Speaker Configuration Guide
If you find yourself confused about power ratings at 4ohms versus power ratings at 2ohms, or how best to wire your speakers to your amplifiers to get the most out of them, then this is the article for you!
Not all that many years ago to get a powerful system meant buying a high power two channel amplifier and a high-powered sub. The amp, say 250 watts RMS x 2 would be bridged to say 600 watts RMS and would then run a single 600 watts RMS sub. This would have to be done for each subwoofer in a system.
These days the more popular route to getting the most out of an amplifier is by using DVC subs.
Voice Coil
Attached to the bottom of a speaker’s cone is a cylinder called a former. Wound around this former is a single coiled length of wire. This former then sits inside the speaker’s magnet. When alternating current flows through the coil it reacts to the magnets field and either moves it inward or outwards depending on weather the current is positive or negative. Inturn, the speaker’s cone also moves inward and outward creating soundwaves.
Dual Voice Coil (DVC) vs. Single Voice Coil (SVC)
In DVC subs, a second coil of the same length and size is wound around the first. This coil is then powered from the amplifier as if it was a second speaker, the DVC will have two sets of connecting terminals. The speaker can then handle twice the power that a SVC counterpart could. Although of course it’s more work for an amplifier to power two speakers then it is one.
Ohms
For the most part, this article we will pretend that resistance and impedance are one and the same. A small explanation of there differences can be found at the bottom of this article.
An Ohm is a rating of electrical resistance. When a speaker with a rating of 4Ohms is connected to an amplifier, that speaker will show a 4Ohm resistance to the power that the amplifier delivers. The higher the resistance on the speaker cables, the lower the power that the amplifier will produce. If the amplifier is shown a resistance too low however, more power then the amplifier can safely handle will be produced and the amplifier will quickly overheat resulting in automatic shutdown or damage.
If two 4Ohm speakers are wired in parallel of one unbridged channel then this will show the amplifier a 2Ohm load. The power from the amplifier now has 2 ways of returning back to the negative amplifier terminal and this will half the resistance shown to the amp. If two 4Ohm speakers are wired in series, the power must now go through two 4Ohm loads showing the amplifier a total 8Ohm load. A single 4Ohm/4Ohm DVC speaker can be wired in either parallel or series just as in the pictures. This will also show the amplifier either a 2Ohm or 8Ohm load.
Bridging Channels
When bridging two channels together (see pic) to run a 4Ohm speaker, a 2Ohm stereo load is presented to the amplifier. Because both channels are sharing the speaker, they also share its resistance resulting in each channel experiencing a 2Ohm load. If the bridged channel was then running 2 x 4Ohm speakers in parallel this would present each channel with a 1Ohm load. With two paths for the power to travel the resistance is half of one speaker, the resistance is then shared by the two channels resulting in a 1Ohm load.
Safe Ohms
Running low resistance means running an amplifier very hot. Always ensure that there is sufficient airflow around an amp that is running low resistance. Theoretically running an amplifier channel at half a rated resistance should produce twice the rated power. This isn’t the case however as the hotter an amplifier is the less efficient it becomes at producing power.
By far the majority of aftermarket amplifiers can run 2Ohm stable and not below. Running a 1Ohm load on an amplifier that is not 1Ohm stable WILL eventually result in damage, so unless your amp is specifically rated for 1Ohm loads do not attempt it!
Head unit amplifiers cannot safely be run 2Ohm stable. The heat generated from doing this (if it was possible) would start to interfere with the other features of the unit (such as playing music). Remember this also means they cannot be bridged.
Speaker Ohm Configurations
SVC speakers normally come in single 4Ohm, however they can also come in 8Ohm configuration. DVC subs are available in many different combinations. The most common are 4Ohm/4Ohm and 2Ohm/2Ohm. DVC subs always have the same resistance for each coil.
Several other multiple voice coil subs are available such as the Digital Designs 17″ Quad Voice Coil sub.
Resistance vs. Impedance
As referred to earlier, impedance (what subs are actually rated in) is not exactly the same as resistance (but similar enough for comparison). Resistance is electrical opposition to the flow of direct (constant) current while Impedance is opposition to alternating (changes from positive to negative) current. The Impedance rating of a speaker is its average opposition to current within its intended frequency range. If you don’t understand this don’t worry as its not really important.
Speaker Configurations
The below pictures represent some possible configurations of subs to a 2 channel amplifier. The amplifier used in this example is an Alpine MRV-1005.
NOTE: Although these pictures illustrate loads less then 2Ohm, this amplifier can not handle loads below 2Ohms.
