Home Theater Hacks

Hack #23. Watts Are Meaningless Without Context

One of the easiest ways to be fooled in receiver and amplifier selection is in the wattage that the component puts out. Learn how to take the raw wattage number and turn it into something meaningful.

Most newbies, when it comes to home theater, immediately want to know how much power a receiver or amplifier puts out. This is natural: most of us home theater guys love to talk statistics and flex our components' muscles. However, there's a lot more going on than meets the eye. You can have an amplifier with a ridiculous amount of power and still have a terrible-sounding setup because you didn't put that wattage into its proper context.

Getting a Handle on SPL

Instead of focusing on wattage, you need to focus on the sound pressure level (SPL) of the unit you're looking at. SPL is the basic measure of how loud something is, and is measured in a unit call the decibel. To further complicate things, decibels are measured on a logarithmic scale rather than a linear scale; in other words, if a doubling of the output level results in a 3dB increase, increasing the output by a factor of 10 results in only a 10dB increase. If decibels were measured on a linear scale, a factor-of-10 increase in output would result in a 30dB increase. The bottom line is the higher you go on the scale, the larger the difference between the levels.

Now, let's make that a little more concrete. For a person to easily perceive a difference between the intensity of two ...