Quick Start Guide
for Sound System Designers
JBL CBT Series
Constant Beamwidth Technology™ Column Loudspeakers
(Note: Some models shown with the included grilles removed to illustrate driver composition.)
Rev A3
CBT Quick Start Guide 2
CONTENTS
Introduction .................................................................................................................... 3
• Understanding the Charts
o SPL Maps
o Frequency Response Charts
• Room Sizes Shown
Example #1 – Flat Listening Plane
CBT 50LA ..................................................................................................................... 4
CBT 100LA in Broad Setting ........................................................................................... 5
CBT 100LA in Narrow Setting ........................................................................................ 6
CBT 70J in Broad Setting ............................................................................................... 7
CBT 70J in Narrow Setting .............................................................................................. 8
CBT 70J+70JE in Broad Setting .................................................................................... 9
CBT 70J+70JE in Narrow Setting .................................................................................. 10
Example #2 – Highly Raked Seating
CBT 100LA in Broad Setting .......................................................................................... 11
CBT 70J in Broad Setting .............................................................................................. 12
CBT 70J+70JE in Broad Setting .................................................................................... 13
Example #3 – Gentle Rake with Balcony
CBT 100LA in Broad Setting .......................................................................................... 14
CBT 70J in Broad Setting .............................................................................................. 15
CBT 70J+70JE in Broad Setting .................................................................................... 16
Example #4 – Three-Tiered, Raked, Large Room
CBT 100LA in Broad Setting .......................................................................................... 17
CBT 70J in Broad Setting .............................................................................................. 18
CBT 70J+70JE in Broad Setting .................................................................................... 19
Design Conclusions ...................................................................................................... 20
• Vertical Coverage Setting vs. Installation Height
• Single vs. Multiple CBT Columns
o For Width
o For Depth
• Front Fill
• How Far Each CBT Model “Throws”
CBT Quick Start Guide 3
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
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.
Red = Close Seating
Blue = Mid Seating
Green = Far Seating
SPEECH Setting Raises
SPL in this region.
CBT
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 4
Example #1 -- Flat Listening Plane
Description -- This is the most basic of rooms. All four CBT models are shown, as well as both
“Broad” and “Narrow” vertical coverage settings for those models that have the switchable
coverage capability (CBT 100LA & 70J)
Listening Plane = 1.2 m (4 ft) above the floor
Mic Placement = 6.1 m (20 ft, red icon), 10.7 m (35 ft, blue icon) and 16.8 m (55 ft, green icon)
CBT 50LA
Trim Height = 3.4 m (11 ft, Top of Speaker)
Down Tilt = 10°
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
SPL Range
4 kHz
Example #1 -- Flat Listening Plane
CBT 100LA in Broad Setting
Trim Height = 4.9 m (16 ft, Top of Speaker)
Down Tilt = 15°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
20
CBT Quick Start Guide 5
105
100
SPL Range
95
15
10
5
0
0 10203040506070
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
110
100
90
80
70
20 50 100 200 500 1k 2k 5k 10k 20k
Example #1 -- Flat Listening Plane
CBT 100LA in Narrow Setting
Trim Height = 3.4 m (11 ft, Top of Speaker)
Down Tilt = 10°
Vertical Coverage Setting = Narrow
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
20
CBT Quick Start Guide 6
105
100
SPL Range
95
15
10
5
0
0 10203040506070
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #1 -- Flat Listening Plane
CBT 70J in Broad Setting
Trim Height = 4 m (13 ft, Top of Speaker)
Down Tilt = 5°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 7
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #1 -- Flat Listening Plane
CBT 70J in Narrow Setting
Trim Height = 3.7 m (12 ft, Top of Speaker)
Down Tilt = 5°
Vertical Coverage Setting = Narrow
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 8
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #1 -- Flat Listening Plane
CBT 70J+70JE in Broad Setting
Trim Height = 5.5 m (18 ft, Top of Speaker)
Down Tilt = 10°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 9
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #1 -- Flat Listening Plane
CBT 70J+70JE in Narrow Setting
Trim Height = 3.7 m (12 ft, Top of Speaker)
Down Tilt = 5°
Vertical Coverage Setting = Narrow
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 10
105
SPL Range
100
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
CBT Quick Start Guide 11
Example #2 –Highly-Raked Seating
Description – This example is somewhat typical of venues such as lecture halls, performance spaces,
and auditoriums. Shown are the CBT 100LA, CBT 70J and the CBT 70J+70JE combination. All are
set at the Broad Vertical Coverage setting.
Listening Plane = Rise of 4.9 m (16 ft) in 15.2 m (50 ft) of depth, beginning 1.2 m (4 ft) above the
floor.
Mic Placement = 6.1 m (20 ft, red icon), 10.7 m (35 ft, blue icon) and 16.8 m (55 ft, green icon) in room
depth.
CBT 100LA in Broad Setting
Trim Height = 4.3 m (14 ft, Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
105
30
100
25
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
SPL Range
Example #2 – Highly-Raked Seating
CBT 70J in Broad Setting
Trim Height = 5.5 m (18 ft, Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 12
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #2 – Highly-Raked Seating
CBT 70J+70JE in Broad Setting
Trim Height = 5.8 m (19 ft) (Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 13
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
CBT Quick Start Guide 14
Example #3 –Gentle Rake with Balcony
Description – This example is also common for performance spaces and auditoriums. Shown are the CBT
100LA, CBT 70J and the CBT 70J+70JE combination. All are set at the Broad Vertical Coverage setting.
Listening Planes = Main: Rise of 0.6 m (2 ft) in 9.1 m (30 ft) of depth, beginning 1.2 m (4 ft) above the floor.
Balcony: Rise of 1.5 m (5 ft) in 7.6 m (25 ft) of depth, beginning 4.6 m (15 ft) above the original floor.
Mic Placement = 6.1 m (20 ft, red icon) and 11.6 m (38 ft, blue icon) on main seating; 10.7 m (35 ft, green
icon) and 16.8 m (55 ft, pink icon) on balcony.
CBT 100LA in Broad Setting
Trim Height = 4.3 m (14 ft, Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
105
30
100
25
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
SPL Range
Example #3 – Gentle Rake with Balcony
CBT 70J in Broad Setting
Trim Height = 4.6 m (15 ft, Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 15
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
Example #3 – Gentle Rake with Balcony
CBT 70J+70JE in Broad Setting
Trim Height = 5.2 m (17 ft, Top of Speaker)
Down Tilt = 0°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
30
25
CBT Quick Start Guide 16
105
100
SPL Range
20
15
10
5
0
0 10203040506070
95
90
85
80
75
4 kHz
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
CBT Quick Start Guide 17
Example #4 –Three-Tiered Raked, Large Room
Description –This is a larger room with a depth of 39.6 m (130 ft). The room could represent a venue
with dual balcony or it could represent an auditorium with a front section having a gentle rake and
a back having a steeper rake. Shown are the CBT 100LA, CBT 70J and the CBT 70J+70JE
combination. All are set at the Broad Vertical Coverage setting.
Listening Plane = Three tiers
Mic Placement = 7.6 m (25 ft, red icon) and 19.8 m (65 ft, blue icon) on main seating; 22.9 m (75 ft,
green icon) and 32 m (105 ft, pink icon) on middle seating plane; the rear of the back seating plane
at 38.1 m (125 ft, light-blue icon).
CBT 100LA in Broad Setting
Trim Height = 4.3 m (14 ft, Top of Speaker)
Down Tilt = 5°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
105
60
40
20
0
0 40 80 120 160
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
100
95
90
85
80
75
4 kHz
SPL Range
Example #4 – Three-Tiered Raked
CBT 70J in Broad Setting
Trim Height = 7.6 m (25 ft, Top of Speaker)
Down Tilt = 5°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
CBT Quick Start Guide 18
105
60
40
20
0
0 40 80 120 160
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
100
95
90
85
80
75
SPL Range
4 kHz
Example #4 – Three-Tiered Raked
CBT 70J+70JE in Broad Setting
Trim Height = 7.6 m (25 ft, Top of Speaker)Down Tilt = 5°
Vertical Coverage Setting = Broad
SPL
(Full rated power, low-Z, SPEECH setting, 4 kHz, scale in feet):
CBT Quick Start Guide 19
105
60
40
20
0
0 40 80 120 160
Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
100
95
SPL Range
90
85
80
75
4 kHz
CBT Quick Start Guide 20
Design Conclusions
Vertical Coverage Setting vs. Installation Height – In general, when the CBT speaker is set to the
Narrow vertical coverage setting, the speaker tends to cover best when installed fairly low and angled at a
fairly narrow down-tilt angle in relation to the seating plane.
Note that this mounting height may still be higher than is typically used with other competitive ‘column’
type loudspeakers which often exhibit a narrowing of the vertical beamwidth as the frequency range
increases. By comparison, the CBT Series products maintain a much more even vertical beamwidth,
allowing for more even coverage of the entire audience area.
When the speaker is set to the BROAD vertical coverage setting, it often results in best coverage with the
speaker installed higher and then angling at a steeper down-tilt angle.
Single vs. Multiple CBT Columns – These examples show sectional views of the venues as being
covered by a single CBT loudspeaker, but multiple speakers may be required.
• For Width -- Excellent coverage results can be achieved across the width of most rooms with CBT
speakers allowing expanded left to right placement given the CBT’s wider horizontal coverage
pattern, more so than is typically expected with conventional speaker systems. However, multiple
CBT’s may be needed to cover the width of a room, so a horizontal coverage assessment via a
plan-view should be done.
• For Depth -- It may be advisable to cover balconies or rear seating areas with a second CBT (or
other speaker). The second CBT may be mounted much higher up on the same front wall and set
at its Narrow vertical coverage setting to throw farther. Or, it may be positioned farther back in the
room – closer to the listeners – and delayed to synchronize with any arrival from the front/main
speaker (or with as much additional delay to keep localization to the front speaker, if that is desired
in the application). In this case, the delay speaker would usually be set to the Broad coverage
setting because it is closer to the listeners.
The designer needs to determine the acceptability of time-offset vs. SPL for any overlap areas.
An example of a venue where multiple speakers would be advisable would be a room where there
could be an issue with reflection from the front of a balcony. Using a second speaker with each
focusing sound on its own listening plane could reduce the amount of sound being sent to the frontof-balcony surface and thereby reduce the amount of sound that is reflected from it back to the
stage (or to seats in the front, which could cause time-smear issues for those listeners).
Front-Fill – While the CBT columns do an admirable job of covering much of the seating area from a
single speaker, it may be worthwhile to add some front-fill speakers to cover front corners of the listening
space. In addition, it may also be useful in some cases to aim the speakers slightly higher or to change
to the Narrow coverage mode and add some mid-high front-fill speakers to cover the first few rows.
This can be a useful technique for further reducing sound reaching a stage area.
CBT Quick Start Guide 21
How Far Each CBT Model “Throws” – Speaker “throw” has many possible definitions, some of which
require knowledge of venue-specific factors, such as acoustics, seating plane particulars, or SPL
differences between one listening location and another.
One speaker-specific definition of “throw” would be the distance at which the speaker can project a useful
sound level. Using that definition, following are the farthest distances at which each model (in each
combination of Vertical Coverage and Voicing settings) can produce a continuous level of 85 dB (peaks of
91 dB).
85 dB Distance Chart
CBT 50LA
CBT 100LA
CBT 70J
CBT 70J+70JE
Vert.°
40°
45°
45°
(low-Z, full rated power, pink noise, 85 dB-SPL at 4 kHz octave band)
BROAD Setting
Music Mode Speech Mode
30 m (100 ft) 46 m (150 ft)
40 m (130 ft) 64 m (210 ft)
40 m (130 ft) 64 m (210 ft)
Vert.°
Music Mode Speech Mode
20°
15°
25°
25°
18 m (60 ft) 27 m (90 ft)
37 m (120 ft) 55 m (180 ft)
52 m (170 ft) 67 m (220 ft)
52 m (170 ft) 67 m (220 ft)
NARROW Setting
This stimulus signal for this chart is 1/3rd octave pink noise centered at 4 kHz at full rated power. This
frequency band is utilized in this chart because it is a challenging range to “throw” long distances yet is
important for articulation, speech intelligibility and musical clarity. 4 kHz also standardizes with the SPL
Maps throughout this Guide.
The distances listed take into consideration the natural attenuation of sound due to air (22°C/72°F, 50%
humidity) – otherwise the distances listed would be even farther.
It should be noted that it may not be advisable to throw these distances if there are also listeners at very
close distances, because levels for the near audience areas may be louder tha n a normal comfort level.
It may also be noted from the chart that while CBT 70J + 70JE produces greater low frequency SPL and
extended bass response, the mid-range throw is the same as the 70J by itself.
Applications Assistance -- More CBT applications assistance is available at JBL Professional’s website
www.jblpro.com
or by calling JBL Pro installed-sound technical assistance (818) 894-8850.
CBT QSG 04/10
RK/DB/JF
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