SWR Sound 2X10C - Manual (Page 12)

12 • WORKINGMAN’S 2X10C
section of the Workingman's 2x10C may occur if speaker enclosures with total impedances less than the minimum loads listed
above are connected to the speaker output section. The owner's manual that came with your speaker cabinet should state its total
impedance. On SWR speaker enclosures, the total impedance is generally indicated on the speaker's input panel.
So how do you determine the total impedance of two cabinets hooked up to your Workingman's 2x10C? Here's a quick key of the
most common setups:
One 8 ohm enclosure (internal) + one 8 ohm enclosure (extension) = 4 ohms total impedance
This is OK. However:
One 8 ohm enclosure (internal) + one 4 ohm enclosure (extension) = 2.6 ohms total impedance
This is NOT OK! The power amp will eventually overheat and fail.
Here's another formula: To figure out the total impedance of two or more cabinets of equal value hooked up in parallel, divide the
impedance of one cabinet by the number of cabinets:
Impedance of one cabinet / number of cabinets = total impedance
(For an even more in-depth discussion of impedance and power rating issues, go to the SWR Website at www.swrsound.com, click on
"Support", then click on "Technical Articles," then click on "Plug and Play - Setup Tips for Amps and Speakers"-an article by SWR
founder Steve Rabe that ran in the August '92 issue of Bass Player Magazine.)
WORKINGMAN'S 2X10C POWER DELIVERY CAPABILITIES (Power Ratings)
After determining how the extension cabinet you wish to use affects the total operating impedance, you need to take into account the
power handling capabilities of that speaker cabinet as compared to what the Workingman's 2x10C can deliver at that operating
impedance. Those ratings are as follows:
260 Watts @ 8 ohms (internal speaker system only)
400 Watts @ 4 ohms (internal system with one 8 ohm extension cabinet)
So if you use an 8 ohm extension speaker cabinet along with your internal speaker system, it will get up to 200 watts of power (400
watts split in half), and more during transient peaks. Make sure your extension speaker cabinet can handle the power.
There is also the situation known as under powering your speakers. This is caused when the power amp, in the process of trying to
drive one or more speaker cabinets, reaches its limit and goes into clipping. That "clipped" waveform (or "square wave") will quickly
heat up the voice coils in speakers, and if operating continually while clipping, eventually will burn the voice coils and cause the
speakers to fail. Speakers abused in this fashion are easy to detect and generally not covered under a manufacturer's warranty.
(Remember, engaging the Limiter will not allow the power amp to clip, so we recommend that you not disengage the Limiter when
running at low total impedances in general.)
Also be aware that when running the amp at 4 ohms, you are operating at the maximum capacity of the power amplifier. With
extreme settings on the Gain and Master controls and the Limiter circuit disengaged, you may hear audible clipping of the power
amp. If so, you have exceeded the maximum capacity of the power amp. POWER AMP CLIPPING CAN CAUSE DAMAGE BOTH TO
ITSELF AND YOUR SPEAKER CABINETS. Either re-engage the Limiter (by pushing in on the Limiter control) to help smooth out the
peaks, or back off on the Gain and Master controls.
Remember, it's always better to have a little too much power than just barely enough. If you find yourself constantly wanting more
power than the Workingman's 2x10C provides, either:
a) tell your bandmates to turn down
b) tell the monitor engineer to turn you up
c) (better option) take the time to investigate getting an external power amp for the additional speaker cabinets to supplement
your rig
d) (best option) investigate getting a larger rig (perhaps something modular, with a large head and two speaker cabinets) for
those gigs where more power and volume is needed