When an audio enthusiast goes shopping for an amplifier, the question of “how much power do I need?” comes up almost every time. There are a few factors to take into consideration when answering this question. This article looks at those factors and provides some technical background to help support your decision.

Why Do We Need Power?

Quite simply, when you send more power to a speaker, it moves farther and produces more output. Two limiting factors within the speaker itself control how much power it can handle. At higher frequencies, the limit is heat. Speakers are notoriously inefficient. The best convert about 2% of the energy sent to them into sound and the rest is converted to heat. When you send 60 watts of power to a speaker, most of that energy heats up the voice coil and the components around it. Eventually, those components will reach a temperature where they will fail. The speaker will usually stop working at this point, or shortly after.

The second limiting factor is how far the speaker can move. Inexpensive midrange speakers may be able to move back and forth about half an inch without creating massive distortion. Higher-end speakers have as much as twice as much cone excursion capability. (Speakers don’t sound the same at high volumes as they do at low. Audition your speakers at the volume you will be using them.)

Power vs. Output

Power works like this: When you double the power going to a speaker, the output increases by 3 dB. That is not a large amount. In fact, it is the smallest change in amplitude that is perceivable across the audible frequency range. (1 dB is the smallest perceivable change in amplitude where our hearing is most sensitive – 1 to 2 kHz).

Perceived volume is a different beast. An increase of 10 times the power sent to a speaker produces a doubling of perceived volume.

Speaker Efficiency

Another consideration in choosing an amplifier is the efficiency of your speakers. An inexpensive conventional midrange speaker may produce an average output of 91 dB when measured 1 meter away from the speaker cone and when driven with 1 watt of power. A high-quality speaker will likely be less efficient, but capable of playing over a wide range of frequencies. A measurement of 85 dB efficiency at the same distance and power level is not uncommon.

How Loud Do We Need it?

A typical RMS sound pressure level for an orchestra, when you’re seated three or four rows back from the musicians, is around 100 dB. If we use our analogy of the 85 dB efficient speaker, we need 31.6 watts to get that speaker to play 100 dB. The problem is that this is the average power, not the peak power. Perhaps the performance crests at 110 dB? In that case, we need a peak power level of 316 watts. Just keep in mind that the speaker components are likely to melt if you keep this effort up for any significant amount of time.

We don’t suggest buying any speaker based on its efficiency. Criteria like linearity, lack of distortion, application limitations and frequency range are far more important. If you need it loud, buy more speakers, or larger speakers.

Distortion Happens

What happens if we run out of power in an amplifier? We get distortion. This distortion creates all sorts of high-frequency harmonic content. That increased high-frequency energy is what causes tweeters to fail. We need to choose an amplifier that will allow our speakers to play loudly enough without running out of power.

You are better off buying a 100 watt per channel amplifier and only using 50 watts than you are buying a 50 watt amplifier and occasionally causing it to distort. Remember, those 50 extra watts only result in an increase in output of 3 dB – assuming the speaker can handle it.

It Takes Power to Make Power

A consideration that many people overlook is the ability to supply an amplifier with the power it needs to produce the power you want. Modern vehicles have electrical systems with reduced power production capabilities. Smaller alternators, smaller batteries and smaller wiring save weight. Reduced weight transforms into better fuel economy for the vehicle.

As a general rule of thumb for power consumption calculations, you can assume that every 100 watts of power from an amplifier will require about 10 amps of current from your electrical system. Yes, some amplifiers are more efficient than others, but this serves as a good, quick guideline.

If you want to purchase a 650 watt amplifier to power your subwoofer, then your electrical system (battery and alternator) has to be able to provide it with about 65 amps of current. This power requirement is on top of what is required to run the vehicle. The computers, lights, ignition system, radio and heater all consume power as well. On a modern compact car, it would be no surprise if you only had 30 to 40 amps of power left over for an amplifier.

You can get away with a big amplifier – but you can’t play it indefinitely, even with the vehicle running. Once you have exceeded the power delivery capabilities of the amplifier, the battery will start to supply current. You can kill a car battery, even with the vehicle running. Once you shut the car off, you may not have enough energy in the battery to restart it.

Blowing up Amplifiers

Amplifiers do not like to be starved for power. When you run out of power to drive your amplifier, in most cases, the amplifier rail voltage starts to drop. Power starvation causes the maximum undistorted power production of the amplifier to decrease. We are back to the same scenario: Distortion causes harmonics, and harmonics can damage fragile speakers.

If you have had an amplifier fail, and the failure was because the power supply section of the amp self-destructed, chances are you were not able to feed the amp properly.

How Much Amplifier Power Do You Need?

The solution: Buy as much as power as you can afford. Buy the biggest that will physically fit in your application. Get the highest-performance amplifier you can. Make sure your installer uses properly sized wiring to install the amplifier. Upgrade your car battery to a high-performance, high-capacity unit if you need more reserve power.

For more information, visit your local mobile electronics specialist retailer. Be honest about your needs and expectations for your audio system. They will be able to suggest a solution that sounds fantastic and will offer years of reliable performance.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.

One of the most critical components in a high-quality vehicle entertainment system is your car audio amplifier. While the concept of increasing the power of an audio signal is simple, it can be somewhat complex to execute elegantly the process. Amplifier design is as much as science as it is an art form. In this article, we will look at everything you need to know to buy the right amplifier for your system.

How We Measure Car Audio Amplifiers

For more than 100 years, people have been using amplifiers to take a small audio signal and increase its power so it can move a speaker. We measure an amplifier’s capacity to do work in watts. Before the industry had a reference set of guidelines for measuring amplifier power, we would see outrageous claims from otherwise minuscule products. The Consumer Technology Association (formerly the Consumer Electronics Association) has worked with industry experts and manufacturers to produce a set of standards to allow the power produced by different brands, makes and models of amplifiers to be comparable. This standard is currently known as CEA-2006A. When you see the associated logo on a product, you can be confident that the power specifications are real and directly comparable.

Features Help Increase Performance

Modern car audio amplifiers are equipped with many different features. These can include crossovers, bass boost circuits, remote level controls and equalization. Crossovers allow your installer to limit the range of frequencies that the amp will reproduce. In the case of a subwoofer amplifier, we can send the entire audio spectrum to the amp. With a low-pass crossover set, only those frequencies below the crossover point will be amplified and sent to the speaker. A high-pass crossover does the opposite, sending only high-frequency information from the input to the output of the amp.

Limiting which frequencies pass through the amplifier allows the speakers to operate within the frequency range for which they were designed. You wouldn’t want bass information to be sent to your tweeters, nor would you want midrange and high-frequency information to be sent to your subwoofer. Almost every car audio amplifier includes crossovers.

Infrasonic or subsonic filters and bass boost controls are additional tuning options that can be used to help maximize the performance of a dedicated subwoofer amplifier. A remote level control – something also found on most subwoofer amplifiers is a volume control for the amp that can be mounted in the front of the vehicle. This control gives you the option of fine-tuning the amount of bass right at your fingertips.

Auditioning a Car Audio Amplifier

Quantifying the performance of a car audio amplifier can be very difficult. The speakers connected to the amplifier are an infinitely bigger contributing factor to how a system sounds. To properly audition an amp, you need to compare it to another using the same set of speakers. A display board in a car audio specialty retailer is a great way to do this. You will want to ensure that the volume level of all amplifiers is the same for the comparison to be valid.

How can the design of an amplifier affect the way it sounds? There are always exceptions, but for the most part, whether the amp is a Class AB or Class D design can have an effect on the high-frequency performance. Class AB amps are often more detailed in the highest of frequencies. Switch back and forth between amplifiers on a display and listen to the ring of a crash or ride cymbal, or that of a triangle. You want to hear clarity and detail.

At the opposite end of the spectrum, the impact and definition of lower frequency information can show off differences in the design of an amplifier’s power supply and the way the amp behaves when amplifying a complex signal. What you want to listen for is the perceived “speed” of the car audio amplifier. When a drummer hits the rim of a tom with his stick or the skin of the bass drum with the pedal, you want be startled. It should be very tight and controlled. The sound should be clear and natural.

One thing you don’t want to hear is warmth. While this goes against what many people perceive as good, warmth can be a sign of even-order harmonic distortion. The best amplifiers don’t change the sound; they just make the signal louder.

What’s Right For You?

When it comes to choosing an amplifier for your mobile entertainment system, the right amp for you is the one that fulfills your system requirements. A four-channel amplifier has always been a great starting point for system upgrades. They can be used to run four speakers and a subwoofer. If a dedicated subwoofer amp is added later on, that four-channel amp can do an even better job of powering those same four speakers. A lot of specialists like to use a four-channel amp to power a set of midrange tweeters and some form of electronic crossover to split up the audio signal between the two.

Amplifiers are available with one to eight channels at power levels from 35 watts per channel to almost 20,000 watts. Always make sure you have enough power for your system. If saving for another few weeks will let you purchase a more powerful amp instead of one that is “just enough,” it is well worth waiting.

The Latest And Greatest

In the past few years, many companies have introduced car audio amplifiers that include powerful DSP processors. These signal processors provide your installer with more control over system crossovers and add time-alignment and advanced equalization options. In the hands of an expert installer, this can add amazing accuracy and realism to a system. When tuned properly, they are the icing on the cake!

A Word About Installation

While car audio amplifiers seem like one of the easiest components to install in a vehicle, the challenge of sourcing a proper audio signal for that amp from a factory radio and dealing with varying current delivery challenges found in today’s automobiles can make proper installation difficult. Having an experienced technician at a car audio shop install and configure your amp is highly recommended. In many cases, manufacturers offer an extended warranty when their products are installed by an authorized dealer.

Visit your local car audio specialist retailer and bring along your favorite music. Listen to as many different amplifiers as you can, then choose the one that meets your system needs, your performance goals and your budget.

This article is written and produced by the team at www.BestCarAudio.com. Reproduction or use of any kind is prohibited without the express written permission of 1sixty8 media.