Volume controls are just big resistors. They aren’t powered, they don’t plug into AC, and they don’t amplify. There are amplified volume controls available, but they are a specialty and will define what they amplify. This article addresses the common volume control.
Volume controls go inline with the speaker wire. They have an input and an output. The input will be the wire coming from your amplified source, a receiver, an amplifier, or if you’re using a speaker selector, from the outputs of the speaker selector. The output will be to the speaker wire going to the speakers.
The proper setup of the levels should have your volume control being at about 75% on most of the time. So the knob or slide control should be almost all the way up. For the first time setup of volume controls, you first turn the volume controls all the way up to their max setting, then go to your receiver/amplifier and adjust the levels to just a tad over the normal levels that you want to hear your music at.
Now, go back to each volume control and turn it down to the level that you want to listen to the music in those areas. Some areas might be at 60% some at 90%, and that’s fine. The reason some of the rooms may be different is that some rooms may be dead or have a lot of carpeting, window coverings, and plush furniture. Some rooms may be really live or have a lot of hard surfaces, like tile, windows and cabinets.
The important thing to remember about the volume controls is that they turn things down. At their top level, they are letting as much of the signal through as they can. Another way to think about this is an analogy to water pipes and faucets in your house. The main water pressure is like your amplifier/receiver power, your volume controls are your faucets and what comes out is the water/sound. The water company should have to only supply a reasonable amount of water pressure to supply the home, otherwise you may accidentally turn on your shower and get blasted with fire hose type pressure.
The same applies to volume controls and amplifiers. If you accidentally turned on one of your areas to top volume with your amp turned up too high (or maybe one of your toddlers turns them up without your knowledge), you could have speaker failure or maybe even worse, a wet pair of pants from being scared out of your begebers! Actually, the main reason for setting up the amplifier/receiver this way is to have it running at a lower main volume and thereby operating at lower temperatures, lengthening it’s life span.