The Rockville CT8-SUB has a built in transformer that will operate at either 70 volts or 100 volts or you can by-pass it and use this as a standard 4 ohm sub.

There is a tap switch that allows the following power options:

70V Power Options:

• 40w
• 15w
• 10w

100V Power Options:

• 55w
• 25w
• 15w

4 Ohm power handling:

• 80w

This subwoofer is the perfect solution to add that low end either in your conference room, restaurant, bar area, or even in your home.

Features:

• Rockville CT8-SUB 8" Black 400w Home Audio Sub Home Theater Subwoofer
• Selectable Taps: 40w, 20w, 10w, 4 Ohm
• Built-in 70v/100v transformer
• 20 oz magnet
• Banana binding post terminals accepts banana cables or regular speaker
• 40w-15w-10w selectable with 70v input
• 55w-25w, 15w selectable with 100v input
• By-pass  option to run sub at 4 ohm: 80w RMS power handling @ 4 ohm
• Frequency response: 40Hz-800Hz
• Sensitivity: 90dB (1w@1m)
• Build with high quality mount bracket
• Unit dimension: 12.4*9.65*12.4inch
• Unit weight: 12.9lbs

Owner’s Manual

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.