JBL Control 24C Micro Application Manual Download Page 4

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This Technical Application Guide is intended as an adjunct to the Owner’s Manual that comes with the JBL
Control Contractor ceiling speaker.   The intent is to assist sound system designers – from the new designer
to the experienced systems contractor – to design superior distributed system installations utilizing JBL
Control Contractor Ceiling Speakers.

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JBL DISTRIBUTED SYSTEM DESIGN is a software utility from JBL Professional that calculates
and displays speaker spacing and positioning of Control Contractor ceiling speakers within a rectangular
room.  Several acoustical calculations are also made and the resulting document  can be saved and printed.
The computations are based on actual measurements of these loudspeakers, yielding results that closely
reflect actual performance of these loudspeakers within the listening space.

Many of the calculations contained in this application guide are provided in the DSD software.  It is a
convenient way to make many of these design considerations and simulate what the performance will be
for various possible design iterations.

The program can be downloaded from the JBLPRO.COM website or obtained from JBL Professional on
diskette.

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The goal in placing loudspeakers in a distributed system is to cover the area effectively, where the sound is
audible and intelligible over the entire area, and where the system is capable of sustaining the required
sound pressure level for the application type.

Understanding Coverage

The JBL Control Contractor Ceiling Speakers are designed to provide extremely even coverage on a
broadband basis over a wide coverage area.  A misunderstanding of the coverage angle specifications can
easily result in mistakes being made in system designs.  The COVERAGE ANGLE is defined as the
included angle at which the sound level is 6 dB down from the on-axis sound level.   The coverage angle on
the listening plane is an important figure for the coverage density computations used later in this guide.

Polar vs. Listening-Plane Coverage Specifications:  There are two different types of coverage
measurements which are often confused with each other.  It is standard in the loudspeaker industry to
state the coverage in a “polar” pattern – in other words, in a sphere that is 1 meter from the microphone
in all directions.  The angle within which the sound levels is within 6 dB of the on-axis level is called
the POLAR coverage pattern.  This is a legitimate specification, but does NOT represent what the
coverage will be over a flat listening plane, such as in a room.  For speakers projecting from a ceiling
onto flat listening plane, the sound has to travel farther off-axis (to the sides) than it travels on-axis
(directly below the speaker) resulting in a much greater drop-off of sound level off-axis.  The end result
is that the actual coverage angle on the listening plane is more narrow than what is claimed.  Some
ceiling speaker manufacturers use their POLAR measurement to claim extraordinarily wide coverage.
DO NOT use this specification to lay out coverage patterns of ceiling speakers!!!

Summary of Contents for Control 24C Micro

Page 1: ...Control Contractor Ceiling Loudspeakers 7HFKQLFDO SSOLFDWLRQ XLGH Rev A Mar 99 Rick Kamlet...

Page 2: ...Square and Hexagonal Patterns 7 Layout Density Factors Edge to Edge Minimum Overlap and Maximum Overlap 8 Considerations for Selecting Layout Density Additional SPL Due to Speaker Density Level Variat...

Page 3: ...C 26NC MTC 26MR Control 19CS 19CST MTC 19NC MTC 19MR 7DEOH XWRXW 6L HV Model Cutout Size diameter Control 24C 24CT 165 mm 6 5 in Control 26C 26CT 220 mm 8 75 in Control 19CS 19CST 305 mm 12 0 in RQQHF...

Page 4: ...pressure level for the application type Understanding Coverage The JBL Control Contractor Ceiling Speakers are designed to provide extremely even coverage on a broadband basis over a wide coverage are...

Page 5: ...can cover 140 degrees over the listening plane In fact the level at the edges of a 140 degree pattern is actually more than 15 dB down compared to on axis NOT 6 dB While the actual LISTENING PLANE co...

Page 6: ...gle is valid regardless of the ceiling height Example If we look at the polar plot of a hypothetical speaker with 140 coverage we see that at 70 off axis 140 total for both sides the level is down 6 d...

Page 7: ...etc can be vastly narrower at higher frequencies and broader at lower frequencies These types of speakers do not provide even coverage throughout the audio spectrum Every spot within the listening ar...

Page 8: ...26C 26CT 10 Ft 3 1 m Ceiling Height 6 dB coverage 14 ft 4 3 m 13 ft 4 0 m 14 Ft 4 3 m Ceiling Height 6 dB coverage 23 ft 7 0 m 21 ft 6 4 m 6RXQG 3UHVVXUH HYHO 63 Maximum Sound Level SPL Capability In...

Page 9: ...times the log of the POWER HANDLING spec plus the SENSITIVITY spec minus 4 dB minus 20 times the log of the DISTANCE from the speaker in meters Max SPL Table The following table shows the maximum con...

Page 10: ...sion We have left power compression out of the formulas because speakers differ in their power compression and because the degree of compression is highly dependent on operational factors such as the...

Page 11: ...hs or depths that would require about 1 2 of the speaker s coverage diameter By offsetting each row of speakers the end speaker in each row can fill in for the lack of speaker at the end of the adjace...

Page 12: ...speakers covering each area within the listening space In some cases substantial increases in SPL can be achieved from high densities The following chart provides the SPL ADDITION within the listening...

Page 13: ...ications where the audience is walking around such as in a retail or grocery store there may be slightly more of an expectation of variations in coverage Room Characteristics In any choice of coverage...

Page 14: ...or pink noise maximum continuous peak SPL maximum continuous average SPL for music speech expected level variation of the direct sound and recommended amplifier power for speakers placed in a rectangu...

Page 15: ...ive crossing over at an affordable price MTC X100 is a preset at 100 Hz 24 dB oct and the MTC XU is a universal crossover module with a wide selection of crossover frequencies These modules solder ont...

Page 16: ...y eliminating the overlap frequency bump in the mid bass region In this configuration the Control 19CS subwoofer takes a greater share of the low frequency burden so more subwoofers may be required Me...

Page 17: ...n cause damage or failure Setting SPL Target Goals While the JBL Distributed System Design DSD software or acoustic design programs like CADP2 or EASE can predict HOW the system will perform in the ro...

Page 18: ...60 Hz 320 Hz 480 Hz 640 Hz etc Depending on the resolution and bandwidth characteristics of your measuring device these can show up as various boosts and dips in your measurement bands These reflectio...

Page 19: ...in parallel to each channel of a 2 ohm capable amp By using a 2 ohm capable amp it is possible to connect a sixteen 16 speaker stereo system eight 8 speakers per channel without having to use 70V 100V...

Page 20: ...a power amplifier capable of full output down to and below the lowest frequency going INTO the amp which is often around 50 Hz An amplifier with low frequency capability is absolutely crucial wheneve...

Page 21: ...uplicate for stereo Bi Amplified Hookup of 70V 100V Full Range or High Passed Speakers with C19CS Subwoofer mono shown duplicate for stereo To Add l Spkrs One Amplifier Channel 70V 100V Output One Amp...

Page 22: ...usiness music environment it is often worth the additional cost to make the system stereo instead of mono Speaker Density for Stereo While stereo can be accomplished adequately with the normal mono la...

Page 23: ...System Design Eargle ELAR Publishing Co 1989 For additional application support from JBL Professional WITHIN THE UNITED STATES Contact Applications Support JBL Professional PO Box 2200 8500 Balboa Bl...

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