Over long-term use, the distortion of acoustic instrument speakers changes as a result of multiple factors, including material aging, mechanical wear, environmental influences, and usage habits. As the core component for sound reproduction, the evolution of its distortion directly affects performance and the listener experience.
From a materials perspective, the diaphragm, voice coil, and suspension system of acoustic instrument speakers are key to distortion changes. Diaphragm materials (such as paper, polypropylene, or composite materials) gradually harden due to fatigue during long-term vibration, leading to a decrease in high-frequency response and low-frequency elasticity. Paper diaphragms are susceptible to humidity; prolonged exposure to humid environments can cause deformation, shifting the resonance peak. While metal diaphragms are highly resistant to aging, prolonged high-frequency vibration can induce microcracks, increasing nonlinear distortion. The voice coil, as the core of electromagnetic conversion, experiences gradual degradation of its insulating varnish and adhesive at high temperatures, leading to a loosening of the connection between the voice coil and the diaphragm, causing phase distortion and transient response deterioration. The elasticity decay of the suspension system (such as rubber or foam) directly results in decreased low-frequency control, manifesting as muddy bass and increased distortion.
Mechanical wear is another important factor. During long-term use, the gap between the voice coil and the magnetic circuit may shift slightly due to vibration and friction, leading to uneven magnetic flux distribution and thus dynamic distortion. Fatigue of the centering support (spider) can cause the voice coil's trajectory to deviate from the center, increasing lateral vibration components and generating unwanted harmonic distortion. Furthermore, oxidation or loosening of connectors and solder joints can cause changes in contact resistance, resulting in intermittent distortion, especially noticeable in music passages with a wide dynamic range.
Environmental factors also significantly impact distortion. Temperature fluctuations cause speaker components to expand and contract, and long-term accumulation can lead to structural stress release, altering the natural frequencies of the vibration system. For example, low winter temperatures can make the diaphragm brittle, resulting in poor high-frequency response; high summer temperatures can accelerate adhesive aging, leading to component separation. Humidity changes have a particularly significant impact on paper diaphragms; prolonged high humidity can cause the diaphragm to absorb moisture and expand, altering its mass distribution and affecting frequency response and distortion characteristics.
Usage habits are also a key factor determining the evolution of distortion. Driving loudspeakers at high power for extended periods accelerates voice coil heating, leading to accelerated aging of the insulation material and even voice coil burnout. Frequent playback of music with high low-frequency content (such as electronic dance music) places greater stress on the suspension system, accelerating elastic decay. Proper usage, such as controlling input power, avoiding prolonged continuous operation, and conducting regular acoustic testing, can effectively slow down the increase in distortion.
Acoustically, increased distortion typically manifests as increased harmonic distortion and deterioration of transient response. With prolonged use, loudspeakers may produce more odd-order harmonic distortion, making the sound harsh; while a slower transient response can cause percussion instruments to sound muffled and lose their original clarity. Furthermore, the accumulation of phase distortion can blur stereo imaging and reduce the positioning accuracy of the sound field.
For acoustic instrument speakers, changes in distortion are not only a technical issue but also crucial to artistic expression. A slight increase in distortion might be perceived by some listeners as "warming the tone," but excessive distortion will destroy the original characteristics of the instrument, making the performance lose its realism. Therefore, professional users typically maintain speakers in optimal condition through regular inspections and component replacements.
