Idiomas disponibles
Idiomas disponibles
750x – SPEAKER OUTPUT SECTION
This section of the manual will deal with the proper connection of speaker cabinets to the power amplifier in
the 750x. 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 deter-
mining how best to operate your new 750x.
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.
Solid-state power amps do not have a pre-determined impedance. They deliver power at whatever imped-
ance 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 under-
standing 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 IMPED-
ANCE 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.
750x Power Amplifier Minimum Impedance Ratings
Here's what this means to the power amp in the 750x. As mentioned previously, the 750x contains a mono
power amp, which makes things fairly simple. The Minimum Impedance Rating of the 750x is 4 ohms. This
means that you can safely connect:
• One 8 ohm speaker enclosure
• Two 8 ohm speaker enclosures
• Two 16 ohm speaker enclosures
• One 4 ohm speaker enclosure
(For an even more in-depth discussion of impedance and power rating issues, go to the SWR Website at
www.swrsound.com, click on "Press," then click on "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.)
750x • 19
