Day after day, we see clients who have purchased extraordinarily large car audio amplifiers and expect them to make their full rated power using the stock electrical system in their car or motorcycle. This article will look at amplifier efficiency, how vehicle charging systems work, and why it takes power to make power.

Let’s Talk About Car Audio Power Amp Efficiency

Mobile audio amplifiers need to draw current from your vehicle’s electrical system to function. They need power to feed the circuitry that operates the amp and processes the audio signal. Of course, they also need power to drive your speakers. On the high end, a thoughtfully designed Class-D amplifier may use 90% of the energy it consumes to drive speakers. On average, this number is closer to 80% and drops into the 60% range when amplifiers are loaded down. Class-AB amplifiers, though they typically sound better, peak in the 60% range at full power and can drop into the 30s and 40s at lower output levels.

Where does that power go? Let’s say you have a four-channel amp that is rated to produce 150 watts per channel. If the amp has an efficiency rating of 86%, it will need to consume 698 watts of power to produce that 600 watts. Where does that extra 98 watts go? Almost all of it is converted to heat because of losses in the power supply and output switching stage components. If your electrical system is running at 13.2 volts, the amp will need to draw about 53 amps of current to produce 600 watts of power to your speakers.

In a second example, let’s say we have a similarly powerful amplifier, but this unit only has an efficiency of 68%. To produce 600 watts of power, it needs to consume 882 watts of power. That’s right; this amplifier is then going to convert 282 watts into heat. As such, the heatsink would need to be three times larger than the preceding amp to maintain reliable operation. In terms of current draw, this second amp will need 67 amps of current to make the same power. That’s an extra 14 amps that will be converted to heat and nothing more.

Which amplifier would you buy?

Automotive Electrical and Charging Systems

At the most basic level, the electrical system in our car or truck, or on a motorcycle or side-by-side, comprises a battery and an alternator. The battery is there to start the engine. Once started, the alternator takes over the operation of the vehicle and recharges the battery. If sudden high-current requirements exceed the current production capabilities of the alternator, the battery will often provide some extra current, albeit at a lower voltage.

Vehicle manufacturers are doing everything they can to improve the efficiency of modern vehicles. The switch from halogen and HID headlights to LED can reduce current consumption by several amps per light. Less current draw means the car can be wired with smaller cabling, which saves additional weight and increases fuel economy while improving handling, road-holding and braking performance.

Let’s say you have a typical pickup truck. It could be a Ford, Chevy or Toyota. Unless you’ve opted for a special towing or heavy-duty package, the truck is going to come with an alternator capable of providing about 200 amps of current. The alternator needs to have enough capacity to run the engine, the computers, safety system, climate control system, lighting and such accessories as security and maybe a keyless entry system. Even the radio needs a couple of amps of current to power the display and keep the processor running. The alternator also needs to charge the battery, which can consume a significant amount of current if the vehicle has been sitting for a few days.

To give you an idea of how much power you have available, a 2015 Civic comes with an alternator capable of producing about 95 amps of current. A 2018 Dodge Challenger with the 5.7L V8 has an alternator in the 160-amp range. A newish EcoBoost Mustang has a roughly 175-amp capacity alternator.

If you want to undertake a little experiment, have four friends hop in the car with you and go for a drive. Turn on every electrical accessory you can find. That will be the defroster, blower motor, high-beams, the stereo and heated seats. Now roll the windows up and down consistently and, if the vehicle has one, open and close the sunroof. You can kill the car battery while driving because a modern alternator only provides enough current for the average load the vehicle will see – not the peak load.

Another consideration is that alternators are rated to produce their current at engine speeds well above idle. If you’re sitting in a parking lot and the vehicle has a 180-amp alternator, it will only produce 130 amps at idle. A 240-amp alternator makes about 115 amps at idle. In the same case size, more peak current capacity results in a reduction of output current at lower engine speeds.

Worse, alternators lose performance as they heat up. A typical three-phase alternator can lose 30% of its output capacity. High-end alternators that use high-quality six-phase windings may only drop 15%. This heat problem is a self-compounding issue, just like under-sizing the wiring in your vehicle. As you approach the limits, you end up with less voltage and the load will demand more current, which makes things hotter and reduces output even more.

Electrical Systems on Motorcycles and Powersports Vehicles

Upgrading audio systems on motorcycles is challenging. It would be best if you chose the most efficient speakers and amplifiers possible. Why? The stock charging system is often only capable of delivering 30 amps of current. Upgraded stators may be able to bump this to over 50 amps, but that still isn’t very much when you have an ignition system to run. Would you have 30 to 35 amps of current leftover for a stereo? Maybe. Even if you have picked the 86% efficient amp we talked about at the beginning of this article, you can only produce about 400 watts to the speakers. If you chose that 68% efficient amp, that number drops to a little over 300 watts as the rest of the energy is wasted as heat.

Lastly, don’t expect the battery to help much. In a typical motorcycle size, as you’d find on a Street Glide, they are rated for 32 amp-hours and have a cold-cranking amp capacity of 500 amps. Compare that to the battery in a full-size sedan at 100 amp-hours and almost 1,000 cold-cranking amps.

Upgrade Your Electrical System for Better Audio Performance

If you plan on having a large amplifier, a high-performance ignition system or lots of lighting installed on your vehicle, then drop by your local specialty mobile enhancement retailer today to find out what upgrades are available. Feeding your amp or accessories with the power they need is the only way to ensure that they will provide the performance and reliability you expect from your investment.

Lead-In Image provide by Luke Schaller at Schallerimages.

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.

For decades, driving has been synonymous with listening to the radio in our cars. From the early days of AM radio, through advances in FM technology to the latest satellite and streaming services, we’ve been able to enjoy someone else’s music collection for about 100 years. Each advance in technology has improved sound quality and noise reduction to make our music sound more accurate and realistic.

AM Radio

One of the simplest means of transmitting audio information over the air is known as amplitude modulation, or AM, as it’s known globally. From a technical standpoint, AM radio modulates the amplitude (level or strength) of a carrier radio frequency (the station you tune to) to transmit the audio signal. In essence, an analog copy of the sound is sent on top of the radio station frequency. In North America, AM radio stations broadcast on carrier frequencies between 540 and 1700 kHz.

One of the biggest problems with AM radio is its sensitivity to noise. If additional information, say from a lightning strike or a noisy piece of electrical equipment, adds noise at the same frequency as the carrier signal, you will hear it on top of your broadcast.

The second issue is bandwidth. AM stations are limited in their ability to transmit high-frequency information. Audio up to 10 kHz is the limit in North America.

FM Radio

FM radio got its start in the 1930s but didn’t begin to make headway into broadcasting popularity until the 1960s. In contrast to AM, frequency modulation (FM) is much more impervious to noise. To transmit audio over the air, the frequency of the carrier signal (the station you tune to) is modulated by the audio waveform. FM radio offers dramatically improved audio bandwidth (up to 15 kHz) and an easy way to transmit stereo signals.

As digital transmission technology became more popular, broadcasters found ways to include additional information in the 200 kHz band allocated to each FM station. Features such as the Radio Data System (RDS) allowed small amounts of digital information to be embedded with the analog audio transmission, including station call signs, song titles and artist information.

Several radio and portable GPS navigation device manufacturers use the RDS Traffic Message Channel (TMC) to display real-time traffic information within their navigation systems. At the time of this writing, 77 stations are broadcasting this information in major cities in the US and Canada.

Digital Audio Broadcasting

Digital audio broadcasting (DAB, for short) operates at much higher frequencies than traditional terrestrial radio and is similar to the signals from satellite radio broadcasts. While it never took off in North America, DAB remains the standard in Europe and is replacing standard FM transmission there. Many aftermarket radio manufacturers such as Kenwood and Pioneer had add-on tuner modules that would work with these satellite frequency signals.

HD Radio

Using technology identical to FM radio in terms of broadcasting frequencies, HD Radio extends the data transmission concept to include a high-resolution digital copy of the FM station and up to three additional audio streams. Broadcasters can choose how they want to use the available bandwidth and balance fidelity and content. Significant amounts of information, including song title, artist name and even album art, can be displayed on the radio screen of a multimedia receiver.

HD Radio is a free service but requires a tuner that is capable of decoding the data stream embedded within the FM broadcast.

Satellite Radio

Though the basis for satellite radio was first conceived in the early 1990s, the first satellites weren’t launched until 2000, with Sirius launching three satellites that year. XM launched its first two satellites on March 18 and May 8, 2001, then began broadcasting Sept. 25 that year. Full coverage of the US was achieved by mid-2002. Sirius and XM Satellite Radio merged into Sirius XM in 2008 to deliver a single solution for North America.

Unlike terrestrial radio, Sirius XM is a pay-for-use service. You’ll need a specific antenna and tuner module to receive the signals.

Being able to drive across the US and almost all of Canada while listening to the genres of music you enjoy is a fantastic feature. If you drive long distances or live in a rural area with few radio stations, then Sirius XM is an excellent option.

Streaming Music Services

Pandora, Spotify, Apple Music, iHeartRadio and Amazon Music are the top music streaming services in North America. Unlike the other systems we’ve discussed, these entertainment solutions rely on the digital data connection of your smartphone to bring music into your vehicle. In most cases, users will launch an associated app on the phone, then use a Bluetooth or wired data connection to feed audio from the stream to their stereo.

Specific apps exist for Apple CarPlay and Android Auto for the services we’ve mentioned above, along with Tidal, Radio Disney and Sirius XM. Using dedicated voice-controlled apps makes enjoying these services easier and safer while driving.

Modern Technology Provides Non-stop Entertainment

Whether you wanted to check the score from the game last night, listen to the news or enjoy your favorite music, dozens of options will let you stay informed and entertained as you drive. If your car or truck doesn’t have the ability to play HD Radio, Sirius XM or accept audio from a streaming service over Bluetooth, drop by your local specialty mobile enhancement retailer today to find out about the upgrades that are available.

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.

HD Radio is a broadcast technology that adds digitally encoded information to an analog AM or FM station. Where once you were limited to listening to, say, 101.1 in New York City, the broadcaster has added a news and talk channel as well as a sports channel to the same 101.1 MHz frequency. The best part is that HD Radio is completely free. If the tuner in your vehicle has this feature, you can make use of it without any activation or subscription costs.

How Does FM Radio Work?

Without getting too technical, each FM radio station in North America is assigned a specific range of frequencies it can use to broadcast its content. The limits for analog FM radio station frequencies are 88.1 to 107.9 MHz, and each station has 200 kHz of bandwidth to transmit both a mono and a stereo signal. The Federal Communications Commission (FCC) in the US and Industry Canada (IC) control the standards and handle licensing in their respective countries. As such, you can’t just build a radio transmitter and start broadcasting a station from your basement.

Technically, with 20 MHz of bandwidth, there is room for 100 stations within 88 and 108 MHz to simultaneously broadcast within the same area. In reality, few cities have that many radio stations. The FCC and IC see to it that radio station broadcast frequencies are spaced far enough apart so they don’t overlap. Likewise, stations that broadcast on the same carrier frequency need a transmitter that is far enough away from a similar station so that the signals won’t overlap within the target market.

Adding HD Radio Digital Information

When a broadcaster decides that it wants to transmit additional information using HD Radio, it is permitted to increase the bandwidth of its transmitted signal and send digital information. This technology is called an in-band on-channel (IBOC) digital radio.

Because this signal is digital, it’s much more resistant to noise. As such, stations rebroadcast their analog signal on HD1 – the first of the four available HD Radio stations available on a single carrier frequency. While the system does use a lossy compression algorithm to reduce bandwidth, most users report that the HD1 channel sounds better than the analog signal.

Broadcasters can divide their available digital bandwidth however they choose. If they want the clearest, most detailed digital option for their main station, they may not broadcast anything other than HD1. In one example, HD1 is the main FM radio station and HD2 is a feed from an AM station owned by the same broadcaster. Talk radio and news-only broadcasts that require less overall bandwidth are also common uses for HD2 and HD3.

Compatible tuners are designed in a way that a failure to decode any of the digital radio stations results in the tuner dropping back to playing the analog audio signal. The technology also allows broadcasters to transmit station information, album and artist details and, in some instances, album or radio station artwork for display on a compatible receiving radio.

Currently, HD Radio signals are broadcast in the US, Canada and Mexico. XPERI Corp., the company that owns HD Radio, reports that India will be the next market to add HD Radio broadcasts.

Upgrade Your Vehicle with an HD Radio-Equipped Receiver

If your car or truck didn’t come with an HD Radio-equipped receiver, drop by your local specialty mobile enhancement retailer to find out how you can upgrade your radio. Sony, Kenwood, Pioneer and Alpine offer solutions to provide a whole new world of entertainment to make your commute more enjoyable.

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.

Though it seems contrary to what I’ve preached, sometimes it’s better to avoid purchasing car audio speaker upgrades based on specifications alone. The information most manufacturers provide does very little to describe the actual quality of the product. A prime example of this are speaker Xmax specification numbers. Does this linear measurement tell us how loudly a speaker plays? Does it describe linearity? Does it inform us about distortion?

Don’t Get Hung Up on the Wrong Numbers

The Xmax specification is a tricky number that gets thrown around a lot when we’re talking about subwoofers and midbass drivers. Historically, this specification has described how far the cone of a speaker can move in one direction without having the voice coil move outside of the top plate. When the coil moves too far, the magnetic field strength is reduced dramatically and distortion will occur.

Many enthusiasts attribute more Xmax to an ability for the speaker to play more loudly. While this seems reasonable in theory, cone excursion is determined by the compliance of suspension components and the strength of the motor assembly.

What if components such as the spider or surround don’t provide the same compliance in both directions? What if the woofer cone might be able to move rearward more easily than it can move forward? Given a specific input signal, this characteristic would deliver what could be described as unbalanced performance. In reality, it results in the addition of distortion to the output of the speaker.

Looking at the graph above, we can see that the suspension offers a resistance of 1.6 Newtons per mm in the forward direction and 2.1 Newtons per mm in the rearward direction.

Another characteristic that might affect speaker performance and our usable Xmax specification is the effectiveness of the motor (voice coil and magnet structure) in delivering linear force in both directions. If the motor is more efficient in one direction, the speaker could potentially move farther (or not far enough) based on a given input signal.

In the graph above, we can see that the motor assembly in this speaker produces a magnetic flux of 4.1 N/A in the forward direction at an excursion of 4 mm, and 4.9 N/A in the rearward direction at the same excursion level.

What Does Distortion Look Like?

In order to explain how nonlinearities in speaker operation affect what we hear, we created a 20 Hz sine wave in Adobe Audition. We manually manipulated the three positive cycles of the waveform on the left channel and boosted their amplitude by 6 dB.

The frequency response plot below shows that the 20 Hz signal has been increased in amplitude by 1.1 dB. Harmonics have been added at 40, 80, 100, 120, 140, 180, 200, 220, 240, 280 and 300 Hz. All of this unwanted information is directly due to the nonlinear behavior of the waveform.

This addition of undesirable harmonic content is called harmonic distortion. Looked at another way, it’s the addition of sounds to the output of a speaker (or any other audio device) that weren’t in the original recording.

Can You Measure Speaker Sound Quality?

There are no characteristics of a speaker’s performance that can’t be measured. We can quantify the frequency response. We can test power handling. We can measure compression. There are tests for inductance versus position and resonant frequency versus excursion. The list goes on and on. What’s difficult is determining when a design has a measurement that is a glaring issue, or just a characteristic. Is some amount of nonlinearity allowable? If so, how much? Does the answer depend on how the speaker is going to be used?

Different measurements have relevance in different applications. If you are looking at detailed specifications of an 8-inch subwoofer, the information you need will be very different than if you were looking at an 8-inch midrange intended for use in a public address speaker in a theatre or concert venue. If you are going to be playing the driver from 300 Hz up, the excursion isn’t much of an issue.

Knowledgeable speaker engineers understand the application of the speakers they are designing and manipulate the component (cone, spider, surround and motor) design to optimize the entire system for specific performance characteristics.

Sadly, for those of us who want the best speakers possible for our car audio systems, manufacturers rarely share this information with consumers. Worse, some don’t have the equipment to make these measurements and optimize their drivers. Nevertheless, your best bet is to visit your local specialty mobile enhancement retailer and audition as many speakers as you can. Quickly you’ll learn to pick out the solutions that are the clearest and most detailed. These are typically the speakers that add the least distortion to their output. Those are the ones you want to use to upgrade the mobile audio system in your vehicle.

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.