M120bt
Installation
CAUTION: Before you begin, make sure your mixer amplifier is unplugged from the power source, the power switch is in
the "OFF" position, and all volume controls are set to minimum level (turned counterclockwise).
Location:
Take the unit out of its packaging (keep it for any return to the workshop). The M120bt mixing amplifier can be installed
in a standard 19” equipment rack or on a shelf. To install the unit in a standard 19” equipment rack, the optional RK-
M3565 Rack Bracket Kit must be ordered at time of purchase. If a table or shelf installation is the chosen route, be sure
to choose a flat surface, with enough space around the unit to allow good ventilation, and that is free of liquids or other
such hazards.
To select an appropriate location for your equipment, you must consider the distance between the mixer amplifier and
the speakers, the need to access the equipment to change the source or adjust the volume, the proximity of the sockets
electrical, etc. You must determine the length of the cables used to connect your equipment to the speakers. Depending
on the type of loudspeakers and the length of the cables, you can choose to route the signals to the loudspeakers in low
impedance or in constant voltage.
If you are using low impedance speakers, you must connect them to one of the low impedance outputs (4 ohms or 8
ohms) of the mixer amplifier with speaker cables. However, pay attention to the diameter and length of the cables.
The other type of installation is using enclosures with built-in 70V transformers, often referred to as constant voltage
systems. The advantage of these systems is that they allow the use of long cables to connect several loudspeakers to the
same amplifier. You can also adjust the level of each speaker by changing the configuration of the transformer. The M-
Series mixer amplifiers are ideal for this type of application as they are equipped with 25/70V output transformers.
Speaker selection
When selecting loudspeakers, you must consider a few important factors, such as the location of the mixer amplifier, the
type of loudspeakers and the need to use a 70V distribution system. The following sections explain how to connect
loudspeakers or a constant voltage system in a typical installation.
Using passive speakers
Before using low impedance speakers (4 or 8 ohms), you must first determine the location of your mixer amplifier. If the
speakers are less than 30 meters away, you can connect the amplifier directly to the speakers in low impedance mode.
Be sure to check the impedance of the speakers. The 4 Ohms output allows you to connect a 4 Ohms speaker or two 8
Ohms speakers in parallel. The 8 Ohms output allows you to connect an 8 Ohms speaker or 2 4 Ohms speakers in series.
If the speakers are more than 30 meters away (approximately), it is best to use a constant voltage system.
Using a constant voltage system
If your setup has many loudspeakers and long cables, you might consider using a 25 or 70V constant voltage system. This
type of system became standard in the field of installations in the middle of the 20th century because it offered an
efficient solution for the use of multiple enclosures and long cables. It is inspired by long distance electrical networks
which use increased voltage and reduced current to carry very high power over long distances with more affordable and
relatively small diameter cables. The voltage is then reduced and then routed to the consumer on a short, large-
diameter cable.
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