Amplifiers are essential in audio systems, whether for speakers, guitars, or other equipment. Most home theater speakers are not powered, so an amplifier is required to operate them. If you're using an A/V receiver, it likely includes a built-in amplifier. When selecting an amplifier or A/V receiver, several factors to consider are impedance, power handling capacity, and sensitivity.
Understanding Impedance
Impedance measures the load that speakers place on an amplifier. Lower impedance requires more power to drive the speaker at the same volume. Most home theater receivers are rated for 6 or 8 ohms. However, it's important to note that the load isn't constant - it changes dynamically as the volume of a recording fluctuates.
Additionally, lower-frequency sounds demand more power than higher frequencies. For instance, the intense sound of an explosion in a movie will place a heavier load on the system than the gentle ambient noise of chirping birds or rustling leaves in a quiet outdoor scene. To maintain compatibility and avoid issues, it's recommended to select speakers within 2 ohms of the receiver's impedance rating and ensure that no two sets of speakers in your system differ by more than 2 ohms.
Matching Amplifiers to Speakers
When pairing an amplifier with speakers, a good rule of thumb is to choose an amplifier that can deliver power equal to twice the speaker's continuous IEC power rating. For example, a speaker with a nominal impedance of 8 ohms and a continuous IEC power rating of 350 watts will require an amplifier capable of producing 700 watts into an 8-ohm load. The amplifier should be rated at 700 watts per channel at 8 ohms for stereo speakers.
This setup ensures that your system can handle dynamic changes in sound and deliver high-quality audio, whether watching a movie or listening to music.