CT800 Series
Installation Manual
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Warranty
Dear customer,
How to claim repairs under warranty
Welcome to B&W.
Should service be required, please follow the following procedure:
This product has been designed and manufactured to the highest quality standards. However, if something
does go wrong with this product, B&W Loudspeakers and its national distributors warrant free of charge
labour (exclusion may apply) and replacement parts in any country served by an official B&W distributor.
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If the equipment is being used in the country of purchase, you should contact the B&W authorised
dealer from whom the equipment was purchased.
If the equipment is being used outside the country of purchase, you should contact B&W national
distributor in the country of residence who will advise where the equipment can be serviced. You can
call B&W in the UK or visit our web site to get the contact details of your local distributor.
Limited Warranty
This limited warranty is valid for a period of five years from the date of purchase or two years for electronics
including amplified loudspeakers.
To validate your warranty, you will need to produce the warranty form, completed and stamped by your dealer on
the date of purchase. Alternatively, you will need the original sales invoice or other proof of ownership and date of
purchase.
Terms and Conditions
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The warranty is limited to the repair of the equipment. Neither transportation, nor any other costs,
nor any risk for removal, transportation and installation of products is covered by this warranty.
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This warranty is only valid for the original owner. It is not transferable.
This warranty will not be applicable in cases other than defects in materials and/or workmanship at
the time of purchase and will not be applicable:
a) for damages caused by incorrect installation, connection or packing,
b) for damages caused by any use other than correct use described in the user manual,
negligence, modifications, or use of parts that are not made or authorised by B&W,
c) for damages caused by faulty or unsuitable ancillary equipment,
d) for damages caused by accidents, lightning, water, fire heat, war, public disturbances or any
other cause beyond the reasonable control of B&W and its appointed distributors,
e) for products whose serial number has been altered, deleted, removed or made illegible,
f) if repairs or modifications have been executed by an unauthorised person.
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This guarantee complements any national/regional law obligations of dealers or national distributors
and does not affect your statutory rights as a customer.
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Owner’s Manual
IMPORTANT SAFETY INSTRUCTIONS
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Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including
amplifiers) that produce heat.
The CT8 XO active crossover is a powered device. Before use, please read and heed the following
instructions:
Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades
with one wider than the other. A grounding type plug has two blades and a third grounding prong. The wide
blade or the third prong are provided for your safety. If the provided plug does not fit into your outlet, consult
an electrician for replacement of the obsolete outlet.
Caution:
To reduce the risk of electric shock, do not dismantle the apparatus and do not expose the apparatus
to rain or moisture. No user-serviceable parts inside. Refer servicing to qualified personnel.
10 Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles and
the point where they exit from the apparatus.
11 Only use attachments/accessories specified by the manufacturer.
Explanation of Graphical Symbols
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Use only with the cart, stand, tripod, bracket, or table specified by the manufacturer, or
sold with the apparatus. When a cart is used, use caution when moving the cart/apparatus
combination to avoid injury from tip-over.
The lightning flash within an equilateral triangle is intended to alert you to the presence of
uninsulated “dangerous voltage” within the product’s enclosure that may be of sufficient
magnitude to constitute an electric shock to persons.
13 Unplug this apparatus during lightning storms or when unused for long periods of time.
14 Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been
damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have
fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or
has been dropped.
The exclamation point within an equilateral triangle is intended to alert you to the
presence of important operating and maintenance (servicing) instructions in the literature
accompanying the appliance.
WARNINGS:
15 When replacement parts are required, be sure the service technician has used replacement parts specified
by the manufacturer or have the same characteristics as the original part. Unauthorised substitutions may
result in fire, electric shock or other hazards.
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Read these instructions.
Keep these instructions.
Heed all warnings.
16 For continued protection against fire hazard, use fuses only of the correct type and rating. Mains fuses are
located inside the casing of the appliance and should be replaced only by an authorised operative.
17 Isolation of the appliance from the power supply is by means of either the switch on the rear of the
appliance or removal of the power cord from the rear of the appliance or removal of the power cord
from the wall power outlet. Either the wall outlet or the rear of the appliance must remain freely
accessible at all times while the apparatus is in use.
Follow all instructions.
Do not use this apparatus near water.
Clean only with dry cloth.
18 This product should be operated only from the type of power source indicated by the marking adjacent to the
power cord entry. If you are not sure of the type of power supply to your home, consult your product dealer
or local power company.
Do not block any ventilation openings. Install in accordance with the manufacturer’s
instructions.
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19 Do not overload wall outlets, extension cords or integral convenience receptacles, as this can
result in a risk of fire or electric shock.
20 Never push objects of any kind into this product through openings, as they may touch dangerous
voltage points or short out parts that could result in a fire or electric shock. Never spill liquid of any
kind on the product. Do not place any object containing liquid on top of the product.
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Introduction
Thank you for purchasing a Bowers and Wilkins Custom Theatre system.
Since its foundation in 1966, the continuing philosophy of B&W has been the quest for perfect sound reproduction.
Inspired by the company’s founder, the late John Bowers, this quest has entailed not only high investment in audio
technology and innovation but also an abiding appreciation of music and movies to ensure that the technology is
put to maximum effect.
Custom Theatre speakers are specifically designed to be built into the fabric of the listening room or into custom
furniture as part of a fully designed theatre concept. To that end, they incorporate several features that enable them
to be adapted to a wide range of installation conditions and deliver superb sound quality. However, they specifically
do not incorporate features found on some other B&W products that are not appropriate to this type of installation.
An example of such a feature would be tweeter on top, which only operates well with a free-standing speaker.
Furthermore, because of the normal custom install practice of hiding built-in speakers with acoustically transparent
cloth that matches the décor, all the models except one are supplied without grilles. The exception is the CT8 DS
surround speaker, which needs to protrude into the room in order for the side-firing drivers to operate properly.
No matter how good the speakers themselves may be, they will not deliver their full potential unless properly
installed. Please read through this manual fully. It will help you optimise the performance of the system.
B&W distributes to over 60 countries worldwide and maintains a network of dedicated distributors who will be able
to help should you have any problems your dealer cannot resolve.
Environmental Information
B&W products are designed to comply with international directives on the Restriction of Hazardous Substances
(RoHS) in electrical and electronic equipment and the disposal of Waste Electrical and Electronic Equipment (WEEE).
The crossed wheelie bin symbol indicates compliance and that the products must be appropriately recycled or
processed in accordance with these directives.
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The Concept
The CT 800 range comprises five products:
CT8 LR A 3-way speaker intended for front left and right channels, one placed in vertical orientation at each side
of the screen.
CT8 DS A full range surround speaker that may operate in either 2-way dipole or 3-way monopole mode.
CT8 CC A 3-way centre channel speaker that is acoustically similar to the CT8 LR, but designed with a more
symmetrical drive unit layout so that it may be used in horizontal orientation immediately above or below
the screen.
CT8 SW A subwoofer that may be added to any or all the above three models to extend their bass response well
below the accepted lower limit of human hearing.
CT8 XO An active, line-level crossover/equaliser that:
a)
b)
c)
d)
is required for each CT8 LR, CT8 CC and CT8 DS and must be configured to the particular speaker
type.
provides active filtering between midrange and bass drivers and between bass drivers and
CT8 SW (if used).
controls whether a surround speaker operates in dipole or monopole mode and, in dipole
mode, controls the direction of the positive and negative polarity lobes.
provides high- and low-frequency level control, plus three adjustable parametric equalisers to
adjust for speaker/room interface effects.
The crossover between midrange and tweeter drive units is accomplished by a passive filter inside each speaker.
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Although the speakers are semi-active and require an active crossover, all power amplification must be separately
sourced. Each CT8 LR, CT8 CC and CT8 DS requires two channels of power amplification, or three if used with a
CT8 SW subwoofer. This allows the user maximum flexibility in choosing these components.
The CT8 SW subwoofer, unlike the majority of subwoofers currently available, does not contain its own power amplifier
and is used in a different manner than is usual. The original concept of home theatre based on various Dolby Digital
and DTS systems advocates five or more main channels plus a single Low Frequency Effects (LFE) channel. The
main channels contain full range signals and the LFE channel contains special effects up to approximately 140Hz.
Recognising that many people do not want five or more full-range speakers in one room, Dolby Digital and DTS
systems allow for the main channels to operate with small speakers having a restricted bass extension. The lowest
frequencies from these channels are filtered off and added to the LFE channel to be reproduced by a subwoofer.
The filter cut-off frequency is normally set at around 80Hz, the rationale being that sound gets progressively less
directional the lower the frequency and localisation becomes less important. This is true to some extent, but the ears
can process directional information at very low frequencies and the more the bass of the main channels is extended,
the more realistic the sound stage becomes. Many high-end processors offer lower filter cut-off frequencies for this
very reason.
To preserve this directional information, a CT8 SW may be added to each of the main channels as desired, extending
the frequency response well below 20Hz. The minimum recommended configuration is to assign one subwoofer to
each of the front left and right channels, restoring some directional information to the action directly on the screen
and full directional information to 2-channel audio programme. The sense of spatial acoustic improves as more
subwoofers are added to the remaining channels. If higher sound levels are required for larger listening environments
and greater realism, up to four subwoofers may be added to each main channel. (It should be noted here that the
addition of more subwoofers to any single channel requires an adjustment of the subwoofer output level of that
channel’s CT8 XO in order to restore the correct tonal balance.) The LFE channel is then distributed to all the main
channels that have a subwoofer assigned by the simple action of configuring the surround processor as if there
were no subwoofer present and specifying where the LFE signal should be routed. Strictly speaking, the phrase “no
subwoofer” here means “no subwoofer dedicated to the LFE channel”.
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Planning the installation
Figure 1
Safety Warning!
A CT800 system is capable of producing very high sound pressure levels. Prolonged exposure to high sound levels
can lead first to temporary and later permanent hearing damage. Do not exceed recommended Leq (equivalent
sound level) exposure levels, for example, those specified in ISO 1999:1990.
Check the contents against Figure 1
Planning the installation
Because of the built-in nature of the installation, the planning stage is of the utmost importance. Any need to adjust
speaker position, for example, is a much more involved process than with free-standing speakers. Care must also
be taken to construct proper support for the speakers. It is all too easy to induce the panels of custom furniture to
vibrate and colour the sound unless precautions are taken to prevent it.
Figure 2
Figure 3
Speaker Position
~120o
Figures 2 to 4 show the recommended locations in plan view for the main speakers in 5.1, 6.1 and 7.1 channel
installations. Some dimensions are marked ~, indicating that there is some latitude allowed each side of the figure,
and some have a recommended range for optimum results. Subwoofers should be placed close to the main
speakers to which they are assigned.
For successful operation of the surround speaker, CT8 DS, in dipole mode, it is important that all listeners sit within
the speaker’s null zone. This is the 60o wide zone of low direct sound level created by the opposing polarity drivers
on each side. You will notice from figures 3 and 4 that for 6.1 and 7.1 systems, the side speakers are shown in
line with the centre of the listening area. This is suitable regardless of whether these speakers are used in dipole
or monopole mode. However, for 5.1 systems, the two surround speakers should be placed somewhat behind
the listeners for effective results in monopole mode, or if you wish to switch between monopole and dipole modes
for different types of programme. If you only ever intend to use them in dipole mode, the two surround speakers
should revert to the in-line position. Please read the discussion on surround modes in the next section for a clearer
understanding of the benefits of each type.
Figure 4
For larger audience sizes, a more even coverage of the surround sound field may be obtained if the surround
speakers are elevated above ear height, as in a commercial cinema. In that case, the speakers may be raised so
that the midrange/tweeter array is approximately 60cm (2 ft) above seated ear height.
For correct operation of the CT8 DS in dipole mode, it is important not to obstruct the side firing drivers. The speaker
should be mounted with at least the front portion containing the side-firing drivers protruding into the room and any
customised covering should be acoustically transparent.
~40o
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Surround speaker dispersion mode
Figure 5
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.
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.
~60o
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 personal preference.
The CT8 DS is a specialist surround speaker and has the advantage of offering a choice of both monopole and
dipole operation. The mode of operation is set by a relay inside the speaker, the state of which is controlled from the
CT8 XO crossover/equaliser assigned to the speaker via a cable connecting the 3.5mm sockets on both products.
If this cable is not fitted, the speaker will only operate in monopole mode. On the CT8 XO is a switch used to
select the mode. In the monopole position, this switch may be overridden by a 12V trigger signal from the surround
processor. Some surround processors can recognise the type of programme being played from a code on the disc
and allow you to assign a 12V trigger to this code. Some other processors allow you to assign a 12V trigger to
the input selection and you may, for example, use a different disc player for audio and movies and set the trigger
accordingly. In both these cases, you may 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.
The two bass drivers operate in both modes. In monopole mode, they cross over to the midrange and tweeter drive
units on the front face and the speaker is acoustically similar to the CT8 LR, but without the swivelling head. In dipole
mode, the bass drivers cross over to the six side-firing drivers. 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. (figure 5)
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Figure 6
Mounting the speakers
For optimum performance, it is important that the speakers are firmly and securely mounted. All the speakers may
be mounted directly at floor level, but, as mentioned above, it can be beneficial to raise the position of the surround
speakers and, if the screen is high, it may also be beneficial to do the same with the front speakers. In that case,
the supporting structure for the speakers should be substantial. If constructed of wooden studding, the framework
should be arranged to be directly beneath the feet of the speaker. (figure 6)
All the speakers are equipped with roller glides on the base panel. These allow the speakers to be easily pushed
into place in custom furniture. In order to position the speakers accurately, we suggest you create circular recesses
15mm (5/8 in) diameter in the support surface to locate the glides.
To avoid rocking when the speakers are in position, it is important that these recesses are accurately positioned and
a foot-positioning template is supplied for this purpose.
The shaded area at the front of the template is to allow clearance for the movement of the bass cones. For the CT8
DS, the side-firing drive units require free acoustic access into the listening room, indicated by the shaded area of
the template extending round the sides. The CT8 DS will normally have the front half of the cabinet protruding clear
into the room. It may, however, be built in to a false pillar, but this must be acoustically transparent at the sides, as
well as the front, as indicated by the shaded area.
If the speakers are to be inset in a false wall, a front template is provided for guidance in cutting the aperture. The
template is the same size as the speaker, so remember to leave some clearance. The height of the template includes
the roller glides.
If the speakers are to be mounted in custom furniture, you should also ensure that it is substantially built and
not prone to induced vibration. It should be braced where necessary and it may be beneficial to glue bituminous
damping pads, similar to those used in motor vehicles, to large unsupported panels. Such pads need to be thicker
on wood than metal and a minimum of 6mm (1⁄4 in) should be used.
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If it is desired to remove the roller glides, use the Torx® key supplied with the speaker to remove the retaining
screws.
Figure 7
An optional, spike foot kit is also available (Part No FP22359). The kit contains 4 heavy-duty feet that have 40mm
(1.6 in) of vertical adjustment, allowing tilt up to 8o if desired. This tilt is in addition to that offered by the adjustable
head unit of the CT8 LR and CT8 CC.
The feet are reversible, having a spike for carpets on one end and a rubber pad for vulnerable surfaces on the other.
Fitting is most easily accomplished during unpacking, when the underside of the speaker is exposed. (figure 7)
Note that if the optional feet are fitted, or if the speaker is tilted, appropriate allowance over and above that allowed
for in the template must be made when cutting an aperture in the wall.
The threaded bosses that hold the feet have a large conical shape on one side of the flange. For maximum height,
fit the bosses with the conical shape towards the floor. (figure 8) For minimum height, have them pointing into the
speaker. (figure 9)
Screw in the feet close to where you think the final adjustment will be, with the spikes or the rubber ends outermost
as appropriate to the floor surface. If you do not intend to tilt the speakers, orient the bosses with the cones inwards
and leave just enough thread exposed to fit the locking rings. Fit, but do not tighten the locking rings.
Stand the speaker upright and adjust the feet using the metal bar provided to give the amount of tilt required and
to take up any rocking. (figure 10)
Figure 8
Figure 9
Finally, tighten the locking ring against the boss, again using the metal bar. (figure 11)
The tweeter drive units are fitted with a protective clear plastic cover on delivery. This is to avoid the danger of
damaging the dome when installing the speakers. Once installed, the protection cover should be removed by simply
pulling it away from the speaker.
Figure 10
Figure 11
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CT8 DS Only
Figure 12
Installation into drywall (figure 12)
So that it can be sunk into a standard drywall up to the level of the side-firing drivers, the CT8 DS has a
relatively shallow cabinet for its height and is front heavy. To maintain stability, it is equipped with a bracket that
enables the rear of the cabinet to be anchored either to a wall surface or the internal studding of a drywall.
In existing construction:
Use a stud finding tool to locate the position of the vertical studs and ensure that the speaker is positioned
between them.
If the speaker is to be mounted above floor level, cut into the drywall panel to expose the stud frame
sufficiently to allow the insertion of a cross-brace at the appropriate height to support the speaker.
Safety Warning!
Ensure the cross-brace is level and fitted strongly enough to take the substantial weight of the
speaker. The speaker can be supported by the cross-brace and the retaining bracket alone
if desired, or a more complex support structure may be constructed, for example to hide the
underside of the cabinet.
Using the front aspect template provided, mark round the outline at the desired position of the speaker. Allow a
little for clearance.
If mounting the speaker at floor level, allow extra height if there is a horizontal stud at floor level.
Cut out the aperture for the speaker
Using the front aspect template provided, mark the centre line of the retaining bracket on the inside surfaces of
the two vertical studs either side of the speaker position.
Screw the two angle brackets (A) to the inside face of the vertical struts.
Attach the wall bracket (C) to the angle brackets (A) using machine screws (D) and trapping the stud plate (B)
in position.
Patch the drywall as necessary.
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Figure 13
CT8 DS only (cont’d)
Installation to wall surface (figure 13)
Using the front aspect template provided, mark the centre line of the retaining bracket on the wall.
The two angle brackets (A) from the kit are not required.
Offer the wall bracket (C) to the wall and mark the screw positions at each end.
Drill and plug the wall to take screws in the range 5mm – 6mm (No.10 to No.12)
Screw the wall bracket to the wall, trapping the stud plate (B) in position.
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Figure 14
CT8 DS only (cont’d)
Continue for all cases
Connect the signal and trigger cables to the speaker.
Using the Allen key provided, remove the aluminium facing plate on the front of the speaker, taking care that
the tweeter protection cover remains in position.
Fit the guide tubes (F) into the two through holes.
Offer the speaker into position, ensuring that the guide tubes (F) locate over the studs of the bracket (B).
When the speaker is fully in position hard against the wall bracket, withdraw the guide tubes.
Using a 1⁄4 inch socket drive with extension and the 13mm socket provided, fit the two flanged nuts (E) onto
the threaded studs and tighten. If the socket drive does not have a nut retaining feature, we recommend the
use of a small piece of Bostik® Blu-Tack® or similar reusable adhesive to prevent the nut falling out of the
drive during this operation.
Replace the facing plate on the front of the speaker and remove the tweeter protection cover.
If the speaker is mounted on the floor and recessed into a drywall having a horizontal stud member on the floor
surface, the height difference may be taken up by fitting the optional spike feet in place of the two front roller
glides. (figure 14) Only one Spike Foot Kit will be required for each pair of CT8 DS.
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Connecting the System
Figure 15
The speakers
All the speakers are provided with a comprehensive choice of connection methods. Binding posts accommodate
6mm (1/4 in) or 8mm (5/16 in) spades, 4mm banana plugs and bare wire ends and a Neutrik® Speakon® socket
provides a professional industry standard multiway connection that makes it easy to make a connection in confined
spaces, especially when it is sometimes difficult to see what you are doing.
For all models except the subwoofer CT8 SW, there are two input channels, one for bass and one for midrange/
tweeter, requiring two channels of power amplification. In all cases, ensure that the positive terminal of the speaker
is connected to the corresponding positive output connector of the power amplifier. Failure to observe this will result
in impaired tonal balance and imaging. Figure 15 shows a typical connection method using binding posts and figure
16 (a & b) the wiring convention for the Neutrik® Speakon® plug.
Figure 16a
Figure 16b
CT8 DS only
SUB -
SUB +
In addition to the audio signal connections, the CT8 DS terminal panel has a 3.5mm stereo jack socket
(figure 17) to input two 12V trigger signals from its CT8 XO unit. Use a stereo coaxial cable terminated at each
end by a 3.5mm stereo jack plug to connect to the complementary output socket (TRIGGER OUT) at the rear
of the CT8 XO.
SUB +
SUB -
Figure 17
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The CT8 XO Rear Panel
The CT8 XO crossover/equaliser
The CT8 XO may be placed on a table or shelf or in a 19-in rack. If housed in an
enclosed structure, proper ventilation must be supplied as stated in the in the safety
instructions.
The CT8 XO is connected between the surround processor and the power amplifiers.
A choice of unbalanced (cinch / RCA Phono) or balanced (XLR) connectors is
provided.
Figure 18
The wiring convention for XLR connectors is:
Pin 1: Ground
Pin 2: Live
Pin 3: Return
For each CT8 XO setup, use only all balanced or all unbalanced connections.
Mixing the type of connectors could lead to a severe tonal imbalance in the system
depending on the other equipment used in the installation.
If 12V trigger switching of the dispersion mode (monopole/dipole) of the CT8 DS
surround speakers is required, the assigned 12V trigger output from the surround
processor is connected to the 12V TRIGGER IN of one of the CT8 XO units assigned
to a CT8 DS. The other CT8 XO trigger inputs are connected daisy chain fashion from
the TRIGGER LOOP socket of one to the TRIGGER IN of the next. The
TRIGGER OUT sockets are connected to the relevant CT8 DS speakers. The
TRIGGER IN and TRIGGER LOOP sockets are mono 3.5mm jacks with the positive
(12V) wire connected to the tip of the plug, whereas the TRIGGER OUT socket is a
stereo 3.5mm jack on both the CT8 XO and CT8 DS loudspeaker.
Figure 18 shows the wiring diagram of a typical 5.1 CT800 system having two
CT8 SW speakers, one assigned to each of the front left and right channels.
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Description of Controls
Description of controls
Figure 19
LF Contour
The unit features a comprehensive set of controls to tune the performance of each speaker according to the
conditions of use. The response may be shaped by a combination of three parametric equalisers, each having
a level range of +4.5 / -12 dB, and low- and high-frequency contour controls, the effects of which are illustrated
in figure 19. In addition, level controls are provided to compensate for any differences in gain between both the
subwoofer and LF power amplifiers compared to the MF/HF power amplifier.
To access the front of the unit, pull off the decorative facing plate.
Refer to figure 20 for the layout of the inputs and controls, which have the following functions:
T1
T2
T3
C1
C2
C3
C4
C5
C6
C7
C8
C9
Test input socket (unbalanced)
Test input socket (balanced)
Output level indicator lights
Low-frequency contour control
High-frequency contour control
Parametric filters-overall gain
Parametric filter 1-gain
To connect external signal generator
To connect external signal generator
To balance levels
± 6dB see figure 19 top graph
± 4dB see figure 19 bottom graph
HF Contour
+4 / -12dB
0.5 - 5
Parametric filter 1-Q
Parametric filter 1-frequency
Parametric filter 2-gain
30Hz - 500Hz
+4 / -12dB
0.5 - 5
Parametric filter 2-Q
Parametric filter 2-frequency
30Hz - 500Hz
+4 / -12dB
0.5 - 5
C10 Parametric filter 3-gain
C11 Parametric filter 3-Q
C12 Parametric filter 3-frequency
C13 LF output gain
30Hz - 500Hz
Figure 20
C1 C2 C3
C7 C8 C9
C13 C14
C14 Subwoofer output gain
S1
S2
S3
S4
DIP switch bank 1
DIP switch bank 2
DIP switch bank 3
DIP switch bank 4
See table
See table
See table
See table
T1 T2
T3
C4 C5 C6
C10 C11 C12
S1 S2
S3 S4
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The DIP switches should be set as follows, where ON is down:
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Examples of typical DIP switch settings at the front of the CT8 XO
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Front left/right channels
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Left surround channel
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These settings apply when all power amplifiers have the same gain,
the parametric equalisers are bypassed, trigger switching is used
to set the dipole/monopole mode of the CT8 DS speakers and one
subwoofer is connected to each of the front left and right channels.
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18
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Configure the CT800 XO to the speaker
Equipment Required
Set Bank 1 Switches 2 & 3 to the type of speaker.
• AC voltmeter
• Signal Generator capable of outputting a sine wave up to 2V RMS
• Flat bladed screwdriver to adjust the rotary controls of the CT8 XO
Set Bank 4 Switches 1, 3 & 4 according to the number of subwoofers attached. The conditions of Switches 3 & 4
are irrelevant if Switch 1 is set to ON.
Configure the unit to the gain of each power amplifier
And to adjust the equalisers to optimise the in-room response:
• Laptop PC with WinMLS 2004 (or later version) software installed
• External sound card
The reference gain is that of the power amplifier feeding the MF/HF drive units. If using the same type or even the
same gain of power amplifier throughout, simply set Bank 2 Switch 1 and Bank 4 Switch 2 both to ON.
• Measuring microphone
If the power amplifier gains are different, you will need a sine wave oscillator and AC voltage meter to set the
correct compensation gain in the unit.
WinMLS may be purchased directly from the software supplier, in which case it should be
WinMLS 2004 or later and be to level 3 license. It should also include the specially created
“B&W CT800” measurement module. Early versions of the software did not include this
During this process, the parametric equalisers should be bypassed by setting DIP switches 2 and 3 in bank 2 to
OFF and the contour controls (C1 & C2) set to zero.
Setting the LF gain
However, a special package that includes a suitable microphone, USB sound card and a cut-
down version of the software that includes everything required for tuning a CT800 system may
be obtained directly from B&W. Contact your country distributor for details.
Disconnect the speakers from the power amplifiers.
Connect the MF/HF power amplifier to the LF output of the unit.
Set the output level of the oscillator to zero and connect it to the appropriate test input socket.
Set the oscillator frequency to 100Hz.
Ths illustrations on the following pages refer to the B&W version of the software. The standard
version will differ slightly.
Set Bank 1 Switch 1 to ON.
Set Bank 2 Switch 1 to ON.
Set Bank 2 Switches 2 & 3 to OFF.
Connect the AC voltmeter to the output terminals of the MF/HF amplifier.
Raise the output level of the oscillator until the meter reads 2 volts.
Substitute the LF power amplifier for the MF/HF power amplifier. Do not alter the output setting of the oscillator.
Set Bank 2 Switch 1 to OFF.
Adjust the LF output gain control (C13) until the meter again reads 2 volts.
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Figure 21
Setting the Subwoofer gain
Disconnect the speakers from the power amplifiers.
Connect the MF/HF power amplifier to the Subwoofer output of the unit.
Set the output level of the oscillator to zero and connect it to the appropriate test input socket.
Set the oscillator frequency to 25Hz.
+
+
Set Bank 1 Switch 1 to ON.
Set Bank 4 Switch 2 to ON.
Set Bank 2 Switches 2 & 3 to OFF.
Connect the AC voltmeter to the output terminals of the MF/HF amplifier.
Raise the output level of the oscillator until the meter reads 2 volts.
Substitute the LF power amplifier for the MF/HF power amplifier. Do not alter the output setting of
the oscillator.
Set Bank 4 Switch 2 to OFF.
Adjust the Subwoofer output gain control (C14) until the meter again reads 2 volts.
Configure the dipole lobe for a CT8 DS
Set Bank 3 Switch 3 as required by figure 21 according to the position of the CT8 DS in the system.
Set Bank 3 Switch 2 as desired according to preference and Bank 3 Switch 3 as required by
figure 21.
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Configure the equalisers
The Theory
Sensible correction of the in-room response requires the ability to measure the acoustic frequency response of
each speaker individually. The measurement microphone does not need to be expensive and suitable electret
microphones are widely available. If the appropriate measuring equipment is not available, we recommend that the
parametric filters be bypassed by setting Bank 2 Switches 2 & 3 to OFF. Setting of the low- and high-frequency
contour controls may be attempted by ear to the user’s preference.
A number of response measurements R1 to Rn are taken and the average or mean
response Rm is calculated.
The microphone is left at position n and further measurements are taken as
adjustments are made to the equalisation. If the measured equalised response at
position n (called Rneq) is multiplied by Rm and divided by the unequalised Rn, one
can review the equalised mean response, Rmeq
Correcting for room resonances requires thought, skill and patience. It is not sensible to attempt to fully equalise
response dips, as this may lead to system overload. Fortunately, dips are less objectionable than peaks. For this
reason, each parametric filter allows just 4.5dB of boost but 12dB of cut.
It is also not advisable to make corrections to a single position measurement. The response of the speaker/room
combination can differ considerably throughout the room and it is all too easy to worsen the response in one position
whilst making it better in another. An average of several measurements taken at different positions throughout the
room should ideally be used to ensure an overall improvement in all listener positions.
The Method
We suggest taking measurements at each seat position and at several points outside the immediate listening area.
Point the microphone towards the speaker being measured.
The resonances change with height. Often seats will be at the same level, so put the microphone at a typical ear
height. If the home theatre room is like a mini cinema with regular rows of raked seating, measure at each seat at the
likely ear height. Do not hand hold the microphone during measurements. Use a tripod or other means of holding
it still. It is advisable to make the last measuring position n (the one used for subsequent equalised measurements)
the primary listening position.
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Figure 22
Procedure
To avoid errors from airbourne background noise and electrical interference, switch off all sources in the room such
as air conditioning, refrigerators etc.
Laptop computer settings:
Run the laptop from its battery and disconnect its transformer power supply when taking measurements. This
will prevent noise being generated by electrical grounding mismatches between the laptop, sound card and
CT8 XO. Make sure the battery is fully charged before starting the measuring procedure.
Open the “Sounds and Audio Devices” window in “Control Panel”. Click on the “Sounds” tab and select the
“No Sound” option in the “Sound Scheme” drop-down menu.
Click on the “Volume” button in the “Sound Playback” section and make sure the Microphone “Mute” box is
checked to prevent feedback.
Click on the “Audio” tab and then on the “Volume” button in the “Sound Recording” section. Set the volume
slider to maximum and make sure the “Select” box is checked.
Figure 23
Set Bank 1 switch 1 to ON to accept an input from the front of the CT8 XO.
Set Bank 2 switches 2 and 3 to OFF to disable the parametric equalisers.
Set the Low- and High-frequency contour controls (C1 & C2) to zero.
Connect the output of the sound card to a front test input socket of the CT8 XO and the microphone to the input
of the sound card.
Open WinMLS2004
From the menu, select Setup…Load… and load the setup called “B&W CT800” from the “Sound System” folder.
Click the
button to open the “Volume and Input Levels” window.
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Place the microphone at the chosen measurement position that is
closest to the speaker under test (where it will measure the highest
sound pressure level). Set the “Input Ch.1” slider to maximum.
Figure 24
Set the “Output” slider to zero and switch on the test signal by
clicking the
button. Increase the output level until the “Input
Ch.1” level meter just goes into the red zone. Decrease the “Input
CH.1” level until the signal peaks between the -6dB and -3dB
marks.
Close the “Volume and Input Levels” window and click the
button to switch off the test signal.
Make sure Plot…Overlay is checked to show the frequency response screen and enable several responses to be
viewed simultaneously.
Figure 25
Press the F7 key to bring up the Measurement Settings window. In the ‘‘Levels’’ box, set the sine sweep to -40dB
FS (full scale).
Perform a number of measurements in different positions by clicking the
button (or pressing the F2 key). Make
the last measurement you take close to the centre of the listening area and leave the microphone exactly in that
position for subsequent measurements. Since Plot…Overlay is checked, the curves will be plotted on top of each
other and, when finished, there will be n curves displayed.
In the example shown in figure 22, n = 10.
Click the
button to display the mean value on top of all the plotted curves. The average room response is then
calculated (figure 23). This is the response we want to equalise.
Un-tick all the plots except the mean response. (figure 24)
Press CTRL+ E to save this mean result in the “Tune EQ” folder (if this folder doesn’t exist, create it in
C:\Program Files\WinMLS2004\Set EQ). Then click Save and name the file, for example, Average_resp.txt
(figure 25)
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To set this curve as a multiplier, press the F5 key. In this dialog box, select the file you just saved (Average_resp)
and, under ‘Compensation of Level’, check the ‘Tune EQ (multiply)’ box as shown (figure 26). This curve is now
the reference and all subsequent measurements will be multiplied by this response.
Figure 26
Click OK. The graphs will change, but ignore these changes.
We now need to set division by the measurement performed in this last position with no equalisation (Rn ).
Press Ctrl + F and make sure this last measurement is selected as shown in figure 27 (in this example #10 was
the last measurement position and that is therefore set as reference).
Click OK.
The graphs will change, but ignore these changes.
When we now perform another measurement with the equalisation applied (Rneq ), the software will calculate the
Figure 27
quantity
. In our case the original measurement at position #10 is Rn.
Now it is time to clean up the display. Make sure the following button is turned off:
To remove the measurements we used to make the reference, click the erase button
and select the settings
shown in figure 28 (this will remove all the curves in the plot and remove the measurements from memory).
There will now be no plots showing on the screen. Make sure the Overlay button is in the down state.
Click
(or press the F2 key) to re-measure the response at the last position. This time on the screen, you will
be presented with the mean response.
Figure 28
Examine this mean response and consider the optimum target to aim for. A flat in-room response is not desirable.
Studies show that a more suitable target is a response that is flat up to 100Hz and then falling uniformly by a total
of 6dB by 10kHz.
Tune the parametric filters first before using the low- and high-frequency contour controls.
There are three filters, each having adjustable centre frequency, gain and Q. Aim to suppress peaks first. Only if
there are fewer than three significant peaks should you consider filling in dips.
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Set Bank 2 Switches 2 & 3 according to the number of filters required.
Set the P (all) gain control (C3) to zero.
Altering the parametric filter controls is likely to also affect the overall gain of the subwoofer and LF
sections. To restore the correct levels:
•
•
•
Switch off all power amplifiers to avoid the danger of overloading the drive units.
Disconnect the sound card from the test input socket.
The markings on the filter control dials are approximate and for guidance only.
Connect the signal generator to the relevant test input socket and set the output to give a 1kHz
sine wave at a level of 1V.
Set the individual filter gain controls (C4, C7 & C10) to -14dB
Set the individual filter Q controls (C5, C8 & C11) to approximately 4.
•
One or other of the two output indicator lights (T3) will probably be lit. If it is the left one,
turn the parametric filter overall gain (C3) anti-clockwise until both lights are out. Conversely, if
the right light is lit, turn the control clockwise until both lights are out.
This enables the centre frequency response of the filters to be readily seen.
Set the individual filter frequency controls (C6, C9, C12) initially to 500Hz. This keeps the filters
away from the frequency range of interest until they are tuned one at a time to compensate the
frequency response.
Disconnect the signal generator and reconnect the sound card and outputs to the power amplifiers.
Taking further measurements to check the results, adjust the low- and high-frequency controls to
suit.
Turn the filter frequency controls (C6, C9 & C12) to the centre frequencies of the peaks or dips to be
equalised. This is an approximate initial setting.
Additional response shelving up to 40Hz may be achieved by altering the subwoofer gain (C14) and
from 40Hz to 500Hz by altering the LF gain (C13).
Take repeated frequency response measurements to see the effects of the adjustments you are
about to make. Every now and then you may wish to discard plots and this may be done by
unchecking those you do not need on the plot list to the right of the screen.
If you need to equalise another speaker, you must reload the CT800 setup within WinMLS
and repeat the above process.
Adjust the filter centre frequencies until the measured dips in the response line up accurately with
the centres of the peaks or dips originally in the response.
Adjust the filter gain controls (C4, C7 & C10) so that the response at the centre frequency of each
filter is at the target level (the desired smoothed level).
Lower the filter Q controls (C5, C8 & C11) to broaden the range of the filters until the response is as
smooth as possible.
The controls are to some extent interactive and it may be worthwhile going round the loop of
checking the control settings a second time.
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Running In and Ancillary Equipment
Ancillary equipment
Running In
Speakers of this ability deserve signals of the highest quality. Choose your electronic equipment and interconnecting
The performance of the speakers will change subtly during the initial listening period. If they have been
cables with care. We can give guidance on what to look for when choosing ancillary equipment, but cannot stored in a cold environment, the damping compounds and suspension materials will take some time
recommend specific items. The standards of such products are improving all the time and your dealer will be able to recover their correct mechanical properties. The drive unit suspensions will also loosen up during
to demonstrate a variety of suitable up-to-date products.
the first hours of use. The time taken for the speakers to achieve their intended performance will vary
depending on previous storage conditions and how they are 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.
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 However, longer run-in periods (as long as a month) have been reported and there is evidence to
3
necessary to achieve reasonable listening levels without audible distortion in the smaller room (less than 60 m or
2000 cu ft). The higher the power you use, the less likely you are to experience amplifier clipping.
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.
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.
26
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Aftercare
The speaker cabinet surfaces and the casing of the CT8 XO usually only require dusting. If you wish to use an
aerosol cleaner, remove any speaker grilles first by gripping round the edges and gently pulling them away from the
cabinet. Spray onto the cleaning cloth, not directly onto the cabinet. The grille fabric may be cleaned with a normal
clothes brush whilst the grille is detached from the cabinet.
When replacing grilles, ensure that the pegs are correctly aligned with the receptacles in the cabinet before pushing
into place.
Avoid touching the drive unit diaphragms, especially the tweeter, as damage may result.
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Specifications
Model
CT8 LR
CT8 CC
CT8 SW
Description
Drive Units
3-way closed-box system
3-way closed-box system
Closed-box subwoofer
1x ø32mm (11⁄4 in) metal dome high-frequency
1x ø150mm (6 in) woven Kevlar® cone FST midrange
1x ø32mm (11⁄4 in) metal dome high-frequency
1x ø150mm (6 in) woven Kevlar® cone FST midrange
1x ø380mm (15 in) carbon fibre/rigid foam sandwich cone bass
TM
TM
2x ø250mm (10 in) carbon fibre/rigid foam sandwich cone bass
2x ø250mm (10 in) carbon fibre/rigid foam sandwich cone bass
Frequency Range
-6dB at 23Hz and 40kHz
-6dB at 23Hz and 40kHz
-6dB at 13Hz and 40Hz (using active crossover/equaliser)
Frequency Response
29Hz – 24kHz ±3dB on reference axis
29Hz – 24kHz ±3dB on reference axis
18Hz – 35Hz ±3dB on reference axis
(using active crossover/equaliser)
Dispersion
Within 2dB of reference response
Horizontal: over 60o arc
Within 2dB of reference response
Horizontal: over 60o arc
Within 2dB of reference response
Horizontal: over 60o arc
Vertical:
over 10o arc
Vertical:
over 10o arc
Vertical:
over 10o arc
Sensitivity
93dB spl (2.83V, 1m) (mf/hf)
93dB spl (2.83V, 1m) (mf/hf)
90dB spl (2.83V, 1m)
Harmonic Distortion
2nd and 3rd harmonics (90dB, 1m)
<1% 45Hz – 20kHz
2nd and 3rd harmonics (90dB, 1m)
<1% 45Hz – 20kHz
2nd and 3rd harmonics (90dB, 1m)
<1% 30Hz – 500Hz
<0.5% 55Hz – 20kHz
<0.5% 55Hz – 20kHz
<0.5% 45Hz – 300Hz
Nominal Impedance
8Ω (minimum 4Ω)
8Ω (minimum 4Ω)
8Ω (minimum 4Ω)
Crossover Frequency
300Hz, 4kHz
300Hz, 4kHz
40Hz
Recommended Amplifier Power
500W – 1000W into 8Ω on unclipped programme
0.1Ω
500W – 1000W into 8Ω on unclipped programme
0.1Ω
500W – 1000W into 8Ω on unclipped programme
0.1Ω
Max Recmmended Cable
Impedance
Dimensions
Height:
Width:
Depth:
1100mm (43.3 in) (without spike feet)
325mm (12.8 in)
Height:
Width:
Depth:
325mm (12.8 in) (without spike feet)
1100mm (43.3 in)
Height:
Width:
Depth:
475mm (18.7 in) (without spike feet)
475mm (18.7 in)
550mm (21.65 in)
550mm (21.65 in)
475mm (18.7 in)
Weight
85kg (187 lb)
Cabinet: Black
85kg (187 lb)
35kg (77 lb)
Cabinet:
Finish
Cabinet:
Black
Black
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Specifications
Model
CT8 DS
Model
CT8 XO
Description
Drive Units
3-way monopole/2-way dipole selectable closed-box surround system
Description
Functions
CT800 system active bass management controller
1x ø32mm (11⁄4 in) alloy dome high-frequency
6x ø100mm (4 in) midrange/high-frequency
Bass/midrange crossover
Subwoofer/bass crossover
TM
1x ø150mm (6 in) woven Kevlar® cone FST midrange
Low-frequency roll-off alignment
High frequency roll-off alignment
Wall proximity response adjustment
Subwoofer in/out
Level adjustment for number of subwoofers
12V trigger switching for surround mode
3 adjustable parametric equalisers
2x ø250mm (10 in) carbon fibre/rigid foam sandwich cone bass
Frequency Range
Frequency Response
Dispersion
-6dB at 26Hz and 40kHz (monopole mode)
-6dB at 26Hz and 22kHz (dipole mode)
31Hz – 22kHz ±3dB on reference axis (monopole mode)
31Hz – 18kHz ±3dB power averaged over front hemisphere (dipole mode)
Inputs
Line In (RCA Phono)
12V trigger (3.5mm jack)
Monopole mode: within 2dB of reference response
Horizontal: over 40o arc
Vertical:
over 10o arc
Outputs
MF/HF Line Out (XLR & RCA Phono)
LF Line Out (XLR & RCA Phono)
Subwoofer Line Out (2 x XLR & RCA Phono)
12V trigger (3.5mm jack)
Dipole mode: horizontal figure of eight
Effective null zone ±30o (250Hz – 18kHz)
Sensitivity
93dB spl (2.83V, 1m)
Rated Power Consumption
Dimensions
10W
Harmonic Distortion
2nd and 3rd harmonics (90dB, 1m)
<1% 45Hz – 20kHz
Height:
Width:
Depth:
44.5mm (1.75 in) 1U
483 mm (19 in)
356 mm (14 in)
Nominal Impedance
Crossover Frequency
8Ω (minimum 4Ω)
300Hz and 4kHz (monopole mode)
300Hz (dipole mode)
Net Weight
Finish
8kg (17.6 lb)
Facing plate: Anodised Aluminium
Chassis: Black
Recommended Amplifier Power
Max Recmmended Cable Impedance
Dimensions
50W – 1000W into 8Ω on unclipped programme
0.1Ω
Height:
Width:
Depth:
1100mm (43.3 in) (without spike feet)
325mm (12.8 in)
250mm (9.85 in)
Weight
Finish
75kg (165 lb)
Cabinet: Black
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UK Group (UK Sales)
T +44 1903 221 500
Copyright © B&W Group Ltd. E & OE
B&W Group Ltd
Dale Road
Worthing West Sussex
BN11 2BH England
Kevlar is a registered trademark of DuPont
Rohacell is a registered trademark of Röhm GmbH
B&W Group North America
T +1 978 664 2870
T +44 (0) 1903 221 800
F +44 (0) 1903 221 801
Printed in Canada.
B&W Group (Asia) Ltd
T +852 2 869 9916
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