Toole’s Five Measurements
Toole defines five measurements as being statistically predictive of subjective satisfaction:
1) On-axis Frequency Response (FR)
2) Listening Window: a spatial average of FRs in the ±10° vertical and ±30° horizontal windows
3) Early Reflections: a spatial average of the FRs of the early reflections from the four walls, ceiling, and floor
4) Sound Power: a weighted average of all of the above to assess the total acoustic energy radiating from the source
5) Directivity Index: the difference between the on-axis response and sound power
http://www.stereophile.com/reference/book_review_isound_reproduction_loudspeakers_and_roomsi/
Reading this book will give you an immense appreciation for Floyd E. Toole's efforts to find where the subjective and the objective overlap, and to introduce coherence to a field still fraught with fantasy and conjecture. Sound Reproduction: Loudspeakers and Rooms won't only change the way you understand audio; it will change the way you listen.— Kalman Rubinson