Cambridgeaudio r 40 owners manual

Page 1

R50

The Cambridge Audio R50 is :1 Monitor quality loudspeaker. It is imperative that the other
components in the chain of reproduction should be beyond reproach.

SPECIFICATION |
Dimensions : 41%" x 170/8" x 13H
Weight : 98 lbs (44. 4 kg)
Crossover frequencies : 400Hz, BkHz, 10kHz
Power rating : 25W continuous sine wave
50W music power
Drivers : K.E.F.: B139, B110, T27; STC: 4001G
Impedance : 8 ohms, nominal
Crossover network : Cambridge Audio Four - Port

The B139 low frequency driver is situated at the bottom of the unit; behind it is an 83" tapered
labyrinth, damped with long haired lambs' wool. The lowest frequency that it is capable of is
dependent upon the size of the listening room and underidcal conditions the response will extend
to below 25Hz. The plane diaphragm of the driver will be seen to respond to very low frequency
signals caused by turntable rumble - even if the turntable is perfect, rumble-free recordings
are exceptional.

The B110 mid range driver is situated above the B139. Behind itis a separate damped tapered
pipe which is vented via a porous plug immediately above it.

The T27 and 4001C pressure tweeters are mounted above the mid-range unit so that they are
at roughly the same level as the seated listener. Their melinex dome diaphragms are designed
to radiate over a wide angle so that directional effects are kept to a minimum.

The drivers are protected from accidental damage by a black grill composed of closely spaced
extruded sections. The grill has no effect on the dispersionof the sound as its dimensions are
small compared to the wavelength of the highest audible frequencies.

R40

The R40 speaker has been designed to match as nearly as possiblethe performance andgeneral
sound quality of the R50 within the limitations imposed by smaller size and lower cost, which
gives the speaker a wider application and makes it more convenient to house.
SPECIFICATION

Dimensions : 31 x 13" x 125

Weight ; 52 lbs (23.6 Kg)

Crossover frequencies : 400 Hz, 3 kHz

Power rating : 25 watts continuous sine wave, 40 watts music power
Drivers : KEF B139, B110, T27

Impedance : 8 ohms nominal

Crossover network : Cambridge Audio Three - Port

General

Maximumbass response will be produced in corner positions, or with thebacks of the speakers
flat to walls. Often, best results are obtained in corner positions by bringing the speakers
out about 1 ft. from the walls, but it will be necessary to experiment patiently both with the
positions and the angling of the speakers into the listening area in relation to the room and the
normal listening seats to obtain the best balance and stereo effect.

It should be noted that at frequencies above 5kHz, only the h.f. units (tweeters) are operative.
Consequently, high power continuous sine wave inputs at frequencies above 5kHz must not be
annliorl to tho P40 (17- 'Rfifle nr (lam-am: fn Han k F nan mu" mam-1+

Page 2

the drive units. The HMV disc "The Enjoyment of Stereo" provides a useful guide to listening
levels. It is not good policy to strive for heavy floor vibrating bass in small rooms. Eigen-
tones are generated, and the results are always unbalanced and unpleasing. It must always be
remembered that the listening room is effectively part of the loudspeaker. Amplifier bass and
treble controls are provided to enable small compensations in response to be made. Once
correctly set, they should seldom need to be touched unless the equipment, or the positions of
the loudspeakers are changed.

WIRING

Peak currents of several amperes will flow in the loudspeaker cables, so that they should be
kept as short as possible, and should have a large current carrying capacity. 23/. 0076 cable
or heavier is recommended.

PHASING

Loudspeakers arranged for stereo reproduction must be connected so that their outputs are in
phase.

If you are equipped with aTest record, for example the Hi Fi Sound test disc, HFS 69, you
will have no problem, for various bands are devoted to channel identification and phasing. If
you are not so equipped, arrange the speakers to face each other about ten inches apart and
try reversing the connections to one speaker. The correctly phased connection is the one in
which the bass sounds fullest.

In the normal course of events, connecting the signal lead to the terminal marked with a red
dot on both speakers will result in correct phasing. (The convention is that if the positive
terminal of abatteryis connected to the positive speaker terminal, the speaker cone will move
outwards.) It is worth checking, for it is not unknown for cartridges to be connected incorre-
ctly in headshells and so forth.

DAMPING FACTOR

The damping factor is defined as the ratio of speaker impedance to the outputimpedance of the
amplifier; it is a measure of the amount of control that the amplifier can exercise over the
excursions of the speaker cone. The amplifier output impedance must be taken to include the
resistance of the loudspeaker plug and socket, and the impedance of the loudspeaker wiring.
Valve amplifiers achieved a damping factor of about 10 into 8 ohm loudspeakers and modern
transistor amplifiers give about 20. We have paid particular attention to this parameter, and
the Cambridge Audio P series amplifiers achieve a factor of not less than 80 into 8 ohm loud-
speakers.

ROOM ACOUSTICS

The dimensions and reverberation time of alistening room will have a considerable effect upon
the performance of any speaker Within it.

The optimum dimensions are in the ratio of 1(H) : 1. 6(W) : 2. 5(L). Avoid using rooms with a
square floor plan and a high ceiling. The lowest frequency capable of reproduction within a
room depends upon its greatest dimension~for example, a 30Hz signal cannot be generated in
a room with a dimension of less than 37 feet.

The optimum reverberation time (defined as the time required for a sound to decay to 60dB
below itsoriginal level) for aroom intended for music Iisteningis about 0.75 seconds at 512Hz.
The response of a loudspeaker is drastically modified if the listening room has any pronounced
resonances - the apparent reverberation time for frequencies near the resonant frequency can
be several seconds. Transients cannot die away. cleanly and any prolonged excitation will
result in standing waves, that is, alternate regions of high and low intensity at the resonant
frequency. Also, low level unwanted signals such as turntable rumble and hum may become
intensified in some regions.

Bulky sound absorbing furniture such as sofas and padded arm chairs, pile carpeting and heavy
curtains should alleviate these effects.

The placement of the loudspeakers and the angle at which they face into the room is a matter
for careful experiment. It will probably take a week of careful listening and adjustment each
dayto locate them finally. No attempt should be made to hurry the process, the same listening
material should be used in each fresh position, and it must be remembered that suits small