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INTRODUCTION
Thank you for choosing LOUD Technologies’
Mackie 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:
1. High precision, high output, and accu-
rate playback.
2. Very wide, smooth dispersion of mid
and high frequencies.
3. Ergonomically correct physical design
for easy transport and set up.
Through the combined resources of our
top-notch mechanical and analog engineers,
and our experienced transducer engineers
at RCF, our transducer manufacturing facil-
ity in Italy, we were able to achieve our
design goals in every aspect. 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 theater.
The Transducers
The SRM450 active speakers feature a
12-inch high-power low-frequency woofer
and a 1.75-inch titanium diaphragm high-
output precision compression driver. This
high-frequency driver is mounted on an
acoustically non-resonant exponential
waveguide, providing a wide, controlled
dispersion and precise reproduction of the
critical upper mid-range and high frequen-
cies. 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 55 Hz. As it approaches
clipping, this shifts up smoothly to
120 Hz, 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.