Abstract: Spatial impression is one of the key factors for evaluating the sound quality of a concert hall, manifested in two main aspects: apparent source width (ASW) and listener envelopment (LEV). This study investigates how reflected sound—varying in intensity, frequency, direction, and delay—affects auditory spatial width (ASW) through superposition, masking, and bridging effects, and establishes a corresponding objective evaluation model. Using a multi-channel sound field simulation system, subjective listening experiments were conducted to identify statistical relationships between objective parameters of reflected sound and subjective ASW ratings. Based on the experimental results, an objective ASW evaluation model grounded in the concept of acoustic moment is proposed. The model is validated using subjective evaluation data from an actual concert hall and objective acoustic field parameters simulated with ODEON software. Results demonstrate that the proposed ASW evaluation model comprehensively accounts for multiple reflective sound parameters and yields predictions highly consistent with subjective evaluations. This preliminary validation confirms the model’s effectiveness in assessing concert hall ASW, providing a reference for acoustic design and optimization.