In the field of energy harvesting from low-frequency random excitation, a technique known as piezoelectric beam plucking or frequency up-conversion has seen increasing interest. This paper presents an experimentally validated model to calculate the voltage response and power output when actuating piezoelectric beams via a pair of magnets. Using magnetic coupling avoids impact on the brittle piezoceramic material. The relevant equations are derived for the piezoelectric beam, and two different approaches to include the magnetic interaction are presented and discussed. After comparing the models to experimental results, their use in predicting the response to changes in the system, eg using thicker magnets, and determination of the optimal load resistance and power output with regards to frequency, are investigated.