You’ve decided to take the leap into car audio and now you are considering purchasing a subwoofer and amplifier to give your system that bump you’ve been missing. Good choice! Welcome to the car audio family! A subwoofer will definitely add those deep notes and bring your music to life.
Since you’ve made this decision, you’ve been trying to choose the subwoofer and amplifier that’s right for you. Well, I’m not going to dive into all the possible brands that you could choose from, but I will try to give you the basic knowledge to help you properly match your amplifier and subwoofer to get the best possible sound out of your setup.
Key System Terms
Before we get started, let’s look at some of the basics when choosing a great match between the subwoofer and amplifier.
Power
Power seems to be the only factor individuals focus on when choosing a subwoofer and amplifier, but it shouldn’t be the only focus. In regard to power, there are two ratings (measured in watts) that you may see when looking at some car audio equipment. One of these power ratings is PEAK. Peak power ratings are the measure of power that the subwoofer can take without damage. But, in most cases, this number is constantly high-lighted to make the subwoofer look like it can handle more power than it is actually capable of.
The second power rating is the RMS (root mean square) rating. This is the power rating you need to consider when choosing your subwoofer and the amplifier. This is the amount of power (in watts) that the subwoofer can handle continuously, and on a consistent basis.
Amplifiers will sometimes have peak and RMS ratings, too, but here, you will also want to focus on the amplifier’s RMS power rating.
Impedance
Impedance is the resistance (electrically) of a subwoofer or a speaker. This resistance is measured in ohms. A speaker or subwoofer’s impedance will affect the power output of an amplifier. The lower the impedance, the less resistance will be for the amplifier creating more power output, on the flip side, the higher the impedance, the more resistance there will be which will equal less power output.
Most subwoofers are manufactured with dual 2-ohm or 4-ohm voice coils, but can also come in single voice coil configurations. You can easily determine if your subwoofer has single or dual voice coils by the number of terminals on the sub. The way these subwoofers are wired (parallel or series) will determine the final RMS power output of your amplifier. This is easy to figure out when you are only installing one or two subwoofers but will become increasingly more difficult to calculate the more subwoofers that are added to the equation. This post will not get into the different wiring options of subwoofers, I will cover that in a future post in detail.
NOTE: Please DO NOT exceed your amplifier’s minimum impedance rating. For example, If your amplifier is rated to create its maximum power output at 1 ohm, make sure your subwoofer(s) final impedance does not go below this number. Unless your amplifier is able to handle such ohm loads, damage will most likely occur to your subwoofers and your amplifier.
A Match Made in Car Audio Heaven
Finding the Right Sub for Your Amplifier
You will have to look at the sub’s voice coil configuration and RMS rating to determine what will match with the amplifier. The subwoofer’s RMS rating needs to match your amplifier’s power output at a specific impedance measurement. For example, if your amplifier is rated at 500 watts RMS @ 1 ohm, you would want to choose a subwoofer that has a dual 2-ohm voice coil (wired in parallel to create a 1-ohm load) and is rated at 500 watts RMS. This example is for a simple single-sub setup, but keep in mind, these variables can change drastically based on the number of subwoofers you are considering. Below I have included some subwoofer impedance configurations to help you quickly see what different wiring options will result in.
Subwoofer Wiring Configurations
| 1-ohm | 2-ohms | 4-ohms |
| 1 Subwoofer ~ 2-ohm DVC | 1 Subwoofer ~ 2-ohm SVC / 4-ohm DVC | 1 Subwoofer ~ 4-ohm SVC / 2-ohm DVC |
| 2 Subwoofers ~ 2-ohm SVC / 4-ohm DVC | 2 Subwoofers ~ 4-ohm SVC / 2-ohm DVC | 2 Subwoofers 2-ohm SVC / 4-ohm DVC |
| 3 Subwoofers ~ 4-ohm SVC / 2-ohm DVC | 3 Subwoofers ~ 2-ohm DVC / 4-ohm DVC | 3 Subwoofers ~ 2-ohm SVC / 4-ohm DVC |
| 4 Subwoofers ~ 4-ohm SVC / 2-ohm DVC | 4 Subwoofers ~ 2-ohm SVC / 4-ohm DVC | 4 Subwoofers ~ 4-ohm SVC / 2-ohm DVC |
Finding the Right Amp for Your Subwoofer
You have your sub picked out, and now you want an amplifier that will give you the maximum potential of your subwoofer. Here I will help you determine what amplifier will work for you. First, you will need to find the subwoofer’s RMS power rating. Remember, this is the amount of power the subwoofer can handle on a continuous basis. Next, you will need to determine what your subwoofer’s voice coil configuration is. For example, dual 2-ohm, dual 4-ohm, etc. This will help you choose the correct amplifier based on the sub’s final impedance and RMS rating. Let’s say you have a dual 4-ohm subwoofer that has an RMS rating of 500 watts. In order to find an amplifier that will match perfectly, you will need to choose an amp that will produce 500 watts RMS at 2 ohms, assuming you are wiring your subwoofer’s voice coils in parallel to create a final impedance of 2 ohms. This final impedance will enable your amplifier to provide its maximum RMS power output to match the maximum RMS handling of your subwoofer.
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