About JBL VRX900 Series Line Arrays
Line arrays are acoustical sources placed closely together in a straight line. For practical reasons drivers are placed in enclosures which are configured vertically.

An advantage of a very large line array is that the sound level drops at about 3 dB per distance doubling. Conventional speaker level drops at 6 dB per distance doubling. This effect is frequency dependence, the longer a line arrays is the more of this desired effect will take place.

VRX900 line arrays benefit from some of these effects, but since they are small and compact, the results are not as pronounced. Each cabinet houses a curved waveguide with multiple HF drivers. They are set to a vertical angle of 15° and can be combined together to achieve the desired coverage. Line arrays like JBL’s VERTEC® can be configured to focus energy to reach distant areas by mechanically designating a straight portion (usually the top) of the hanging line array vs. a curved section (usually the end closer to the audience) which will result in less focused energy.

Since VRX900 does not provide the option of mechanically manipulating the angles between the cabinets, it has an ACS (Amplitude Configuration Selector ) built in. The technique is called Amplitude Shading or Gain Shading and allows the adjustment of the HF levels for each cabinet. When the ACS system is correctly set, a very homogenous sound field can be achieved. The level in front of the stage (ACS = -3 dB ) will not be excessively loud. The far-reaching areas (ACS = +3 dB ) will have adequate sound levels. Since the levels near the stage are lower in comparison to a conventional loudspeaker system, microphone feedback problems will be minimized.

Another advantage of line arrays are that their vertical directivity is high. This means that the sound can be aimed directly at the audience and the room acoustics will have less impact on the final listening experience. The sound operator has more control.