You want more power. That's the whole point of adding amps. But first you should define your power needs, so think about your system goals. If you're going to your local shop, expect your installer to pose a few questions: What kind of music do you listen to? Is it bass heavy? Are you planning to install a subwoofer? Do you listen to your music loud? Do you drive a convertible or a hot rod? How much money are you willing to spend?
If you like your music loud and bass heavy, and you’re planning to install a subwoofer, you will definitely need big power. The same holds true for people with cars that inherently have lots of road noise, such as convertibles. For most basic applications though, a quality 50-watt x 2 or 50-watt x 4 amplifier will work wonders to amplify your factory, component or coax speakers. For example, a basic system might consist of two 6 1/2” coaxes in the front doors and two 6” x 9”s in the rear. Using a 50 x 4 amplifier you end up with one dedicated amp channel per speaker. If it is not in your budget to purchase a 4-channel, a 2-channel amp could be substituted to either run the front speakers or both front and rear (with resistors to attenuate the rear). To be assured of good, “clean” power, always buy the proper amount of power for the given speakers you plan to amplify. If you underpower your speakers, you may risk pushing your amp to the limit, which could diminish sound quality by generating distortion and cause speaker and/or amplifier damage. Extra power means your amp will run cooler and more efficiently, translating into better quality sound.
How many channels?
If possible, you’ll want to dedicate one amp channel per speaker. But no worries, there are also perfectly acceptable ways to have your installer wire a 4-speaker system with a 2-channel amp. A 50 x 2 or 50 x 4 amplifier will be fine for basic 2- or 4-speaker systems. If you’re planning to power a subwoofer, a 5-channel amp is a godsend, with the fifth channel dedicated to your sub. Since bass demands more power, the fifth channel usually delivers more wattage. A 5-channel amp might spec out like this: 50 watts x 4 plus 100 watts x 1.
Most amps today are capable of being bridged. With bridging, multiple amp channels are combined to get more power from a single amp channel, allowing for excellent installation flexibility. A 50 x 4 amp could be morphed from a 4-channel into a 3- or 2-channel amp. Here’s how it might spec out: 50 x 2 plus 200 x 1 or 200 x 2. Bridging is great for sub applications.
Note: some amps include a remote level control allowing you to manage the bass level from the driver’s seat. Since bass varies greatly from one musical genre to the next, a remote sub control is a super convenient feature.
Compare Power Ratings and Specs
When it comes to power ratings, manufacturers have many different ways of saying the same thing, making it confusing for consumers. You’ll need to know what to look for when you’re shopping around. One thing you should know is that your car battery and alternator are responsible for generating the voltage and current that power your amp. But voltage is not regulated equally from car to car and may vary from engine idle to that of a higher RPM. More voltage typically equals more amp power (with the exception of amplifiers using tightly regulated power supplies). This is very important since most manufacturers rate their product at 14.4, 13.8 or 12.5 volts. Respectively, an amplifier (those using unregulated or loosely regulated power supplies) rated 50 watts x 2 at 14.4 volts may see a decrease in power output by as much as 15 percent when powered with 12.5 volts. In retrospect, a 50-watt x 2 amplifier rated at 12.5 volts may see up to a 15 percent increase in power at 14.4 volts. That, my friends, could be the difference of up to 30 watts between two 50-watt x 2 amps. It is important to know that you are comparing apples to apples since there is no governing body verifying the product specifications in car audio. While this may be problematic with certain brands, there is a way to confirm some products’ specifications. The CEA (Consumer Electronics Association) developed the CEA-2006 specification guidelines that confirm specifications. Mobile electronics carrying the label must remain true to the published specifications taken at 14.4 volts (just look for the CEA-2006 label). More information on participating manufacturers can be had at www.ce.org. However, when in doubt, ask your installer.
Some amps state “RMS” power while others utilize “continuous average” power. These monikers can be construed as the same, leaving amplifiers using this verbiage open for comparison. An amp that’s 50 watts RMS x 2 into 4 ohms (we’ll discuss ohms in a second) can effectively deliver 50 watts x 2 at the onset of or below a clipped output level (clipping is when a sine wave turns into a square wave otherwise noted as distortion). In contrast, “maximum” or “peak” power ratings are marketing terms that typically use figures relating to at least double the RMS power and are generally not practical for comparing amps (and in some cases should be followed by the clause “when lightning strikes”). An amp rated at 50 watts x 2 maximum into 4 ohms more times than not is equivalent to an amp that’s 25 watts RMS x 2 into 4 ohms.
Other amps offer “total” power ratings, such as 100 watts total RMS power. This is another tactical marketing maneuver manufacturers use that essentially is the sum of all the channels of the amplifier. In the case of my example, this could relate to an amp that is 50 watts x 2 or 25 watts x 4 into 4 ohms.
Now, back to the issue of “ohms.” Amp ratings are typically given at 4 ohms. Ohms refer to impedance or electrical resistance. Every speaker has an internal resistance due to the wire on the voice coil and additional components such as those of a crossover. Heck, even speaker wire has resistance—but let’s not get sidetracked. The majority of car speakers are 4 ohms, so that’s why amplifier manufacturers generally rate them as such. Often there will be other impedance ratings such as 2 ohm and sometimes 1 or 0.5 ohm depending on the amplifier. Again, power ratings and specs come in many different and often misleading forms, so don’t be fooled. Make sure you’re comparing apples to apples.