Description: The Rockville CC8-SUB is an 8" in-ceiling subwoofer with a built in transformer that will operate at either 70 volts or regular 8 ohm. This can install into a sheet rock ceiling or a drop-ceiling with the included metal rough-in bracket.. What is 70 volt ? 70 volt systems are the number one choice for applications where you want to install many speakers. With 70 volt there are a lot of advantages over 8-ohm systems. One of the main advantages is the simplicity of the wiring as well as how easy it is to match up speakers with the amplifier. For example, you can buy one 70V amplifier with 350 watts and you can install speakers that total close to 300 watts. It does not matter if it is 15 speakers that are 20 watts each or 50 speakers that are tapped at 5 watts each. You always want your 70 volt amp to have at least 15 or 20% more power than the combined watts your speakers are tapped at.. . When we say the word tap, what we are referring to are the selectors these speakers have on them. For example, these speakers have selectable options of 2.5w, 5w, 10w, 20w. What this does is limit how many watts the built-in transformer on the speaker will allow the speaker to get from the amplifier. This gives you full customization over the sound for your space. In a restaurant for example you can tap your dining room speakers at 5 watts, the speakers by the bar area at 20 watts, and the ones in the hallway at 2.5 watts.. . Another great feature with 70 volt is you can mix and match any 70 volt speakers whether they are ceiling speakers, wall mounted speakers, subwoofers, etc.. . 70 volt systems allow you to run very long lines of speaker wire without signal loss. This is ideal when running long speaker leads.. . The wiring is simple. You just wire all the positive terminals of the speakers to the positive 70 volt terminals of the amplifier. The negative terminals on the speaker simply get wired to the negative terminals on the amp. You do not have to worry about impedance. The power is constant.