Hammond Model A, Manual, Page: 57 / 298

DISTRIBUTION
The sound energy from the organ should be distributed as evenly as possible
throughout the enclosure. In order that this may be accomplished, it
is important
that the sound be distributed in the auditorium above the listeners and that a large
percentage of the sound reaching the listener is by numerous reflections from the
walls and ceiling. Direct projection as well as direct reflection from the speakers
should not reach the listener. Focusing effects of curved surfaces such as barreled
ceilings often cause difficulty in sound distribution unless the tone cabinet is so
located as to reduce the direct sound energy that reaches these surfaces.
It must be remembered that although sound is reflected in a manner similar to light,
the reflecting surface must be large in relation to the wave length of the sound.
Therefore, a reflecting surface of a given size will reflect sounds above a certain
frequency, while sounds of lower frequency will be diffracted or spread out. To
reflect fully the lower tones of the organ a reflector thousands of square feet in
area is necessary. This, together with the fact that different materials absorb
sounds of certain frequencies more than others explains why identical tone colors
produced in different enclosures will sound very different to the ear.
BALANCE
The placement of console and tone cabinets should be carefully planned so that the
following conditions are fulfilled:
1. The organ should sound as loud or slightly louder to the organist at the console
than it does to the audience. This allows the organist to accurately judge the
musical effect he is producing and make any necessary corrections before the
audience appreciates the need for them.
It
also reduces
the
tendency of playing too
loud which is usually evident when the organist hears the organ at a lower level
than the audience.
2.
The organist should hear the organ and the choir with the same relative loudness
that the audience hears them, otherwise a perfect tonal balance between organ and
choir from the organist's point of hearing will result in an unbalanced effect as
heard by the audience. When we refer to the choir we also include instrumental
groups or soloists who may have occasion to perform in conjunction with the organ.
3.
The tonal equipment of the organ should be so located that the choir, while
singing, has adequate support from the organ when played at accompaniment volume.
They should not, however, hear the organ so loudly as to have difficulty in singing
with
it.
Good tonal balance and ease of performance should result if the average
distance between choir and tone cabinets is about the same distance as between tone
cabinets and organist.
4.
The audience should hear the choir and the organ as a balanced ensemble, and
the tone cabinets should be so placed that the choir voices will not be obscured by
the organ tones.
REVERBERATION
Reverberation is the prolongation or persistence of sound by reflection, what we
usually mean by
echo. It is measurable by
the
interval
of
time required for the
sound to decay to inaudibility after the source of the sound has been stopped. It is
present in a varying degree in all enclosures and most types of music are more
pleasing to
the
ear when accompanied by a certain amount of reverberation.
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