6
Room Acoustics
The SA1521z loudspeakers are designed to sound as
neutral as possible; that is, to reproduce the input signal
as accurately as possible.
Roomacousticsplayacrucialroleintheoverallper-
formance of a sound system. Here are some additional
placement tips to help overcome some typical room
problems that might arise:
• Avoidplacingloudspeakersinthecornersofa
room. This increases the low frequency output and
can cause the sound to be muddy and indistinct.
• Avoidplacingloudspeakersagainstawall.This,too,
increases the low frequency output, though not as
much as corner placement. However, if you do need
to reinforce the low frequencies, this is a good way
to do it.
• Avoidplacingthespeakersdirectlyonahollow
stage floor. A hollow stage can resonate at certain
frequencies, causing peaks and dips in the fre-
quency response of the room. It’s better to place the
loudspeakers on a sturdy table or stand designed to
handle the weight of the SA1521z.
•
Positiontheloudspeakerssothehigh-frequency
drivers are 2 to 4 feet above ear level for the audience
(makeallowancesforastanding/dancingintheaisles
audience). High frequencies are highly directional
and tend to be absorbed much easier than lower
frequencies. By providing direct line-of-sight from the
loudspeakers to the audience, you increase the over-
all brightness and intelligibility of the sound system.
•
Highly reverberant rooms, like many gymnasiums
and auditoriums, are a nightmare for sound system
intelligibility. Multiple reflections off the hard walls,
ceiling, and floor play havoc with the sound. Depend-
ing on the situation, you may be able to take some
steps to minimize the reflections, such as putting
carpeting on the floors, closing draperies to cover
large glass windows, or hanging tapestries or other
materials on the walls to absorb some of the sound.
However, in most cases, these remedies are not possi-
ble or practical. So what do you do? Making the sound
system louder generally doesn’t work because the
reflections become louder, too. The best approach is to
provide as much direct sound coverage to the audience
as possible. The farther away you are from the speaker,
the more prominent will be the reflected sound.
Usemorespeakersstrategicallyplacedsotheyare
closer to the back of the audience. If the distance
between the front and back speakers is more than
about 100 feet, you should use a delay processor to
time-align the sound. (Since sound travels about
1footpermillisecond,ittakesabout1/10ofa
second to travel 100 feet.)
THERMAL CONSIDERATIONS
The SA1521z has two powerful built-in amplifiers
capable of producing a combined 500 watts of power.
As amplifiers produce heat, it is important to dissipate
the heat as quickly as possible. This results in increased
reliability and longevity for the amplifier.
The amplifier module is mounted on a large heatsink,
which is cooled by convection where cool air is drawn
through it’s fins, carrying the heat away. In order for this
convection cooling to work efficiently, it is important
to provide adequate airspace behind the loudspeaker.
WhenyoupositiontheSA1521z,werecommendleaving
at least six inches of air space behind it.
In the unlikely event of the amplifier overheating, a
built-in thermal switch will activate, which mutes the
signalandlightstheTHERMALLED.Whentheampli-
er has cooled down to a safe operating temperature, the
thermal switch resets itself, and the SA1521z resumes
normal operation.
If the thermal switch activates frequently, try turning
down the level control a notch or two on the mixing con-
sole (or the back of the SA1521z) to avoid overheating
the amplifier.
If the temperature in the room is too high, it could
cause the amplifier to overheat. In this case, you should
try aiming a fan at the rear panel to move more air
through the heatsink fins.
AC POWER
Be sure the SA1521z is plugged into an outlet that
is able to supply the correct voltage specified for your
model.Ifthevoltageshoulddropbelow97%ofthe
specified line voltage, the built-in amplifiers will no lon-
ger be able to supply rated power. (They will continue to
operatedownto80%oftheratedlinevoltage,butwon’t
reach full power, resulting in lower headroom.)
Be sure the electrical service can supply enough am-
perage for all the components connected to it.
Werecommendthatastiff(robust)supplyofAC
power be used because the amplifiers place high cur-
rent demands on the AC line. The more power that is
available on the line, the louder the speakers will play
and the more peak output power will be available for
cleaner, punchier bass. A suspected problem of “poor
bass performance” is often caused by a weak AC supply
to the amplifiers.
Neverremovethegroundpinon
the power cord of the SA1521z or
any other component. This is very
dangerous.
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