Mechanical overload remains a primary limitation in high-output loudspeaker operation, particularly at low frequencies where large coil excursions are required. Conventional mechanical protection strategies are typically implemented as signal-domain limiters or filters, which act indirectly on the loudspeaker’s mechanical state; may introduce discontinuities, spectral modification, or unnecessary attenuation.
This paper proposes a methodological framework for mechanical loudspeaker protection based on the virtualization of admissible system behavior. The approach is formulated within a nonlinear wave digital loudspeaker model; realized using a direct–inverse–direct architecture. Mechanical protection is embedded directly into the virtual loudspeaker dynamics by shaping the nonlinear suspension compliance as a function of voice-coil displacement. As the excursion approaches a prescribed admissible limit, the virtual compliance is progressively reduced using a smooth raised-cosine law, resulting in a continuous increase of the virtual mechanical stiffness. Excessive excursion is therefore prevented as a consequence of the system dynamics, without explicit limiting, clipping, or signal-domain intervention.
The proposed framework is evaluated through numerical simulations using steady-state low-frequency sinusoids; low-frequency sine bursts under free-air loading. Results are compared against an unprotected loudspeaker; a fixed high-pass filter configured to meet the same excursion constraint. The simulations verify that the proposed method enforces a soft excursion ceiling without discontinuities, preserves low-frequency output in the near-limit operating region,; exhibits stable; immediate recovery following transient excitation. Distortion behavior is characterized; shown to increase smoothly as a result of the introduced mechanical nonlinearity.
The results demonstrate that mechanical protection can be realized as an emergent property of a virtual loudspeaker model rather than as an external control action. The proposed approach provides a physically interpretable; numerically robust foundation for virtualization-based loudspeaker protection.
