Handbook for Sound Engineers

1312 Chapter 34

(or ringing) frequencies can usually be eliminated
before a point of diminishing returns is reached.

34.5.2.2.13 Equalization Using Source-Independent
Measurement (SIM)

Developed by John Meyer of Meyer Sound Laborato-
ries and Brüel & Kjaer Instruments, the Source Inde-
pendent Measurement method of equalization uses the
sound source, voice or music, as the equalization test
signal and an FFT (Fast Fourier Transform) analyzer as
the test equipment. While more complex than tradi-
tional equalization, the promoted advantages of this
equalization method are that it can be used during a
concert performance to correct and recorrect changes in
system response due to changes in audience size or
room humidity.

34.5.2.2.14 Automatic Equalization

Some manufacturers have offered systems that, when
properly set up, could actually equalize themselves.
However, most designers believe that equalization is
complex enough to require the engineering judgments
of an experienced human operator. For this reason, there
are few such systems on the market, Fig. 34-77.

34.5.3 Rigging the Cluster

There are three sections to every rigging system:

1. The loudspeakers and their internal hardware.


2. The building structure.


3. Everything between the loudspeakers and the
   building structure.

The loudspeaker manufacturer must certify that the

loudspeaker is designed for suspension. Do not suspend

any loudspeaker unless the manufacturer has certified it

for suspension. The manufacturer must also specify any

limitations on rigging such as the number (or weight) of

additional loudspeakers that can be suspended below a

single loudspeaker.

For a new facility, the building architect or struc-

tural engineer must certify the building structure as

being capable of supporting the weight of the cluster

with a suitable design factor (safety factor). The system

designer must supply the architect or structural engineer

with the installed cluster weight. For an existing facility,

the owner or system designer should contact the original

architect or structural engineer for approval to suspend

the cluster in the desired location. If the original archi-

tect or structural engineer is no longer available, find

another architect or registered professional engineer

(PE) to inspect the structure and approve the system

suspension in the desired location(s).

The rigging system itself is the responsibility of the

system designer and the installing contractor. This

includes rigging cables, any suspension grid, and all

associated hardware (the loudspeaker manufacturer may

supply eyebolts for its loudspeakers). The system

designer or installing contractor must present the

rigging system design, with associated drawings, to an

outside registered architect or professional structural

engineer for official approval.

The system must be installed by experienced, profes-

sional riggers. Always use hardware that is designed

and certified for rigging usage, Fig. 34-78. The system

designer should supervise the cluster installation to

confirm the aiming points of each loudspeaker.

When finished, the loudspeaker cluster should be

inspected for proper loudspeaker aiming and rigging

safety. Document the entire installation with as-built

drawings.

34.5.4 System Documentation

Here are the most important system documents and their

purposes.

Figure 34-77. A (discontinued) self-equalizing sound
system. Courtesy JBL Professional.