Matching a Subwoofer to an Amplifier- How to Calculate Your Subwoofer Amp

You simply just can’t throw good money at subwoofers and expect your car’s sound quality to impress significantly, especially when we’re talking about the bass. The thing is, just as important as buying quality subwoofers is to make sure that your money is spent on a good amplifier that’s evenly matched and work together with your subwoofer.  

Scroll down below if you’d like to learn more about matching a subwoofer to an amplifier.

matching a subwoofer to an amplifier

Important Terminologies to Remember

If you’re new to using subwoofers and amplifiers, you most likely don’t have a full understanding of the common terminology used in car audio equipment.   

The two most common are impedance (ohms) and power (RMS).  

What is Impedance (Ohms)? 

Impedance simply refers to how much electrical resistance a speaker or a subwoofer is capable of, and it is measured in “ohms”. How much impedance a subwoofer has will affect how big of a load an amplifier can handle.   

So, for example, an amplifier can only run 550 watts if the subwoofers are wired at 4 ohms but it can run 1100 watts if you wire the subwoofers at 2 ohms.   

Matching subwoofer impedance with the amplifiers isn’t too hard unless you’re talking about installing multiple subwoofers, in which case, you might want to consult an experienced professional.  

What is Power (RMS)? 

The amount of power a subwoofer can handle is represented via its peak power rating and RMS, which stands for Root Mean Square.   

RMS is the most important number you should consider because it refers to how much power a subwoofer can handle consistently. Although peak power handling is still important, it only refers to how much power a subwoofer can handle before it starts to suffer from any lasting damage.

Importance of Pairing a Sub and Amp

By design, subwoofers help increase audio bass frequency. This results in deeper and heart-pounding sound. For a proper and more noticeable boost, it’s important to pair it with an amplifier. But, if you don’t pair it with the right amplifier, you might as well not use one at all. In most cases, improperly paired subs and amps won’t work or will perform worse.


Finding the Right Amp For Your Sub 

The usual scenario is that you might already have a subwoofer installed in your car, but you want more so you go and get yourself an amp.   

How do you do that? Well, first of all, you’ll need to find the RMS rating of your subwoofer. If it’s only one subwoofer, then it’s simple. Just go with the RMS rating written on the specifications. However, for multiple subwoofers, you’ll need to add all the RMS ratings of your subs.   

Either way, you’ll want to go with an amp that can power at least 75% and up to 150% cumulative RMS rating of the subwoofers installed in your system.   

Once you’ve done that, you’ll need to find out the total impedance of your subwoofers, specifically, if they are a single voice coil, dual voice coils, or two pairs of terminals.   

This is where things can get tricky, especially with multiple subwoofers installed. If you’re unsure, consult a professional or better yet, consult multiple professionals in your area for better peace of mind. 

Finally, once you’ve figured out the RMS wattage of your subwoofer and the impedance load when wired, you’ll want to look for an amplifier that can handle the RMS wattage (75% to 150%) at the ideal impedance form.  


You have two 4-ohm subs rated at 350 watts (RMS) each, which means that you need an amplifier that can handle total RMS watts of 700 into either a 4-ohm load or 1-ohm load.   

Just keep in mind that, as long as you get high-quality amplifiers, you won’t really have to worry if you’re producing the 700 watts RMS via a 4-ohm load or via a 1-ohm load. The volume produced and the quality of the audio will both remain the same.


For better-sounding and deeper bass, it’s important that your amplifier and subwoofers have just the right amount of power handling capabilities and impedance. The more closely matched the two are, the better. More importantly, by doing so, you guarantee that your car is operating as safely as can be.   

This is because, in addition to improving sound quality, closely-matched amplifiers and subwoofers are less likely to overheat. So next time you buy a subwoofer, make sure you have a matching amplifier to give it the power it needs to operate smoothly. Now that you know how to calculate your subwoofer amp and how to match your devices properly, you’re ready to start your upgrade!