How to Control Ohms on a Car Amplifier

What an actual ohm is would be the resistance in a speaker, which is called impedance. The ohms are the measurements of the impedance (or resistance). You will hear many terms about this measurement along with single voice coil, dual voice coil and so on. But how do you control the ohms?

• Remember that as your ohms drop your amplifier will turn loose more power. The reason that so many self installed amps shut down and retreat into protection mode is because many people do not understand that fact.


• Look at the amplifier ratings when shopping and you will see that there are two (perhaps more) shown. Of those two main ones you will find the output at four ohms and another at two ohms. Notice that the rating at two ohms is always higher than the one at four ohms. That is due to the fact that when the impedance is lower the output is higher. All mono amps are very stable at two ohms but few are at one ohm.


• Vary the wiring on dual voice coils because the subwoofer has two positives and two negatives. This will allow for options on the final impedance.  Although this variation does not make one speaker more powerful than another the variance in the impedance does make the output quite different.


• Wire your speakers in parallel and you cut your impedance in half. If you have a dual voice coil four-ohm subwoofer and wire it in parallel you would make it a two-ohm load. This is done by tying two positive and two negative terminals together and then wire them to straight to the positive and negative of the amplifier.


• Wire your speakers in series and you will double the impedance. With a four-ohm voice coil you have two terminals, positive and negative for coil number one and another pair for voice coil number two. To make this a series you connect your positive from coil number one to your amp and connect the negative from number one to the positive of coil number two and the negative from coil number two to the amp. In effect you have doubled your impedance. On this four ohm subwoofer the impedance is now eight ohms.