By Beranek and Mellow.
Winter 2012 Boston Audio Society Volume 34, Number 4
Dr. Leo ("Acoustics") Beranek (Leo
Beranek; the home-page image is of the Tokyo Opera City concert hall,
Japan, whose acoustical design consultant was Beranek) is still involved in
enhancing our knowledge of acoustics with ACOUSTICS:
Sound Fields and Transducers (Academic Press; ISBN:
978-0-12-391421-7), an update of sorts co-authored with Tim Mellow (engineer,
audiophile and musician; Mellow
Acoustics). This 720-page tome is "focused on electroacoustics with the
needs of a broad range of acoustics engineers and scientists in mind" (from
Elsevier website). This book covers the latest in microphones, electrodynamic
and horn loudspeakers, box and bassreflex enclosures, transmission-line
enclosures (e.g.: Bose Wave Music System), crossover filters, cellphones,
soundfields in small enclosures and in large rooms, rooms for loudspeaker
listening, plus radiation and scattering from all sorts of surfaces mounted in
finite and infinite baffles. Lumped circuit elements are employed at low
frequencies and exact equations at high frequencies. The text ends with
state-variable analysis of circuits. The book assumes knowledge of electrical
circuit theory. It is directed toward experimenters, hobbyists, and
audio-equipment engineering designers.
The eBook and print editions can be purchased from the
Academic Press Elsevier bookstore. The print edition is $104 at [Mellow's
website considers this book to be less a Beranek update and more a Mellow
project with Beranek's 1954/1986 reference as a starting point. In Mellow's own
A few years later, ...I was thinking that what the world of engineering acoustics needed was a text book that covered everything from lumpedelement theory using circuit analogies, as covered in Leo Beranek's book, to wave theory and sound radiation/scattering problems. However, I could not cover the fundamental principles any better than Leo had already done and I did not want to plagiarize anything. The idea of writing an updated version of ACOUSTICS suddenly hit me like a thunderbolt. It seemed like completely the right thing to do even if it would involve a huge amount of work....
I wrote to Leo Beranek who
amazingly wrote back informing me that he held the copyright and that I could
use anything I liked. However, he was not keen on being a coauthor because he
was too busy contributing to the current literature on concert hall acoustics,
even if I wrote all the new material and he simply reviewed it. This was hardly
surprising since at the time since I was completely unknown with only a handful
of published papers to my name. However, as time went on, Leo became more
enthusiastic about the project and contributed much new material, including two
whole chapters on sound in enclosures and rooms for loudspeaker listening.
I was certainly delighted when he eventually decided he would like to have his name on it as that was the best possible endorsement of all the hard work involved....
Leo paid particular
attention to the ordering of contents and specifically asked me to include a new
section on transmission-line loudspeakers because so many had asked him about
how the Bose Wave system worked. He also requested a new chapter on cell phone
acoustics because he was curious as to how so much sound could be produced by
something the size of a deck of cards and felt that it would bring the book
right up to date.
A new version of ACOUSTICS had to include the work of Neville Thiele and Richard Small. They proposed just six parameters to completely describe the low-frequency behaviour of a loudspeaker, which are now commonly known as the Thiele-Small parameters, and Small showed how to obtain them from the input impedance. Also, they produced tables/charts which enable anybody to choose a frequency response shape for a given drive unit and engineer the cabinet and bass-reflex port accordingly. Leo is rightly proud of the fact that these authors used his book as their starting point and that it led to the development of smaller loudspeakers using the acoustic suspension principle."
[Something appears partly misemphasized in this last assertion
about Thiele/Small, ports, development of smaller speakers, and acoustic
suspension (which was famously the work of Edgar Villchur in the 1950s). -- DRM]
Also from the new book: "The
audibility of phase distortion has provoked a lively debate over the years, but
why not design the loudspeaker correctly in the first place so that there need
not be any doubt about its accuracy? As we shall see in the next section, the
solution to this problem need not be complicated if we approach it holistically
and take into account all the factors that affect the response of the
loudspeaker, including the baffle effect."
[Loudspeaker phase has been demonstrated for decades to be
audibly unimportant, and in any case the term does not appear in Beranek's
original index. Finally, Mellow's website also contains not only an audioXpress
reprint of his article about a d-i-y output-transformerless tube amp
but a 15-page PDF document listing more than 300 errata for this new Beranek/Mellow
book. Admittedly, most of the errata appear to be typographic, editorial, and/or
simple re-incrementations of the sort ‘replace chapter 5 with chapter 4'.
Still, it does little to solidify a slightly sketchy feel to this whole Mellow
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