Speaker
Description
Electrodynamic loudspeaker suspension stiffness degrades over time, altering resonance frequency and compromising long term reliability. The aim of this paper is to characterize stiffness evolution during loading and recovery phases to isolate specific degradation mechanisms. An automated measurement system applies a continuous 20 Hz sine wave to induce high excursion, monitoring applied mechanical work and extracting resonance frequency via the circle fit method on impedance data. A two exponential model characterizes stiffness loss as a function of cumulative work, capturing rapid initial break-in and gradual mechanical fatigue. Subsequently, a time dependent two exponential model describes stiffness recovery during rest periods. Equating the loss and recovery models at the load-recovery transition establishes a mathematical relationship that successfully decouples reversible viscoelastic effects (creep and the Payne effect) from irreversible structural damage (break-in and fatigue). Estimating coefficients from the recovery model isolates purely reversible behavior, allowing for the direct calculation of permanent stiffness loss. Separating the mechanisms prevents temporary viscoelastic variations from obscuring actual structural fatigue, providing critical insight into permanent suspension degradation and improving the accuracy of future loudspeaker durability testing.