Bowers & Wilkins 800 Serie Manuel Du Propriétaire page 9

Test for flutter echoes by clapping your
hands and listening for rapid repetitions.
Reduce them by the use of irregular
6
shaped surfaces such as bookshelves
and large pieces of furniture.
DS8S only
In monopole mode, the high-frequency
output level may be adjusted using the
top toggle switch on the front baffle.
(figure 39)
In the centre 0 position, the system
response is nominally flat. The +
position gives more output, which may
be required, for example, if the acoustic
of the room is dull, if circumstances
dictate that the speakers have to be
placed more off line than
recommended, or if the speaker is built
into custom furniture and placed
behind fabric that is more absorbent
than that on the grilles supplied.
Conversely, the – position reduces the
level for when the room acoustic is too
bright or if you want to reduce your
awareness of the speakers' location.
Experiment to find the mode settings
best suited to your requirements.
Typical combinations are:
• All surround speakers monopole.
• Side speakers dipole, rear speakers
monopole.
• All surround speakers dipole.
It would be unusual, but not
impossible, to set side speakers to
monopole and rear speakers to dipole.
6 RUNNING IN
The performance of the speaker will
change subtly during the initial listening
period. If the speaker has been stored in
a cold environment, the damping
compounds and suspension materials
will take some time to recover their
correct mechanical properties. The drive
unit suspensions will also loosen up
during the first hours of use. The time
taken for the speaker to achieve its
intended performance will vary
depending on previous storage
conditions and how it is used. As a
guide, allow up to a week for the
temperature effects to stabilise and
15 hours of average use for the
mechanical parts to attain their intended
design characteristics.
However, longer run-in periods (as long
as a month) have been reported and
there is evidence to suggest that this has
little to do with the speaker changing and
more to do with the listener getting used
to a new sound. It is especially so with
highly revealing speakers such as these,
where there may be a significant increase
in the amount of detail portrayed
compared to what the listener has
previously been used to; the sound may
at first appear too "up front" and perhaps
a little hard. After an extended period of
time, the sound will seem to mellow, but
without losing clarity and detail.
7 ANCILLARY EQUIPMENT
Speakers of this ability deserve signals of
the highest quality. Choose your
electronic equipment and interconnecting
cables with care. We can give guidance
on what to look for when choosing
ancillary equipment, but cannot
recommend specific items. The
standards of such products are
improving all the time and your dealer will
be able to demonstrate a variety of
suitable up-to-date products.
In the specification we recommend a
range of amplifier powers. The higher
figure is defined by the power handling
capability of the speaker. When
calculating the power handling, it is
assumed that the amplifier is not run into
clipping, which distorts the frequency
power spectrum of the signal, and that
the signal is normal programme material.
Test tones from oscillators and the like
are not applicable. The lower figure is the
minimum we consider necessary to
achieve reasonable listening levels
without audible distortion in the smaller
room (less than 60 m 3 or 2000 cu ft). The
higher the power you use, the less likely
you are to experience amplifier clipping.
You can often tell how good an amplifier
is at driving complex speaker loads by
looking at its power rating into both 4Ω
and 8Ω loads. The nearer the ratio is to
2:1 the better, as it indicates a good
current capability.
In order to reduce the effect the cable
has on the frequency response of the
speaker to inaudible levels, the
impedance of the cable at all frequencies
(measuring both positive and negative
conductors in series) should be kept as
low as possible and certainly below
0.1Ω. At low frequencies, the DC
resistance of the cable is the dominant
factor and you should choose a gauge of
wire sufficient to achieve the impedance
requirements over the length of cable
you need to use. At mid and high
frequencies the inductive component of
the impedance can dominate the DC
resistance. This and other properties
influenced by the detailed construction of
the cable become important. Ask your
dealer for advice on the best cable for