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.
