The
Advent
Loudspeaker…
and The Smaller
Advent Loudspeaker
First of All, Who and What Is
Advent?*
Advent Corporation is a new company formed to
develop new kinds of home entertainment products. Most
of us involved have had long prior experience in making
and marketing high-performance audio products for the
home. We are in business now to produce new home entertainment products, both audio and visual, that go well
beyond the generally limits generally accepted at any
given moment, and explore new or significantly different
approaches to design. One of our main product objectives
is a color television system that uses a projected image
instead of a conventional picture tube, producing a picture
of 41/2 by 6 feet.
Our President and General Manager, Henry E.
Kloss, was previously President and a founder of KLH
Research and Development Corporation, and, prior to that,
General Manager and a founder of Acoustic Research,
Incorporated. He has been directly responsible, over the
past fifteen years, for a major proportion of the important
and lasting audio products for the home, including roughly
half of the total number of loudspeaker now in use across
the country in component stereo systems and high-performance three piece music systems, radios and phonographs. His credits would be embarrassingly long to present complete, but they include:
• The longest lived best selling component speaker system on the market, unchanged in design and undiminished in popularity after twelve years.
• The revolutionary miniature full range speaker
that made it possible to provide sound of high quality in
radios and phonographs of modest size.
• The first high performance FM radio.
• The first high performance portable stereo
phonograph.
• The development of the three piece compact
stereo system as a primary medium for home audio.
All of us at Advent share with him some convictions developed over several years of working together,
about the way in which products can and should be developed. The Advent Loudspeaker is one result of those convictions, and we will have some more to say about them as
we describe the speaker.
What is the Advent Loudspeaker?
Our first Product, the Advent Loudspeaker, is
based on a premise that is not easy to accept. We believe
that it is possible to produce a speaker system, for a moderate price, that will be nothing Iess than the right, completely satisfying choice for most people with a demanding
interest in music and sound. The Advent speaker is
designed to combine the following objectives:
• To fit the highest category of loud speaker quality, with overall performance at least the equal - in every
audible and useful respect - of the most expensive speakers available.
• To do that for about half the average cost of the
speakers now generally considered the best available.
• To be small enough, unobtrusive enough, and
uncritical enough in placement to fit gracefully and usefully into a home.
• To produce enough output at low distortion to
permit listening to music at satisfyingly loud levels in even
the largest living room.
• To be driven comfortably by the majority of
good amplifiers and receivers now available, with a power
margin sufficient for the most demanding musical material.
• To sound convincing not only on the best recordings, but on the great majority of recordings of all kinds.
In developing the Advent Loudspeaker, our initial
interest was in the category just below the “ultimate” in
performance and a long way below it in price - the category in which most serious listeners, believing that further
improvements are not worth the added cost, decide to buy.
We knew that we could produce a speaker that would be
both significantly better and significantly less expensive
than the speakers considered the best value in that category. Our aim was to do that and establish a new point of
diminishing returns that would be closer to the highest
level of speaker performance.
But as we began to apply some new thinking
about old concepts and to take advantage of new materials
and manufacturing techniques, it became really clear that
we could provide a really tremendous gain in performance-per-dollar. So much, in fact, that the difference
between something very good and the highest level of performance was essentially nonexistent in actual cost. It
made no sense, then, to stop short of a speaker in the best
category.
We didn’t stop short of that point. As difficult as it
may be to believe of a speaker system of this cost and
apparent simplicity, we know of no way to make any useful improvement in its performance.
*About our name: When you form a new business, and are eager to get on with things before the lawyers get all the papers signed
and the incorporation proceedings over with, you (our) lawyers call you “an advent company”. We decided the term suited our continued desire to get on with things, so we appropriated it for our permanent company name.
How is all that possible?
The performance of the Advent Loudspeaker is
due in great part to some important specifics of design and
construction. But the key to all of them, and to the entirely
new level of value the system represents, is that it is the
first loudspeaker system to exploit the full potential of two
way loudspeaker design.
For just about as long as home audio has been of
real importance, it has been assumed that the three-way
speaker system, which assigns at least one specialized
speaker to each of the three segments (low, middle, high)
of the frequency range, is a necessity for optimum sound.
The two-way system has been accepted as a “good” medium-price expedient, but the idea of extra speakers and further specialization for optimum quality fits in both with
the idea of separate, specialized audio components and
with the widespread feeling that “more is better”. But the
superiority of the three-way system is one of those
“absolutes” that remain true only so long as no one really
challenges them. After a thorough review of today’s materials and manufacturing technology, we knew that the old
assumption no longer need be true.
The trouble with the concept of the three-way system - a crucial one - is that it’s based on the limitations of
an earlier generation of loudspeakers. When high fidelity
first gained wide interest for home listeners, the only suitable speakers available for use in a home audio system
were those used in theater and public address systems. The
individual speakers in theater systems were specialized
and restricted in range for the purpose of maximum powerhandling to fill large public spaces, and they converted to
full-range use in home systems only in three-way designs.
As new cone materials and new techniques were
developed specifically for home loudspeakers, the need for
three-way systems has disappeared. It’s simply no longer
true that if a woofer is to be able to deliver excellent bass
response, it will not have enough mid-range output, or that
a tweeter can not combine excellent high frequency and
mid-range response. Nor is it true that the three-way system is somehow capable of wider range or subtler characteristics.
Today’s three-way systems fall into three categories:
• Those that sound genuinely excellent.
• Those designed that way because of the severe
limitations or their individual (and outmoded) drivers.
• Those that simply throw in an extra speaker or
two because It looks better as a selling point.
Of these three, only the second has to be a three-
way system.
The Two-Way System
We began the design of the Advent Loudspeaker
with the knowledge that the two-way system had basic
advantages, both theoretical and practical, over any other
way of designing a full range speaker system for the home.
They include:
• Less interference between drivers than any other
practical system, Yielding more uniform characteristics
over the listening area. A single speaker would be better
here as an ideal, but lacks either the range or power-handling required in the ‘“best”’ category, or both.
• A better transition between drivers than the
three-way system, because there is no need to sharply cut
off the operating range of any driver. Whether such a cutoff is made for good reasons or simply to satisfy the arbitrary parameters of three-way design, its ill effects are
audible.
• One simple crossover network instead of the two
more complex networks needed in a three-way system.
• A cost significantly lower for excellent sound
than that of an equivalent system of three-way - or any
other - design.
Those advantages are important enough in themselves, but there is an overall advantage that seems even
more important to us. It is that simplest feasible approach
to an objective produces the best kind of engineering - a
concept not too far from the notion that the shortest distance between two points is either a straight line or the one
that is straightest under the circumstances “Over-engineering is a common problem in audio equipment, and one for
which the customer often pays heavily in many ways.
Good design to us is represented by the simplest approach
that permits reaching an objective without compromise,
not by an over-elaboration that makes the buyer pay for
our painting the lily.
If the two-way system has effective limitations,
they apply to the tremendous power-handling required for
use in a theater auditorium or in some laboratory applications. An extra driver provides (all other things being
equal) both greater power-handling for these purposes, and
the extra radiating area helpful both for radiating power
and dispersing sound over a large public area. But those
are the only significant limitations of two-way design.
They have no importance in the design of the best possible
speaker system for use in a home.
The Specifics of the System
The Advent Loudspeaker is a “system” in the
fullest sense of the term. All of its components, including
the cabinet, have been designed from the outset for no
application other than this one, and all of them are interdependent. That interdependence is worth stressing here. The
relationship of cabinet size and speaker size, for instance,
is critical. If the size of the low frequency driver were
increased (all other things remaining equal), the result
would be less bass: a larger driver in the same cabinet
would raise the effective stiffness of the air in the enclosure and would establish a higher bass roll-off frequency.
Some other factors are equally important and we
will try to make them clear as we go along.
The Low-Frequency System
The operating range of the low-frequency driver
extends from the lowest frequency of musical importance
to the upper crossover point of 1,000 Hz. To achieve this
objective, we chose to build the driver on a standard 12inch frame that provides at low cost the width and frame
depth needed for maximum cone excursion at lowest frequencies and highest power. The piston diameter of the
cone combines maximum usable response at 30-35 Hz
with a maximum of dispersion in the upper part of the
operating range.
The driver’s capabilities at lowest frequencies is
made possible in great part by a new outer suspension
design of thermally-formed fiber-reinforced poly-urethane.
The new suspension, a highly durable and reliable centering design, permits long linear cone motion, yet remains
an effective airtight seal that maintains the full operating
effectiveness of the system’s sealed cabinet. In the
acoustic-suspension design used for low frequencies in the
system, the mechanical rigidity of conventional suspensions is replaced by a combination of a free-moving suspension and the stiffness of the air trapped inside a sealed
enclosure. For optimum performance both at first and over
years or continuous operation, the free moving suspension
of the speaker should have no tendency to develop air
leaks, however small. The new suspension of the Advent
Loudspeaker is more effective than any in our experience.
The felted cone of the low frequency speaker is
formed by a low-vacuum process developed to assure high
uniformity from speaker to speaker and the proper resistance to the transmission of excess energy through the
cone, (The “live” energy-transmitting cone still used in
many speaker systems is a prime source of the kind of distortion generally called cone “break-up”). The composition
of the cone is as important as any other factor in achieving
the smooth operation of the driver in the upper part of its
range.
The heavy magnetic structure of the low-frequency driver is designed to provide “critical damping” for the
speaker in its specific cabinet volume - that is the amount
of damping that could not be increased without rolling off
bass response unnecessarily). (Like everything else in
speaker design, the improvements secured from increasing
the weight and flux density of a magnet go only so far;
increasing beyond that point just rolls off bass response).
Also part or the magnetic system is a double-wound, fourlayer voice coil that is significantly longer than the magnetic gap in which it operates. This is to allow a uniform
portion of the coil to stay in the gap at all times, even
when cone and voice coil make their longest excursions,
and is a vital factor in keeping bass harmonic distortion
low at even the highest listening levels.
The efficiency of the system has been carefully
chosen to provide for reproduction of the lowest usable
frequencies with amplifiers and receivers of good quality
and medium power. While efficiency is lower than that of
some comparably priced speakers of more limited range,
and will require a slightly higher setting of a volume control for the same acoustic level, it is no more likely to tax
the actual power capabilities of the amplifier or receiver
used in a home. This doesn’t hold for auditoriums or, in
many cases, for large (and sometimes noisy) audio showrooms, but it is emphatically so for home listening at even
the highest usual loudness levels.
The Advent Low-Frequency Driver
The High-Frequency System
The high frequency driver is a new and distinctive
design that is at least as important as any other factor in
the performance of the system, and directly responsible for
the clarity and definition of instruments at all loudness levels. Its unique diaphragm is formed in one piece, and is
made up of a very small inner dome and an outer rolled
ring that serves as both as both the driver’s suspension and
as a highly effective radiating surface over half its area.
The design is such that no part of the radiating surface is
very far from the voice coil driving the diaphragm, and it
combines exceptional uniformity of driving force over the
entire surface with the ability to radiate large amounts of
high-frequency power.
The rolled ring form of the Advent Loudspeaker’s
high-frequency cone not only is itself a radiating surface
for optimum high-frequency power response, but is also a
free-moving and linear suspension that permits exceptional
cone excursion and power handling down into the midrange of music. The advantage of one driver for both midrange and high frequencies shouldn’t be underestimated,
since it avoids all of the disturbing interference effects
common to combining separate drivers for those ranges. In
addition, by requiring mid-range power handling in one
small speaker, the two-way concept takes the designer in a
direction in which he should be going anyway for the sake
of high-frequency power handling.
The driver also uses a two-layer voice coil in a relatively heavy magnetic system. The magnet is heavier than
it otherwise need be in order to provide a gap wide enough
to avoid eventual “rubbing” of the voice coil because of
slight changes in its centering over a long period of use.
Other factors include the careful choice of cone size and
weight as part of the system concept, to provide sufficient
output with proper efficiency with no need for an overelaborate and over-expensive magnet structure.
Also part of the system design is the placement of
the driver in a mounting position forward of the front inner
surface on which the low-frequency driver is mounted.
This arrangement minimizes unwanted reflections from the
front of the enclosure and consequent irregularities in
response at random points in a room. To prevent damage
in normal use around a household, the cone is protected by
a metal grille.
About High-Frequency Power, Dispersion and Other Matters
It wasn’t generally realized until few years ago that the effective high-frequency response of a speaker
depended on the total amount of high-frequency power radiated in several directions from the speaker - not just
along the narrow axis directly in front of the speaker. The sound perceived by a listener across the room from any
loudspeaker is made up more of indirect sound reflected from room surfaces than of direct radiation from the speaker. If high-frequency power is not spread out in proper proportion to the more easily-spread middle frequencies of
music, the overall sound will range from “overbrilliant” to “raspy”, depending on how much high-frequency power
is going out along the speaker’s axis. It will not sound right under any conditions.
What makes this question of appropriate dispersion a difficult and complex one is that the dispersion itself
is not enough. The kind of design chosen for a high-frequency driver, and particularly its diaphragm, must be capable
of handling and radiating power, enough of it to provide not only for the tremendous high-frequency content of some
kinds of musical material, but also for the loud levels at which many people want to reproduce that material at home.
Many present systems that were designed for good dispersion of high frequencies do not relate it well
enough to the requirement for high-frequency power, and some provide their performance only up to the point where
the demands of music begin to get heavy. Many systems that do justice to string quartet do not do the same justice to
The Crossover and
High-Frequency Balance Switch
The single crossover network between low-frequency and high-frequency drivers is a simple LCR design
that is also used for contouring of electrical input to the
requirements of the system’s design across the frequency
range. The contouring action at various points in the frequency range represents a careful choice of octave to
octave musical balance based on some fifteen years of
experimenting with a wide range of recordings of improving but still variable quality. The overall octave to octave
balance, a critical concept that no other manufacturer to
our knowledge fully explores, was chosen on the basis of
exhaustive listening both to recordings and to wide and
narrow band noise inputs. Although ours is not the only
possibly “right” choice, we think you will find it convincing over the widest range of musical material.
A factor that still varies widely in recordings is the
overall high-frequency characteristic - a function both of
the amount of high-frequency musical material present and
of the amount of extraneous noise and distortion present
along with (or instead of) it. To provide for the range of
characteristics that exist, a three-position switch on the
rear panel of the cabinet provides three different high-frequency contours above 3000 Hz. The three contours were
chosen to suit actual conditions, and are more precise ad
useful than the changes which a simple variable potentiometer on the tweeter can provide. Although the switch
was designed for variations in program material, it also
can also compensate to some degree for extremes of high
frequency reflection or absorption in a listening room.
The Advent high frequency driver (with protective grille)
Just How Good is the Advent
Loudspeaker?
We strongly believe that the Advent Loudspeaker
is the equal in useful measurable performance of any system now available at any price, and that it has significant
advantages over the systems widely sold as the “best” on
an absolute basis. We realize that at the same time, the low
price and simplicity of the system will encourage comparing it simply with systems in its general price range, and
that there is not much we can do about the understandable
human assumption that something costing $200 must be
better somehow than the one pegged at $100. So we urge
you, whether or not you might buy it anyway because its
“great for the money” to compare it under equal conditions
of placement and relative loudness to anything you care to
at any multiple of its price.
The low-frequency capabilities of the Advent
Loudspeaker are the usable equivalent of any speaker’s.
Specifically, it will reproduce the 30 Hz organ pedal note
that begins Richard Strauss’s Also Sprach Zarathustra as
room shakingly as one could ask, providing, as in the case
of London CS-6609, the note is actually present on the
record. For the most part, its ultimate low-frequency capabilities are beyond those of most recordings and broadcasts, and will be revealed in full only by master tapes.
The high-frequency capabilities of the system provide the subtle but audible advantage over many systems
of excellent performance and far greater cost. Part of the
unstrained clarity and the “open” quality of the system is
due to the excellent power response at high frequencies,
and part to the simplicity and lack of unwanted interaction
between drivers in its two-way design. Whatever the reason for its performance on a particular kind of musical
passage, we believe you will able to hear the difference. It
isn’t blatant (the system isn’t more “brilliant” or “mellow”
or just plain louder than any other of similarly excellent
performance), but a matter of important degreed. The
absence of any form of high frequency stridency or “edginess” is such that you will not be particularly aware of
high frequencies at all until a passage with demanding
high-frequency content appears. For the most telling indication of the importance of high frequency power response
in the system, we suggest that you listen comparatively, at
healthy volume, to a good pop recording with cymbals,
brushes, heavy brass, or other instruments of high treble
intensity.
There is no objective scale for measuring the
much-discussed matter of the lack of audible “coloration”,
but we believe the Advent Loudspeaker rates as least as
well in that regard as any loudspeaker ever made. The only
way we can suggest to judge this critical absence is to note
just how quickly you tend to cease listening to the speaker
and to listen to the music.
“The shape of the curve above 6 kHz corresponds
almost exactly to the calibration curve of our microphone,
which indicates that the true response of the speaker is virtually flat to 15 kHz.
“The low-frequency performance of the speaker is
even more impressive than its high end. The flat, extended
response to below the lowest audible frequencies is genuine, not the result of added distortion products, that can
make an inferior speaker sound better than it really is. The
harmonic distortion of the speaker, with a 10-watt drive
level remains under 10% all the way down to 20 Hz, and
is only 6% at 30 Hz. Heretofore we have measured this
order of bass distortion only with the most expensive
acoustic-suspension systems, or with other types such as
horn loaded speakers which are much costlier...
“In designing this speaker, the manufacturer had
the goal of producing a speaker comparable in performance to the best acoustic suspension types previously
available, at a substantially lower price. We listened to the
speaker by itself, and in A-B comparisons with some considerably more expensive types, and we feel that the company has essentially achieved its aims. It has a silky
smooth, balanced sound with well dispersed highs, and
lows which can really be felt, rather than merely heard. We
can’t recall having heard another speaker in its price class
that can match it.”
ELECTRONICS WORLD
JuIian D. Hirsch
“After several weeks of listening [to the Advents]
we still hadn’t found anything to complain about. We
couldn’t even find any sonic characteristics to hang adjectives on, In order to try to describe their sound. They were,
in fact, the least colored loudspeaker we have ever heard,
and this includes the highest-priced system currently available.
“Probably for just that reason, the Advent proved
eminently easy to live with, and sounded equally comfortable and natural at low or room filling listening levels.
Dispersion was excellent and so, as a consequence was the
stereo imaging. Driver blending, too, was excellent, and
the speakers did an outstanding job of reproducing the
front-to-back perspective in stereo and mono program
material…
“By all the accepted standards of evaluation... the
Advents are as accurate reproducers of sound as any top
line systems we have heard.
THE STEREOPHILE
Box 49, Elwyn, PA 19063
“The lows, ..remained strong and clean all the way
down to 20 Hz with very low distortion… Without a
doubt, the Advent is one of smoothest and widest-range
speaker systems we have had the pleasure of testing...
“The tone burst response was excellent throughout, ranking with the best we have seen from any speaker…
“The extreme low bass reproduction, which is one
of the most expensive characteristics to build into a speaker system, sets the Advent speaker apart from anything
else in its price class. In this respect, it can only be compared to the best acoustic-suspension speakers selling for
twice it’s price, or more”.
STEREO REVIEW
“… the frequency response was flat, with only +/3 dB variations over the major portion of its range. What
is more important is that the 45 degree off-axis response
follows the on axis response to a remarkable degree,
denoting excellent high frequency power response…
“One could say that at twice the price the Advent
speaker would be a good value, but at $121 it is a bargain”.
AUDIO
Press Comment on the Advent Loudspeaker
The Advent loudspeaker
is also available in a walnut
finish vinyl clad cabinet
The Smaller Advent Loudspeaker
The proven way to design a good small speaker
system is to give up the lowest octave or two of bottom
bass, and some amount of power handling, for the sake of
very good overall sound at low cost. Since genuinely low
bass (60 Hz and under) Isn’t present in most music, this
approach has been responsible for some excellent lowpriced systems that on most material sound remarkably
like the best speakers of any size or price.
But it is also possible, and has become more and
more worth considering, to design a small speaker system
that would sound as good as the best speakers of any size
or price on all musical material - one that would give up
none of the bandwidth, lowest bass included, associated
with them. For that formidable a speaker at small size and
low cost, a designer has to accept these conditions:
• If it is to fill a living room with high sound levels, organ pedal tones included, it will need a more expensive voice coil and magnetic assembly than those in the
lowest ($45-60) price category. But it doesn’t have to cost
much more.
• If it is to go as far into the bass as larger systems, with as low distortion, it can’t be as efficient as they
are. But it can be efficient enough to use in a home with
present equipment of modest cost.
• There is no practical way to bring its maximum
Iow-frequency power handling capability up to the limit of
an equivalent larger system. But you can come so close
that most people, even those playing demanding music
under demanding conditions, will never have reason to
need or want the larger system.
Those conditions outline The Smaller Advent
Loudspeaker. It is a small, moderately priced speaker system of unique performance. Its effective frequency bandwidth is exactly the same as the original Advent
Loudspeaker’s, and it sounds as close to it in overall character, octave for octave, as any loudspeaker model can to
another.
On all kinds of musical material, and under most
listening conditions likely to apply in most homes, it is the
equal of any speaker system available.
The Smaller Advent Loudspeaker is a more pertinent product than it could have been earlier. New manufacturing techniques help account for its price, which previously would have had to be outside the moderate category. It also can now be driven by low-priced amplifiers and
receivers, more powerful than earlier models for their price
and more likely to approach their rated power at the
extremes of the frequency range. Its 4-ohm impedance is
designed specifically for present solid-state units, which
deliver their maximum power into that impedance, and it
can be driven satisfactorily by present receivers in the
$200 class.
It’s worth stressing that no technical sorcery - in
the way of “revolutionary” design principles or exotic new
raw materials or, as sometimes happens, wishful thinking is responsible for the surprising performance of The
Smaller Advent Loudspeaker. Its bass performance in particular is based (see “How It’s Done”) on thorough understanding of basic design factors, including the way in
which four rigidly related characteristics affect such matters as efficiency, power handling, and the shape of a lowfrequency response curve. As in the design of our original
speaker, The Smaller Advent Loudspeaker’s performance
derives from an engineering approach that sees the shortest
distance between two points as either a straight line or the
one that is straightest under the circumstances.
What’s Inside
The basic approach to the system design of The
Smaller Advent Loudspeaker is exactly that of our original
speaker. The drivers are designed solely for their function
in the system, and have no redundant features or performance capabilities.
The low-frequency driver has the same effective
excursion capability as the driver in the original Advent
Loudspeaker, so that the system’s overall power handling a function largely of woofer area and excursion - equals or
exceeds that of other speaker systems of its size (although
it is not identical to that of our larger system). The materials and fabrication processes used in the manufacture of
the woofer are identical to our larger system’s, and the
magnetic motor (again, see “How It’s Done”) is somewhat
stronger. The nominal low-frequency speaker size (a
whimsically variable measurement in speakers these days)
is nine and a half inches.
The cone and rolled suspension of the high-frequency driver are also identical to that of our original system, with the 1/8-inch center dome helping account for
unusually good high frequency dispersion. Since the
slightly lower efficiency of the bass driver calls for correspondingly less high-frequency efficiency, the magnetic
structure of the new high-frequency driver is lighter and
smaller than the original. This allows a small but worth-
while saving in cost, in keeping with our intent of building
no redundant costs into the final price the listener pays for
the system.
Also omitted to save costs is the three-position
high-frequency switch provided with our more expensive
system. The high-frequency balance chosen for The
Smaller Advent Loudspeaker is the same as the “Normal”
setting of the original system.
How It’s Done
Although inventive advertising sometimes denies it, there is no mystery about the low frequency performance of sealed speaker systems. Four basic factors - the mass of the moving system (cone, voice coil,
and suspensions), the area of the speaker cone, the strength or the magnetic “motor”, and the volume or air in
the cabinet - are tied together, and changing one factor either changes performance predictably or forces you
to make easily calculated changes in one or more of the other factors to maintain the previous performance.
Suppose, for instance, that you increase the magnetic motor strength of a speaker to make it more
efficient. That alone will be enough to produce greater mid-band efficiency, but if the speaker had previously
been properly damped (“critically damped” is the engineer’s term) to achieve a given level of bass performance, with a magnetic assembly chosen to suit a particular cabinet size and cone weight, the new stronger
magnet will provide extra, unwanted damping that causes bass response to fall off sooner. So, to get more
efficiency and the same bass as before, you would have to increase not only the magnet strength but also the
cabinet size and probably the mass of the moving system.
Now. To achieve our own objective of the same bass in a smaller cabinet, the easiest expedient actually would be a significantly smaller speaker cone for the woofer. (The smaller the cone size for a given cabinet, the lesser the effective stiffness of the internal air volume of the cabinet, and so the less air resistance to
a speaker’s low-frequency excursions). But since we also wanted to maintain as much as possible of our original system’s cone excursion and power-handling capability, which are partially a function of cone size, we
chose to shave the size of the original cone by only a small amount and to allow a more massive moving system with a larger voice coil – which, together with a new magnetic assembly, results in a stronger (and equally high-priced) speaker “motor” than that of our original system.
What that yields is a speaker system significantly smaller than our original with the same bass cut-off
and slightly lower power-handling capability. The engineering trade for this, not avoidable even with the
stronger magnetic assembly of our smaller speaker, is a corresponding slight reduction in efficiency. To make
that tolerable efficiency loss even less in its real significance, we designed our new system to have a 4-ohm
impedance that would draw more effective power from present solid-state equipment. That effectively offsets
much of the efficiency loss, and insures that our low-priced speaker will not turn out to be so power-hungry
that its low-cost status might be compromised by the need for an expensive, high-powered amplifier. In fact,
it makes it possible to drive our new system, with a comfortable margin of power for demanding home listening, with present receivers in the $200-250 range. While a receiver in that price range may be hard pressed
to drive the speaker to loud levels in a noisy audio showroom, it will have no trouble doing so in a home.
The Smaller Advent Loudspeaker represents our
best effort to supply, for the lowest practicable cost and
smallest practicable size, every sonic characteristic that
most people associate with the best possible loudspeaker.
Not just the same kind of sound, but the same bandwidth
and other performance characteristics -with no compromise that will be either audible or measurable under most
conditions of use.
Believing that we have done that, and opened the
highest level of speaker performance to people who
wouldn’t have the money or space (or both) for it, we hope
that people will or won’t buy It for the right reasons.
While we have nothing, for instance, against anyone using it with an ambitious amplifier or receiver, we
hope that its lower cost won’t simply be a spur to buying a
more expensive amplifier or receiver than you reaIly need.
Anyone interested in maximum performance per dollar
should investigate using a low-priced amplifier or receiver
even if it sounds inadequate in a showroom – arranging - if
possible, for a home trial.
We hope, too, that it won’t be bought for features
it doesn’t have. It is not as suitable as the original Advent
for use in elaborate installations in very large living rooms
or small auditoriums.
What it will do is provide an absolute maximum
of performance in normal use for a fraction of the size previously considered necessary and for far lower cost roughly $200 less, counting the less elaborate equipment
with which it can be used - than ever before.
Why You Should, Or Shouldn’t, Buy It
About Listening to Speakers In a Showroom
For meaningful comparisons of the speakers (ours or anyone else’s) in a showroom,
some simple guidelines will be of great help.
• First, the speakers should be compared (“A-B’ed”) at exactly the same loudness level. If the levels
are different, the louder speaker - regardless of its basic quality - will almost always sound better at the
instant of comparison.One convenient way of doing this in a showroom that doesn’t permit the levels of
stereo pairs of speakers to be matched for an A-B comparison, is to readjust the volume control at the instant
of comparison. Another way is to listen monophonically to one speaker against one competitor, with each on
different channels of a stereo amplifier and with amplifier’s balance control set to equalize the output of the
two speakers.
• The speakers should be side-by-side so that you hear only the differences between the speakers
and not a combination of speaker and room placement differences. It is not always possible to arrange for this
in a showroom. However, you should be aware that speakers with widely disparate placements, such as one
on the floor and one on a shelf, or one in a corner and one away from a wall, cannot be meaningfully A-B’ed.
In fact, two identical speakers so placed will sound considerably different!
• Rapid switching comparisons from moment to moment can be helpful in defining low frequency
and high frequency range differences between two speakers on the same material. However, you will also
find it helpful to listen to each speaker for periods of a minute or more on the same musical passage so that
balance and the subtleties of a recording can be genuinely evaluated.
• “A-B-C” comparisons, in which three speakers are compared at once, are useless. It simply isn’t
possible to remember the basic sound of system “A” by the time you get around to “C”. Compare two speakers at a time, and then compare your favorite against another.
“Although it occupies exactly half the volume of
its larger relative (which is simply called ‘The Advent
Loudspeaker’), weighs far Iess (27 pounds vs. 42 pounds),
and is 40% cheaper, its acoustic properties are identical to
those of its big brother. This was the goal of the designers,
and we can verify that they achieved it, and with perhaps a
little to spare ...
“… when appropriately used, it will perform very
well indeed with any good amplifier in the 15 to 20 wattper-channel power-output range ...
“In our tests, the averaged acoustic output of the
Smaller Advent Speaker varied less than +/- 3 dB between
120 and 13,000 Hz which is an uncommonly smooth
response ... It did not fall below the midrange level until
we reached 32 Hz. Overall, the frequency response would
be noteworthy in a speaker system of any size (or price) ...
“We made ‘A-B’ comparisons of the Advent with
several excellent speakers many times its cost. Using a
wide range of program material, we could not, in many
cases, detect any difference in sound quality when switching between speakers. In respect to balance, low frequency
solidarity, clarity, and definition, the Smaller Advent
ranked with some or the best ...
“Even if you are not as impressed as we were, any
preconceived ideas you may have about the limitations of
sub-compact speaker systems will, we think, be shattered.”
STEREO REVIEW
“Response data taken at CBS Laboratories show
speaker response running within plus or minus 6dB from
33 Hz to 17,000 Hz, an excellent mark for any speaker
system and particularly remarkable for one in this price
class ...
“The speaker could not be driven into significant
distortion with steady state power input of 100 watts, and
it did just as well with pulse power peaks of up to 460
watts at which level the measured output was 108.2 dB.
These data indicate robust construction, good dynamic
range, and the Advent’s usability with just about any competent amplifier or receiver on the market.
“We ran the Smaller Advent from several low
powered, moderately priced receivers and amplifiers and
were able to enjoy extremely clean, room-filling sound.
Like its larger ancestor, the new speaker system has a neutral, honest quality on all types of music. Its size and cost
recommend it particularly for use in modestly priced
stereo systems, built around an amplifier or receiver that
furnishes at least 15 watts per channel into a 4-ohm load
(of which there are many now available) …”
HIGH FIDELITY
“… The new system is ... virtually identical in per-
formance to its bigger cousin ...
“The tone burst response of the Smaller Advent
Loudspeaker was very good, displaying no signs of ringing
or spurious frequencies at its output ...
“We also did considerable A-B comparing of the
Smaller Advent Loudspeaker against several other systems, all far larger and more expensive. To our amazement, the Smaller Advent proved to be just as good as
many of them and better than others under practically any
listening conditions we could devise. The Smaller Advent
can deliver a room-filling 30 Hz fundamental which must
be heard to be believed!”
POPULAR ELECTRONICS
Press Comment on the Smaller Advent Loudspeaker
Recommended Amplifier Power
ADVENT LOUDSPEAKER
20 watts rms per channel (8 ohms)
SMALLER ADVENT LOUDSPEAKER
15 watts rms per channel (4 ohms)
Actual power requirements vary for any speaker
according to the size of a room and the listening level that
is considered satisfying. These recommended powers
should be used as a starting point in determining your own
specific requirements.
For example, if your room is 1500 cubic feet or
Iess (as most rooms are), then you wilI not need as much
power. On the other hand, if your room is very large and /
or you like your music reproduction louder than real life,
then you will want more power than we’ve recommended.
Dimensions:
Advent Loudspeaker: 14 1/4” x 25 5/8” x 11 ½” deep
Smaller Advent Loudspeaker 11 1/2” x 20” x 9 ¼” deep
ADVENT
Advent Corporation
Cambridge, Massachusetts, 02139
85-054-031
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