No single upgrade to an audio system offers a larger improvement in sound quality than the addition of a car audio subwoofer. Adding a subwoofer not only improves the low-frequency performance of your sound system, it can also improve the clarity of the entire system and enhance the volume level capabilities of the smaller speakers in your car. In this issue of Bang for Your Buck, we are going to look at a few popular subwoofer upgrade options available for adding bass to your vehicle.

What is a Car Audio Subwoofer?

In the simplest of terms, a subwoofer is a large speaker designed to play frequencies below 100 Hz at relatively high output levels. Subwoofers are most commonly available in 10- and 12-inch sizes, but 6.5-, 8-, 13.5- and 15-inch subs are also readily available.

To reproduce low-frequency information with authority, a speaker has to move a lot of air. In fact, for every octave lower a speaker is to play, it has to move four times as far to produce the same volume level. If your sub is moving 1 mm back and forth at 80 Hz, it has to move 4 mm at 40 Hz and an impressive 16 mm at 20 Hz. Most people find a pulsing bass line of 40–50 Hz to be fun. That said, feeling the rumble of deep bass like the introduction to “Boom Boom Pow” by the Black Eyed Peas or the pulse in Pink Floyd’s “Time” can cause goosebumps.

Subwoofer Power Handling

Most people associate subwoofers with their power-handling capabilities. While not a direct determining factor in the quality of a subwoofer, power handling is important in terms of choosing the right subwoofer for your sound system. If you want to listen to your sound system at high volume levels, you need powerful amplifiers and speakers that can handle that power while being able to move adequately to reproduce sound at high levels. It is no surprise that the output and power handling are directly related, since it takes amplifier power to make a speaker cone move.

Picking “enough” subwoofer depends on several factors. How loud is loud enough? How much space can you afford to give the subwoofer system? How powerful of an amplifier can your vehicle’s electrical system support? It can be difficult to choose the right sub based on these criteria, especially since different vehicles offer different amounts of cabin gain. Would a single 10-inch sub in a sealed enclosure in the back of a Honda Fit be a suitable solution in a Cadillac Escalade or short-cab Ford F-150?

Custom-built Subwoofer Solutions

Your best choice to upgrade your vehicle with a subwoofer is to have your local mobile electronics specialist retailer design and construct a subwoofer system that is specific to your vehicle and your expectations. This process will start with your input in determining just how much bass you want. From there, your system designer can suggest a subwoofer or subwoofers that will meet your expectations.

The next step is to decide where to install the subs. The simplest of custom enclosures would be a rectangular wooden cabinet that sits in the trunk or cargo area of your vehicle. The dimensions of the enclosure can be optimized to make the most use of the available space. This optimization may include angling the back of the enclosure to follow the angle of the seats.

Depending on your goals and expectations, you may choose to have the enclosure finished in a material that matches the interior. For a more-customized look, you may want the enclosure wrapped in vinyl that is the same color and grain as the trim panels in your vehicle.

If you want something truly unique, then ask about including LED lighting in the enclosure. You can choose to have a Lexan or Plexiglas window added and illuminate the interior of the enclosure or add acrylic plastic accent pieces that light up. Upgrades at this level are often combined with enclosures finished with multiple materials – different colors of vinyl can provide amazing cosmetics.

Advanced Subwoofer Enclosure Designs

The next step, beyond a simple wooden enclosure, would be one that is shaped to fit the unique contours of your vehicle. Enclosures of this type are often built using a combination of wood and fiberglass or layers of wood that are stacked one on top of another to create complex contours. The most-common application like this is where a subwoofer is being fitted into the corner of a trunk or hatch area, but is also often placed under the trunk floor in a spare tire well. The passenger-side footwell of a two-seat vehicle is another popular location for this type of enclosure.

Due to the complexity of these enclosures, they will typically cost more. The trade-off is that they integrate better into your vehicle – providing you with the acoustic performance you want without taking up valuable cargo area.

Application-specific Subwoofer Systems

Companies like JL Audio, MTX and Kicker offer subwoofer systems designed for specific models of vehicles. These enclosures are designed to offer impressive performance while minimizing how much space they use. Some companies construct these enclosures from fiberglass in large molds, while others use thick plastics. In most cases, while these enclosures are visible once installed, they are available in materials that match the color of the vehicle interior. An application-specific enclosure is a great way to add amazing bass to a vehicle quickly and efficiently.

A subsection of these application-specific enclosures is truck boxes. No, not the thin, wedge-style enclosures that fit behind the seat, but complex enclosures that use the space under a rear bench seat in a pickup. Companies like Audio Enhancers, Bassworx and Atrend offer cost-effective solutions that will accept the subwoofer of your choice. In most of these applications, you need a shallow subwoofer because mounting depth is quite limited.

Shallow Subwoofers

You’ll note that we haven’t discussed the specific features of subwoofers that differentiate one from another. This omission is quite deliberate because we will dedicate an entire article to that topic. In the meantime, it is worth discussing the difference between a conventional subwoofer and a shallow-mount design.

Shallow subwoofers were originally designed for use behind the seat of a pickup truck. Shallow cones, baskets and motor structures provide mounting depths of around 3 to 3.5 inches. Historically, the tradeoff for this reduced mounting depth has been a dramatic decrease in cone excursion capability. Over the past few years, companies like JL Audio, Illusion Audio, Kicker, Focal, Rockford Fosgate, ARC Audio and Audiomobile have worked hard to maximize the performance of their shallow-mount subwoofers to the point that they offer similar, if not better, performance than some conventional designs.

Audition a Subwoofer System Today!

We will leave you with this as the starting point for choosing a subwoofer solution for your vehicle. In the next article, we’ll explain the performance benefits and drawbacks of different subwoofer enclosure designs, then wrap up our buyer’s guide series with an explanation of advanced subwoofer design features that offer audible improvements in performance. Until then, visit your local specialist mobile enhancement retailer and audition one of their demo vehicles that has a subwoofer. We are sure you’ll be impressed and want one for your car or truck.
No single upgrade to an audio system offers a larger improvement in sound quality than the addition of a car audio subwoofer. Adding a subwoofer not only improves the low-frequency performance of your sound system, it can also improve the clarity of the entire system and enhance the volume level capabilities of the smaller speakers in your car. In this issue of Bang for Your Buck, we are going to look at a few popular subwoofer upgrade options available for adding bass to your vehicle.

What is a Car Audio Subwoofer?

In the simplest of terms, a subwoofer is a large speaker designed to play frequencies below 100 Hz at relatively high output levels. Subwoofers are most commonly available in 10- and 12-inch sizes, but 6.5-, 8-, 13.5- and 15-inch subs are also readily available.

To reproduce low-frequency information with authority, a speaker has to move a lot of air. In fact, for every octave lower a speaker is to play, it has to move four times as far to produce the same volume level. If your sub is moving 1 mm back and forth at 80 Hz, it has to move 4 mm at 40 Hz and an impressive 16 mm at 20 Hz. Most people find a pulsing bass line of 40–50 Hz to be fun. That said, feeling the rumble of deep bass like the introduction to “Boom Boom Pow” by the Black Eyed Peas or the pulse in Pink Floyd’s “Time” can cause goosebumps.

Subwoofer Power Handling

Most people associate subwoofers with their power-handling capabilities. While not a direct determining factor in the quality of a subwoofer, power handling is important in terms of choosing the right subwoofer for your sound system. If you want to listen to your sound system at high volume levels, you need powerful amplifiers and speakers that can handle that power while being able to move adequately to reproduce sound at high levels. It is no surprise that the output and power handling are directly related, since it takes amplifier power to make a speaker cone move.

Picking “enough” subwoofer depends on several factors. How loud is loud enough? How much space can you afford to give the subwoofer system? How powerful of an amplifier can your vehicle’s electrical system support? It can be difficult to choose the right sub based on these criteria, especially since different vehicles offer different amounts of cabin gain. Would a single 10-inch sub in a sealed enclosure in the back of a Honda Fit be a suitable solution in a Cadillac Escalade or short-cab Ford F-150?

Custom-built Subwoofer Solutions

Your best choice to upgrade your vehicle with a subwoofer is to have your local mobile electronics specialist retailer design and construct a subwoofer system that is specific to your vehicle and your expectations. This process will start with your input in determining just how much bass you want. From there, your system designer can suggest a subwoofer or subwoofers that will meet your expectations.

The next step is to decide where to install the subs. The simplest of custom enclosures would be a rectangular wooden cabinet that sits in the trunk or cargo area of your vehicle. The dimensions of the enclosure can be optimized to make the most use of the available space. This optimization may include angling the back of the enclosure to follow the angle of the seats.

Depending on your goals and expectations, you may choose to have the enclosure finished in a material that matches the interior. For a more-customized look, you may want the enclosure wrapped in vinyl that is the same color and grain as the trim panels in your vehicle.

If you want something truly unique, then ask about including LED lighting in the enclosure. You can choose to have a Lexan or Plexiglas window added and illuminate the interior of the enclosure or add acrylic plastic accent pieces that light up. Upgrades at this level are often combined with enclosures finished with multiple materials – different colors of vinyl can provide amazing cosmetics.

Advanced Subwoofer Enclosure Designs

The next step, beyond a simple wooden enclosure, would be one that is shaped to fit the unique contours of your vehicle. Enclosures of this type are often built using a combination of wood and fiberglass or layers of wood that are stacked one on top of another to create complex contours. The most-common application like this is where a subwoofer is being fitted into the corner of a trunk or hatch area, but is also often placed under the trunk floor in a spare tire well. The passenger-side footwell of a two-seat vehicle is another popular location for this type of enclosure.

Due to the complexity of these enclosures, they will typically cost more. The trade-off is that they integrate better into your vehicle – providing you with the acoustic performance you want without taking up valuable cargo area.

Application-specific Subwoofer Systems

Companies like JL Audio, MTX and Kicker offer subwoofer systems designed for specific models of vehicles. These enclosures are designed to offer impressive performance while minimizing how much space they use. Some companies construct these enclosures from fiberglass in large molds, while others use thick plastics. In most cases, while these enclosures are visible once installed, they are available in materials that match the color of the vehicle interior. An application-specific enclosure is a great way to add amazing bass to a vehicle quickly and efficiently.

A subsection of these application-specific enclosures is truck boxes. No, not the thin, wedge-style enclosures that fit behind the seat, but complex enclosures that use the space under a rear bench seat in a pickup. Companies like Audio Enhancers, Bassworx and Atrend offer cost-effective solutions that will accept the subwoofer of your choice. In most of these applications, you need a shallow subwoofer because mounting depth is quite limited.

Shallow Subwoofers

You’ll note that we haven’t discussed the specific features of subwoofers that differentiate one from another. This omission is quite deliberate because we will dedicate an entire article to that topic. In the meantime, it is worth discussing the difference between a conventional subwoofer and a shallow-mount design.

Shallow subwoofers were originally designed for use behind the seat of a pickup truck. Shallow cones, baskets and motor structures provide mounting depths of around 3 to 3.5 inches. Historically, the tradeoff for this reduced mounting depth has been a dramatic decrease in cone excursion capability. Over the past few years, companies like JL Audio, Illusion Audio, Kicker, Focal, Rockford Fosgate, ARC Audio and Audiomobile have worked hard to maximize the performance of their shallow-mount subwoofers to the point that they offer similar, if not better, performance than some conventional designs.

Audition a Subwoofer System Today!

We will leave you with this as the starting point for choosing a subwoofer solution for your vehicle. In the next article, we’ll explain the performance benefits and drawbacks of different subwoofer enclosure designs, then wrap up our buyer’s guide series with an explanation of advanced subwoofer design features that offer audible improvements in performance. Until then, visit your local specialist mobile enhancement retailer and audition one of their demo vehicles that has a subwoofer. We are sure you’ll be impressed and want one for your car or truck.

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.

When it comes to designing car audio systems, retailers need to take into account how their clients want their music to sound. Everyone seems to have different preferences for the amount of bass or high-frequency content. These tonal balance preferences can change based on the choice of music and the listener’s mood. In most cases, a well-designed sound system can handle any music listening preferences.

A preference that is harder to change is where the music seems to come from. Many mobile audio aficionados prefer the music to come from a virtual soundstage as much in front of them as possible. Many people also prefer their music to wrap around them, with as much coming from behind as in front.

There is no right or wrong, so long as you are happy with the way your system sounds.

In this article, we discuss how the client’s preferences can affect the way a mobile audio system is designed. We’ll also look at a few options for the performance of these systems.

Recording Studio Sound

Up until recently, most recording studios used a pair of high-quality speakers placed equidistantly in front of the mixing console. The recording engineer would balance the level and placement of the instruments and performers, using these speakers as his reference. The result was a soundstage that spanned the distance between the speakers.

Attending an outdoor concert may yield a similar listening experience. In a venue like that, the sound comes from in front of you – be it the sound created directly by the instruments, or from the PA gear set up on or beside the stage.

In your car, this can be recreated by focusing on the placement and quality of the front speakers. A good set of components can offer similar performance. Adding a digital signal processor (DSP) can dramatically improve the accuracy of the system by compensating for frequency response, arrival time and speaker volume level differences. When you listen to a quality recording, each performer will seem to be in a specific location on the soundstage.

What about Club Sound?

There are lots of ways to describe the experience of having the music come from all around the vehicle, but the analogy of a nightclub or – as we old fogies like to call them – a disco might work best. The concept here is that the music will seem to come from all around you. Unlike a performance where you can point to the source of sound from each instrument, it envelops the listening space. In most of these systems, we still balance the system with dedicated left and right channels.

What about those cars and trucks with all the PA speakers in the doors? Not a pair of speakers, but something like eight speakers in each door, with several high-efficiency bullet tweeters. In these designs, if indeed the goal is sheer volume, it might make more sense to forego keeping the music in stereo and use a processor to combine the left and right channel, so it’s simply as loud as possible.

You Haven’t Mentioned a Concert Hall

You may have noticed that we haven’t talked about a live performance that takes place in a concert hall or indoor venue. This has been quite deliberate.

Imagine heading out for dinner to a local restaurant that has a small band playing. Maybe it’s rock music with a guitarist, bassist, drummer and lead singer. Or perhaps it’s a three-piece jazz ensemble with a piano, saxophone and upright bass. If the performance is acoustic, other than for an amp for an electric guitar or bass, the source of the music will be easy to define as coming from the instruments – but that isn’t the extent of the experience.

Every confined space, except an anechoic chamber, causes the sound to reflect off the floors, walls and ceiling. You hear the music directly from the instrument or performer first, then those same sounds as they reflect off objects and surfaces. The total experience is defined by the mixture of all these sounds.

Live Performance Sound

A great example of a live performance sound would be a venue like the Ryman Auditorium in Nashville. Known primarily as the home of the Grand Ole Opry, this amazing auditorium continues in operation today and has hosted performers like Bruce Springsteen, Mumford and Sons, Tom Petty, the Foo Fighters, Coldplay and Kesha, along with classic country music performers. The Ryman Auditorium is considered by many as having the best acoustics in the world. Coldplay said it is “the greatest theatre in the world,” bested only by the Mormon Tabernacle in Salt Lake City.

What does this mean? If you have been to the Ryman or the Mormon Tabernacle, you know that these spaces have distinctive echoes, reflections and reverberations. You can quite literally hear a pin drop on the stage from almost any seat in the house. It is this incredible live sound that performers and attendees enjoy. How do we recreate that experience in our cars and trucks?

If the music you are listening to was recorded in a live venue and not in a studio, then the reflections and reverberations will be contained in the recording. Recordings of orchestras and choirs performing classical music are good examples of this. If your sound system is tuned well and offers an accurate soundstage with excellent imaging, it will reproduce the ambiance and a sense of the room size of these recordings.

Signal Processing Solutions

Another option is to use a signal processor to create a sense of room size. In the 1990s and 2000s, lots of processors had presets for jazz, concert and club settings that added reverberation and delay to dedicated rear channel outputs. These technologies have evolved to more-advanced processing algorithms like Bose Panaray and Quantum Logic Surround from Harman. These systems can analyze the content of a stereo recording and extract information that should be reproduced by side and rear speakers to create an immersive listening experience. If your vehicle has one of these technologies, your local mobile enhancement retailer can make it sound even better by adding a premium subwoofer system, since factory stereo systems rarely offer great bass performance.

The forthcoming Audiofrog Multiseat processor works similarly, analyzing the content of the music and directing it to left, center, right, left and right side, and left and right rear speaker outputs. Sure, you need a lot of speakers and amplifier channels to make full use of the system, but enjoying a realistic musical experience from any seat in the vehicle is worth the effort.

What to Know Before Going Shopping

If you want to upgrade the sound system in your car, truck or SUV, do a little homework before you start shopping. Play with the fader control in your car to determine how you want the new system to sound. If you can tell the salesperson how you want your new system to sound, they can help you choose the right products much more quickly and let the installer know how to configure the system so it sounds exactly the way you want. If you aren’t sure which you prefer, ask if they have a demo vehicle you can audition. That’s a great way to experience a high-end audio system.

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.

Just as the invention of the transistor eliminated the need for vacuum tubes, advances in technology allow us to create new and unique entertainment solutions with more and more features. We thought it would be fun to take a quick look at a few important car audio technologies throughout history.

Transistors

The first car radios used vacuum tubes as integral parts of their tuner and amplifier circuitry. Tubes required high-voltage power supplies and consumed a lot of power. They produce a lot of heat and are fragile. The result was finicky products with limited performance. The first transistor was theorized in 1926 but wasn’t built for the first time until 1947. It wasn’t until 1955 that we saw Chrysler and Philco announce the first automotive transistor radio – the Mopar model 914HR.

The transistor is considered one of the greatest inventions of the 20^th century. Transistors improved the efficiency and reliability of electronics components and led to the creation of microchips and ultimately computers. The Apple A11 Bionic CPU, found in the iPhone 8, 8 Plus and iPhone X, has 4.3 million transistors built into it. The Microsoft Xbox One main CPU has more than 7 million transistors inside. More impressively, a 128 gigabyte stick of DRAM memory has more than 137 quadrillion transistors!

Broadcast Radio

Radio was truly the technology that drove car audio systems. The first radio broadcasts were weekly special events that included concerts in 1914 and daily news broadcasts in 1916. On May 20, 1920, XWA – the experimental station of the Canadian Marconi Co. – began regular broadcasts in Montreal. XWA claims status as the first commercial broadcaster in the world. These were all AM (amplitude modulation) stations. FM (frequency modulation) radio was patented in 1933, but it wasn’t until the late ’30s that FM broadcasts became popular. The broadcast of a stereo FM signal was first considered by the FCC in the late 1950s, and a standard was approved in 1961.

The Compact Cassette and 8-Track Tape

Reel-to-reel recording on magnetic tapes was popular in the 1940s but wasn’t suitable for use in mobile applications. The 8-track was preceded by the Stereo-Pak 4-track cartridge in 1962. The endless-loop cartridge could store both sides of a vinyl album. The 8-track, known originally as the Lear Jet Stereo 8 Track Cartridge, was launched by Bill Lear in 1963. In 1965, Ford offered factory and dealer-installed 8-track options on its Mustang and Thunderbird and on several high-end Lincoln vehicles.

Call it a tape or a cassette, the first compact cassette (as we know it) was introduced by the Phillips Corp. in 1963 as a storage medium for dictation machines. Widespread use of the compact cassette in the mid-’70s and the introduction of chromium dioxide (CrO2) as a premium recording medium and Dolby B noise reduction spelled the end of the 8-track.

Digital Audio

Most people don’t realize that digital audio (known then as pulse code modulation) was invented in 1937 in Britain and was used in telecommunications. In the late ’60s, Denon pioneered commercial digital recording. The BBC used digital audio transmissions to link its broadcast center to its transmitter in 1972. Sony and Mitsubishi drove the consumer popularization of digital audio in the early ’80s and brought about acceptance by major record companies. The first compact disc was released in 1982 using the Red Book Compact Disc Digital Audio (CD-DA) standard that is still in use today. The first OEM-installed CD players were in the 1987 Lincoln Town Car.

Class D Amplifiers

The benefit of Class D amplifiers is their efficiency and low-to-moderate power levels. Class D amps use high-frequency pulse-width modulation waveforms to switch MOSFETs (metal-oxide-semiconductor field-effect transistors) on and off very quickly to amplify signals. Filter networks on the output of the circuits remove high-frequency noise so that only the audio signal is left to drive our speakers. Class D amplifiers allow manufacturers to produce much more powerful amplifiers that take up very little space. These amplifiers consume less current than their Class AB counterparts.

Computerized Source Units

Around 1980, we saw the first digitally tuned car radios. Mechanical tuning knobs and presets were replaced with vacuum fluorescent displays and electronic buttons. This would lead to computerized source units that included electronically controlled cassette players and equalizers with spectrum displays around 1982. By the late ’80s, with the growing popularity of CD players, having a microcontroller built into a car radio was commonplace.

Around 1992, companies like Alpine and Clarion were selling in-vehicle navigation systems that included LCD screens, and by 1993, digital communication solutions were available to transmit computer information to vehicles. In 1998, Clarion launched the AutoPC in conjunction with Microsoft to become the first in-vehicle computer. Modern multimedia receivers now run embedded versions of Windows and Linux operating systems.

The Apple iPod

The Apple iPod was introduced in the fall of 2001. The original compact digital media players were only compatible with computers running the Apple Macintosh operating system and as such, sales were limited. In 2003, the iPod 3G was launched with a standard USB port instead of Firewire, making it compatible with Windows-based PCs as well. By June 2003, Apple had sold 1 million iPods.

In June 2005, BMW announced that an iPod adapter would be available for the 3 Series, the Z4 Roadster, the X3 and X5 and the Mini Cooper, and was backward compatible to many 2002 models.

By 2005, the iPod was a popular solution for carrying thousands of songs, and Clarion launched its VRX745VD – a single-DIN multimedia receiver with a dedicated iPod interface. The iPod quickly replaced the CD changer as a means of storing a large number of songs in vehicles.

Bluetooth

Though incorrectly perceived as a hands-free and audio streaming technology, Bluetooth was created in 1994 as an alternative to RS-232 wired communication. Within the Bluetooth communication standards are dozens of profiles, including fax, cordless telephony, printing, file transfer, dial-up networking and of course, the hands-free and audio distribution profiles that we know and love! In 2002, the Audi R8 was the first to apply Bluetooth technology in a car. DaimlerChrysler, Acura and BMW joined in 2003.

Apple CarPlay and Android Auto

Since the very first car radios were built, people were concerned about them being a distraction. Turning the tuner knob to find a local station meant you weren’t focused on the road in front of you. In the late ’90s, we saw drivers with headsets and earpieces making phone calls while they drove. Adding a headset was a common purchase with a new phone. In the mid-2000s, Bluetooth communication replaced wired hands-free connections.

Data distractions took off in the late ’90s and early 2000s with the Blackberry. When smartphone technology took off in the 2000s, so did text messaging. We now had lots of ways to distract us from our driving duties.

Apple realized that the smartphone was as much of a problem as it was a solution in the early 2010s. In 2013, Siri Eyes Free was offered as a dealer-installed accessory for several Honda and Acura vehicles. In 2014, the Ferrari FF became the first new vehicle to come equipped with Apple CarPlay.

CarPlay is a software application that runs on the multimedia source unit in the vehicle and uses the Siri voice recognition engine built into the iPhone to allow voice commands to be executed. You can send a text message, make a phone call or choose the music you want by simply asking. Turn-by-turn navigation is also included.

The Open Automotive Alliance announced in 2014 that it would introduce a competing technology for Android-based smartphones called Android Auto. The 2015 Hyundai Sonata was the first OEM implementation of Android Auto. Few car audio technologies have rivaled the importance of CarPlay and Android Auto.

Technology for Safety and Entertainment

There have been hundreds, if not thousands, of milestones throughout the 100-plus years of automotive technology advances. These innovations are just a sampling of the way mobile electronics have evolved and changed. If you are looking for the latest and greatest car audio technologies, or simply want to improve the performance of your entertainment system, visit your local mobile electronics specialist retailer.

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.

(ipod photo:KAMiKAZOW [CC BY or CC BY 3.0-2.5-2.0-1.0 (https://creativecommons.org/licenses/by/3.0-2.5-2.0-1.0)], from Wikimedia Commons)

In our Bang for your Buck series, we talk about product features and component designs that offer increased value and performance. We’ve discussed source units and speakers, and now it’s time to take a deep look into amplifiers and what separates one amplifier from another.

Years ago, a prominent mobile audio enthusiast claimed that all amplifiers sound the same under strict test conditions. He even backed up the statement by offering a large cash reward to anyone who could pick one amp 10 times out of 10 under controlled listening tests. While there is value in his claim and it would be very hard to determine the difference between two amplifiers in blind testing 10 out of 10 times, that doesn’t mean that all amplifiers are the same. In fact, there are some big differences.

This articles focuses on two widely different areas of performance that many manufacturers refuse to discuss in detail: distortion and noise.

Is Power Important?

Does the ability of one amplifier to make more power than another determine its quality or performance capabilities? Well, if the less-powerful amplifier is driven into distortion, then certainly the more-powerful amplifier will sound better. While they’re operating within their rated power ranges, though, does maximum power matter? Not so much.

What’s this Damping Factor Thing?

For decades, manufacturers of high-end amplifiers have provided damping factory specifications. This number is a ratio of the output impedance of the amplifier to a specified load impedance. The story goes that an amplifier with a higher number would produce a tighter, more-controlled sound because the low impedance of the amp would short the back-EMF signal from the speaker.

Depending on your version of physics, the damping factor can be a large number, or a very small one – making it potentially relevant or a complete red herring.

For solid-state amplifiers, the damping factor or output impedance ratio is high enough that the load impedance has very little effect on the resulting frequency response of the system. For tube amplifiers with impedance-matching transformers, this isn’t always the case. Worrying about, or even considering, the damping factor is way down the list of concerns.

Background Noise

We’ve talked about signal to noise ratio in detail in our discussion of head units. It’s a big deal in a discussion of amplifiers and will rear its head again when we talk about signal processors.

Any electronic device creates unwanted noise when a signal passes through it. Even something as simple as a resistor creates a small amount of noise. In this example, it’s likely too small to be audible – but it’s there. In a complex circuit with gain (an increase in signal amplitude), creating unwanted noise is a common byproduct of questionable design.

How does noise manifest itself in an amplifier? It’s the background hiss you hear from your speakers when no music is playing. Ideally, you don’t want any noise adding content to your music.

If you have those really efficient PA speakers, then choosing amplifiers with excellent noise specifications is crucial. The speakers themselves offer 5 to 10 dB more output for a given input signal, so any noise that is present will be 5 to 10 dB louder.

Signal to Noise Ratio Specification

We’ve covered this before, but we are going to do it again now because it’s important. There are two ways manufacturers publish SNR or S/N Ratio specs: either rated to a specific output level (1 watt into 4 ohms) or relative to the maximum power production capabilities of the amplifier. You can’t compare the two directly, but you can estimate.

Let’s look at two full-range amplifiers. In this example, we’ll use a pair of similarly rated four-channel amplifiers. Amplifier A has a S/N Ratio published at -104 dB and amplifier B amplifier rated at -88 dB. Assuming the numbers are published using the same standard, amplifier A produces 16 dB less noise than amplifier B. Unfortunately, in this example, the -104 specification of amplifier A is published related to its rated power, while amp B is relative to 1 watt of output. Using the same specifications, amp A produces -84 dB of noise, 4 dB more than amp B.

Distortion Considerations

Distortion is, in the simplest of terms, the addition of unwanted information to a signal. Just as with noise, all electronic devices add some amount of distortion to signals as the signals pass through. In most cases, unless something has gone very wrong, the original signal passes through the device unchanged. Distortion is generated by the addition of unwanted information.

Harmonic distortion is the addition of multiple instances of the original signal. Many high-end home amplifiers are tested using a 50 Hz tone at rated power. Analysis of the resulting spectral content shows just how much unwanted information is produced.

The image above shows amazing performance from a very high-end solid-state home amplifier. As you can see, there is a little bit of 150 and 175 Hz content, but it is at almost -120 dB below the stimulus signal.

In this example, we can see the harmonics created in a high-end home audio Class D amplifier. A 100 Hz signal is present at a level of -85 dB and a 250 Hz signal is present at a level of -90 dB.

To really highlight the potential for unwanted behavior, we have included the spectral content of a high-end vacuum tube amplifier. You can see that there is spectral content at 100 Hz at a level of -42 dB, 150Hz content at -54 dB and 200 Hz content at -67 dB. This distortion would be audible during listening.

Intermodulation Distortion

Another kind of distortion is created when two signals passing through an amplifier interact with one another to produce distortion that is the difference between the two signals. The industry standard test for intermodulation distortion is to play a test signal that contains two sine waves – one at 19 kHz and a second at 20 kHz. Two things will happen when distortion is produced using these stimulae: Content will be created on either side of these tones and at a difference between them, i.e., at 1 kHz.

This graph shows a high-end home amp with excellent IMD behavior. The two side-bands are at -119 dB and would be completely inaudible.

This graph shows the same Class D as in the discussion of harmonic distortion. It is easy to see that the test stimulae created a significant amount of information. The peak is at -78 dB, so it’s not a complete disaster.

Shopping for a Car Audio Amplifier

Since nobody in the mobile electronics industry seems willing to submit their products for this level of scrutiny, how does one go about picking an amplifier that offers exceptional performance? The only way is through extensive listening. A handful of amplifiers on the market offer exceptional performance, and not all of them are expensive. At the same time, some very expensive amplifiers perform poorly.

If you want to find the best, then see if you can borrow that amp in question from a friend and put it into a reference system. If your music suddenly sounds warmer, that’s a sign that there is additional harmonic content. It is “nice” to listen to in some cases, but it is certainly not accurate.

Once you have developed a strong reference for accuracy, you will be able to pick out amplifiers that offer excellent performance. Your local mobile electronics retailer should have a demo vehicle that you can audition. Happy shopping!

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