Where do I come from?
Where am I going?
Who am I?
questions are with us still. With only the slightest of changes, they can be
recast into a form that provides a guidepost to the music lover, the
audiophile, the hobbyist, and the artisan-engineer.
Where does the art of sound reproduction come from?
Where is it going?
What do I seek from this art?
This chapter is a quick tour of the art
and its beginnings; the following chapters explore the realm of loudspeakers,
including how to build one, and go on to broader questions of finding your own
personal style and design philosophy.
The Radio & Movie Years
In the first years of Electrical
Amplification, engineers had their hands full just trying to master the complex
and non-intuitive mathematics of vacuum tube amplifiers and oscillators. In the
early 1920's, Major Armstrong (who went on to invent superregeneration, the
superheterodyne, and FM radio) got things rolling by accurately characterizing
the electrical behavior of the simple triode and establishing the requirements
for correct biasing and plate loading. This opened the door to rational and
predictable design of audio and radio-frequency (RF) amplifiers, which led to a
very rapid expansion of the radio industry and the introduction of electrical
In the days of narrow bandwidth
broadcasting and noisy, fast-wearing 78rpm records (the best-quality
long-distance lines of the Bell System limited the signal to 50Hz - 8kHz), the
best that could be hoped for was “Good Tone.” Although hundreds of
manufacturers of radios and phonographs were continually striving to improve
quality, the built-in limitations of 78rpm shellac records and the AM
broadcasting networks made it difficult to go very far in improving
loudspeakers and amplifiers without further exposing the problems of the
source. (Doesn’t this sound kind of familiar ... as in “Perfect Sound Forever,”
The real advancements came from the
movie industry, which was free to build complete sound systems from (dare I say
it?) scratch, without the many limitations of the AM broadcast system and
shellac records. In addition, the major studios owned and operated the
theatres, so they had an incentive to take advantage of the new movie-sound
medium in the most dramatic (read profitable) way possible.
Movie producers and directors quickly
discovered that sound was the “heart” of the movie, conveying emotions
powerfully through music, underpinning the dialog and the images, giving the
sound-movie a profound emotional impact denied to the silents. The industry
also discovered that improved fidelity (from optical sound, better amplifiers,
and better speakers) deepened the emotional effect of the sound-track. For the
first time in the history of the movie industry, sound quality, even if it
wasn’t consciously noticed by the audience or the critics, became a powerful
and profitable box-office draw.
Both Western Electric (the
manufacturing and R&D arm of the Bell Telephone System) and the RCA/NBC
system competed to design the highest-quality sound possible. In the 1930’s,
movie sound was the leading edge of the entire electronics industry, as new
tube types like the Western Electric 300B, the RCA 50, and the RCA 6L6 were designed
and built specifically for theatre and professional use.
In the brief span of less than ten
years, the entire foundation of the modern high-fidelity industry was created.
Between 1929 and 1939, the world saw:
• The first demonstration of long-distance
high-fidelity using all-FM transmitters, repeaters, and receivers by Major
Armstrong and his Yankee FM Network. This could well have been the first public
demonstration and commercial sale of full-frequency-range, low-distortion,
high-fidelity sound to a mass audience.
The Yankee FM Network was almost certainly
the first opportunity the public had to experience full-frequency-range,
wide-dynamics, and low distortion on a day-to-day basis. The only alternatives
were noisy shellac 78rpm records, low-fi network AM with limited-bandwidth
intercity relays, and optical soundtracks with modest performance at best.
Armstrong’s network was the first complete high-fidelity system to make it out
of the lab into the hands of the public.
• Two and three-channel stereo sound
demonstrations by RCA, Western Electric, and Alan Blumlein, and the first
full-length movie to use a multichannel soundtrack, Walt Disney's Fantasia, released in 1940.
Alan Blumlein went on to invent, patent,
and prototype an entire stereo signal
chain, with crossed-pair figure-8 microphones, matched low-distortion
electronics, 45-45 moving-coil cutterheads with motional feedback, moving-coil
45-45 phono cartridges, stereo-optical soundtracks, and matched stereo
speakers. Blumlein also analyzed and found means to circumvent what is now
called Miller capacitance, and invented the long-tail pair differential
• Low-distortion, full frequency range
microphones, phono pickups, amplifiers, and speaker systems from Western
Electric, RCA, Decca, EMI, E.F. Scott, Brook, and others. The most advanced
equipment was used for transcriptions of radio shows (via 16" 33rpm
acetate masters) and in high-end radio sets.
• Electroacoustic analysis and modeling of
microphones, moving-coil cutterheads, optical modulators for movie soundtracks,
phono pickups, direct-radiator loudspeakers, and theatre horns.
• The introduction of the Western Electric
300A and 300B direct-heated power triode, the RCA 27, 56, 76, 6P5, 6J5, and
6SN7 family of indirectly-heated triodes, and the RCA 45, 50, and 2A3
directly-heated power triodes. These triodes remain the lowest distortion
amplifying devices ever made. No pentode, bipolar transistor, JFET, or MOSFET
has ever approached the distortion performance of triodes. In addition to low
distortion in the absolute sense, the distortion spectra of triodes is
favorable, with a rapid fall-off of the upper harmonics. (This is not true for
beam tetrodes, pentodes, or solid-state devices, which are fundamentally less
• The first application of loudspeaker
time-alignment. (Designed at the request of a director who was not satisfied
with the realism of the tap-dancing on the soundtrack!)
• Bi-amplification for lower speaker &
amplifier distortion and wider dynamic range. This was used in theatre systems
and top-of-the-line radio sets.
• And many other innovations still in use today.
Both the “Golden Age” of High-Fidelity
in the Fifties and the “Ultra-Fi” movement in the Nineties have drawn deeply
from the wellspring of knowledge created in this decade. The papers of Major
Armstrong, Alan Blumlein, and the RCA and Western Electric research labs make
fascinating and instructive reading today.
Baton is Passed
The War Years of the Forties represent
a fallow period for audio, as the best minds of the electronics industry turned
away from audio to devote their energies to building high-frequency radar
systems, and after the war, the fast-growing television industry. This period
also represents a turning of the generations, as the first wave of audio
pioneers passed the baton to the engineers who would later build the Golden Age
of High-Fidelity in the 1950’s.
One of the most important developments
of the late 1940’s was the introduction of the Williamson amplifier, which
ended the use of power triodes in high-fidelity (except for a very small group
of French, Italian, and Japanese hobbyists). With the introduction of the
high-feedback, high-power, and high-efficiency KT66 Williamson, the great power
and distortion-lowering race began in earnest, and would continue relentlessly
for the next 40 years.
Although it may seem easy in retrospect
to criticize the high-feedback Williamson now, we should remember what the
speakers of the day were like: there was no real understanding of the
properties of closed-box or vented-box systems, and most speakers were boomy or
thin-sounding (mistuned) by modern standards.
With a closed box (known then as
infinite-baffle or acoustic-suspension), the tuning problem is straightforward
... just adjust the box volume for flattest response and best sound. However, a
vented box is a fourth-order system,
and system tuning becomes horrendously difficult by the cut-and-try methods
then available. Even something as basic as measuring
a closed or vented box is quite a difficult trick. Modern analytic and
near-field measuring techniques were still 20 years in the future, awaiting the
AES publication of the Neville Theile and Richard Small papers in 1971.
The high damping (due to the high
feedback) of the Williamson was just what the boomy speakers of the day needed,
offering a very real improvement in bass quality. The increased power was also
appreciated, since the 2A3 was the only power triode then available to the
public ... the much larger 300B was not available to the public, and the 211
and 845 transmitting triodes require costly high-voltage supplies. The
combination of high power, high damping, and easily available power tubes in
the 6L6, 807, KT66, and 5881 family met the needs of a new generation of postwar
A more significant event of the late
Forties was the introduction of the Ampex magnetic tape recorder, based in turn
on captured German Magnetophon AC-bias machines. What was a little odd was that
the German AC-bias technology was known in America before the war, but ignored
by the American and British audio industry in favor of low-quality wire
recorders using DC bias. In the immediate postwar period, the problems with
manufacturing iron-oxide coated magnetic tape were mastered by 3M, and the new
Ampex tape recorders quickly surpassed the German originals. The introduction
and rapid improvement of magnetic tape recording was the prerequisite for the broad advances of the 1950’s.
The advent of high-quality 30 and 15
IPS master-tape recording (which still sound astonishingly good 40 years later
... check out the RCA Living Stereo reissues) meant that the recording, movie,
and broadcasting industries finally had the means of making very high-quality
original productions ... but no way of distributing them to the public! The
fruits of this research ignited the second wave of audio, the Golden Age of the
Columbia Records introduced a
Long-Playing 12" 33 1/3 rpm record, and RCA introduced a competing 7"
45 rpm record (later known as the “single”). Both formats combined a
standard-width microgroove, low-noise vinyl, sapphire or diamond styli, and
much lower playing weights. This resulted in a phonograph record with far
better durability, dynamic range, and playing time. What was known as the
“battle of the speeds” ended with short popular songs being released on 45rpm,
and longer “serious” jazz and classical music coming out on 33rpm. (The “rock
album” didn’t appear until the mid-1960’s.)
At the same time, the broadcast industry
opened hundreds of new high-quality FM stations carrying classical, jazz, and
light popular music, which at the time were subsidized by the mass-market AM
stations. (The FM subsidy came to an end by FCC decree in the mid-Sixties,
resulting in more FM stations, but also a sharp decrease in unprofitable
classical and jazz FM programming.)
The movie industry started using 6
discrete channels of magnetic sound on the 70mm wide-screen film, a tremendous
advance on the traditional single optical channel on 35mm film. Cinerama,
CinemaScope, VistaVision, and Todd-AO 70mm gave the movie-goers a dramatic new
experience. (Modern 35mm films exhibited in small theatres are lower quality than the 70mm
films of the 1950’s. The IMAX and OmniMAX films shown in specialty theatres is
the only modern format that exceeds the performance of 70mm and 3-screen
All of these parallel advances (which
happened in less than a decade!) led
to the birth of a new industry, quite separate from the mass-market “consoles”...
the “High Fidelity” industry. The industry grew in direct response to the
explosion of high-quality music from many different sources; without all of
these new sources of high-quality, high-fidelity music, there couldn’t have
been a Golden Age of audio.
Many treasures from this era still
delight us today ... truly wonderful recordings that are clearer, more natural,
and more lifelike than contemporary digital recordings made 40 years later. We
also have legacy of superb products made by Acrosound, Altec, Ampex, Brook,
Leak, Marantz, McIntosh, Ortofon, Quad, REL Precedent, Tannoy, and Thorens, to
name just a few. Even the budget-priced Dyna Stereo 70, made in the hundreds of
thousands, still gives great musical pleasure with the very latest speakers and
CD players of the mid-Nineties! This was a period when the pioneering advances
of the Thirties spread out across the world, with many millions now enjoying
high-fidelity for the first time.
The decade saw a major transition from
a hobbyist-driven pastime to a widespread domestic industry, with products
growing more elegant, easier to use, and domestically acceptable. Amplifiers
became more powerful, receivers were introduced, and speakers followed the lead
of AR and KLH in getting smaller. Relative to the rapid decline of the early
transistor era, though, the sonic compromises of the 1950’s were modest, and
more than offset by a great abundance of new music from stereo reel-to-reel
tape, superb LP recordings, and live FM radio transmissions (with none of the
compression and EQ that is standard commercial FM practice today).
One of the things not mentioned in the current nostalgia boom for the 1950’s is that
the pace of technological and social change in the late 1950’s and the 1960’s
was stunningly fast ... much faster than the decade of the 1990’s, which has a
great deal of excitement in the computer field, but precious little elsewhere,
and is actually a period of social and political reaction.
By contrast, in the time-span of 1954
to 1964, TV changed from black-and-white to color, audio changed from table
radios and massive “French Provincial”
consoles to well-designed stereo components, very high-quality FM radio
became widespread, aircraft changed from slow and noisy Super Constellations
and DC-7’s to fast and quiet Boeing 707’s, interstate travel changed from
congested 2-lane roads with many traffic lights to freeways, and space
exploration changed from an impossible science-fiction dream to everyday
reality. The social changes were profound ... rock-n-roll emerged from the
unsavory ghetto of “race music,” the civil rights movement began to reverse
centuries of racial brutality, and the stodginess, conformity, and social
repression of the 1950’s relaxed into the Utopian freedom and experimentation
of the 1960’s.
Returning to our little pond of hi-fi,
this dramatic era of technical and social advancement was a perfect time to
change a fast-growing industry from monophonic to stereophonic sound. The
decision-makers in the record industry sat down at a table in Los Angeles in 1958 to decide which of the 3 competing
systems was going to be the world standard ... and even more remarkably, they made the right choice! (Compare
that to the corporate infighting and complete lack of compromise just 14 years
later when quad sound was developed.) The Westrex 45-45 stereo system became
the world standard for 33 and 45 rpm records, and in less than 2 years time,
nearly all titles were being simultaneously released in both stereo and mono.
As stereo sound gradually replaced
mono, the large horn and infinite-baffle speakers of the early 1950’s fell out
of favor. It’s one thing to have a handsome big speaker in the corner of the
room ... after all, it’s kind of a conversation piece, like a piano ... but two behemoths (with additional demands
for stereo symmetry in room placement) are quite another story!
The advent of stereo moved the
“bookshelf” speakers (so-named because they were always shown in the
advertisements of the day as fitting in a bookshelf of a built-in library) from
a New York studio apartment curiosity to the hi-fi mainstream. Acoustic
Research was the pioneer with the “acoustic-suspension” principle used in the
AR-1 in 1954, and as the decade moved on, the AR-3, AR-2, and AR-4. Kloss, one
of the co-founders of AR, went on to form KLH, which made speakers very much in
the pattern of the original AR family.
It wasn’t just small size that made the
bookshelf speaker a success. The AR and KLH speakers had much flatter frequency
response than the big competitors, and the smaller cabinets were far more rigid
than the large and thin plywood cabinets of the old-timers. Although the big
speakers had lots of dynamics and impact, the AR’s and KLH’s had much less
coloration, and introduced the concept of accuracy to the public at large. In
North America and Britain, the low-efficiency compact speakers became the
dominant metaphor for true high-fidelity, and the big horns were seen as
archaic and regressive. In other parts of Europe and Japan, though, the big horn
speakers never lost their following, since audiophiles in those markets put
more value on dynamic range and low distortion than flat response and
“accuracy” in the Anglo-American sense.
At the same time as AR and KLH were
making a big splash in North America, D.E.L. Shorter of the BBC was laying the
foundation of modern speaker design by uncovering and measuring the elusive
“delayed resonance” that didn’t show on up on conventional swept frequency
measurements ... eventually leading to the FFT and MLS techniques used today.
Although it took many decades, the delayed resonance measurement technique
finally made it possible to build conventional dynamic speakers that rival the
single most advanced speaker of the 1950’s ... the Quad electrostat.
Click here for larger image.
The Quad electrostat occupies a very
select circle of classic speakers that still sound “modern,” even advanced,
today. Even in strictly objective terms, the Quad has superb transient
response, with nearly perfect square waves, as well as vanishingly low
distortion. Very few modern speakers combine excellent transient response with
low distortion; most speakers, then as now, force the buyer to choose between
very low distortion (horns and studio monitors) and excellent impulse response
(linear-phase audiophile speakers).
As efficiencies of the “bookshelf”
speakers gradually dropped, amplifier power increased to compensate, with the
15 watts of the Williamson growing to the 35 watts of EL34 family of amplifiers and the 60 watts of the KT88/6550
family. The enduring classic of this era is the well-loved Dynaco Stereo 70,
with over 500,000 in production over 30 years. Although the circuit of this
amplifier is hardly sophisticated or even very linear, a thoughtfully-restored
Stereo 70 still sounds better than many high-end amplifiers made today!
In 1963, the FCC selected the Zenith
subcarrier system for stereo FM (which was probably not as good as the Crosby
system, but still a reasonably good choice), and now FM radio became
stereophonic as well. The only offshore competitor was the inferior Halstead
system, which was actually a mono signal steered left and right by a
low-frequency control signal. Fortunately, when the BBC was deciding on a
stereo FM system, they were wise enough to discard the home-grown system, and
adopt the foreign Zenith system. In time, the Zenith system became a world
standard, a rather rare example of international harmony in broadcasting
standards. Anyone who has followed the endless wrangling regarding color and
high-definition television knows how rare it is for US and European technical
committees to agree on anything!
A year later, stereo sound for
television was set aside by the FCC at the request of the three major TV
networks (so they could avoid additional costs during the time they were converting
(The absence of any TV standard
resulted in the German discrete FM-FM system in 1975, the American BTSC
subcarrier system in the early 80’s, and the British digital NICAM system in
the late 80’s. At present, the PAL/SECAM nations use a mix of FM-FM and NICAM,
and the NTSC nations use BTSC ... which is a direct descendent of the Zenith TV
proposal abandoned in 1964!)