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Quad Electrostatic Loudspeaker Instruction Booklet
QUAD ELECTROSTATIC LOUDSPEAKER
This Loudspeaker is fundamentally different from other loudspeakers and it is essential that these instructions be followed if proper performance is to be obtained.
Attention is drawn to the heavy type on page 10. This point in particular
must receive attention before any attempt is made to use the loudspeaker.
The Loudspeaker pack contains:-
The Loudspeaker, 3 legs, 12 screws, 2 signal plugs, 1 mains plug, 1 Instruction Booklet.
The legs are removed to avoid damage in transit, etc., and should be
re-assembled before the loudspeaker is put into use. The three legs are
not interchangeable. The one with the different off-set angle is the rear
leg and when in position it should point towards the rear. The remaining
two legs are slightly off-set right and left respectively. They should be
mounted so that they point forward and slightly outward. Screws are pro-
vided for fixing and the operation does not involve dismantling any part
of the loudspeaker. As the expanded metal front grille marks rather easily,
it is recommended that care be exercised when laying the speaker down on its
It is a good plan to connect temporary long leads to the speaker so that
it may be moved round the listening room to find the optimum position for
listening (see page 5).
Having set the voltage adjustment tapping to the appropriate voltage the
AC mains and earth leads can be connected to the three pin socket provided.
The three connections are marked inside the cable end connector L, N and E,
corresponding to live, neutral an earth respectively. It will probably be
found most convenient to connect a pair of wires to L and N and to connect
their other end to the two pin cable-end mains socket leading into the power
amplifier. In this way the loudspeaker power supply will be switched on and
off by the amplifier volume control switch.
The E connection should be taken to any convenient earth point. As the
amplifier should already be earthed, it may be convenient to connect the E
terminal to the " earthy side " of the signal input to the loudspeaker (since
this is already earthed in the amplifier).
As with any mains operated apparatus, the services of a competent
electrician should be sought if there is any doubt.
The signal output from the amplifier is connected to the sockets provided
on the back of the loudspeaker. The phasing (which way round) is immaterial
except for instances where more than one loudspeaker is used in the same
room--stereophonic reproduction for example.
The signal and the mains supply may be carried on a multiple four or five
core cable and in most cases this will he the most convenient method.
The thickness of the wire carrying the signal can be of the calibre of
ordinary lighting flex for lengths up to 20 or 30 ft. For longer runs
correspondingly thicker cable should be used.
The indicator lamp above the mains plug should glow upon switching on,
and the loudspeaker will be reasonably well charged within about half a
minute. It can thus be used immediately although the frequency response and
maximum power may not be strictly correct in the first minute.
With any type of loudspeaker the room will affect the performance quite
considerably. This effect will be less with the QUAD Electrostatic than with
most other types of speaker but care taken initially in finding the most
suitable position in the room is always worthwhile.
As a general guide, radiation of the sound waves from both front and rear
of the speaker should be restricted as little as possible, while corners and
positions close to and parallel with walls should be avoided. A corner
position is often necessary for other types of
loudspeakers because it accentuates the low frequencies but such a position
for the QUAD will both reduce the bass seriously and cause deterioration at
middle frequencies due to standing waves.
If the loudspeaker has to be close to a wall, however, it should be stood
at an angle so that reflections from the wall are not returned trapped. For
example one end of the speaker could almost touch the wall provided the
other end were say two feet away from it.
The best position may now be found experimentally amd should be that which
gives the best perspective.
The objective on a concert programme is that the loudspeaker should appear
as an open window beyond which lies the Concert Hall. The " closeness " of
the orchestra is dependent upon the acoustics and microphone placing at the
transmitting end. With modern studio practice the window should appear to
open into a position about halfway down an idealised Concert Hall (front row --
dress circle). Of course, in these tests for optimum perspective, the volume
level must be adjusted with care so that the intensity is commensurate with
the perspective as broadcast or recorded (see page 7).
It is practically impossible to predict which positions in a room are
likely to be best and two symmetrical positions in an apparently symmetrical
room do not necessarily give similar results. Possible positions should
take into account that for mono the listeners should be seated within 35° of the
loudspeaker axis and not nearer
than 5 feet as illustrated. The ideal stereo arrangement is also shown, but
time spent in trying the loudspeaker(s) In all possible positions is usually
very well worth while.
THE LOUDSPEAKER AND THE CONTROL UNIT
At first thought it would appear that the purpose of a volume control is
solely to enable the listener to have his music loud or soft according to his
whim. Whilst it, of course, fills this requirement, it has a further purpose--that
of adjusting the intensity of sound so that it is correctly related to the
perspective as recorded or broadcast.
If a voice is picked up close to a microphone in a very absorbent studio,
then on reproduction that voice will take up a position at the centre of, and
in the plane of the loudspeaker. For natural sound, therefore, the loudspeaker
should radiate similar power to that of the original voice. If on the other hand
the voice is picked up some way from the microphone in a more live studlo, then
the voice on reproduction will take up a position through the loudspeaker and
a considerable distance behind it. It is clear that the power required for the
loudspeaker for natural sound is now very much less than in the first case.
The position or perspective of the reproduced sound is fixed at the studio end
and there is little that can be done at the listening end to alter it.
It follows that the volume setting for natural sound is to a large extent fixed
at the studio end.
Studio monitoring is usually carried out at a reasonable level and the whole
aim is to produce listening as from a favourable seat in the Concert Hall.
Adjusting the volume control to a level to give this correct acoustic perspective
will produce the most natural reproduction The level is usually such that it is
quite possible to speak to a person sitting next to the listener without raising
the voice or turning down the sound level -- as indeed this is possible in the
Raising the level to "bring the orchestra into the room" or turning it down
to a low background will both distort the perspective, although this may have to be
tolerated on certain occasions. It should be pointed out that no amount of tone
control or loudness control can affect the perspective, although these effects
can be used to produce a new sound which although quite unlike the original is
sometimes found acceptable.
Popular music is often recorded or transmitted with close microphone technique
and would therefore tend to require reproduction at higher levels. It is in fact
generally monitored at a higher level. There are number of other factors which
have a strong bearing on optimum listening levels but it is outside the scope of
this handbook to deal with these adequately. It will be realised that the volume
control setting should receive careful attention and it can be emphasised that much
listening is spoilt due to insufficient care on this point.
Radio on V.H.F.
With the QUAD Electrostatic Loudspeaker used with B.B.C. broadcasts, it is
recommended that no tone controls or filters be used, and they may be conveniently
switched out of circuit by using the CANCEL position on the Control Unit. The
greatest care is taken during transmission and only rarely can this quality be
improved at the listening end.
It can be argued that some broadcasts are inferior in quality and that these
can be improved by judicious use of tone control. Whilst this is true, such
broadcasts are usually confined to those where the subject matter and not the
quality is important.
The reproduction of gramophone records is a matter of compromise if the best
performance is to be obtained.
There are many makes of records and almost with out exception a programme is
fed through various variable tone controls during the making of the record in
order to obtain the effect which the manufacture considers desirable. It is
therefore understandable that there will be considerable variation in tonal
balance among the recordings offered to the public. (This variation in balance
is not to be confused with the recording characteristic, which is fully corrected
in QUAD control units when the Disc pushbutton is pressed).
Musical balance should be adjusted if required by means of the treble and bass
controls, referring to CANCEL to ensure that any adjustments are truly an improvement.
Few modern recordings will require more than plus or minus 2 on bass or treble
controls and the best recordings should require no adjustment at all.
Virtually all recordings, even the latest and best, will require some degree
of filtering for the best possible quality. This is no reflection on the recordings
themselves but is an inherent feature of the disc system of reproduction.
The higher the frequency the less easily can the stylus trace the groove, hence
tracing distortions (and noise) increase. As the frequency increases, therefore
the ratio of musical content to unwanted sound reduces. Minimum distortion is
obtained where the filter slope corresponds to the slope of the distortion rise.
This will vary with the type of musical content and the recording level.
With the best recording the filter should be set to 10 K and with the slope
initially at level, the slope control should be rotated until the reproduction
is clean yet without sacrificing any other aspect of quality. The optimum will
usually be found somewhere between LEVEL and 15. With many good modern recordings
the same procedure should be applied with the filter set to 7 K.
Older recordings and 78 r.p.m. recordings will usually require the filter at
5 K with more severe settings of the filter slope.
The filter controls are very carefully designed and their correct use is
important in obtaining a satisfactory musical sound.
The loudspeaker is symmetrically designed so that all frequencies have the
same line or point source. This arrangement is the ideal one for stereo reproduction.
Proper stereo should produce a complete picture of the orchestra and concert
hall acoustics evenly spaced over the area between the loudspeakers. failure to
achieve this objective can be due to unsatisfactory recording technique or
unfortunate room reflections. The loudspeakers should be moved to find the best
positions. In difficult rooms optimum result may sometimes be obtained by directing
the speakers inwards.
The QUAD loudspeaker requires no routine maintenance. Should a fault occur,
the dealer supplying the loudspeaker or other competent engineer should be consulted.
The pilot lamp at the rear indicates that the AC mains is reaching the loudspeaker.
THIS LOUDSPEAKER IS DESIGNED FOR OPERATION WITH STANDARD QUAD II OR QUAD 303
POWER AMPLIFIERS, AND IT IS ESSENTIAL FOR BOTH PROPER PERFORMANCE AND RELIABILITY
THAT IT IS USED ONLY WITH THESE AMPLIFIERS OR ONE KNOWN TO BE SUITABLE.
Other amplifiers if they are properly regulated (not more than 33 peak volts with
any load) are unlikely to cause damage to the loudspeaker, although they may not
necessarily provide the correct perforrnance because of the very strict stability
In many cases the amplifier manufacturer can indicate the suitability of his
product but we regret that we cannot accept responsibility for damage caused by the
use of unsuitable amplifiers.
|6 ft. on axis in free space 93 dB referred to .0002dynes/cm²|
in frequency range 50 c/s.-10 Kc/s
|MAXIMUM OUTPUT||100 dB referred to 0002 dynes/cm² in range 70 c/s. - 7 Kc/s.|
Total integrated radiation equivalent to 95 phons in enlclosures
up to 5,000 cubic feet with average reverberation.
|BANDWIDTH||45 c/s.-18 Kc/s. Rate of attenuation outside band asymptotic to 18 dB/8ve.|
|DISPERSlON||Approximately 70° Horizolltal 15° Vertical.|
|IMPEDANCE||30-15 ohm in range 40 c/s.-8 Kc/s. falling above 8 Kc/s.|
RANGE||100-120, 200-250 volts 50-60 c/s.|
Last updated on April 03, 1998