Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms,   ISBN:9780240520094

Customer Rating: 

Epic, well-researched, and thoughtfully organized. Having read dozens of texts on related subjects, and spent years designing and measuring sound systems, I can say that this is among the best resources available. While not lacking in theoretical rigor, Toole critically evaluates the correlation between predicted and measured responses in more widely accessible terms. Most importantly he chisels away at the mythology surrounding acoustics, acoustical measurement, and industry standards by firmly establishing the relevance of theory and measurements to perception. The result is an extremely practical tool for small listening room consultants and enthusiasts. Not falling too much into either of these categories, I still found tremendous relevance to the large-scale live sound industry, which stands to benefit from similar investigations.

Customer Rating: 

For years the film industry has been using methods and "science" (I use the term loosely) that has set the film industry apart from every other audio technology. Odd for such a large business like film to take a "separate path" from esteemed organisations like the Audio Engineering Society (AES). For many years theatre owners were "bullied" into adopting THX (a pseudo-scientific marketing approach to sound created by non-engineer Tomlinson Holman), although no benefits were apparent from these systems.

Then these flaws were exported to the home theatre market with the branding of "THX Approved" speakers and receivers. All in the ill-fated attempt to "recreate the mixing room". It's all a complete fraud, and hasn't resulted in better sound anywhere. And people like Tomlinson Holman got Oscars for this junk. Can you believe it? Someone should go by and pick 'em up, they weren't earned, that's for sure.

For some reason the film community has been loathe to criticise this flawed technology, although most theatres don't display the THX logo anymore and universally ignore the concept.

The rest of the professional audio business has advanced dramatically - specifically live concerts, where the distorted, noisy, and unintelligible horn speakers have been replaced with line arrays, a much more appropriate technology for movie theatres, as well.

Floyd Toole to his credit completely disparages all this THX/Dolby/Constant Directivity horn nonsense for film, and while he doesn't propose any solutions he encourages the appropriate engineering talent at SMPTE to work to replace these flawed standards with actual working technology.

Thanks, Floyd, for finally saying the Emperor has no clothes.

Customer Rating: 

Toole explains just about everything you need to know to create or fine-tune your listening room or home theater in a way that's easy for even the layman to understand. It's the most comprehensive, authoritative, and well-written book I've seen on the subject.

Customer Rating: 

Absolutely the best book on sound reproduction. A must for anyone serious about reaping the most from his/her audio equipment.

Customer Rating: 

This book goes well beyond your typical technical paper on audio and even most books on the subject, and I must admit that in some ways it is a tour de force when it comes to certain important aspects of the discipline. Nobody else that I have read even comes close when it comes to the totality of information, although there are some important omissions and dismissals that I will discuss up ahead.

Within the text Dr. Toole dwells on some topics at length, and often refers back to them as the reader progresses through the book. He is obviously trying to get serious points across, and does so with obvious enthusiasm.

To cut to the chase, I liked the book a lot, and it has information in it that I have pretty much agreed with for years, particularly as it refers to the need for wide and smooth broad-bandwidth dispersion, smooth off-axis response, the importance of a center channel, the requirements of surround channels (placement and performance), and the lack of importance of comb-filtering, phase integrity, and similar artifacts in typical home listening rooms. It was good to see some input regarding digital codecs for surround sound, too, and it was nice to read some refreshing opinions regarding tube (high output impedance) power amps and wire, although those topics are not the main thrust of the book.

Of course, a number of other rational writers and research-oriented manufacturers have been saying the same thing about the book's basic ideas and conclusions for many years, although maybe not on so comprehensive a scale, nor with the kind of documentation we find here.

Indeed, a fair amount of what Dr. Toole is saying in the book is almost self-evident from a "this makes total sense" standpoint.

For example, he lauds the idea that a speaker needs to not only be smooth responding on axis but also needs to be smooth off axis. Well, does anybody reading this review know of anybody would say that a speaker is OK if its frequency response is rough either on or off axis? Competent audio designers and perceptive reviewers have been on the "smooth is best" bandwagon for decades. And all one needs to do to prove to themselves that three channels up front is better than two channels up front is do a quick comparison with decent multi-channel source material or a processor that can do a decent job of deriving a solid center feed from the phantom part of a two-channel image. Ditto for wide-dispersion monopole surround speakers vs. narrow-dispersion types aimed at the listener. Of course, codecs, phase behavior, and things like amp distortion, tubes vs. solid state, and speaker-wire issues remain debated within the audio-tweak community, and Toole does everybody a service with his analysis of those issues. Even so, I am pretty sure that they will remain issues for scads of enthusiasts for close to forever, Dr. Toole`s prestige notwithstanding.

However, there are a few beliefs and themes Dr. Toole works with that are not covered in enough detail to satisfy certain rational enthusiasts (including me), and the book actually leaves out or dismisses some important historical and technical information that work to undermine conclusions he presents regarding the best sound possible from speakers. The flaws with the book are not so much what he says as what he does not say. While it may be esoteric hair splitting on my part, I do want to mention some of those omissions.

For example, he references some of Roy Allison's work and even reproduced one of Allison's early Audio Engineering Society Journal article diagrams (showing how Roy's original, angled-front Model One was configured to flatten mid-bass suck-out dips), and yet Toole never managed to obtain a pair to measure and check for results. I think that he might have been impressed by what the speaker could do, not only in the realm of smoothing boundary-related mid-bass suck-out artifacts, but also by the way very wide and smooth broad-bandwidth dispersion works to simulate a live music sense of soundstage realism.

Regarding such dispersion, Dr, Toole points out that wide and smooth broad-bandwidth behavior is very important for main-channel speakers in normal rooms. However, nature of the suggested wideness is actually rather constricted when it comes to what the Allison Acoustics company's triangular shaped models could do. (Roy Allison also designed the AR-LST system before he left Acoustic Research, and it also exhibited the characteristic.) The Allison tweeter and midrange drivers are nearly as flat and smooth - and loud - at ultra-wide angles as they are on axis. The Allison tweeter is this way to beyond 12 kHz, which is almost unique in the world of such drivers. Even typical .75-inch diameter tweeters seem pinched in terms of dispersion uniformity, compared to that tweeter. This means that reflections from adjacent room boundaries when employing those front-channel systems are not only smooth (which Toole prefers), but also fairly powerful, a characteristic Toole seems not interested in dealing with.

The only type of system illustrated in the book that exhibits this wide-dispersion characteristic is the surround-channel model he discusses, which also has angled front panels that allow it to deliver both wide dispersion and, at least with proper drivers that are given proper crossover control, flat power input to the room. As best I can tell, there was no analysis at all concerning just what advantages a main-channel speaker with this kind of dispersion characteristic might exhibit.

As with the surround-channel system Toole illustrates and discusses, a typical Allison triangular-shaped system will actually deliver surprisingly uniform wide-bandwidth polar response over a 270 degree arc. Indeed, in terms of spectral balance these Allison designs sound nearly the same directly to the sides as they do directly in front. Of course, since the standard placement for such systems is up against the wall the result might be problematical, due to the very powerful front-wall reflections and of course the strong early reflections from side walls, as well. However, there is no reference to any main-channel speaker research in the book that analyzes just what speakers of this type can do, be the results bad or good. Interestingly, on page 137 Dr. Toole mentions that listeners appear to prefer the sound from wide-dispersion loudspeakers (not wide by Allison standards, but wide by more mainstream ones) with somewhat colored off-axis behavior to the sound from narrow-dispersion models with less colored off-axis behavior. However, what about speakers that have BOTH ultra-wide dispersion and minimal coloration at those wider angles?

On page 340-341, Dr. Toole mention obvious performance limitations with the AR-3, a speaker that was very highly regarded in the 1960s; its rather high up, one-kHz woofer/mid crossover point being obviously problematic. Yet the book never discusses whether he went on to check out the later AR-3a model - which mostly solved the speaker's major defect by dropping the woofer/mid crossover frequency down to 575 Hz. (It did so with the aid of a new midrange driver able to handle that extension.) He also mentions (page 340) that the AR-3 was considered "dull" sounding by some of his listening test subjects, and while that may be true under some listening conditions, the later AR-3a was judged to be a somewhat brighter sounding speaker by many critics, at least when located in typically furnished home-listening rooms. (Allison and Bob Berkovitz themselves proved this in a paper published in the AES Journal way back in the early 1970s.) Given the almost cult status of the AR-3a even today, I find the lapse by Dr. Toole rather odd.

I should also note in one part of the book he may actually have the AR-3 and the AR-3a mixed up. On page 340 he states "... The Acoustic Research AR-3 (figure 17.2b) was famous for its novel acoustic suspension woofer, and it came to be one of the reference loudspeakers of that generation. Its acoustic performance was well documented in the literature (e.g., Allison and Berkovitz, 1972), which was a great credit to the company..." However, actually, Allison and Berkovitz were studying the room response in the Boston-area homes using the AR-3a and not the AR-3. Both speakers were references of a sort for the industry during their production runs, but the AR-3a was a better speaker than the AR-3.

Sticking with the AR issue for a further moment, on page 14 he mentions the "live-vs.-recorded" concerts designer Edgar Villchur did in the 1960s with the AR-3 (Villchur is the father of the acoustic-suspension woofer, as well as the man who came up with the half-dome tweeter and midrange concept), but he seems to ignore their import. All Dr. Toole has to say about the what transpired is that numerous later-design speakers made by a variety of other companies are better. But if the AR-3 (a speaker that is by definition somewhat inferior to the later AR-3a) was "dull" sounding as he says his listening panel described it and lacking in terms of impressive performance by modern standards, how was it that Villchur could use a pair of them to impress not only serious audio enthusiasts but also serious audio journalists during those sessions? We are not talking about situations like the earlier Edison demos, where listeners were astounded to hear sound coming from speakers at all. We are talking about demos where audience members were seasoned listeners who were carefully checking for discrepancies.

It may be that the very success of those concerts partially undermines many of the premises about speaker/room sound and speaker improvementsthat Toole puts forth in the book. I mean, if a speaker like the AR-3, designed more than four decades ago, can get us far enough toward reproductive realism to make it, at the very least, difficult to detect differences when compared to a live ensemble, then just how much better can modern speakers improve things to be significant? It is preposterous to dismiss those concerts as insignificant, and also preposterous to hold them up as an example of an outdated and wrong-headed approach to speaker design.

Another very highly regarded speaker that showed up after the AR-3 era was the AR-LST, which achieved an almost iconic status, and is still considered a reference standard by some reputable individuals. Yet, he did not audition that one for analysis in the book, either, even though many astute individuals considered it to be a paradigm example of wide-dispersion performance. Even Consumer Reports used it as a reference speaker for years, as, so I am told, did audio writer and reviewer Julian Hirsch.

Both the Allison Model One and the LST were designed by Allison, and both made use of multiple drivers on angled panels for much wider dispersion than what we have with systems having a single, forward-facing panel. Love it or hate it, I think this approach should have at the very least rated a certain amount of analysis, and yet virtually none of the front-channel speakers Dr. Toole dealt with in the book appear to have made use of multiple drivers on angled panels. Admittedly, this approach has not been used by many other manufacturers, but it still certainly rates as much text and response-diagram copy as any British-made Quad model, two of which were discussed in the book, with their response curves also presented.

Given Dr. Toole's admonition about "aiming" speakers at the audience in home theater installations (and perhaps music installations, too) I think it becomes doubly important to deal with designs that essentially do not need to be aimed or only need to be aimed in a general direction towards the listening area. I saw nothing about that in the text. If ultra-wide dispersing speakers are not what we want for left, center, and right channel use, the book should have at least discussed their designs and shown just why they are not viable.

Regarding that approach to sound, another interesting thing is that Dr. Toole made no mention I could find of Bose at all, or the 901 series systems. Now, that design certainly has its detractors (and enthusiasts, too), but it sure did make a splash when it appeared (Julian Hirsch went on and on about the design in his 1968 review), and yet there is no documentation in the book on just why the system might be good or bad, or in-between. However, that speaker is a legend (or nightmare, depending on your approach), and its design certainly should have been analyzed, especially in a book that deals so emphatically with room reflections, cross correlation, envelopment, etc. Given that Bose Corporation is a major audio manufacturer, I find the omission rather odd. Toole may not like the speaker (anybody`s guess), but it seems unfair for him to simply ignore it in a book about speakers and speaker/room interactions.

Another speaker that made a big splash in its day was the original Larger Advent. As best I can tell there are no comments about that item, either, even though the system was probably as much of a cult item as any AR or Bose model. Perhaps it was one of those units that were discussed and measured, but only listed as "speaker A" or "speaker Y" in the text. If anything, the fact that it was a two-way speaker with a largish woofer/mid driver should have elicited some justifiably negative comments. Popular speakers that exhibit deficiencies deserve to be analyzed, just like speakers with mostly positive attributes.

Another missing link in his series of analyses was the Klipschorn, which almost certainly is an iconic item that some buffs would kill to own. While anything but a big seller, the speaker is an interesting enough design to warrant at least a comment or two, even if the conclusion might dismiss the speaker as an untenable dead end.

Still another speaker that made quite a psychological and technical splash when it first appeared was the original dbx Soundfield model, a wide-dispersion speaker that was still configured to be aimed - but not at the audience. Yet there is nothing in the book about that speaker or any discussion of the approach designer Mark Davis used to analyze the time/intensity concept and then configure a package that would achieve what he wanted. No mention, either, of the omni-directional approach to speaker radiation patterns that we find with speakers like the Ohm/Walsh models. Mark Davis and John Strohbeen (designer of the Ohm product line) obviously went beyond anything even Roy Allison attempted in the realm of super-wide dispersion. Speakers like these and the Allison models (as well as the AR-LST and AR-3a) certainly ought to have rated at least a footnote-level comment here and there.

Of course, let's be realistic. If Dr. Toole wrote a book that covered all of the above models in addition to those it did cover it would probably be a thousand pages long. In addition, just getting hold of the various models and doing the work (when Toole was at the NRC and later Harman) would have been prohibitively time consuming, tedious, and expensive. However, I do find it troubling that so many innovative designs and design approaches were ignored, both in the book and also in a number of Dr. Toole's earlier JAES articles, particularly when so many of them have been lionized by the audio public through the years, and their designers were so often considered among the best.

It may be that some of the above speakers were analyzed by Toole when he was with the Canadian NRC and later on at Harman, but what we are dealing with here involves what the book discusses, and they were not discussed in the text.

Over four decades ago Edgar Villchur did that previously mentioned series of live-vs.-recorded concerts with speakers that were marginally inferior to the best of those being produced today. Just how good do today's speakers have to be to back up Dr. Toole's claim that we have come a long way since the AR-3?

Anyway, it was a pleasure to read the book and I have recommended (with some caveats, of course) to several of my friends. I recommend it here, too.