Bowers & Wilkins DS8S - Manual (Page 5)

2
Most films are originally balanced for
cinemas, where a large number of
speakers spread around the auditorium
are used to create the surround sound
field. In that case there are more
surround speakers than there are discrete
channels of information and a less
precise image is created that gives an all-
enveloping effect. Dipoles and similar
diffuse speakers are better at recreating
this type of sound field in the home, but
using fewer speakers to do it. Image
positioning with these types of speaker is
never as precise as it can be with
monopoles. However, they do have the
advantage of making it easier to balance
the system for a larger listening area.
You may well receive conflicting advice
from different sources on the best type of
surround speaker to use. The truth is
that there is no one perfect solution for
all situations and the final choice for any
given application will be influenced by
several criteria, some of which may have
a degree of conflict.
DS8S only
Within the 800 series, the DS8S is the
only speaker to offer dipole operation.
In fact, this specialist surround speaker
has the advantage of offering a choice
of both monopole and dipole
operation, either via a switch located
on the front baffle, behind the
removable grille, or remotely, using a
12V trigger from the surround
processor. You may therefore choose
whichever type of operation best suits
the conditions of the listening room, the
size of audience and the type of
programme being played. Indeed, you
may even change the characteristic for
different types of programme and, as
the total energy into the room is the
same in both modes, no recalibration
of the installation is necessary when
switching between them.
In monopole mode, only the two drive
units on the front face operate. In
dipole mode, the front tweeter is
disconnected; the side firing drivers are
brought into operation and the
crossover frequency to the bass unit is
lowered. The drive units on opposing
sides are connected out of phase with
one another, which creates a wedge-
shaped null zone, approximately 60º
wide, at right angles to the wall. If the
listeners sit within this zone, they
become less aware of the location of
the speakers and hear more reflected
sound; hence the diffuse nature of the
sound field.
Use the bottom switch on the front
baffle when selecting between
monopole and dipole modes. In the
• position, the speaker defaults to
monopole. (figure 8)
However, if a 12V signal is applied to
the trigger input, internal relays switch
to dipole mode. In the •• position, the
speaker is always in dipole mode,
whatever the trigger signal. (figure 9)
Set the direction of the positive and
negative dipole lobes using the centre
toggle switch marked >< on the front
baffle. The stem of the switch points in
the direction of the positive lobe.
For the smoothest panning of sounds
between all the speakers in the
installation, side speakers for all
applications and rear speakers for 6.1
and 7.1 applications should have the
polarity of the lobes set according to
figure 10.
Application f Go to
5.1 channel surround 2.4
6.1 and 7.1 channel side 2.5
6.1 channel rear 2.6
7.1 channel rear 2.7
2.4 5.1 CHANNEL SURROUND
DS8S only
If you are using the DS8S in dipole
mode only, place the speakers on the
side walls approximately 60cm (2 ft)
above ear height and in line with the
centre of the listening area. (figure 11)
If you are using the DS8S and switching
between dipole and monopole modes
for different applications, place the
speakers on the side walls
approximately 60cm (2 ft) above ear
height and slightly behind the centre of
the listening area, keeping the listeners
within the 60º wide null zone. (figure 12)
All models except DS8S
Place the speakers approximately 120º
round from front centre. The shape of
the room will dictate whether they are
placed on a side or rear wall. (figure 13)
f Go to section 2.8
2.5 6.1 AND 7.1 CHANNEL SIDE
Place the speakers to the side, in line
with the centre of the listening area.
(figures 14 & 15)
f Go to section 2.8
2.6 6.1 CHANNEL REAR
The rear channel of 6.1 EX recordings
may be reproduced by a single speaker
placed directly behind the centre of the
listening area. (figure 14)
f Go to section 2.8
If you are also using the speakers for
movies, you should try to match the
audio image to the size of the screen.
That generally means that the speakers
should be closer together. A good
starting point is to put the speakers
about 0.5m (20-in) from the edges of the
screen. (figure 4)
Bookshelf or on-wall speakers should be
placed at a height that brings the
tweeters approximately to ear level. In
the vertical plane, the dispersion narrows
in the crossover region between the
midrange and tweeter drive units, when
both units are working together. To
preserve the optimum sound balance, try
to keep within ±5º of this.
Floor-standing speakers have the angle
of their optimum listening window
adjusted for the height of the speakers
and the typical range of ear height of
seated listeners.
f Go to section 3.
2.2 FRONT CENTRE
If you have an acoustically transparent
screen, place the speaker behind the
centre of the screen. Angle it towards the
listeners if the tweeter is more than 5º
from ear height. (figure 5)
If you have a normal screen, place the
speaker immediately above or below the
screen, whichever is nearest ear height.
Angle it towards the listeners if the
tweeter is more than 5º from ear height.
A stand with tilt adjustment is available
for the HTM2D, HTM2S and HTM4S.
Consult your dealer for details. (figure 6)
If you are just listening to audio, place
the speakers centrally and mount
bookshelf or wall mount speakers with
the tweeters at ear height. (figure 7)
f Go to section 3.
2.3 SURROUND
Surround speakers generally fall into two
main types – those that one might
describe as 'normal' speakers – so-
called monopoles, where the sound
comes from a set of drive units mounted
on the front of the enclosure – and those
that give a more diffuse sound field, such
as dipoles. Each type has its
advantages.
Most multi-channel music is recorded
with home entertainment in mind and is
monitored using monopole surround
speakers, whatever the multi-channel
recording format. This enables better
location of side and rear images,
although the formation of such images is
never quite as precise as it is between
the front speakers.