Abbingdon Music Research LS-77 Reference Class - Manual (Page 18)

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Appendix B - LS-77 OptiArray®
B.1 Introducing AMR's OptiArray® scalable acoustic system
Above and beyond the role of an exceptional quality midfield monitor, the AMR LS-77 is designed to form
the main element of the AMR OptiArray® scalable, modular loudspeaker system. The OptiArray® sys-
tem takes account of several basic acoustic facts.
i. The larger a room, the louder must a speaker play for a given sound level at the listening
position.
ii The larger a room, the more and to lower frequencies must the speaker directionality increase
to maintain the same ratio between direct sound (that of the recording - wanted) and indirect
sound (reverbrations in the room, - unwanted).
Large listening spaces invariably require more acoustic power applied to the air volume in the room to
excite the same amount of pressure change (a bottle of beer will nearly fill a pint glass, however in a large
bucket it will barely moisten the bottom), this much is quite obvious, so the need for more output from the
speaker as rooms get larger is simple and intuitive.
However, large listening spaces are invariably also less well damped, in an acoustical sense, than small
ones. This and the much longer dimensions with the thus increased delay between reflections lead to
much longer reverb times in the room. The room reverbrant field (that is sound radiated and re-radiated
by the walls, floor and ceiling) will interfere most crucially with the percieved space of the recording and
will secondarily often change the tonality of the sound as well.
For a striking example compare the sound of a portable radio in an equal size empty room and one well
furnished. In the empty room the sound will be clattery, echoy, phasey and indistinct as well as subjec-
tively too bright. In a normally furnished room with carpeted floor the sound will be much more natural.