Mackie SRM 450 Manuale utente
2
SERVICE ON THIS EQUIPMENT IS TO BE PERFORMED BY
EXPERIENCED REPAIR TECHNICIANS ONLY
3
CONTENTS
Introduction.....................................................................3
Blockdiagram..................................................................4
Specifications...................................................................5
Overview..........................................................................6
Safety test........................................................................8
Bias adjustment...............................................................9
Test points.........................................................................10
Parts...................................................................................A-1
Fold-out Sections
Schematics and PCB layouts
Main board.................................................................227-1
INTRODUCTION
This manual contains basic service information. It is essential that you have a copy of the
user’s manual as this contains the complete operating instructions.
SERVICE TECHNICAL ASSISTANCE
MackieDesigns, Service TechnicalAssistance, is available 8AM -5PM PST, Mondaythrough
Friday for Authorized Mackie Service Centers, at 1-800-258-6883. Feel free to call with any
questions and speak with a carefully-calibrated technician. If one is not available, leave
a detailed message and a qualified Mackoid will return your call asap.
DISCLAIMER
The information contained in this manual is proprietary to Mackie Designs, Inc. The entire
manual is protected under copyright and may not be reproduced by any means without
express written permission from Mackie Designs, Inc.
SERVICE ON THIS EQUIPMENT IS TO BE PERFORMED BY
EXPERIENCED REPAIR TECHNICIANS ONLY
Click on any item to open that page
4
Block Diagram
INPUT
THRU
1
J15
1
HI-PASS
LOW CUT CONTOUR
COMPRESSOR
THRESHOLD
COMPRESSOR
SWEEPING
FILTER
LO-PASSDELAY
176uS
HI-FREQ
40-120 Hz LO-FREQUENCY
DRIVER
TWEET
LO-FREQ
AMP
HI-FREQ
AMP
SENSE
RESISTOR
BASS CONTROL SERVO LOOP
WOOF
PEAK
LIGHT
PEAK
DETECTION
THRESHOLD
LPF
THRESHOLD
+
Ð
MIDVDC
+
Ð
LOVDC
+
Ð
HIVDC
TOROIDAL POWER
TRANSFORMER
FUSE POWER
SWITCH
ON
OFF
+15VDC
SIGNAL
SENSE
SIGNAL
SENSE MUTE
ON/OFF
CONTROL
MUTE MUTE
POWER
LEDS
THERMAL
LED
THERMAL
SWITCH
LOW AC
VOLTS SENSE
TIMED
TURNOFF
SIGNAL
LED
5
Specifications
Low-Frequency Transducer
Diameter 300mm (12”)
Voice Coil Diameter 63.5mm(2.5”)
Sensitivity (1W@1m) 98dB
NominalImpedance 8ohms
PowerHandling 300W
FrequencyRange 50Hz – 3000Hz
High-Freq Driver and Horn
Diaphragm Diameter 44.5mm (1.75”)
Exit Throat Diameter 24.5mm (1”)
Diaphragm Material Titanium
Sensitivity (1W@1m) 106 dB
NominalImpedance 8ohms
PowerHandling 150W
FrequencyRange 1000Hz – 20,000Hz
Low-Freq Power Amplifier
Rated Power 300 watts
RatedTHD <0.1%
Cooling: Convection Extrusion
Design: Class G, Parametric Servo
Feedback
High-Freq Power Amplifier
Rated Power 100 watts
RatedTHD <0.1%
Cooling: Convection Extrusion
Design: Conventional Class AB
System specs
InputType Balanced Differential
Input Impedance Line: 20k ohms
Input Protection RFI and level protected
Sensitivity Line: +4 dBu (centered)
Mic:–36dBu
Maximum Input Level Line: +22 dBu
Low-CutFrequency 75Hz, Second-order filter
EQ Peaking+3dB@ 55Hz,
+3dB@20kHz
Over-Excursion Protection
Second-Order High-Pass
Filter
Thermal Protection Amplifier shutdown, auto-
reset
Low-Line Voltage Shut Down: 60% Nominal line
Acoustic Freq Response: 45Hz – 20,000Hz
Low-Freq –3 dB Point: 55Hz
MaximumSPL@ 1m: 123 dB
Low-Freq Crossover: 24 dB/octave, time offset
corrected
High-Freq Crossover: 24 dB/octave
Crossover Frequency: 1600Hz
Driver Protection IndependentLFand HF
compressors
Low-Freq Roll-Off: Dynamic-signal level de-
pendent
Accessory Interface ±15V DC
OperatingTempRange –10ºC- 45ºC (14ºF -113ºF)
Line Input Power
US 120V, 60Hz
Europe 230V, 50Hz
Japan 100V, 50/60Hz
Disclaimer
Since we are always striving to make our products
better by incorporating new and improved materi-
als,components,andmanufacturing methods, we
reserve the right to change these specifications at
any time without notice.
©1999 Mackie Designs Inc.
All Rights Reserved.
6
Overview
The SRM450 is an active two-way loudspeaker system capable of extremely high sound
pressurelevels.
The Transducers
The SRM450 active monitors 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 acoustically 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 distortion 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, distortion 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 maintains 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 blinking often or continuously. If it is, turn down your mixer faders, or
preamplifier gain, or turn down the SRM450 LEVEL control.
7
The Crossover
The built-in electronic crossover is a 24 dB/octave Linkwitz-Riley design.
Although more expensive than other crossover designs, the benefits provided by the
Linkwitz-Riley design have been well documented. These benefits include:
• Absolutely flat frequency response throughout the bandpass, without the characteristic
ripple near the crossover point exhibited by other designs.
• The sharp 24 dB per octave roll-off of the filters ensures that the transducers aren’t
reproducing frequencies outside of their capabilities.
• The acoustic sum of the two driver responses is unity at the crossover frequency, resulting
in perfect power response.
• Our heroic engineers have worked carefully to ensure that the SRM450 also provides
perfectphase response. This diligence hasyielded phenomenal accuracy, even ifyou are
standing 20 feet away.
The Cabinet
The SRM450 cabinet was designed to be the strongest molded composite cabinet on the
planet. This material is as strong as concrete, and rigid enough to prevent unwanted
vibrations in the cabinet. It has built-in fly points for hanging, and a socket in the bottom
for mounting on a tripod stand. Although it is an exceptional choice for installed sound
situations, its light weight and durable finish also make it ideal for portable sound system
use. The asymmetrical trapezoidal design of the cabinet makes it easy to use as a floor
wedge for stage monitor applications.
8
You must perform the following leakage test before returning the unit to your customer.
Take every safety precaution to protect yourself while doing this test.
1. Make a small loading RC circuit as shown in the diagram below, and connect the AC
volt meter between the AC power source ground and any exposed metal on the unit
under test.
2. Connect the unit under test to an AC power source using a ground-lift adaptor, leaving
the unit’s safety ground floating. Turn the unit on.
3. The meter reading should be less than 750mVAC (note: this is equivalent to 0.5mA of
leakagecurrent).
4. Flip the plug over in the receptical so the hot and neutral are swapped.
Verify that the reading is still less then 750mVAC.
5. If either reading is greater than 750mVAC, then you must investigate and repair the unit
before returning it to your customer.
Safety test
9
Bias adjustment
1. Place the SRM450 on its side so that the heatsink fins are horizontal.
2. Connect the power cord and turn it on, with no input
signal applied. Make sure that the TIMED TURNOFF switch is
OFF.
3. Let it sit this way for an hour or more to allow the heatsink
temperature to rise. You can play music through to speed
things up. If you have a thermometer, the bias adjustment
procedure is best done when the heatsink temperature is 45 to
50 deg C.
4. Turn off the SRM450 and remove the power cord.
5. Remove the complete amplifier/heatsink assembly from the plastic
speaker case but leave all wires connected, including the speaker wires.
Support the amplifier so it can be safely turned on again.
6. Replace the power cord and turn on the amplifier and take care not to touch any
exposed live AC components.
7. No input signal is applied.
8. Low frequency amplifier bias adjustment:
While the heatsink is still warm, measure the DC voltage across the 2 pins of J21. Adjust
R202 until a reading of 4mV to 4.5mV is reached. See sheet 2 for the location of J21 and
R202.
Important: When finished adjusting, secure R202 with a small drop of paint, such as nail
varnish.
9. High frequency amplifier bias adjustment:
Measure the DC voltage across the 2 pins of J20. Adjust R212 until a reading of 4mV to
4.5mV is reached.
Important: Secure R212 with a small drop of paint.
10. This completes the adjustment procedure. Reassemble and perform a full test.
The Amplifier Bias of every SRM450 must be carefully adjusted as follows.
10
LOW FREQUENCY
BIAS TEST POINT LOW FREQUENCY
BIAS ADJUSTMENT POT
HIGH FREQUENCY
BIAS TEST POINT
HIGH FREQUENCY
BIAS ADJUSTMENT POT
+80V
+15 VDC
-15 VDC
-80V +45V -45V
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