Setting the Acoustic Space Switch
The Acoustic Space switch is a 3-position switch used to select the "Acoustic
Space" in which the speaker is placed—Half Space (speakers against wall, 0dB
position), Three-Quarter Space (speakers in corners or close to wall, -2dB
position), or Full Space (speakers away from wall, -4dB position). The benefits of
using this switch are explained in the following paragraphs.
The bass response of any loudspeaker will differ depending on its placement. If
the speaker is placed close to a wall, the bass will sound louder than when it is
placed on a speaker stand. The technical term for this phenomenon is called
Diffraction Spreading and can be explained as follows:
Below a certain frequency, the sound emitted from a speaker begins to change
its polar radiation pattern, from 180 degrees to 360 degrees.With the speaker
placed close to a wall, its energy can be physically radiated only forward, thereby
limiting the radiation polar pattern to 180 degrees.When the speaker is placed
on a stand, the low-frequency energy is free to radiate in 360 degrees. While
there is a theoretical difference of about 6dB in low-frequency response
between these two placements, the loss (from the wall placement to the speaker
stand placement) is, in practice, normally found to be about 4dB.
Note: At medium and high frequencies, Diffraction Spreading losses do not
occur because the front baffle of the speaker affects low-frequency energy
radiation much like a large area (like a wall). So at medium and high
frequencies, the radiation pattern is always limited to 180 degrees.
The Acoustic Space switch compensates for (Diffraction Spreading)
low-frequency loss by introducing a complimentary correction filter with the
three filter settings (0dB, -2dB and - 4dB) and allows you to place the BX5
speakers close to a wall, on speaker stands, or somewhere in between these two
(such as on a small table top) with the same resulting low-frequency output
produced from each placement.