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Excellent coverage of a wide variety of room types can be accomplished using JBL's CBT Line Array Column
Loudspeakers. This guide shows some starting-point examples of placement, aiming and resulting
performance of the various CBT models in a variety of simplified sectional-view examples. There are 16
simulations in total, comprised of 4 examples of room-size / seating-plane scenarios.
These simulations allow you to compare the 4 CBT models (3 full-range models plus the CBT 70J+70JE
combination) and their settings as to:
•
Overall SPL capability.
•
Evenness of coverage.
•
Consistency of SPL.
•
Consistency of Frequency Response at various distances.
•
How much sound goes outside the audience area.
Understanding the Charts:
SPL Map
All SPL maps use the same colors for the
same absolute levels, allowing SPL
comparison between various simulations.
SPL Range Arrows – The SPL range of the
microphone locations (at 4 kHz) is shown by
the arrows on the SPL chart to the right of
the SPL Mapping.
Frequency -- The frequency shown in the
SPL mapping in this guide is 4 kHz, which is
an especially challenging frequency at which to achieve acceptable coverage.
Power Drive Level & Air Absorption -- The SPL level represents the speaker as driven at full rated power
(in low-impedance, for those models that are selectable between low-impedance and 70V/100V taps).
Also note that air absorption, which in the real world reduces the high frequencies reaching the farther
areas of the room, IS included in these simulations, so this is representative of real-world SPL levels.
Frequency Response
At Multiple Points: The examples where
there are three mics represent Close, Mid,
and Far seating points. All are shown in
the SPEECH position and no external EQ
equalization is being utilized. Of course,
the speaker can be set in MUSIC (Flat)
position, and/or the frequency response
can be further EQ'd externally.
Speaker Models Shown -- In the first application example (Example #1 – Flat Listening Plane) ALL CBT
speaker models and all settings are included. The subsequent examples, (Examples #2, #3 and #4) show only
those speakers that would be primary selections for that particular application.
Room Sizes Shown – The first three examples (the first 13 simulations) are shown using the SAME room size
with a depth of 18 m (60 ft). This allows comparisons with only two variables – seating plane and speaker
type – being changed (one at a time), however CBT's may be used in larger spaces.
Therefore, Example #4 (the last 3 simulations) shows a substantially larger room size with a depth of 38 m
(125 ft). Note that even though the graphs are shown as the same size on the page, the room size in the #4
example is a much larger room, illustrating that CBT's can indeed be utilized in large rooms, depending on the
SPL requirements of the application.
CBT Quick Start Guide 3
Red = Close Seating
Blue = Mid Seating
Green = Far Seating
SPEECH Setting Raises
SPL in this region.
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