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How to pick the perfect Power Amp for your car subwoofer

How to pick the perfect Power Amp for your car subwoofer

Choosing the best car subwoofer for your ride is the first step towards a bigger, better sound system. But a subwoofer alone is useless - you need the right kind of power amp to bring it to life. Since low frequencies have such long wavelengths, car subwoofers have to move a lot of air to get those deep bass sounds you want to enjoy. Even the best car audio systems don't have the power to move air through the subwoofer, if you just connect it up like you would with regular car speakers. This is why you need a power amp - without it, your subwoofer is largely useless.

So, we've put together this mini-guide to explain what kind of power amp you need. Problem is, there are many different types of power amps, and each is designed to power different types of speakers and subwoofers. You can't simply pull a power amp off a shelf and assume it's going to work with your chosen set-up. Some important specifications need to match up before you can add that epic bass to your morning commute. If you want to test your new system, we recommend these top bass tracks.


The best power amplifier for a car subwoofer is a single-channel amp. This means that the amp processes a single audio signal through one channel, which is wired to your subwoofer. You can wire multiple subwoofers to this single channel, but each sub receives the same mono frequency. Low-end frequencies aren't generally heard stereophonically like the midrange and high-range frequencies your car speakers produce, so one channel is all you need. The best power amps also have filters and tone controls that allow you to optimize the bass reproduction.

This Rockford Fosgate amp is well rated, and available as a single or 4-channel amp.

(Image credit: Pixabay)

RMS Watts

Subwoofers have two power-handling specifications: RMS watts (also referred to as continuous power handling) and peak watts (or peak power handling). The RMS (root mean square) wattage of the subwoofer indicates the amount of power the subwoofer can handle on a continuous basis. The peak wattage indicates the maximum amount of power the subwoofer can handle for brief periods before experiencing damage.

You need to match the RMS watts of the subwoofer with the RMS watts of the power amp. Many power amps list an RMS watts range. This range indicates the minimum and maximum power range that the amplifier is capable of producing. If the power amp has a wattage range, you want to ensure the minimum power is 75% of your subwoofer's RMS watts and the maximum is 150% of the RMS watts. If you're ever in doubt, remember an overpowered subwoofer is better than an underpowered one.

For every additional subwoofer you install to your system, the power amp's wattage range needs to reflect the additional sub's RMS watts. For example, if you install two subwoofers with a 300 RMS watts rating, then you need a power amp with a power range of 450 to 900 watts. Otherwise, both subwoofers only receive half the power they need to operate effectively. If you decide to add a second or third subwoofer to your car audio repertoire, you need to upgrade your power amp as well.

This amp is highly rated, and is a good choice for most systems: BOSS Audio R1100M Monoblock.


Impedance measures electrical resistance. Matching the impedance with your power amp is like matching a water pipe to a faucet - the water won't flow effectively if you try to fit a small pipe on a large faucet, and vice versa. Impedance works much the same way. If you fail to match the impedance correctly, your power amp and your subwoofer could over heat, leading to damage and terrible audio.

Most car subwoofers give you the option to purchase a model with an impedance of either 2 ohms or 4 ohms. Matching impedance seems like a fairly simply concept on the surface, and most of the time it is simple if you're just installing one or two subwoofers. However, it can get complicated when you're dealing with multiple subs or dual-voice coil subwoofers, which have two input and output connections. For example, if you're installing two 4 ohm subwoofers, you need a power amp with 8 ohm impedance. If you're installing a dual-voice coil subwoofer with 2 ohms, you need a power amp with a 4 ohm impedance because each connection has 2 ohms.

Once you've found a power amp that matches the RMS watts and impedance of your subwoofer, all you have to do is connect the subwoofer to the power amp and connect the power amp to your car stereo. A properly powered subwoofer can be the difference between listening to a lifeless playlist on your commute and rocking out wherever you go.