Stereo Operation; Parallel Operation - Omnitronic SMA SERIES User Manual

Example for the calculation number of speakers/impedance
Number of speakers
1 speaker at 8
2 speakers at 8 each
2 speakers at 8 each
3 speakers at 8 each
3 speakers at 8 each
4 speakers at 8 each
• The input impedance of the speaker systems should at least be the same or even higher than the output
impedance of the amplifier.
Information on choosing appropriate speaker cables
•
Speaker systems must only be connected via sufficiently dimensioned cables. Too thin cables lead to cable
heatup or enormous power loss and loss in sound quality.
•
For all speaker systems up to 400 Watts, we recommend a cable diameter of 2.5 mm², for all other speaker cables
4 mm².
•
A high damping factor of your amplifier supplies a clear sound reproduction. Unnecessarily long and thin cables
will influence the damping factor and thus the low frequencies in a negative way. In order to safeguard good sound
quality, the damping factor should lie around 50. The longer a cable has to be, the thicker it should be. In this
respect, a damping factor of 200 will be reduced to 47 (8 ohms) when using a 10 m long, 2.5 mm² speaker cable.
The power loss at 8 ohms is 1.63 %, at 4 ohms 3.25 % and at 2 ohms even 6.5 %.
•
The maximum cable length is 30 meters.
General information on installing cables
• Always treat cables carefully and protect them from damages during transportation.
• Install cables always in a structured way and protect them from damage.
• Cables must be installed in a way that no person can stumble over them. Always fix cables with an appropriate
tape.
• Cables should be installed directly (no loops, S-shaped overlengths).
• Always install cables far away from power cables (never closely parallel).
• Never put heavy objects like speaker systems, flightcases etc. on cables.
• Never operate cables wound up.

7.2.1 Stereo operation

The most frequently used operating mode of an amplifier is stereo operation, where both channels are
operated independent of each other. The highest output power during stereo operation is achieved by
connecting 4 speakers. With 8
use both Speaker pairs or for models SMA-1500, SMA-2000 alternatively the pairs of screw
connectors. Set the selector switch for the operating mode to position "STEREO".

7.2.2 Parallel operation

In parallel operation the amplifier can be operated in mono mode, i.e. via one input channel. The voltage
remains the same, the current is doubled. Consequently, the output impedance is limited to the minimum
value of one individual channel. For parallel operation, use both Speaker jacks or for models SMA-1500,
SMA-2000 alternatively the pairs of screw connectors. Set the selector switch for the operating mode to
position "PARALLEL".
7.2.3 Bridge operation
In bridge operation the amplifier can be operated in mono mode, i.e. via one input channel. The voltage is
doubled and subsequently also the output impedance. For stereo operation two amplifiers are needed. For
bridge operation, use the upper Speaker jack for channel 1. For models SMA-1500, SMA-2000 the
red screw connectors can alternatively used for bridge operation. For this purpose connect the positive pole
of the speaker to the positive terminal of channel 1 and the negative pole of the speaker to the negative
Impedance
8
4 (parallel)
16 (in line)
2.66 (parallel)
24 (in line)
2 (parallel)
speakers the output power will be slightly reduced. For stereo operation,
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