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| By: mycarjams.com on Sat, 4 Oct 02:05:20 -0500
| | First off, one must realize that every speaker has a nominal current resistance at which it operates. This is noted in an ohm rating, the standard for any electrical device. This rating comes from the direct resistance that the speakers voice coils demonstrate when confronted with power. This rating is extremely important, as it determines what kind of power input the speaker can receive.
In the past, most subwoofers used a single voice coil wrapped around the former for the whole driver. However, some drivers had more than one voice coil. Another common voice coil alignment seen a lot today is a dual-voice coil (DVC) where there is more than one coil wrapped around the speaker's former. A lot of people become confused with this, but it is actually very simple. The only difference is that the resistance of the each of the coils must be combined in some way to produce a single resistance.
There are two ways to accomplish coil wiring..series and parallel. These are two commonly used terms in electrical and physics applications. A series arrangement simply means that two coils are being combined in this way: The positive lead of one coil is connected to the negative lead of the other coil, thus leaving one with a single positive and a single negative. This causes the resistance of each coil to be added together for a single rating. For example, if one has two subwoofers, each with a single 4 ohm coil where both are wired together in series, the resulting impedance would be 8 ohms. The same holds true for a speaker with a 4 ohm DVC coil arrangement. This means that the woofer has two coils, each are four ohms. When wired in series, an 8 ohm load is achieved.
Parallel wiring is just the opposite however. In this method, voice coils are "combined" together. The positive leads from each coil are combined, and the negative leads from each coil are combined, then sent to the amplifier. The ohm rating can be calculated in this way, providing the impedance of all the woofers is the same:
Resistance of subwoofers / Number of subwoofers
Use the above situation as an example. Two 4 ohm woofers would wire in series to a load of 4/2 = 2 ohms. Three 4 ohm woofers would do this 4/3 = 1.333 ohms. The same rule applies do multi-voice coil subwoofers with the following exception.
For this example, I will use standard DVC woofers. Imagine that you have two woofers that are both DVC. In order to wire them to a single defined impedance, you must wire each subwoofer by itself, then wire the subwoofers together. For instance, let's say you have two 8 ohm DVC subwoofers, which means that each woofer has two 8 ohm coils.
You must first decide how you want to wire the woofers by themselves. Let's say that you wanted to wire them both in parallel. So after combining the coils, each woofer would have an impedance of 4 ohms (8/2 = 4 ohms). But what to do next? You want to use both woofers, but you don't know what to do next, as each woofer already has a set impedance. Well here's the trick... you must now wire the subwoofers together in either series or parallel. Since both woofers now have an impedance of 4 ohms, you can combine them again in parallel mode for a final impedance of 2 ohms (4/2 =2 ohms) or wire them in series for a final load of 8 ohms (4+4 = 8 ohms). This is the beauty of DVC subwoofers, as they make wiring options much more flexible.
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