How Many Speakers Can Be Connected To An Amplifier?
Updated: Feb 7, 2019
This topic is essential knowledge for any sound man because not knowing this could cause you to destroy your speakers.
You don't need to memorize this but there is a law in electronics that states the maximum transfer of electrical energy between a power amplifier and its speakers can only occur when the output impedance of the amplifier is equal to the impedance of the speakers connected to it. If the impedance is not matched, energy will be lost as heat, and in the worst case scenario, heat will be generated from the speaker coils burning and smoke will be visible.
There are basically single channel amplifiers and more common are the stereo amplifiers with a separate power output for the left and right main speakers.
If you look closely at the back of the amplifier you will see a label or words stamped on the chassis indicating the impedance of the power output connector. You will see 8 ohms, 4 ohms and 2 ohms. You may also see the power output rated for each of the impedance ratings. Notice that the power output increases as the impedance goes lower. Yes, the power realized is directly inverse to the impedance of the amplifier.
Now in a two channel or stereo amplifier you will have the power output of each of its channels.
Now for the Speakers - A speaker here is defined as a two way speaker cabinet generally with a 12 or 15" woofer and a horn or tweeter for the high frequencies.
Each Speaker is 8 ohms impedance, meaning on an amplifier with 8 ohms you can connect a single 8 ohm speaker to it.
It is more common to find amplifiers at 4 ohms which means you can connect 2 sets of speakers to that 4 ohm output. Because two 8 ohms speakers connected in parallel together will equal to 4 ohms. If the output is at 2 ohms, then 4 speakers can be connected to that single output.
It is more common to see a single speaker on each side of the stage / amplifier in a small to medium size venue of about 300 guests or so.
Contact me if you have any questions on this, we're glad to help.
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