Upgrading your car's audio system with the best head unit and speakers available will not make much difference in improving sound quality if you're not providing it with ample and clean power. In much the same way that a small four-cylinder engine can have trouble accelerating a vehicle up a steep hill — no matter what electronics it has or tires you put on it — the limited amplifier circuitry in most stock stereos is lacking when it comes to adequately driving speakers.
In most cases, the amplifier built into a stock head unit is barely powerful enough to battle road noise, much less produce acceptable sound quality at louder volumes without distortion. Bass response especially suffers, since it takes considerably more power to accurately produce lower frequencies than higher notes. If you want louder and better sound, you'll need an external amplifier — one that easily integrates into an existing system.
If the sound quality of your car audio system leaves you wanting more, adding an aftermarket amplifier is a sure way to get it. With the easy OEM integration features of the amps mentioned below, even your basic factory system will sound better with more power driving the speakers.
What To Look for
When you are choosing an amplifier to provide your car stereo system with more power, the first consideration is how it will interface with the system's head unit. If you have an aftermarket head unit, you probably have at least one set of RCA "line-level" or unamplified output jacks available. These make hooking up an aftermarket amplifier quick and easy.
But if you would like to stick with your stock head unit to save money or to maintain factory features like steering-wheel controls and built-in navigation, adding an amplifier can still be straightforward. In this case you'll want to look for an amplifier that has "speaker-level" inputs that can accept amplified signals intended for factory speakers.
In some cases, as with premium OEM sound systems containing proprietary amplifiers, you may need special adapters to interface with the amp. It's a good idea to consult with a knowledgeable car stereo installer to find out the options available — and hassles and costs involved — if you want to add an amplifier to a premium OEM audio system.
Enough Channels To Go Around
Most car stereo systems feature speakers in at least four spots: left and right in both the front and rear of the vehicle. If you want to improve the sound of the speakers located in these positions, you can narrow your search to a four-channel amplifier. And if you're not using a huge, power-hungry subwoofer, you can look for an economical, compact amplifier with a modest watts-per-channel rating that's suitable for most stock speakers.
The DX200.4 ($200) from Kicker is an economical way to improve the sound of your factory system. The four-channel amp delivers 25 watts per channel and can be "bridged" into two-channel mode for 100 watts per channel. In addition to a standard line-level input, this amp can accept speaker-level inputs and offers a choice of three automatic "turn-on" modes to make interfacing with an OEM head unit easier. A built-in high- or low-pass crossover that routes the appropriate frequencies to the appropriate speakers and a 9-decibel bass boost centered at 40 hertz (cycles per second) can help you fine-tune the sound of your system.
The GTA-504 ($250) from Boston Acoustics is a compact four-channel amplifier delivering 50 watts per channel. It has both RCA line-level jacks and speaker-level inputs. Built-in adjustable low-pass and high-pass crossovers allow flexibility in matching the amp to your speaker's abilities. An optional remote gain control allows subwoofer-volume adjustments from the driver seat.
The MTX Terminator TN400/4 ($270) four-channel amplifier puts out 45 watts per channel, or you can use it as a two-channel 150-watts-per-channel amp in bridged mode. All that power creates heat, so the amp includes a variable-speed internal cooling fan that speeds up as system volume increases. It also has a "Smart Engage" feature that powers up the amp when it senses a signal through the speaker-level inputs, which allows it to interface with an OEM head unit without the need to run a separate "turn-on" wire.
The JL Audio JX360/4 four-channel amplifier ($300) delivers a lot of bang for the buck, with an output of 90 watts per channel. It also features an onboard crossover for properly directing frequencies that can be used in high-pass or low-pass mode, depending on your system's needs. In addition to speaker-level and line-level RCA inputs, it also has pass-through preamp outputs for adding another amplifier to your system, such as a dedicated subwoofer amp.
Blaupunkt makes both OEM head unit and portable media integration possible with its THA 475 PnP ($400) amp. Via vehicle-specific adapter cables, this amplifier can be connected to many OEM systems in a true plug-and-play fashion. In addition to speaker-level inputs and traditional line-level RCA input jacks, it also features an auxiliary input designed for connecting an iPod or MP3 player. In standard four-channel operation it delivers 75 watts per channel, or it can be bridged into a three- or two-channel mode.
Word of Warning and Wiring
A word of warning when shopping for an amp: Don't be fooled by claims of "max power" that some unscrupulous aftermarket amplifier suppliers use to sell amps. A better specification to look for is the RMS power rating, which is more realistic. Even better, look for amplifiers that have been rated using the industry-standard CEA-2006-B spec.
Professional installation is never a bad idea when adding amplifiers, but if you decide to install your amplifier yourself, you will need various installation connectors and cables to complete the job. This may include wiring for power, ground and remote turn-on as well as a fuse holder, RCA cables and various connectors.
For simple amplifier installations, many manufacturers offer complete "amp kits" that have all of the wiring and connectors needed for the job. Any aftermarket retailer that sells car audio products will also carry amplifier installation kits. Also make sure that you purchase an amp-install kit with a large enough power wire for your amplifier; the more powerful the amp, the thicker the main power wire to your vehicle battery will need to be.
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