How to Use an Amplifier to Drive Two Speakers

An amplifier is an electronic device used to magnify an input signal into a higher output. You can use an amplifier to drive two or more speakers. For this to be successful, the output of the amplifier must match half the impedance of one speaker. This helps produce optimum sound quality through the same system. The following steps specify how two speakers can be driven by one amplifier.

Instructions

Difficulty: Moderately Easy

Things You’ll Need:

• Amplifier
• Two speakers
• Wire
• Multimeter

1. Check to see if your amplifier has a connector for two speakers. If it doesn't, then you need to buy one.
2. Determine the impedance of the two speakers. The impedance is labeled on most speakers as a value in Ohms. If no indication of Ohm value exists, use a multimeter set to Ohms to measure the speaker's impedance.
3. Set the amplifier's internal impedance. Most amplifiers have a selector switch. If the amplifier is set for one impedance, note its value.
4. Match the impedance of the amplifier to the impedance of the speakers for best performance. A 4-Ohm amplifier is supposed to drive a 4-Ohm speaker. When two equivalent speakers are connected in parallel, their combined value is half that of one speaker. So two 8-Ohm speakers are equivalent to 4 Ohms. If the two speakers aren't equivalent, use a multimeter to measure their combined impedance.
5. Use resistors if the impedances are incompatible. Connect the resistors in series between the speaker and each amplifier.
6. Ensure that the amplifier's impedance is slightly lower than the speakers' combined impedance. There will mean output loss, but it's a good trade-off for possible amplifier damage or overheating.

Tips & Warnings

• Don't connect an amplifier with a lower impedance than the recommended value as this can damage or overheat the amplifier.
• Avoid using the secondary terminals with either of the two speakers.

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