Let's create an example. Say I just ran out and bought myself an Audison Amplifier. I have decided
I want my car to have a trio of twelve's in a nice ported box to do what I want. Checking the manufacturer's specs I
see that this particular amp makes the most power into a mono 4 Ohm load. So, I decide to buy three
JL Audio 12W6v2 woofers. These woofers each have a pair of 6 Ohm voice coils. You will soon realize that you have a great many options with this configuration. We need an analogy for this discussion, and the favourite is the pump and the water
Here's how the analogy works. The pump is our battery and the water is the flow of electrons. Remember that the water has to flow back to the source (as a loop), so we can keep the circuit operating. If we connect a pipe to the pump outlet and the other end to the pump inlet, though the water will flow in the pipe, but no work will be done, because we haven't made our loads do anything. Now, we have two options for connecting up the six loads we have (remember, we are using dual voice coil speakers, so there are two 6 Ohm voice coils in each). We can use a combination of Series and Parallel wiring to get the load we want. Let's talk about series wiring first.
The concept of wiring speakers in series serves to increase the apparent resistive load on the amplifier, and decrease the current required. If we take a single 12W6 driver, and look at the terminals on it, we find two positive and two negative terminals, one pair for each voice coil. Let's use our analogy here. Each voice coil is a
load and we want to drive run water in both of them. The analogy goes as follows. Take your pipe from the pump, and connect it to the first
load input ( + ). The output from there ( - ) goes to the input ( + ) of the second
load, then the output from that ( - ) goes to the pump inlet. These pipes would
be considered to be connected in Series as one follows the other.
What does this do for you? Well, here's the characteristics of a series load (pipes, resistors, speakers, etc..). The same amount of water flows through each of the pipes. Anything that opposes flow in either pipe will affect the other one as well. Assuming both pipes are equal, they will both provide equal resistance to flow.
Let's look exactly at how we wire this up. Take a wire from the positive terminal of the amplifier, and connect it to one of the positive terminals of the speaker. Now take a wire from that voice coils negative terminal and connect it to the positive terminal on the other voice coil. Run a wire from the remaining negative terminal back to the negative terminal of the amplifier. The same current passes through each voice coil and returns to the amplifier.
Now, here's the technical mumbo jumbo of series connections. Firstly, resistance. If you take two six Ohm voice coils, and wire them in series, the resultant resistance if the sum of the two individual loads. In our case: 6 Ohms + 6 Ohms = 12 Ohms. Now, here's where things get a bit more complicated. We must use another law, known as Kirchoff's Voltage Law. This law states that the sum of voltages dropped across multiple loads connected to a single source, will be equal to the potential of the source itself. Follow that? OK, I'll translate. Let's use light bulbs, 3 of them, connected in series, and to a 9 Volt battery. Each light bulb, assuming they are identical, will have the same voltage across it, if measured with a meter. This measurement will be 3 Volts. So, the voltage of the source (Battery, pump, whatever...) is divided amongst the loads. This means that the power each one gets is proportional to it's resistance as the current flowing through the circuit it common to all loads.