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.
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 ......................................................................
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.
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.
CBT Quick Start Guide 5 Example #1 -- Flat Listening Plane CBT 100LA in Broad Setting Trim Height = 4.
CBT Quick Start Guide 6 Example #1 -- Flat Listening Plane CBT 100LA in Narrow Setting Trim Height = 3.
CBT Quick Start Guide 7 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): 105 30 100 SPL Range 25 95 20 90 15 85 10 80 5 0 0 10 20 30 40 50 60 70 75 4 kHz Frequency Response (Full rated power, low-Z, speech setting, mic positions as designated above):
CBT Quick Start Guide 8 Example #1 -- Flat Listening Plane CBT 70J in Narrow Setting Trim Height = 3.
CBT Quick Start Guide 9 Example #1 -- Flat Listening Plane CBT 70J+70JE in Broad Setting Trim Height = 5.
CBT Quick Start Guide 10 Example #1 -- Flat Listening Plane CBT 70J+70JE in Narrow Setting Trim Height = 3.
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.
CBT Quick Start Guide 12 Example #2 – Highly-Raked Seating CBT 70J in Broad Setting Trim Height = 5.
CBT Quick Start Guide 13 Example #2 – Highly-Raked Seating CBT 70J+70JE in Broad Setting Trim Height = 5.
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.
CBT Quick Start Guide 15 Example #3 – Gentle Rake with Balcony CBT 70J in Broad Setting Trim Height = 4.
CBT Quick Start Guide 16 Example #3 – Gentle Rake with Balcony CBT 70J+70JE in Broad Setting Trim Height = 5.
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.
CBT Quick Start Guide 18 Example #4 – Three-Tiered Raked CBT 70J in Broad Setting Trim Height = 7.
CBT Quick Start Guide 19 Example #4 – Three-Tiered Raked CBT 70J+70JE in Broad Setting Trim Height = 7.
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.
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.
