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INTRODUCTION
Thank you for choosing Mackie Designs’
active sound reinforcement speakers.
The SRM450 is an active two-way loud-
speaker capable of extremely high sound
pressure levels, and designed to give you the
best performance of any loudspeaker in its
class and price range.
Our design goal was to build a sound re-
inforcement speaker with the same fidelity
and flat frequency response found in our
reknowned HR824 studio monitors. We
think you’ll agree that the SRM450 sound
quality and accuracy reaches this goal and
more. The result is a sound reinforcement
system equally at home in a concert setting,
in the studio, impromptu concerts on the
studio roof, in the cinema, or in a home the-
ater.
Mackie Designs’ entry into the sound
reinforcement loudspeaker market began
with the acquisition, in June of 1998, of
Radio Cine Forniture (RCF), headquartered
in Reggio Emilia, Italy. RCF has a long tra-
dition in developing speaker technology for
the high-end pro-audio market.
The Transducers
The SRM450 active speakers feature a
12” high-power low-frequency woofer and
a 1.75” titanium diaphragm high-output
precision compression driver. This high
frequency driver is mounted on an acousti-
cally non-resonant exponential waveguide,
providing a wide, controlled dispersion and
precise reproduction of the critical upper
mid-range and high frequencies. The result
is an unbelievably smooth off-axis response
that allows everyone in the audience to
experience the same high-resolution audio
no matter where they are seated.
Each driver has been specifically designed
by our engineers for optimum performance
in the lightweight high-strength cabinet.
FR Series Power Amplifiers
To power these beautiful things, each
SRM450 includes two of our acclaimed FR
Series “Fast Recovery” power amplifiers. Our
exclusive design uses low negative feedback,
yet allows the amplifiers to maintain low dis-
tortion and stability and to quickly recover
when driven into clipping.
The amplifiers include the following
features:
• The low-frequency amplifier produces
up to 540 watts peak (300 continuous)
before clipping.
• The high-frequency amplifier produces
up to 150 watts peak (100 continuous)
before clipping.
• Each amplifier has its own compressor
circuit that acts when the input signal is
large enough to cause clipping, distor-
tion and excessive voice coil heat. The
compressor will automatically decrease
the input signal to a safe level. The
compressor in the low-frequency amp
works independently from that in the
high-frequency amp.
• The low-frequency amp uses a servo
feedback loop which senses the current
flowing in the woofer coil. This controls
the low-frequency response and main-
tains low distortion at high output levels.
• The low-frequency amplifier also has a
sweeping filter. This will automatically
move the low cut-off frequency up or
down depending on the amplifier
output. For example, if the amplifier is
below clipping, the low-frequency cut-
off point is 55Hz. As it approaches
clipping, this shifts up smoothly to
120Hz, providing more power reserves
and less distortion before clipping. This
happens quickly and continuously,
protecting the amplifer and the woofer
and reducing any noticable distortion.
Warning:
Although the
amplifiers have these
protection circuits, you
must still make sure the
PEAK
light is not blink-
ing continuously. If it is, turn down your
mixer faders, or preamplifier gain, or turn
down the SRM450
LEVEL
control.
