A Virtual Performance System (VPS) is a real-time 3D auralisation system which enables a musician to
play in simulated acoustic environments. Such systems have been used to investigate the effect of stage acoustics on the performance technique of musicians. This article describes how a VPS can be calibrated using omnidirectional, energy-based quantities. It goes on to describe how the spatialisation accuracy of specific reflections can be assessed using time-frequency analysis. The energy-based calibration has been shown to produce a reasonably accurate simulation of a test space in terms of known acoustic metrics such as T30. However, the time-frequency analysis has shown significant differences in the spatialisation of particular early reflections in the virtual version of a test space.