Tannoy B475, Руководство пользователя

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9. Positioning
When a bass loudspeaker is used in an environment with boundary surfaces, its
placement affects its frequency response. When such effects are properly
understood, they can be used to great effect in producing the desired sound quality
without the aid of additional amplification.
Consider Figure 9a in the diagram below, here we see a loudspeaker in free field or
anechoic conditions. We measure its sound pressure level at a distance D, and refer
to this as our reference level, or 0 dB SPL.
If we now place a large reflective surface (i.e., a wall, ceiling or floor) next to the
loudspeaker, see
Figure 9b , the sound that is radiated towards the boundary is
reflected. As a result, the sound pressure level can increase by as much as 3 dB
(effectively doubling the available amplifier power). The loudspeaker is radiating its
power into half as much space, this is known as
half space loading . For each
additional boundary the SPL can increase by 3dB. Corner placement or eighth space
(
Figure 9d ) loading can increase a bass speaker’s efficiency by up to 9dB.
This effect is not the same at all frequencies. Loudspeakers are only essentially omni
directional at low frequencies (where the wavelength is large in comparison to the
loudspeaker). At high frequencies sound radiates in a more directional manner. We
can position full range loudspeakers next to a boundary in order to boost the lower
frequencies while the highs remain unchanged.
Coupling, or placing bass cabinets together will also increase bass output.
Figure 9a. Free-Field Figure 9b. Half Space
Figure 9c.
Quarter Space Figure 9d. Eighth Space