SWR Sound SM-900 - Manual (Page 16)

in mono, move the switch to the bottom “Bridge/Mono” position. Your speakers must then be
plugged into the Speakon
® jack marked “Bridge” (see diagram, page 17).
We recommend using caution when connecting your system in “Bridge/Mono” mode. Because the
SM-900 delivers 650 watts RMS minimum into 8 ohms and 900 watts minimum into 4 ohms,
damage can result ver y quickly to speakers not capable of handling this much power. If you have
or need to use a single enclosure with a power handling capacity of less than 650 watts (8
ohms), or 900 watts (4 ohms), run the amp in Stereo and use just the LEFT speaker output. No
harm will come to your amplifier by leaving the Right speaker output disconnected.
Minimum Load in the Bridge/Mono mode is 4 ohms.
Minimum Load in the Stereo mode is 2 ohms per channel.
SPEAKER FUSES
Speaker fuses are provided to protect your speakers in the unlikely event of a power amp failure,
incorrect connection procedures, or impedances below recommended ratings. Size and rating of
the fuses are 3AG, 10 amp, fast-blo. Do not defeat the purpose of this feature by using a higher
rated fuse as it could fur ther damage your amp and void your warranty.
The fuses can open if there is a fault in the speaker cable or the speakers themselves. Therefore,
it is wise to carr y extra fuses at ALL TIMES.
SPEAKER OUTPUT JACKS
Unlike most amplifiers on the market, all SWR amplifiers can be used for recording purposes using
only the XLR Balanced out, and without speakers connected to the speaker output jacks.
Note: If you are using only one channel (in stereo mode), use the left channel speaker output
as the thermal sensor for the fan is located on the left heat sink.
When used in the stereo mode, the internal power amplifiers of the SM-900 will deliver 500 watts
per side into 2 ohms, 400 watts per side into 4 ohms, and 240 watts per side into 8 ohms. For
optimum per formance, we recommend using a total of 4 ohms per channel. When using 2 ohm
loads, the amplifier will run hotter than normal and the internal fan will be running most of the
time. Minimum speaker load in the stereo mode is 2 ohms per side.
When used in Bridge Mode, the SM-900 will deliver 440 watts into 16 ohms, 650 watts into 8
ohms and 900 watts into 4 ohm loads. Please make sure the speakers you use in this mode can
handle the power. Minimum load in Bridge Mode is 4 ohms.
LEFT & RIGHT SPEAKER JACKS
There are two 1/4" jacks and one Speakon
® jack provided for each side of the SM-900’s output
section. The Left and Right speaker jacks are provided for use in the Stereo Mode only. DO NOT
use these jacks when the SM-900 is switched to the Bridge Mode. Balance between left and right
channels can be obtained by using the Stereo Master Volume control located on the front panel.
Make sure all speakers are connected BEFORE turning on the SM-900. Never plug or unplug your
speakers while the unit is on.
SPEAKER CABLE
Speaker cable should be made of 18-gauge, or heavier, wire. (The thicker the wire, the lower the
gauge, so 18-gauge is heavier than 20-gauge and so on.) Do not use instrument cables to hook
up your speakers. This can result in intermittent power loss, cause your power amp to oscillate
14 • SM-900 USER GUIDE