An amplifier can greatly improve your listening experience as it gives your speakers enough power to drown out road noise and engine sounds. If your car audio setup contains multiple speakers or subwoofers, then you’re better off buying a multi-channel amplifier.
In this article, I’ve reviewed what I consider to be the best 4 channel amplifiers for 2019.
Car Amplifier Buying Guide
In order to buy a unit that suits your needs perfectly and is compatible with your existing car stereo set up, you need to know a little bit about amplifiers. Hence, in this section, I’m going to be talking about the factors you need to consider when you’re picking an amplifier, including a few important technical specs. Don’t worry, I’ll go easy on the jargon and break down everything into the simplest language.
Class And Efficiency
When you’re browsing through 4-channel amplifiers, you’ll come across talk of ‘classes’ but what exactly does it mean? There are four main classes of amplifiers: A, B, A/B and D and the main distinguishing factor between them is efficiency. Where amplifiers are concerned, efficiency is a measure of how much Alternating Current (AC) a device can pass to another while consuming the least amount of Direct Current (DC). Due to differences in the circuitry, efficiency varies between each class of amplifier:
Because of the simple way in which their circuits are designed, Class A amplifiers conduct electricity 100% of the time. The benefit of this is that it allows Class A amps to provide the purest signal path out of all.
On the other hand, there are two major drawbacks to this continuous conduction. Only a small percentage of this electricity will be utilized by speakers, which puts the efficiency of a typical Class A amplifier at an appalling 30%. The excess electricity is eventually converted to heat energy. As a result, a lot of Class A amplifiers tend to overheat with prolonged use.
Class B amplifiers only conduct electricity half the time, when compared to Class A. This drastically reduces the percentage of electricity that is wasted which in turn increases efficiency to 70%. However, there is one major downside to the way Class B amplifier circuits are set up: you’ll have to deal with a tiny amount of distortion.
Class A/B circuits combine elements from Class A and Class B amplifiers. Class A/B amplifiers don’t have issues with distortion despite having a Class B chain in their circuits. This is due to the presence of biasing diodes that help to cancel it out. With class A/B amplifiers you get the best of both worlds: the signal purity of Class A with the power efficiency of Class B.
Class D amplifiers have the highest efficiency (95%). This is largely because they’re output transistors don’t retain any electricity when the unit is turned off. Hence, there is no excess electricity left to be converted to heat. Class D amplifiers, however, have the least signal purity out of all the aforementioned classes.
The Technical Specs
When you’re buying an amplifier you need to pay attention to a few important technical specs including power output, frequency response, and speaker sensitivity. These will help you determine whether or not an amplifier is compatible with your current set up.
Amplifiers provide more power to speakers – that’s how they boost signals and make things louder. If you’re like me and you love blasting music out loud on a regular basis, then the more power the better. However, there’s actually a limit to how much power your speaker can handle. If you go beyond this limit, you’ll risk heat damage to the speaker’s internal components.
There are two main metrics that tell you about a speaker’s power handling: the Maximum RMS and Peak Power. The former indicates how much power (in watts) a speaker can safely receive on a continuous basis. The latter lets you know what the absolute limit is in terms of how much power the speaker can handle. Peak Power is essentially the point of no return. Go beyond this threshold and you’ll definitely cause some irreparable damage to your speakers.
Likewise, amplifiers have RMS and peak power ratings as well but they indicate the power output. Hence, when you’re buying an amplifier, make sure that the speaker’s RMS is equal to or greater than that of the amplifier. The same goes for peak power.
Speaker sensitivity is a measure of how loud (in decibels) a speaker will get when you drive it with one watt of power. Let’s say your speaker has got a sensitivity that’s around 85 dB. This essentially means that if you supply the speaker with one watt of power, it’s going to output sound at a moderately loud volume. For each additional watt you supply, the volume increases by 3dB.
Speaker sensitivity helps you determine how much power output your amplifier will need to have. If your speaker is highly sensitive (i.e it’s rating is above 90dB) then you won’t actually need a powerful amplifier since it can get loud without a whole lot of power behind it. If you’ve got a speaker with a low sensitivity rating, on the other hand, you’ll need to give it more power in order to reach the same volume level.
Frequency response tells you what range of frequencies an amplifier can handle. While some amplifiers are capable of handling the entire audible spectrum (20 Hz to 20 Khz) some are only capable of processing bass signals (20 Hz to 250Hz). The former is compatible with any type of speaker while the latter is made specifically for subwoofers.
The Number of Channels
How many channels do you need in an amplifier? That mainly depends on what type of speakers you’ve got and how many. For instance, if you’ve got two stereo speakers mounted on either side, then you’ll need a stereo dual-channel amplifier to get the best out of it. Stereo channels transmit the left and right channel separately which makes for a more accurately panned sound (i.e all of the instruments in the song will be correctly positioned).
Mono channels, on the other hand, send both right and left panned signals together. If you’ve only got a single speaker, then a mono one channel amplifier is what you’ll need.
If you’re buying an amplifier just to power a subwoofer, you’ll need a high-powered mono channel since subs need more power than regular speakers. However, you can also bridge a dual or 4-channel amplifier into a single or dual-channel mode respectively that’s capable of delivering a lot more power.
- 1000 Watts Max Power
- Automatic signal sensing and Turn-On
- Variable high pass filter
- Adjustable bass boost
Wide Frequency Response
With a frequency response of 20 Hz to 20 kHz, the Pioneer GM-A6704 is able to cover the entire audible spectrum from sub-bass to upper-treble signals. This means the amplifiers are compatible with both regular speakers and subwoofers.
Each of the four channels in the GM-A6704 has a maximum RMS of 60W which I found to be more than adequate for my daily listening sessions. I quite enjoyed cranking the volume on my stereo and having the music drown out all the annoying road noise.
The Pioneer GM-A6704 can be bridged into a 2-channel mode, allowing you to pair it up with a couple of subs. When bridged, the GM-A6704 is able to output 190 W RMS through each channel.
Variable High Pass Filter
High Pass Filters cut off frequencies that are below a certain threshold. For instance, if the cut-off frequency is set at 50 Hz, the filter will allow all higher-pitched frequencies to pass through while blocking out the rest. The Pioneer GM-A6704’s High Pass Filter allows you to adjust the cut-off frequency between 40 Hz to 500 Hz, which is greater than you’d normally get. Typically, amplifier high pass filters have an upper limit of around 250 Hz so this was a welcome change.
A filter like this is quite useful if you’ve got a speaker that isn’t so great at handling sub-bass. You can simply cut off those frequencies altogether, getting rid of any distortion in the low end.
Variable Bass Boost
If you like your bass particularly loud and prominent in the mix, then you might find this boost quite handy. It allows you to spike up the low-end volume by up to 12 decibels.
With a width of 14 inches, the GM-A6704 is definitely a bit on the bulky side which limits your mounting options. However, it’ll still fit under the seats of most cars.
- Wide Frequency Response
- Bridgeable into a 2-channel mode
- Variable high pass filter which allows you to clean up the low-end distortion
- Variable bass boost
- A bit bulky
- 50 Watts x 4 @ 4-Ohm / 75 Watts x 4 @ 2-Ohm / 150 Watts x 2 @ 4-Ohm...
- Accepts High Level & RCA Level Input
- Cast aluminum heatsink with Top Mount Controls
- 12dB/octave crossover
- Class A/B Circuit Topology
Wide Frequency Response
Just like the Pioneer GM-A6704, the Rockford Fosgate R300X4’s frequency response spans the entire audible range from 20 Hz to 20 kHz. Hence, whether you’re looking to power your speakers or a pair of subwoofers, the R300X4 should be able to handle it.
50 Watts Rms
The R300X4 is able to output 50 watts of power through each of its four channels on a continuous basis without over-heating. Whether you’ve got a highly sensitive speaker or not, this should be quite enough to blast your music to the point that your ears start to ring. Not that I’d recommend it, of course!
Compatibility With Subwoofers
Like the Pioneer GM-A6704, the R300X4 can be converted to a 2-channel mode if you need to hook up a pair of subwoofers to it. Once the amplifier is set up in this mode, each of its channels will output 150 RMS.
Variable High- And Low-Pass Filters
The R300X4 features both high- and low-pass filters that can be set to any frequency between 50 and 250 Hz. Low-pass filters work in the opposite manner to high-pass filters. They block out signals that are higher-pitched than the cut-off frequency while letting the lower ones pass through.
Selectable Bass Boost
This boost works just like the one I found in the Pioneer GM-A6704. It focuses specifically on 45 Hz sub-bass frequencies, allowing you to boost them by either 6 or 12 decibels. This causes those really low bass beats to become more prominent in the mix and so I find that it’s very appropriate for electronic dance music.
Having a width of 13 inches and a depth of 7, this amplifier is a bit on the bulky side.
- Can be paired up with both regular speakers and subwoofers
- 50 Watts RMS with each channel
- High and low-pass filters allow you to cut out distortion
- Selectable bass boost helps to add more ‘attack’ to the low-end
- It’s not very compact
- Rms power
- 4o: 50 watts x 4
- 2o: 75 watts x 4
- Peak power: 600 watts
- Signal sensing turn-on
Handles all Frequencies
Like both of the aforementioned amplifiers, the KAC-M3004’s frequency response also spans the entire audible range (20 Hz to 20 kHz). This ensures that all the frequencies in your music are boosted instead of some being ‘missed out’ by the amplifier.
Kenwood KAC-M3004 is able to output a maximum of 50 watts from each of its channels consistently. Hence, it’s perfect for any speakers with low sensitivity as you’ll be able to get really loud volumes out of them.
Like most great top-quality 4 channel amplifiers, the Kenwood KAC-M3004 can be bridged into 2-channels, allowing you to connect to a pair of subs. When bridged, the amplifier will output 150 watts through each channel, which I find is adequate for most high-powered subs.
The KAC-M3004’s are covered with a conformal coating which is a kind of polymeric film that is both dust and water-resistant. This very useful if you’re the off-roading type and you tend to drive through rough dusty terrains on occasion.
High- and Low-Pass Filters
The KAC-M3004 allows you to set the cut-off frequency anywhere between 50-200 Hz and you can choose whether to cut off frequencies higher and lower than this mark. If you don’t have a subwoofer and your speaker tends to rattle while handling sub-bass beats, then I’d recommend setting the high-pass filter at around 60 Hz to get rid of the excess distortion.
KAC-M3004 measures 7 inches in width, 3 inches in depth and an inch in height. Hence it’s quite a compact unit and pretty easy to mount.
- Handles all frequencies from sub-bass to upper-treble
- 50 Watts RMS with each channel
- The circuit is dust and water-resistant
- Variable high- and low-pass filters
- I’m having trouble thinking of any
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Taramp’s claims that the TS 400X4 has a frequency response of 18Hz to 30kHz. However, this appears to be nothing more than a marketing ploy considering that the human audible range is between 20 Hz to 20 kHz. That being said, I didn’t notice any details missing from the music while I was using this amplifier which meant that it covered the full audible range.
100 W RMS
The TS 400X4 is able to output a maximum of 100 W through each channel on a regular basis, provided that the impedance (resistance) is set at 2 ohms instead of 4. This is way more than the average person needs to power their speakers.
When bridged into 2-channel mode, each channel is able to output double the amount of power (200 W). However, make sure that your subs can handle this much power before you purchase the TS 400X4.
High- and Low-Pass Filters
Both the high and low-pass filters in the TS 400X4 have the same fixed cut-off frequency at 90 Hz. Personally, I would have liked the cut-off frequency to have been adjustable or at the very least have it set to 60 Hz which is the upper-threshold for the sub-bass region.
With a width of 5 inches and a depth of just 2 inches, the TS 400X4 is extremely compact. Hence, it’s very easy to mount inside a car.
- Handles the full range of frequencies
- 100 W RMS with each channel
- High and Low-pass filters
- Extremely compact
- Filters aren’t adjustable
- 500-Watt MOSFET 4-Channel Class A/B Power Car Amplifier
- RMS Power at 2 Ohms: 125 Watts x 4 Channels
- RMS Power at 4 Ohms: 75 Watts x 4 Channel
- User Adjustable Controls: Gain, Variable LPF, HPF, Bass EQ Switch (0,...
- 4 Way Protection Circuitry | Frequency Response: 20 Hz - 20,000 Hz
Like all of the amplifiers reviewed above, the Skar Audio RP-75.4 covers the full range of frequencies you’ll hear in any piece of music, from the low, heavy sub-bass signals to the highest screeching upper-treble sounds.
125 Watts RMS
125 watts is more than anyone really needs and it’s more than what speakers can typically handle. Fortunately, you can switch the impedance to 4 ohms with this amplifier and bring the RMS down to 75 watts, which is way more manageable.
When bridged into 2-channel mode, the Skar Audio RP-75.4 audio is able to output up to 230 watts through each channel. Hence, this amplifier is designed to work with the most powerful subwoofers in the market.
Variable Gain Control
This feature allows you to limit the amount of signal that is received by the amplifier. With some tweaking, you’ll be able to increase the ‘cleanliness’ of the signal by cutting out unwanted distortion.
Variable Low- and High- Pass Filter
The Low-pass filter is adjustable from 50 Hz to 500 Hz which covers a range from mid-bass to midrange. On the other hand, the high-pass filter extends up to the 5000 Hz range, allowing you to manipulate treble frequencies as well.
Bass EQ Boost
The Bass EQ switch lets you boost the low-end by either 6 or 12 dB. If you feel like your music is lacking bass, then this can help make the lower frequencies more prominent in the mix.
- Full-range amplifier
- Variable gain control helps remove excess distortion from the signal
- Comes with a selectable Bass EQ switch
- Can only be paired with really high-powered speakers
The Best Overall
Choosing my overall favourite was quite a difficult task, especially considering that all these amplifiers had many similarities. In the end, I chose the one that I thought had a bit more edge compared to others: the Kenwood KAC-M3004.
There were several things about this amplifier that strongly appealed to me. First of all, the RMS of 50 watts was perfect; not too high and not too low. The last thing I wanted was to blow out my speakers by cranking the volume too high. I liked the variable high-and low-pass filters as they allowed me to minimize the distortion in the sub-bass and upper-bass regions. Lastly, the amplifier was compact enough so that I had multiple mounting options.
Frequently Asked Questions
How Many Speakers Can I Put On A 4 Channel Amp?
You can connect one speaker to each channel, so that makes four speakers in total. With right wiring, some 4 channel amplifiers may allow you to connect two speakers to one channel, allowing you to have up to 8 speakers in your set up. This is typically true if the amplifier has a 2-ohm setting, which causes the amplifier to pump out twice the usual RMS.
If your 4 channel amplifier is bridgeable, you’ll be able to connect two subwoofers.
Is A 4 Channel Amp Strong Enough For Subs?
If your amp is bridgeable then you’ll have a way to drive more power into a couple of subwoofers. Having a 2-ohm setting will also come in handy as it’ll allow the amplifier to put out more power.
How Is A 4-Channel Amplifier Different From A 2-Channel Amp?
Sometimes the 2-channel mode present in 4-channel amplifiers tends to throw people off. It’s less confusing if you think of the latter as being two 2-channel amplifiers. When wired correctly, you can ‘bridge’ the amplifier so that it uses only 2 channels.
Will An Amp Make My Speakers Sound Better?
It’ll certainly make your speakers louder which in turn will help it overpower background noise. As a result, you’ll be able to hear your music with greater clarity.
Can I Connect An HU Which Has Only 2 Channels To A 4-Channel Amplifier?
Yes, you’ll be able to do this with two RCA Y adapter cables. Connect your head unit’s left RCA jack to the front and rear amplifier inputs and do the same for the right RCA jack. And that’s it!
The products featured on this page were last updated on 2020-02-23 at 01:23 /. Affiliate links / Images from Amazon Product Advertising API.