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VTX B
15
| User Manual
10.1 RECOMMENDED SETUPS
B15 subwoofers can be used in a number of ground-stacked or flown cardioid configurations depending on available space and the
number of cabinets available. Cardioid configurations are typically differentiated by the ratio of front-facing to rear-facing cabinets, the
spacing between stacks, and the position of rear-facing subwoofers within the stacks. Since all configurations and ratios use the same
set of amplifier presets (e.g. VTX B15 80 REAR), the amount of rear rejection is controlled by the front-to-rear-facing cabinet ratio. Lower
ratios produce higher rejection, higher ratios result in lower rejection. The B15 factory presets were engineered to work with blocks hav-
ing
2:1
and
3:1
ratios, with 2:1 delivering the greatest rear rejection. Subwoofers arrays designed around a 2:1 ratio can easily generate
broadband rejection of 20 to 30 dB. These ratios can be considered as building blocks from which any ground-stacked or flown array
can be built.
10 - CARDIOID CONFIGURATIONS
The directivity of a subwoofer is understood to be omnidirectional, meaning that it projects energy equally in all directions. In reality,
most subwoofers do exhibit some front-to-back directivity (about 1 to 3 dB, depending on the frequency), but not enough to have any
meaningful impact. In some situations, the omnidirectional nature of subwoofers is desirable, but in others, a more controlled (direc-
tional) coverage is appropriate. The most common use case for directional subwoofers involves preventing excessive low frequency
energy from reaching the stage. Other directional subwoofer applications include avoiding over-energizing a room with low frequency
energy or minimizing noise pollution from outdoor concerts located near residential areas. A single VTX B15 radiates omnidirectionally,
but cardioid coverage can be achieved with an array of B15s in which the physical orientation of some cabinets is reversed and an
appropriate amplifier preset selected.
Example 1: 2:1
CAUTION: The level of the rear-facing subwoofers was carefully selected to allow B15 cardioid arrays to reach
maximum SPL without dynamically compromising low-frequency directivity, and should not be adjusted .
Example 2: 2:1
Example 3: 3:1
Example 4: 3:1
Summary of Contents for JBL Professional VTX Series
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