the closest approach to the original sound.
ESL 2805 & ESL 2905
Reference
s e r i e s
2
The
Quad ESL
Contemporary Electrostatic Loudspeaker Design
The new ESL-2805 and ESL-2905
Electrostatics are Quad’s latest reference
loudspeakers and like their predecessors
should be regarded amongst the finest
loudspeakers in the world today. In
areas such as transparency, and lack of
colouration, they are without peer.
It should be noted that whilst movingcoil loudspeakers are the norm, the
physical principles upon which they
work are fatally flawed - and not even
the latest advances in materials science
can address their shortcomings.
Quad alone has sought a different path
- to push the boundaries of electrostatic
technology to the point where our ESLs
are closer to the ideal loudspeaker than
any other.
Quad’s patented panel technology
results in a combination of the speed
and accuracy only possible from an
electrostatic loudspeaker; together
with the imaging and soundstaging
only possible from a theoretically ideal
point source; and the coherence and
continuity of a single drive unit.
With possibly the lowest distortion
of any loudspeaker, the ESL can be
enjoyed for hours on end without
fatigue; never adding or subtracting
from the original recording. Even at low
volume levels, they retain the full detail
and drama of the music.
In short, the Quad ESL technology is
unique in its clarity of sound, lack
of distortion, lack of interference and
continuity of response.
The ESL-2805 and ESL-2905
loudspeakers are the absolute pinnacle
of that technology. Engineered without
compromise, they are destined to
become modern classics.
4
Quad products stand alone in the hi-fi
world - renowned for their longevity;
quality of build; and consistently high
standard of performance. Our awardwinning service department regularly
maintains products over 50 years in
age. Products which still bring their
owners immeasurable pleasure.
Quad products are designed with the
single aim of reproducing recorded
music as accurately as possible.
Simplicity of use and elegance of
design are purely consequential to
the application of sensible engineering
principles.
We have never sought to design
statement pieces or style icons, yet
almost every Quad product has
become regarded as such.
The case for a
closer
approach...
The moving-coil conundrum
A moving-coil speaker consists of a
wire coil suspended inside a magnet.
When an audio signal passes through
the coil a varying magnetic field is set
up which interacts with the magnet and
causes the coil to move back and forth.
A cone (or in the case of high frequency
speakers, a dome) is attached to the
coil, which compresses and rarifies the
air generating sound waves.
Flexible
Surround
Back Plate
Voice Coil
Pole Piece
Coil Former
Rear Suspension
Front Plate
Air Vent
Dust Cap
Speaker Cone
Chassis (or Basket)
Because large speaker drive-units
cannot reproduce high frequencies
well, and small ones cannot reproduce
low frequencies at all, practical hi-fi
loudspeakers use two or more driveunits connected via a ‘crossover
network’ which divides the frequencies
between the bass and the treble units.
Additionally, because even a large
bass- unit is very small compared to the
length of a low-frequency sound wave,
some form of box is needed to prevent
the waves from the back of the cone
cancelling the sound from the front.
Moving-coil speakers have undeniable
advantages of cost and ease of
manufacture, and the cabinets can be
designed in many different shapes, sizes
and finish. However, the cabinet is also
a prime source of colouration in the
bass region. Additionally, because the
cone of a bass-unit is large and heavy,
it cannot start and stop instantaneously.
Some of the energy is stored and
releases over time, causing smearing
and ‘boom’ in the bass. In the crossover region, where not only are the
masses between the drive units hugely
dissimilar but so are their dispersion
patterns, this shows up as unevenness
of response and a confused image,
precisely in the critical area where the
ear is at its most sensitive.
The
Electrostatic
alternative
Although deeply flawed, their cost and
convenience advantages are such that the
overwhelming majority of loudspeakers
in today’s marketplace are moving-coil,
and at Quad we manufacture some of
the finest examples of this genre. But,
as a counsel of perfection, we have to
look elsewhere.
Electrostatic speakers have long been
renowned for their superlative accuracy
and clarity in mid-range and upper
frequencies but deficiencies in the bass
response and indifferent dispersion
characteristics have presented
difficulties which few manufacturers
have satisfactorily overcome. Many
hybrids have been attempted over the
years which combine moving-coil
speakers in the bass with electrostatics
handling the upper registers, but these
designs have not been successful.
An electrostatic speaker is a plastic
membrane which is coated with a
resistive material and suspended
between two perforated metal plates. A
polarising voltage of several thousand
volts is connected to the membrane
which at rest is suspended at an equal
distance between the two plates. When
an audio signal (also stepped up to
a few thousand volts by a matching
transformer) is applied to the metal
plates, the varying signal across the
plates attracts or repels the membrane,
and sound is reproduced. Because
the membrane is extremely light, and
driven across its entire surface, transient
response and freedom from overhang is
exemplary – quite unlike moving-coil
loudspeakers.
Of course, if it were as simple as this,
there would be many more electrostatic
loudspeakers. The challenge has been
to produce an electrostatic loudspeaker
with extended bass response and a
satisfactory dispersion. Virtually none
have succeeded. A combination
of acoustic problems and extreme
difficulties of manufacture has resulted
in a bare handful of true full-range
electrostatic loudspeakers being
available to the audiophile and in this
field Quad are pre-eminent.
6
"I know of no other speaker I'd rather own,
regardless of price. I think it's the finest hi-fi
purchase you could ever make in terms of
performance and value-yes, it's that good.
Speaker of the year? Nah. Speaker of the
centuries. This one and the last.’'
– Stereophile , Sam Tellig
The
electrostatic
Naturally produced sound emanates
from a point. Virtually no loudspeaker
comes close to achieving this – but the
Quad approach comes closest of all.
The ESL is dipolar, producing front
and rear radiation. It has no box so
there is no colouration. Using large
panels ensures well-maintained bass
to well below 40Hz. The centre two
panels in each Quad ESL Loudspeaker
incorporate concentric rings on the
outer grid-plates around the diaphragm.
Each ring is subjected to a minuscule
time delay and attenuated by its own
individual circuit, the sound spreading
gradually from the centre outwards
through each successive ring. This
carefully structured delay line creates
a near-perfect spherical wave front
originating from an apparent point
400mm behind the loudspeaker.
Imaging is pinpoint and there is no
‘sweet spot’ – all listeners receive a full
sonic presentation.
The result is a loudspeaker of
unsurpassed accuracy. The Quad
ESL is probably the lowest distortion
loudspeaker ever made.
principle
A perfect point source produces a
1.
spherical wave pattern.
The air particle movement at a plane
2.
some distance from the source.
An identical movement in the ESL
membrane produces and identical
3.
wave front
The membrane carries a constant
charge. The charge on the electrodes
4.
fluctuates according to the music
signal.
The music signal is fed first to the
5.
centre section, then to each ring in turn
via delay coils
1.
2.
3.
4.
Electrodes
High Resistivity
Membrane
8
Input
Transformer
5.
Polarising
Voltage
Input
Construction process of an
ESL 2905
The
ESL
for
home theatre
Whilst for most ESL customers the
important factor is performance with
two-channel stereo sources, be those
analogue or digital, for a growing
number of customers 'home cinema' or
even multi-channel music is now also
becoming an important consideration.
To create a system which is able to
excel at both is a difficult task. Typically
the dispersion of traditional moving
coil loudspeakers and also the use of
three screen channel speakers; create
various unwanted interference patterns,
which effect quality of the sound and
ultimately your enjoyment.
10
For home cinema use, the ESL is quite
remarkable. Although there is no
dedicated centre channel to match
the new ESLs, most Home Cinema
amplifiers feature a 'phantom' centre
channel mode.
Such is the ability of the ESLs to project
a stable central image, the lack of a
centre channel has been regarded by
many as an advantage.
The unbroken frequency response and
natural presentation of the vocal track
is uncannily realistic - a hypnotically
immersive experience.
"By the highest standards, the 2905s get
everything right to a degree that had me
shaking my head in awe. This is easily
one of the most revealing and accurate
loudspeakers I have ever heard."
– Hi-Fi World , Noel Keywood
12
The
original
sound...
Ask many of the most respected music
industry professionals in the world what
their speaker of choice is - the answer
is surprisingly common. The Quad ESL
opens a window on a recording unlike
any other speaker.
More hi-fi critics regard the Quad ESL as
an absolute reference for their listening
than any other loudspeaker. They are
regularly praised by leading magazines,
winning Golden Ears from The Absolute
Sound (USA); and not just ‘Product
of the Year’, but also ‘Component of
the Year’ from Stereophile (USA); a
Diapason D’Or award (France); and a
‘System of the Year’ award from Hi-Fi
News magazine - all of these within the
last three years alone.
For those involved in the recording
industry, their reputation is unsurpassed.
The transparency of their reproduction
has won them many fans. For
professional musicians and studios, this
is an invaluable asset. It allows them to
hear exactly what has been recorded in
perfect balance.
Because of their speed and neutrality,
they are unaffected by the overhang
and self-imposed character of movingcoil alternatives.
The Quad ESL has been used by Tony
Faulkner (shown left recording at Henry
Wood Hall in London) for many years.
He started using the ESL-63, the ESL-63
Pro, and now uses a pair of ESL-989s
for his critical monitoring.
Tony has produced over a thousand
classical music recordings using the
Quad ESL because he knows he can
trust what he hears - that the very
essence of the performance is being
transferred.
Using the Quad ESLs for listening
at home, you can be sure that your
experience will mirror that of the
concert hall. You will hear detail and
depth never before noticed and each
listening session will draw you into the
music - transforming your appreciation
of every great performance and every
great recording.
Tony Faulkner, mastering a classical
recording at Sir Henry Wood
Hall, London - using a pair of ESL
loudspeakers
Quad
ESL-2905
The ESL-2905 is the larger of the two
models - it employs a grand total of
six electrostatic panels; the inner
two utilising the concentric rings
of anodes used to create the point
source image.
The ESL-2905 has a fifty-percent greater
diaphragm area than its smaller brother.
This increase allows for a markedly
improved bass response, and greatly
enhanced dynamics. The ESL-2905 is
therefore a good choice for those in
larger rooms, or those seeking more
drama on big pieces. However, this
speaker doesn’t compromise on detail
and subtlety - far from it. After all, it
is an electrostatic design and so has
considerably less inertia and overhang
than any moving-coil loudspeaker.
Construction is a combination of
tensioned aluminium extrusions
coupled to stainless steel support
structures, with a piano gloss wooden
trim. The substantial base construction
is finished with piano gloss side cheeks
and high-quality terminations.
Internally, the highest quality
components are used, including rare
c-core transformers and high-grade
audiophile capacitors. Three types of
protection system are used to ensure
the speakers are difficult to damage
when over-driven.
A rigid three-dimensional structural
support system, combined with
an overall speaker mass of 41.6kg
ensures the maximum transmission of
sound energy. This results in the most
dynamic and powerful Quad ESL ever
produced.
14
Quad ESL 2905
Horizontal Directivity
Quad
ESL-2805
The ESL-2805 is the smaller of the two
models and uses four panels rather
than six. The inner two panels of the
ESL-2805 again utilise the concentric
anode rings for point source imaging,
and the outer rings are again linear in
their response.
Whilst the absolute bass extension and
dynamic ability are less than its larger
brother (it lacks the two supplementary
panels of the 2905), the ESL-2805 offers
a sublime performance nonetheless. In
all other areas the ESL-2805 will sound
identical to the ESL-2905 - particularly
with regard to imaging, detail resolution,
and lack of colouration. This is due
to both speakers sharing the same
technology and components.
The clarity of mid-range - for which the
Quads are most famed - is fully in evidence;
the sparkling detail and transparency has
long been the hallmark of this series.
With a base weight of 34.8kg, together
with the rigid bracing, the ESL-2805
is an incredibly stable platform that is
ready for a lifetime’s work.
For chamber music, light orchestral,
jazz, folk, blues, or indeed, for any
afficionardos not requiring the
additional bass extension and weight
of the larger model, you will find the
ESL-2805 to be your perfect transport
for the journey into audio nirvana.
16
Quad ESL 2805
Horizontal Directivity
ESL 2805 & 2905
Specifications
Model
Construction
Format
Type
Membrane
Panel Elements
Time Delay
Chassis Structure
Acoustic Performance
Maximum Output
Sensitivity
Impedance
Impedance Variation
Maximum Input
Frequency Response
Distortion (100dB at 1m)
Electrical
AC Input
Power Fuse
ESL 2805 ESL 2905
Floor-Standing Dipole with 3˚ Tilt Back
Full-range Electrostatic
Ultra Low Mass (0.5g/m2) Tensioned Film
4
Progressive Concentric Rings
Heavy Duty Composite Aluminium / Steel
2N/m2 at 2m on axis
1.5 mbar per volt referred to 1m.
(86 dB/2.83V rms equivalent)
8 Ohms nominal
4 - 15 Ohms
Continuous input voltage (rms): 10V
Programme peak for undistorted output: 40V
Permitted peak input: 55V
37Hz - 21kHz (-6dB)
33Hz - 23kHz (useable)
Above 1000Hz 0.15%
Above 100Hz 0.5%
Above 50Hz 1.0%
220-240V or 110-120V
63mA anti-surge, 200-240V
100mA anti-surge, 100-120V
Floor-Standing Dipole with 3˚ Tilt Back
Full-range Electrostatic
Ultra Low Mass (0.5g/m2) Tensioned Film
6
Progressive Concentric Rings
Heavy Duty Composite Aluminium / Steel
2N/m2 at 2m on axis
1.5 mbar per volt referred to 1m.
(86 dB/2.83V rms equivalent)
8 Ohms nominal
4 - 20 Ohms
Continuous input voltage (rms): 10V
Programme peak for undistorted output: 40V
Permitted peak input: 55V
32Hz - 21kHz (-6dB)
28Hz - 23kHz (useable)
Above 1000Hz 0.15%
Above 100Hz 0.5%
Above 50Hz 1.0%
220-240V or 110-120V
63mA anti-surge, 200-240V
100mA anti-surge, 100-120V
18
General
Power Consumption
Dimensions (HxWxD)
Weight
6 Watts
1040mm x 695mm x 385mm
(add 25 - 55mm for feet)
Net 34.8kg
6 Watts
1430mm x 695mm x 385mm
(add 25 - 55mm for feet)
Net 41.6kg
Quad Product Range
Refer ence
s e r i e s
Electrostatic Loudspeakers
• ESL - 2805
• ESL - 2905
P e r f o r m a n c e
s e r i e s
ESL - 2805
Loudspeakers
• L-ITE2 5.1 System
• L-ITE2 Mini Loudspeaker - Pair
• L-ITE2 Centre Loudspeaker - Single
• 9L2 Loudspeaker - Pair
• 11L2 Loudspeaker - Pair
• 12L2 Loudspeaker - Pair
• 21L2 Loudspeaker - Pair
• 22L2 Loudspeaker - Pair
• L2 Centre Loudspeaker - Single
• L2 Subwoofer - Single
• L-ITE2 Subwoofer - Single
Clas s i c
s e r i e s
Electrostatic Loudspeakers
• ESL - 989
• ESL - 988
Amplifiers
• II-forty Power Amplifier (mono)
• II-Classic Power Amplifier
• QC-twenty four Pre Amplifier
• QC-24P Phono stage
Electronics
• 99 CDP-2
• 99 CD-S
• 99 Pre
• 99 Stereo
• 99 Tuner
• 909 Stereo
• 909 Mono
99 - Pre Amp
99 - Power Amp
Quad ll-Forty Power Amp
QC24 Pre Amp
Quad Elect roaco ustic s Ltd,
IAG House, Sovereign Co urt, Ermine Busi ness Park,
Huntingdon, Cam bs, PE29 6XU
Tel :- 01480 447700, Fax :- 01480 431767
www.quad-hifi.co.uk
The inf orm ation in t his b rochure is sub ject to change wi thout
notice.All rights reserved © 2 004 Q uad
Quad is a mem ber o f the Internatio nal Aud io Group
Qu.ESL.8.200 6
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