SmartSMS User Manual
Soft dB inc.
User Manual
p. 92
Condition
Ceiling Height
Plenum Height
spk distance
Coverage (sqft)
Low Ceiling/Low plenum
8
1
13
169
Low Ceiling/high plenum
8
4
16
256
Normal Ceiling/Normal Plenum
9
3
16
256
High Ceiling/Low Plenum
10
1
13
169
High Ceiling/High Plenum
10
4
18
324
Special Situations:
Surface Speakers: In the case of surface-mounted speakers, speakers can generally be installed
at a distance equal to the ceiling height plus two feet. So on a 9 foot ceiling, surface speakers can
be installed 11 feet apart.
Fiberglass Tiles: Some ceiling tiles made of fibreglass have very low transmission loss. This can
creates hot spots right below the speakers. We recommend reducing the normal distance between
speakers by 2 feet when fibreglass tiles are used.
Very High Plenum: When the plenum is exceptionally high, (more than 6 feet), if you need to
constrain the sound to a more or less specific location, we suggest installing the speakers facing
down, 4 feet above the suspended ceiling. Otherwise, if the speakers are facing up, the sound will
“escape” everywhere and you will lose the ability to adjust the sound level locally. Coverage should
be approximately the ceiling height plus 5 feet.
Figure 86: Speakers facing down with very high plenum
Insulation on deck or tiles: In some cases, a layer of fibreglass or rockwool insulation is installed
on top of the ceiling tiles to improve sound transmission loss and absorption in the plenum. This
layer will increase the sound transmission loss of the ceiling tiles and result in a reduced sound
level in the room. To ensure a sufficient level in the room, we recommend setting the speaker’s
rotary switch to the highest levels, either 2 watts or 4 watts.
