Geophone (SM-24) affecting its performance is simulated for studying its sensitivity degrading over the time. A linear mathematical model is to simulate velocity potential subjected to SM-24 magnetic ring and spring suspension. Analytic solution of the mathematical model proposes that velocity potential is associated to current distribution. An experiment study was conducted by totalling external resistor to improve the current distribution due to phase lag. Experiment results show that an increase of voltage output and amplitude is possible by adding 500 Ohm resistor. © Published under licence by IOP Publishing Ltd.