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Car Audio

Product Spotlight: Sony XAV-AX3700 Multimedia Receiver

Sony XAV-AX3700

Car audio source unit manufacturers are constantly developing new products to fill the gaps between entry-level and flagship models. Sony recently released a new 2-DIN digital multimedia receiver called the XAV-AX3700, which slides into the mix just below the XAV-AX4000. This new radio features a 6.95-inch touchscreen display, Apple CarPlay connectivity and iDatalink Maestro vehicle integration. Read on to learn about what else it offers.

Sony XAV-AX3700 Source Features

The XAV-AX3700 starts with extensive support for digital media files stored on a USB flash drive. The radio can decode MP3, WMA, WAV, AAC, FLAC, ALAC, DSF and DSDIFF audio files. It also has Bluetooth, which includes the A2DP and AVRCP profiles, which allow music to stream from a smartphone or digital media player. The radio supports LDAC for impressive wireless sound quality and SBC and AAC for maximum device compatibility.

Of course, the radio has a high-quality AM/FM receiver, which captures RDBS information so you can see album and song title information if the station provides it. The retailer installing the radio can upgrade it with a SiriusXM satellite radio receiver, allowing you to listen to genre-specific music or your choice of entertainment channels nonstop from coast to coast. Sony provides a rich SiriusXM interface, including the channel logo and the album art for the track being played if the station you’re tuned in to provides it.

Sony XAV-AX3700
The XAV-AX3700 can be upgraded with a dedicated SiriusXM satellite radio receiver for uninterrupted entertainment.

Apple CarPlay Smartphone Connectivity

The XAV-AX3700 includes support for wired Apple CarPlay. Plug your phone cable in, and you’ll have access to all the music on your phone or your favorite streaming services. You can choose whatever you want using intuitive voice commands. Of course, you can make phone calls, send text messages or get detailed turn-by-turn directions to any address or business in North America using your favorite app.

Sony XAV-AX3700
Wired Apple CarPlay connectivity makes it easy to communicate while driving.

Vehicle Interface Features

As mentioned, the XAV-AX3700 supports the iDatalink Maestro SR, RR and RR2 interfaces. These modules allow communication with the computers in your vehicle to provide access to climate controls, as well as factory-installed infotainment components like microphones, steering wheel controls and a rear-vision camera.

If your application does not have an RR or RR2 module, your installer can integrate steering wheel controls using other modules, like the Maestro SW. Talk to the Product Specialist you are working with for details about your vehicle’s specific make, model and trim level.

Sony XAV-AX3700
The Sony XAV-AX3700 supports the Maestro SR, RR and RR2 vehicle integration interfaces.

Intuitive Interface Simplifies Operation

Sony is the benchmark when it comes to human-machine interfaces. Not only does the XAV-AX3700 boot incredibly quickly, but the button layout on the screen and the menu functions are super-intuitive. The 6.95-inch touchscreen display is bordered by a row of six buttons along the bottom edge.

The main display menu includes five user-configurable options. You can set your favorite sources or commonly used functions, like the backup camera display, to be readily available. When an iPhone is connected, a dedicated icon for Apple CarPlay appears to the left of the clock.

You can also customize the wallpaper image behind the icons from several included options or upload your own image to personalize the radio. A new customizable clock layout feature gives you an option for either an analog or digital clock in the center of the screen, or a smaller digital clock in the top right corner.

Sony XAV-AX3700 Audio Features

This new Sony radio includes a full suite of audio integration features to maximize the sound system’s performance. A five-channel time alignment screen helps improve staging and imaging. A 14-band graphic equalizer can smooth out peaks and dips in the system frequency response. Built-in electronic crossovers with adjustable slopes maximize the performance of your speakers.

The radio includes a four-channel amplifier rated to produce 20 watts per channel, making driving the factory speakers easy. Thanks to dedicated front, rear and subwoofer preamp outputs, you can easily upgrade the radio with an external amplifier. An integrated subwoofer level control makes fine-tuning your system to suit your music or mood easy.

Sony XAV-AX3700
Time alignment, a 14-band equalizer and adjustable crossovers make it easy to fine-tune your audio system.

Single-DIN Chassis Simplifies Installation

A feature that car audio installers will love is the single-DIN chassis behind the 2-DIN display. This 2-inch tall chassis design leaves room for wiring, integration modules and wire harness adapters. Notably, the space is available beneath the radio, where these parts typically rest. The depth of that chassis is shallow as well, allowing use in vehicles with a tight fit behind the radio screen.

Upgrade Your Driving Experience with Sony

Whether you’re looking to add Apple CarPlay or high-quality audio streaming to an older vehicle, or you have to replace a factory-installed radio that’s kicked the bucket with one that requires the use of a Maestro module that retains some factory features or settings, the new Sony XAV-AX3700 is an excellent choice. Drop by a local Sony car audio retailer today and ask for a demonstration. You can find a retailer using their online locator tool. Also, follow Sony on Facebook and Instagram to keep up with the latest new car audio products.

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.

Filed Under: ARTICLES, Car Audio, Products, RESOURCE LIBRARY Tagged With: Car Audio, Sony

What is Bluetooth?

BluetoothIf you have been around the mobile electronics industry for any amount of time, you will know that certain terms are often used incorrectly. One term that has been over-abused lately is Bluetooth. Product manufacturers, retailers and consumers have developed an expectation of what Bluetooth is, and what it does. Sadly, those expectations can lead to confusion and undesirable results. This article explains what Bluetooth is, and how it is used.

What is Bluetooth?

BluetoothBack in the dark ages, we had to connect electronic devices with wires. We also created wheels from boulders using animal bones as tools. RS-232 was a popular type of communication protocol for devices like modems, printers, scanners and cameras. Two wires would carry data between these devices and your computer. In 1994, Ericsson – a telecommunications and network equipment manufacturer in Stockholm, Sweden – introduced a wireless alternative to RS-232 called Bluetooth.

Bluetooth is a low-power, high-speed wireless communication protocol. Bluetooth operates using short-wave UHF radio waves in the frequency band of 2.4 to 2.485 GHz. Within this range of frequencies are 79 dedicated Bluetooth channels. Bluetooth uses Frequency Hopping Spread Spectrum to reduce errors and allow multiple devices to operate within the same frequency spectrum.

Bluetooth is used for short-range data communication between devices like computer and keyboards, video game controllers and consoles, and cellular phones and wireless devices. There are applications for medical applications such as monitoring heart rate, blood pressure and glucose levels. That said, many industrial applications exist between sensors in production systems and control computers.

Bluetooth Profiles

The misconception many people in the mobile electronics industry have is that Bluetooth exists to let cellular phones make calls and stream music to our radios. Bluetooth is far more involved and flexible than that.

Any talk of Bluetooth functionality is a perfect segue to introduce us to profiles. A Bluetooth profile is a set of instructions and commands that operate over a Bluetooth connection. Profiles simplify the communication between devices. In our industry, we are used to four common profiles:

PBAP – Phonebook Access Profile

HFP – Hands-free Profile

A2DP – Advanced Audio Distribution Profile

AVRCP – Audio Video Remote Control Profile

These profiles are used in varying combinations to allow you to connect your phone to your car radio so you can make phone calls and stream music. A few companies that have wanted to provide an Internet connection to their radio have used DUN to accomplish this task.

PBAP Profile

The Phone Book Access Profile allows your source unit to receive phonebook entry information, as well as manage it. Phonebook entries are transmitted and managed by the radio in vCard 2.1 or vCard .0 formats. Missed, received and dialed numbers are listed as well.

HFP Profile

The Hands-free Profile carries monaural audio between the phone and a secondary device. The profile also supports commands to answer or reject incoming calls; place a call; use memory data to place a call, terminate a call or manage phone volume level; and send phone status information, including battery, roaming status and signal strength . These functions are included in version 1.5 of the Hands-free Profile. Future versions, such as 1.7, will include support for wideband speech and the use of external audio compression and decompression codecs.

A2DP Profile

The Advanced Audio Distribution Profile operates within another profile called the Generic Audio/Video Distribution Profile (GAVDP). A2DP is responsible for allowing us to stream audio from a device such as a smartphone to a radio or powered speaker. The basic profile allows for stereo audio to be transmitted at a sampling frequency of 44.1 kHz at up to 328 kb/s. The use of a third-part codec such as aptX from Qualcomm or LDAC from Sony may further improve on bandwidth.

AVRCP Profile

Functioning alongside the GAVDP profile is the Audio Video Remote Control Profile. AVRCP is responsible for the display of song title, artist and album information, and control over playback device functions. If you can imagine a button on a DVD remote control, the AVRCP is likely to support it. Most car audio source units include functions like play, pause, fast-forward and rewind. The most recent versions of AVRCP include support for folder navigation and searching.

What Bluetooth Doesn’t Do

Although the Bluetooth Special Interest Group (SIG) works to manage the different Bluetooth communication and profile standards, there are variations in functionality between profile versions and, more importantly, between smartphone vendors. This latter fact can be a significant issue for buyers of car audio source units. The expectation that it “should work,” while not unreasonable, is not always possible. To expect a seven- or eight-year-old radio to work flawlessly with a brand-new iPhone 7 or Samsung Galaxy S8 isn’t reasonable. The hardware in the older units cannot be upgraded.

How to Buy Bluetooth

BluetoothIf you are shopping for a new source unit, take any smartphone you want to use with it to the retailer. Ask to pair your phone with the demo unit on display. Check that your entire list of phone contacts transfers as expected. Make sure you can use voice control functions if they apply to your phone. See that you can make calls easily. Finally, check that your phone reconnects reliably to the source unit by cycling power on the source a few times.

If you purchase a new radio and have it installed, only to find out it is not compatible with your smartphone, there is often nothing that can be done quickly. Some manufacturers do release updates for Bluetooth functionality, but these updates are not going to turn a Bluetooth 3.0 system into a 4.0, or add AVRCP 1.4 to a system that shipped with AVRCP 1.2. Do your research before you buy!

If you are looking for a hands-free solution to make phone calls or stream music to your audio system, drop in at your local mobile electronics specialist retailer. Bring your phone, pair the Bluetooth connection and experiment with the options.

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.

Filed Under: ARTICLES, Bluetooth, Car Audio, RESOURCE LIBRARY

When it Comes to Subwoofer Specifications, Some Numbers Don’t Matter

Subwoofer SpecificationsIf you are a mobile electronics enthusiast like we are, then it’s quite possible that you enjoy reading product specifications. You can learn a lot about the design and application of a product from the specs. Amplifier power ratings are probably the most popular specs, but there are a lot more. One product specification that tends to confuse people more than help them is speaker efficiency. This article explains what the numbers mean and how you should analyze the appropriateness of subwoofer specifications, one subwoofer to another.

Speaker Efficiency

Subwoofer SpecificationsIn a nutshell, the efficiency specification attempts to quantify how much sound a speaker will produce when provided with a given amount of power. Manufacturers provide the specification in two common methods. The most common are decibels of output when fed with 1 watt of power and measured at 1 meter from the speaker, written as 1 W/1 m. The other specification method involves replacing the 1 watt power measurement with 2.83 volts. For a 4 ohm car audio speaker, 2.83 volts works out to 2 watts of power or 4 watts into a 2 ohm speaker. Make sure to take the impedance of the speaker into consideration with the latter format.

For a subwoofer, we derive this efficiency number with a formula that includes the driver’s resonant frequency, equivalent suspension compliance and driver’s electrical Q. In reality, the resulting number is purely theoretical and applies most directly to output in the frequency range above where most subwoofers play. There is the heart of the matter: The efficiency specification doesn’t describe how loud the subwoofer is at low frequencies. The only way to predict and compare performance is to model the behavior of the driver in simulation software.

Frequency Response Simulation

Let’s compare two 10-inch speakers. For sample A, we will use a very high-quality car audio subwoofer. Since we want to make this example somewhat extreme, we will use a 10-inch pro audio woofer as Sample B in our comparison. We will use BassBox Pro 6 to make the comparisons.

Sample A has a calculated efficiency of 93.21 dB when driven with 2.83 V. Sample B has an efficiency of 95.07 dB. Without modeling the low-frequency behavior of the driver, you’d happily think that Sample B was the louder of the two by 1.86 dB.

We modeled each driver in a sealed enclosure with a volume that provides a total system Q (Qtc) of 0.707. The car audio subwoofer is in 0.694 cubic feet, and Sample B is in 0.378 cubic feet net.

Subwoofer SpecificationsAs you can see from the graph, the output of the two woofers varies dramatically. Sample A is louder at 40 Hz by an impressive 4.95 dB. That is contradictory to the efficiency specification, isn’t it? It is, however, not wrong.

Subwoofer Specifications

When an engineer designs a speaker, the first thing to decide is the application. Will this be a high-SPL car audio speaker, or a pro-sound speaker? The differences make a great deal of difference.

Our sample subwoofers also have dramatically different excursion capabilities. Sample A has an Xmax of 17.6 mm and Sample B has an Xmax of only 4 mm. It is worth noting and reminding everyone that cone excursion quadruples for every halving of frequency. If these speakers were given enough power to play 100 dB at 80 Hz with an excursion of 1 mm, then they would need to move 4 mm at 40 Hz. At 20 Hz, they would need to move 16 mm. An excursion requirement of 16 mm is no problem for Sample A, but will likely rip Sample B to shreds.

Comparing the output of two drivers requires that we ensure the driver can handle the excursion requirements necessary to meet our needs.

Subwoofer SpecificationsIn the case of our subwoofer simulations, due to excursion limits, Sample B can produce a maximum output of only 94.9 dB at 40 Hz. Sample A can produce 108.3 dB at the same frequency. That is a difference of 13.4 dB. This difference is significant. Sample B simply cannot produce 100 dB of output at 40 Hz in this enclosure. Thus, Sample B not a suitable choice for a subwoofer, which makes sense, since it was designed to be a bass guitar speaker.

Choosing the Right Subwoofer

Subwoofer SpecificationsUnless you own speaker-modeling software and know how to use it, it can be tricky to determine the performance of one subwoofer versus another. Even more difficult is attempting to predict how one sounds when compared to another. Frequency response is just one of the many criteria that differentiate one subwoofer from another. Excursion capabilities, enclosure requirements, distortion characteristics and – of course – cost are all factors to be considered.

Many people think that just because it is harder to hear distortion at low frequencies, the design of a subwoofer matters less than that of a midrange speaker. You would be stunned at how a good subwoofer can bring out details in your music that you may have never heard before.

When it is time to go subwoofer shopping, visit your local mobile electronics specialist retailer. Discuss your needs with them and work with them to find a subwoofer solution that fits your application. You will be happy that you did.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

Why are Speakers Different Sizes?

Speakers Different SizesWhen you head to your local mobile electronics specialist in search of new speakers, there are a few criteria to keep in mind. Choosing a speaker size can go one of two ways: You can pick something that fits a specific mounting location or you can choose based on the characteristics of the speaker relative to its size. Are you interested in knowing why speakers come in different sizes? Good! You’ve come to the right place.

What Does a Speaker Do?

It is the job of a speaker to convert the electrical signal from your amplifier into motion. The motion of the speaker cone excites the air around it. As the cone moves forward, the air in front of the cone is pressurized. As the cone moves rearward, the air is rarefied. These pressure waves extend out from the speaker and our ears detect these minute changes in pressure as sound. Pretty simple, isn’t it?

Things to Consider in Terms of Reproducing Sound

Speakers Different SizesWhen it comes to reproducing sounds, the lower the frequency, the harder it is to produce the sound. For every doubling of frequency, the speaker cone has to move a quarter the distance to produce the same level of output. As example, if your subwoofer has to move 2 mm to produce 95 dB of output and 40 Hz, it only has to move 0.5 mm to reproduce 95 dB at 80 Hz. To reproduce 95 dB of output at 160 Hz, the cone only has to move 0.125 mm.

The size of a speaker cone affects how much sound the speaker will create for a given amount of input signal. Let’s generalize things a little (because a lot of external factors affect this statement): A 12-inch speaker cone has to move twice as far as a 15-inch speaker cone to produce the same amount of output at a given frequency. That also means the 12-inch speaker requires more power to produce the same sound as the 15-inch.

Bigger is Always Better, Right?

Based on this logic, you should simply select the biggest possible speaker for every application, right? Well, it’s not quite that easy. When we get into midrange and high frequencies, the speaker cone has to move back and forth very fast. A 1,000 Hz tone requires that the speaker move forward and backward 1,000 times a second. A 10 kHz tone requires 10,000 of these same motions per second. If we use a big speaker with a relatively heavy cone, it’s very hard to keep up with the input signal. Why? Inertia.

Speakers Different SizesLet’s use an analogy to help explain this. Imagine that you are at a parade and waving a flag. The pole is 6 feet long and the flag on the end is 3×5-foot. You wave the flag back and forth as fast as you can. Even if you are really strong, the fastest you can wave it back and forth is once, maybe twice a second. Now, look at the little kid standing beside you at the parade. He has a little paper flag that’s 2×3 inches on a 5-inch-long plastic stick. His little hands can wave that flag back and forth five or six times a second.

Speaker engineers have to balance several characteristics to achieve specific goals for a given design. Let’s compare the weight of a speaker cone for a 10-inch subwoofer to that of a 10-inch midrange used in concerts and public address systems. A typical 10-inch sub that is designed to play frequencies below 150 Hz has a cone assembly (cone, voice coil, former, half the spider and half the surround) that weighs around 150 grams. A 10-inch speaker designed to be used for midrange frequencies (150 to 1 kHz) has a cone mass assembly of around 40 grams.

Clearly, the lighter assembly can move faster and keep up with the reproduction of higher frequencies.

Is Lighter Better?

Now we face the conundrum of balancing low- vs. high-frequency output. A lighter cone will move faster and is capable of producing extended high-frequency output. A heavier cone has a lower resonant frequency and thus, can produce more low-frequency output. Combine these generalizations with electrical issues affecting voice coil inductance, and we further hinder high-frequency output. It starts to become clear that we need different-sized speakers for different applications.

Subwoofers

Speakers Different SizesMost subwoofers are sized from 8 to 18 inches. Since subwoofers are designed to play frequencies below 100 Hz in car audio applications, they need a lot of excursion capability and a low resonant frequency. This means subwoofers will have relatively heavy cones. At high excursion levels, cones are exposed to significant stresses, so the cone has to be strong, and this further contributes to their weight. Subwoofers have to handle a lot of power. This power allows us to move the cone over relatively large distances. Power handling requires bigger components in the form of large-diameter voice-coil formers and windings.

Midbass Drivers

Speakers Different SizesA dedicated midbass driver is typically designed to play from around 50 to 500 Hz. Sizes are typically 6.5 to 8 inches in size, but some people have used 10- and 12-inch drivers. The cone has to be heavier than that of a midrange, but not heavy enough to slow it down for higher frequencies.

If you look at the frequency content of a performer, you will see that many voices extend down to 100 Hz. Accuracy in speed is important in this frequency range. Resonances and non-linear behavior causes harmonic distortion. This is often perceived as “warmth” in the midbass region. We do not want anything extra in our music, so accuracy is what matters.

Midrange Speakers

Speakers Different SizesMidrange speakers become a balancing act of several different characteristics. Of course, the cone has to be relatively light, but managing linearity and distortion becomes an even higher priority. It’s easier to hear distortion at midrange frequencies. The cone has to balance mass, damping and strength to prevent deforming and cause harmonics. The suspension has to be very linear.

Managing inductance also becomes a more significant issue because it can reduce high frequency output. Midrange drivers for typical car audio applications vary in size from 6.5 inches and 6×9 inches on the large side down to as small as 2.5 inches. Many midrange drivers try to do double-duty as midbass drivers for use in two- or three-way audio systems. While this is a minor compromise, it is a necessity. We consider midrange speakers to cover the range from 100 Hz to 3,000 or 4,000 Hz.

Tweeters

Speakers Different SizesTo reproduce frequencies above 2.5 kHz, tweeters need very light cones. Tweeter cones don’t move very far, so they don’t require much excursion, but there still has to be a suspension. Resonances in the cone can wreak havoc with frequency response. Premium tweeters may make use of features like ferrofluid in the gap to improve power handling. Premium tweeters may also include a copper pole-piece cap to reduce inductance and distortion.

Directivity Considerations

Another consideration when choosing speakers is that all speakers above a certain frequency start to become directional. Directivity refers to a reduction in high-frequency output as you move off-axis to the speaker. If you choose your speakers and design your system carefully, you can minimize the effect of directivity. The only real consideration would be to have your tweeters pointed at you.

The Balancing Act

The applications for the information in this article vary, depending on your overall goal for your audio system upgrade. A simple set of coaxial replacement speakers will be chosen by the size application. If you are building a high-end audio system with multiple amplifiers, channels, digital signal processing and custom speaker mounting locations, then choosing the right speakers in terms of their quality and intended application becomes more important.

Learn More about Speakers and Their Different Sizes at Your Local Retailer

Your local mobile electronics specialist retailer can help you choose the right speakers for your application and performance goals. Drop in at a local shop today and have a listen to their demo board or demo vehicle. It’s an amazing experience!

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

What Is An MP3 File?

MP3

You cannot have talked about audio and computers any time in the last 15 years and not have heard of an MP3 file. MP3 audio files and websites, like the original Napster, started a shift in where, how and when people acquired music. If you are on the older end of the spectrum, like many of us in the mobile electronics industry, then you bought your CDs, cassettes and maybe even your vinyl at a record store. Computers and the Internet changed that. You could go online after dinner and download an illegal copy of a song in a few minutes. It was wrong, but people acquired tens of millions of songs this way.

In the 1990s and early 2000s, accessing the Internet was slow. We started connecting to the Internet using phone lines and modems. Each byte of information took time to transfer to your computer, so anything that would speed up the process was a treat. Downloading (stealing) music using the Internet is where the popularity of the MP3 audio file met its calling.

A Primer on Digital Audio

MP3We could write 10 articles about digital audio – and we just might. For now, we are going to look at the basics and use the compact disc (CD) as our reference. CDs store digital audio sampled at 44.1 kHz with a resolution of 16 bits. These numbers mean each sample can have an amplitude that is a single value within a range of 65,536 different levels (2 to the power of 16). The information is sampled 44,100 times a second. Sampling at what is known as 44.1/16 allows capturing the audible range of audio (considered 20 Hz to 20 kHz) with good detail and accuracy.

To store 1 second of audio at this resolution, we need to store 1,411,200 bits of information. Anyone who has played with audio transcoding software may recognize 1,411 kbps as a standard data rate. This number is calculated by multiplying the number bits per sample (16) times the number of samples per second (44,100) times 2. The times-2 factor is because we record in stereo – which is two channels. So, a 3-minute long song is 254,016,000 bits or 31,752,000 bytes.

Let’s round it off to 31 megabytes of information. Can you imagine how long it takes to download that with a dial-up modem running at 14,400 baud? The answer is at least 3.5 minutes – without error checking, line noise and other factors that slow the real download time to about 5.5 minutes.

Data Compression

What if someone found a way to shrink the size of the audio file to speed up download time and reduce bandwidth usage? The caveat is that the audio still sounds essentially the same on most basic audio systems, such as a TV, computer speakers or a 1990s factory car radio. In 1991, a group of companies, including the Fraunhofer Institute, France Telecom, Philips, TDF and IRT, started working on a way to reduce file size while maintaining relevant information. That is the key to how file size is reduced using MP3 compression.

The MP3 file format is a “lossy compression” algorithm. Lossy compression means that information is thrown away to reduce file size. The development team worked on a compression method called perceptual encoding to decide what information to remove. Perceptual encoding is based on how we hear sounds relative to other information, and the limits of our hearing.

What MP3 Files Throw Out

We are going to analyze the information that MP3 files remove to reduce file size. One of the easiest ways to cut back on information storage is to reduce the highest frequency that will be reproduced. If we analyze a 128 kbps MP3 file, we see that the highest reproduced frequency is just below 16 kHz. If that were the only information that was removed, our new bitrate with 16-bit samples in stereo would be about 1,004,800 kbps instead of 1,411,200 kbps for 20.05 kHz.

MP3The next part of the compression process analyzes content that is common to both channels. It is common for some parts of a recording to be virtually in mono. The encoding process removes duplicated information from the file and adds code to copy the opposite channel. If the audio track were purely mono, the file size would be divided in two. Few tracks are completely mono, but we can see more space saving from this process.

Subsequent processing looks at low-level information during high-amplitude passages. Let’s use the example of a song with a lot of bass in it and some very quiet harmonic midrange information. Perceptual encoding processes like MP3 will remove this low-level information from the audio track. This process is called audio masking. There is enough audio information at other frequencies to distract you from hearing what is removed.

Can You Hear the Difference?

Dozens – nay, hundreds – of tests have compared MP3 files to full CD-quality audio tracks. Are there differences? There most certainly are. One thing became apparent during our research: How an MP3 file is created is crucial to its subjective sound quality. Different encoders work in different ways with different results.

Perhaps the best way to describe the difference between a CD-quality recording and an MP3 file is to look at the difference between the two. I wish we could share some samples here for you to listen to, but that would break copyright laws. What we can do is visually show you the difference.

We took a 3-second sample from Daft Punk’s “Give Life Back to Music.” We chose this track because of Daft Punk’s clear and conscious effort to make a high-resolution version of the album commercially available. We want to thank them for that! The sample is from 31.5 seconds to 34.5 seconds into the song.

This Spectrogram shows the frequency content of the sample. The horizontal scale is time. The vertical scale is frequency. Finally, the color intensity shows the amplitude.

MP3
This is the original sample.

You can see that there is frequency content up to 30 kHz, clearly demonstrating the high-resolution nature of this track. Each vertical color band represents a drum machine beat – more or less.

128 kbs MP3 File Analyzation

MP3
This is the sample converted to a 128 kbps MP3 file.

It is clear that audio information above 16 kHz has been removed. Infrasonic frequency content is clearly different as well. There is more information in the MP3 file below 30 Hz compared to the original. This increase in information will, however, present itself as less-dynamic range.

MP3 Vs Original File

MP3
This is the difference between the Original sample and the MP3 Sample.

We inverted the MP3 file and added it to the original sample to make the image you see here. The net result is the difference between the two tracks. You can see the high-frequency content that was removed above 16 kHz. In fact, information was removed at all frequencies, and that information follows the intensity pattern of the audio file.

The original file has a peak amplitude of -0.1 dB for both channels and an average amplitude of about -14.2 dB. The removed information has a peak level of -10.9 dB and an average amplitude of -37.01. The removed information is buried deep below the peak amplitude information.

MP3What does the removed audio sound like? We would describe the clip as the sound of a distant marching band. The audio is mostly high-frequency information. The track has a decidedly warbled texture to it as well: The drum machine beats are clear and present, but they sound like distorted cymbal hits.

Even with a high-end headphone preamp and studio grade headphones, the difference is hard to perceive when switching between the original track and the MP3 file. In a listening environment with a larger soundstage, it may be more apparent.

Conclusions about MP3 Files

Purists will tell you that you should have the highest-quality recordings available. There is no fault to this logic. Why skimp when you can have it all? High bitrate MP3 files, like those at 320 kbps, for example, are excellent in quality. Repeated testing has shown that when created with quality compression algorithms, the sound difference between a CD-quality recording and a 320 kbps MP3 file is almost impossible to detect. Lower bitrate MP3 files start to dispose of more information, and the differences become bigger.

The latest source units on the market are capable of playing WAV and FLAC audio files of great resolution and bit depth. Shortly, we will see units that will play MQA files over digital connections. Almost every source will handle MP3 and WMA files.

Drop into your local mobile electronics specialist retailer today, and bring along some music to enjoy. We think you will be impressed – no matter what format you choose.

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.

Filed Under: ARTICLES, Car Audio, RESOURCE LIBRARY

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Window Tinting

Window Tint

Tinting the windows of your car or truck is a great way to add comfort and style to the vehicle. The automotive window … [Read More...]

Remote Car Starters

Remote Starter

Remote Car Starters One of the most popular product categories at Elite Car Customs is remote car starters. Imagine being able to start your vehicle with the push of a button so … [Read More...]

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Location


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Address

Elite Car Customs
1176 Park Rd
Unit A10,
Reading, PA 19605
Phone: 484-671-2343

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Services

  • Car Audio
  • Remote Starters
  • Driver Safety
  • Window Tint

Store Hours

SundayClosed
Monday9:00 AM - 5:00 PM
Tuesday9:00 AM - 5:00 PM
Wednesday9:00 AM - 5:00 PM
Thursday9:00 AM - 5:00 PM
Friday9:00 AM - 5:00 PM
SaturdayClosed

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