A speech reinforcement system may be divided into various sections:
Each section has several important criteria all of which must be satisfied before a final choice may be made. Choices in each section affects the available choices in the other sections. The microphones and loudspeakers must be pleasing to the eye, be positioned correctly and be compatible with the mixer/amplifier. The mixer/amplifier must be adequate for present and future requirements.
The choice of microphone is as important as
the choice of loudspeaker. A speech reinforcement system is only
as good as the signal it receives. To achieve a quality signal
it is important to position microphones in every position from
which any person talks during a service. Uniformity in microphone
type is also a good idea to reduce the sublte differences heard
between different microphones.
The loudspeaker is probably the most visible
part of any Speech Reinforcement system and therefore the choice
of loudspeaker is fundamental to the production of a satisfactory
system. Large buildings with minimal soft furnishings, emphasise
the low frequencies and increase reverberation time, ie. prolong
the duration of sounds, both of which reduce the intelligibility
of speech. In a well designed system the loudspeaker signal should
only go where it is needed, into the congregation, and not into
the roof void to add to the reverberant field. The use of high
quality directional loudspeakers helps to send the reproduced
sound to the correct places. Bridge Microphones almost exclusively
uses cardioid column loudspeakers as these not only blend in well
with the majority of architectures but also have very accurate
reproduction and dispersal patterns. Column loudspeakers are designed
primarily for speech reproduction, but if the system is to be
used for live or foreground music then a more music orientated
speaker must be selected. Several manufacturers have produced
loudspeakers which have many of the features required by speech
systems but also incorporate most of the music requirements. Column
loudspeakers are generally 100volt line units, the high voltage
helps to reduce the signal loss caused by long speaker cable runs,
whereas music speakers are generally low impedance, 8ohms. Again
this affects the choice of amplifier which may be used.
The choice of microphone is important both from the aesthetic point of view and from the effectiveness to pickup all the required signal, no system can successfully amplify a poor signal. Every location in the church, from which a person will speak, must be covered by a suitable microphone. Uniformity in microphone type helps to produce a more pleasing system, both visually and acoustically. Good quality directional microphones will provide a clear distortion free signal with a minimum of background noise and help to avoid undesirable feedback. Balanced microphones should always be used to reduce the possibility of external; interference, from local radio transmitters and electrical switching affecting the system. Many modern, quality microphones require 'Phantom Power' to be supplied by the mixer to power the microphone circuitry, as this is not available from all mixers, this will again affect the choice of mixer/amplifier. Radio microphones can often reduce the number of required fixed microphones and will produce a very flexible system allowing totally free movement for the user. It is essential that a suitably DTI approved system is used.
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The heart of the system is the mixer/amplifier. This may take the form of either two discrete pieces of equipment, mixer and amplifier, or it may be a single integrated unit. The latter being more common in speech only systems. It is very important that the inputs are balanced as this reduces the possibility of external interference, see Microphones above. Most modern microphones will require the use of phantom power, where power to drive the microphone circuitry is taken from the amplifier so doing away with extra battery packs etc. A simple bass and treble control with individual volume controls is sufficient for a speech only system, but more elaborate equalisation may be desirable for a combined music and speech system. the positioning of the amplifier is an important consideration. Although for speech only systems there is little need for adjustments during a service, it is still worth considering positioning the mixer/amplifier within or behind the congregation area. This means that should any adjustment be required then the effect of the adjustments will be heard immediately. Under certain circumstances some simple speech only systems may be operated with the mixer/amplifier in a vestry or similar, in these cases a single volume control should be fitted at the back of the church.
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To complete a speech reinforcement system, consideration should be given to incorporating an Audio Frequency Induction Loop System (AFILS). This system assists the hearing aid user by transmitting the sound directly to the hearing aid so reducing any background noise and distractions. The amplifier feeds its signal into a single thin wire fastened to the walls of the church, so giving coverage over the entire building. It is obviously very important that when designing a Loop System, that all service leaders are covered by a microphone. Compatibility/suitability is again important. A loop amplifier is more than a simple PA amplifier. The induction loop amplifier uses current rather than voltage as the drive, it also uses several compression and dynamic range reducing circuits to improve the signal for final processing by a hearing aid. All this is invisible to the hearing aid user who simply switches their aid to the 'T', telecoil, position and continues to listen as normal. An induction loop system may be added to an existing system or designed as part of a new installation. All equipment used passes all the relevant British Standards and RNID recommendations.
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A full range of products may be obtained through Bridge Microphones, from handheld microphones to Radio Microphones, from cardoid column loudspeakers to music or extension crèche speakers. Mixer/amplifiers from integrated speech systems to mixing desks and high power amplifiers.
A complete service is provided from initial free consultation and system design to installation and commissioning, including preparing papers for submission to Diocesan approvals board or similar.[Return to top of page]
If you have any questions about Bridge Microphones or any of