Specifications

Learning Spaces Guidelines
AV & Teaching Station: 21
Microphones in teaching spaces provide signal input to some or all
of the following:
Assistive listening system e.g. induction loop (see Section
2.09)
Vocal sound reinforcement
LectureCast (see Section 3.12)
If any of the above three systems are present in a teaching space
then a suitable microphone system should be deployed. The most
suitable type of microphone system to deploy in a particular space
will depend upon the following variables:
the size of the space
the ceiling height above the ‘teaching zone’
the opportunity to install microphone cables running from
the teaching station to ceiling locations
Different microphone solutions for different categories of spaces
are detailed in the relevant sections of these guidelines.
The selection of audio amplifiers and loudspeaker systems should
take into account the size, acoustic properties and intended
usage of a space. Appropriate placement of loudspeakers is as
important as the correct choice of loudspeaker. As a general
principle loudspeakers should not be located in room corners as this
negatively impacts the amount of direct vs. reflected sound the user
will experience.
Another general principle is that it is better to have multiple
loudspeakers working at lower volumes than it is to have only a
single stereo pair at the front having to be driven loud.
Audio amplifiers for learning spaces should be specified such that
in normal use they are never being used at beyond 70% power
to ensure there is sufficient ‘clean’ headroom before distortion or
clipping.
Different types of amplifier/loudspeaker systems exist:
Stereo pair (typically on the teaching wall) – the simplest
system comprising of a two channel power amplifier and a
pair of individually connected loudspeakers. This solution
is only suitable for small spaces but can offer better stereo
imaging and high audio quality.
Multi-channel speaker system – this will require either
a four or six channel amplifier or a number of separate
power amplifiers. In larger spaces this solution can have
the benefit of being able to apply a delay to the speakers
further away from the presenter to compensate for the time
the direct sound from the presenter (or more precisely the
loudspeakers at the front) takes to the reach the rear of the
space. In reality no teaching spaces are likely to need this
type treatment. However another advantage of a multi-
channel system is that the sound levels in different parts of
the space can be easily adjusted.
Constant-voltage speaker system – also known as a 100V
Line system. By using step up and step down transformers
TASK
Microphones
3.08
TASK
Amplifiers
and
loudspeakers
3.09