An amplifier (or amp for short) is a device that takes sound signals and makes them the way, way louder. Your car’s sound system already has one — even if it’s factory default — there’s a little amplifier built into your stereo console. Your amplifier controls a lot of things: how big your speakers can be, how many speakers you can have, how loud your speakers can get, and how clear your speakers sound at some volumes.
Your amp and speakers work together in tandem to deliver sound. It’s important to make sure that they’re matched well. This means you want to buy an amp with a channel for each speaker, enough power to get the most out of the speakers you’ve chosen, and the juice to match the impedance of your subwoofer.
Table of contents
- 1 channel car amplifiers
- 2 channel car amplifiers
- 4 channel car amplifiers
- 5 channel car amplifiers
- 6 channel car amplifiers
- 8 channel car amplifiers
- Things to consider when buying car amplifier
1 channel car amplifiers
Our Pick: Rockford Fosgate R250X1 Prime 1-Channel Mono Block
Rockford Fosgate offers a nice, small unit that’s specially designed to power your subwoofer. It runs very cool and offers a boost control at 45 Hz in addition to gain. It powered all of the subs we hooked it up to beautifully, even with the gain turned way down. It offers 150 watts RMS at 4 ohms and 250 watts at 2 ohms.
The lights on this unit are really bright. This isn’t a major concern — you can just cover them with electrical tape or a marker — but you probably want to do this before you install the unit, not after. It can be a little distracting to have your entire interior glowing bright blue.
Runner-Up: BOSS AUDIO AR4000D Armor 4000-Watt Monoblock Class D
Unlike the Rockford Fosgate, this amp works all the way down to 1 ohm of impedance. Also unlike the Rockford Fosgate, it runs fairly hot. We had our overheat and shut itself off during our test run. When we looked around online we found some advice about upgrading the capacitors inside the unit to help things out thermally.
BOSS’s amp has a wired remote, bass boost and both high and low-pass cutoffs to play with. It’s rated at quite a bit more power than the Rockford Fosgate: 750 watts RMS at 4 ohms all the way down to 3000 watts RMS at 1 ohm. If you have a 1-ohm sub or you need the extra power at a higher impedance, it’s a clear choice. If not, we think that the Rockford Fosgate is a much safer choice — the BOSS can overheat in a couple hours on a hot day, while the Rockford Fosgate ran completely cool.
2 channel car amplifiers
Our Pick: Rockford Fosgate PBR300X2 Punch 300-Watt 2-Channel Boosted Rail Amplifier
This thing offers 100 watts RMS at 4 ohms and 150 watts RMS at 2 ohms. There are a few fancy features, like a 12db/octave Butterworth crossover and a MOSFET output stage, but we were mostly interested in the price, stability, and wattage of this unit. It’s small, easy to install, and ran great in all tests. It’s priced quite competitively with other 2-channel amps in this watt range.
Runner-Up: Pyramid PB918 2,000-Watt 2-Channel Bridgeable Mosfet Amplifier
Pyramid’s 2 channel amp is set up so you can run either two smaller speakers on separate channels or one big speaker bridged. It’s got fantastic power, especially for the price, offering 2000 watts peak when bridged. It’s also fantastically cheap, coming in at about half of the cost of the Rockford Fosgate model at the time of this writing. Pyramid claims that it’s entirely free of any heat problems because of its unique design, in which the entire outer shell acts as a heatsink. It offers both high pass and low crossover options for powering both subwoofers and normal speakers.
It’s worth noting that you may experience some difficulty using a 0 gauge wiring kit with this amp. Be sure to check out the power inputs on the unit itself before buying a kit — the inputs are a bit small for 5000-watt wiring. Still, we think this is one of the best ways to power most subwoofers between 1000 and 2500 watts peak.
4 channel car amplifiers
Our Pick: Alpine MRV-F300 4-Channel RMS 50 Watts x4
This amp is incredibly tiny for how clear it sounds and how powerful it is. It’s actually rated at about 95 watts RMS per channel at 2 ohms, which is some 20 watts higher than Alpine advertises it. We found it ran fantastically cool in our tests, delivering amazing sound to everything we threw at it. It’s priced VERY competitively, too — it’s cheaper than a lot of 4 channel units we looked at that delivered far less power in bulkier packages.
Runner-Up: Rockford Fosgate R400-4D 400 Watt Full-Range Class-D 4-Channel Amplifier
Rockford Fosgate’s 4 channel amp delivers 100 watts RMS / channel at 2 ohms. It’s got built-in thermal protection and the ability to boost 45 Hz by up to 18 dB on the unit itself. The controls are clear and easy to access, giving you the ability to fine-tune your sound. Like other units, it’s got separate gain knobs for front and rear speakers, meaning you can run this with a mismatched set.
In our tests, this unit ran great with no heating issues. It sounded very clean and clear, especially at lower gain settings. It’s quite comparable with the Alpine above, but it’s a little bit pricier at the time of this article. We recommend the Rockford Fosgate if you can pick it up on sale or if you need the little bit of extra wattage it provides.
On the Budget: Planet Audio AC1200.4 ANARCHY
Planet Audio’s offering claims to be superior to both Alpine and Rockford Fosgate’s 4 channel amps in every way, at half the cost. It offers 225 watts RMS at 2 ohms (113 @ 4), with a variable low pass and a bass boost. We thought it was too good to be true — and it was. Above about 70 watts RMS at 4 ohms, the unit distorts sound quite noticeably.
What this means in practice is that you shouldn’t use this amp at high gain. Below 70 watts, it’s great — it runs a bit warmer than the Alpine, but it never got hot enough to turn off in our tests. For smaller speaker systems on a budget, it’s a great choice.
Need more options? See our complete review of best 4 channel car amps.
5 channel car amplifiers
Our Pick: Alpine MRV-V500
Alpine again offers a fantastically compact unit. Refer to our comments on the 4 channel version: this is the same amp with an additional high-wattage channel for 2 and 4-ohm subs. The subchannel offers 250 watts RMS at 2 ohms and 150 watts RMS at 4 ohms.
Runner-Up: JL Audio XD700/5v2
This unit comes in at about twice the cost of the Alpine model — and for some systems, it’s totally worth it. JL Audio manages to deliver 100 watts RMS at 2 ohms to the 4 channels while maintaining 300 watts at 2 ohms for your sub. The amp is low profile, easy to install, and runs incredibly cool. It delivers clear sound at ludicrous volumes — this thing seemed to get even louder than the numbers would suggest in our test setup.
Our biggest beef here is the way this interacts with subwoofers. For the price, we’d expect to be able to handle powerful, low impedance woofers. The JL can support a slightly larger range of subs than the Alpine — but only slightly. Considering we can comfortably buy the Alpine and a 1-channel amp for the price of this JL, we’re not entirely convinced.
On the Budget: BOSS AUDIO PV3700 Phantom
Boss oversells this unit significantly. In reality, it offers about 960 watts RMS total across all channels at 2 ohms. This gives you about 150 watts for your front and back speakers and about 300 watts for your sub. It’s got variable low and high pass filters, separate level controls for the sub, and an adjustable bass boost. It runs a bit hot but was fine through our testing.
If you can get over the misleading power rating Boss gives you, this unit is fine — it delivers more than enough power for most systems, to the point where you’ll probably wind up turning the gain way down. It’s pretty cheap, coming in at about 2/3’s the cost of the Alpine at the time of this article. If you’re looking to save some money and don’t mind the heat or the lower-than-advertised wattage, this amp is a fine choice.
Need more options? See our complete review of best 5 channel car amps.
6 channel car amplifiers
Our Pick: Lanzar HTG668BT Heritage Series
Offering 250 watts RMS at 4 ohms, this is a powerful unit for serious systems. Frustratingly, it seems that Lanzar skipped out on quality control to build Bluetooth streaming directly into this amp. Our unit worked for about two hours on high gain before shutting itself off due to heat.
Realistically, this amp is more than fine for your system — you probably won’t want to use anything close to the full output — 250 watts is ridiculous. The ability to bridge channels and deliver 1000 watts makes it competitive with the 5 channel units for running a sub, although the lack of bass control can make this a bit tricky. Still, it’s pretty cheap, coming in cheaper than two of the 5 channel units we reviewed.
If you’re plugging this in somewhere where you benefit from the Bluetooth (unlikely; all of our stereos already hooked up with our phones) or you have a high wattage system that you don’t plan to run at high volume all the time, this is a great pick.
8 channel car amplifiers
Our Pick: Lanzar HTG888 Heritage Series
Lanzar’s 8 channel amp is about the same price as the 6 channel — because they skipped the Bluetooth. Offering similar power, it comes with a similar set of problems, It’s got a colossal amount of wattage under the hood, but it suffers from quality control issues and produces more heat than we’re entirely comfortable with.
Again, though, it’s fantastically cheap and freakishly overpowered. For most systems, you’ll be running this at maybe 30% gain most of the time. Being able to run 8 individual speakers off of one amp — or 6 and a sub, or 4 and two sub setups, or even 4 bridged setups at 1000 watts RMS at 4 ohms — is incredible, especially considering the price.
Things to consider when buying car amplifier
Number of channels
You need one channel on your amplifier for each speaker you want to run from it, with some consideration for your sub. This means if you have two speakers in front and two in the back, you’ll need a 4 channel amplifier with no subwoofer.
If you want to run a sub off the same amp, you usually want a 6 channel amp so you can bridge two channels together in order to provide enough power to run your subwoofer. You can also run your sub off of a separate one-channel amp.
These are specially designed to work with the low impedance of subwoofers and have special controls to help you fine-tune your bass.
Somewhere in your speaker specifications is a power rating (something like “10-75 watts RMS power range”). In order to determine how powerful your amp needs to be, take 75% of the higher number. That’s the minimum RMS wattage per channel you want to look for in an amp.
You can go up to about twice that (or 150% of the higher number) before you start overpowering your speakers. If your speakers have a really low power rating, don’t worry too much about this — you can turn down the gain on your amp enough that it won’t completely fry things.
You won’t find too much difference In between 75% and 150% of the speakers’ top power rating until you get to higher volumes. You’ll tend to get clearer sound at higher volumes with higher wattage amps. If you think you’ll be turning your speakers up all the way a lot, try to get an amp that’s rated a bit higher up within that range.
Impedance is a measure of the load your subwoofer puts on your amplifier. Amplifiers are rated to work with different ranges of impedance. Ideally, you find an amplifier that’s rated to provide 75%-150% of your sub’s wattage at your sub’s exact impedance.
In a multi-subwoofer system, you can wire your subs together in different ways to change their impedance to better match your amp. Multi-channel amps often don’t work with subs under 4 ohms, so be extra cautious when using these in the same system.
Sometimes, matching the exact impedance value isn’t possible. You can estimate wattage at odd impedance values with a bit of math: at 4 ohms, the amp puts out about half as much wattage as it does at 2 ohms and twice as much as it does at 8 ohms. This means if you have a 1.3-ohm sub, for example, you can use your amp’s 1-ohm wattage and just take away a couple watts to estimate how things will work.
Sometimes, matching the exact impedance value isn’t possible. You can estimate wattage at odd impedance values with a bit of math: at 4 ohms, the amp puts out about half as much wattage as it does at 2 ohms and twice as much as it does at 8 ohms.