealing technology in the manufacturing of high-end audio equipment.
