Top positive review
Gives good insight into loudspeaker measurements and perception
Reviewed in the United States on October 9, 2017
This review is for the third edition of the book, for which deliveries from Amazon began around the end of August 2017. The book has been extensively changed from the first two editions, which, according to the author, are identical except for the publisher. Because of these extensive changes, comments from reviews earlier than the above date may not necessarily apply to the third edition. The changes consist not only of the addition of new research results since the earlier editions, but also considerable reorganization to introduce the concepts in a more logical sequence.
The book collects decades of research into loudspeaker measurements and subjective preferences determined under controlled, double-blind conditions. From the perspective of a loudspeaker designer, it makes the connection between how a collection of anechoic frequency response measurements, sampled across an imaginary sphere surrounding the loudspeaker, can be performed and processed such that a design yielding results meeting specified criteria will lead to high subjective ratings when tested under double-blind conditions. From the perspective of a consumer, it demonstrates how, if the appropriate processed data are provided (unfortunately still not widespread), one can visually inspect the data to gain insight into subjective quality. For more information about this approach than I could ever provide here, check out the online video by Dr. Toole titled, "Floyd Toole - Sound reproduction – art and science/opinions and facts". This video will give you a very good idea of what the book is about - at least in part.
Contrary to critics who claim that Dr. Toole is just repeating the Harman party line, he developed these measurement techniques while working at the National Research Council of Canada (NRCC) and brought them to Harman with him. They were originally published in a 1986 AES Journal article titled, "Loudspeaker Measurements and Their Relationship to Listener Preferences: Part 2" while he was still working at the NRCC. These calculations can accurately predict a so-called "room curve" from a collection of the loudspeaker's anechoic measurements. He shows that a loudspeaker having a flat on-axis anechoic response will have a room curve that tilts downward with increasing frequency. A "room curve" in this context is a measurement of the loudspeaker's steady-state frequency response using typical measurement software, smoothed to eliminate the "hash" that shows up in the unsmoothed measurement. This is why equalizing a system to a flat room curve results in a subjectively bright sound. It's somewhat disheartening how little this is understood. People who have made this mistake could lose confidence in the efficacy of audio measurements in general.
The above techniques break down when dealing with in-room bass response. In the modal frequency region of a room, the room itself dominates the system frequency response, so for optimum bass performance, room modes and their interaction with the loudspeakers and/or subwoofer(s) must be taken into account. Chapter 8 contains a very good discussion of room modes, and how equalization, the placement of listening position, and the placement of one or more subwoofers interacts with the room modes to affect what is measured and heard. He refers to the latter technique as "mode manipulation". With multiple subs and a given set of sub positions, the possibility exists for reducing the seat-to-seat variation of the frequency response in the modal region. This technique requires individual equalization of each sub, combined with optimization software. Harman calls their implementation "Sound Field Management" (SFM). Unfortunately, it is only available on JBL Synthesis custom installation products. DIY alternatives to Sound Field Management exist, however.
I've already gone on way too long, yet I've only scratched the surface of what's covered in the book. If you have the previous edition and liked it, getting the third edition is a no-brainer, as there's plenty of new material and the organization of the book is much improved. Those who are committed to a rational approach to achieving good sound and willing to put forth the necessary effort to enhance their understanding of how to do it will benefit the most from the book.