SWR 350x Operating Instructions Manual page 17

SubWave™ Activator Footswitch
Your 350x comes equipped with the capability for hands-free control of the SubWave™ effect. To achieve
this function, locate the footswitch included in your 350x packaging. Connect the cable to the SubWave™
Footswitch jack on the rear of your 350x. Turn the effect on and off by stepping on the switch; the illumi-
nated switch above the SubWave™ Level control on the front panel should alternate on (blue) and off, and
the effect should engage and disengage accordingly.
Note: The type of switch contained inside the footswitch chassis is momentary, normally open. If you
connect the footswitch to the unit while the unit is on, the SubWave effect may engage. This is nor-
mal.
Cooling Fan & Fan Mode Switch
With the Fan On/Off switch in the "On" position, the internal cooling fan will run at slow speed when the
internal heatsink temperature is below 55 degrees C and at high speed when the temperature is above 55
degrees C. The Fan On/Off switch should be left in the "On" position for normal operation.
With the Fan On/Off switch in the "Off" position, the internal cooling fan will be off when the internal
heatsink temperature is below 55 degrees C and at high speed when the temperature is above 55
degrees C. SWR recommends that the "Off" position be used ONLY in situations where fan noise might
be audible and therefore problematic—such as when miking the internal speakers in a recording situation.
SPEAKER OUTPUT SECTION
This section of the manual will deal with the proper connection of speaker cabinets to the power amplifier
in the 350x. Some of this ground has already been covered in the "Getting Started – Connecting Your
Speaker Cabinets" section in the beginning of the manual. This is meant to supplement that section and
provide information in greater detail, as power amplifiers, impedance and speaker cabinets are all crucial
in determining how best to operate your new 350x.
How Impedance Affects Power Ratings
People often have questions about impedance. What is it? The root of the word "impedance" is the verb
"impede," which means to block or resist. That's what impedance is: resistance to power.
Power amps do not have a pre-determined impedance. They deliver power at whatever impedance the
speaker cabinet tells it to. That's why you hear the term "slave amp" – amplifiers only do what they're
told. So if someone tells you that they have a "4 ohm power amp," their terminology and understanding of
the concept is way off the mark.
Unlike power amps, every speaker cabinet has a pre-determined impedance rating measured in "ohms." In
most cases this rating is either 4 or 8 ohms (though there may still be some old 2 ohm creakers out
there). The higher the impedance of the speaker cabinet, the more resistance to power it will offer. The
lower the resistance of the speaker cabinet, the less resistance to power it will offer. In other words,
HIGHER IMPEDANCE MEANS LESS POWER CAN ENTER THE SPEAKER CABINET. LOWER IMPEDANCE
MEANS MORE POWER CAN ENTER THE SPEAKER CABINET.
You may be thinking that you've found the solution to the universe – just use speaker cabinets with really
low impedances and you can get skull-crushing power out of your amplifier, right? Wrong. There's a catch.
Power amps have limits as to how low an impedance they can drive safely. This is what's known as an
amplifier's "Minimum Impedance Rating." If you try and operate a power amp below its minimum imped-
ance rating, it will give you lots and lots of power for about five minutes...and then overheat, short out and
fail completely. In other words, THE LOWER THE OPERATING IMPEDANCE OF THE AMPLIFIER, THE HOTTER
IT WILL GET.
350x • 17