WHAT IS HI-RES AUDIO?
LEARN EVERYTHING YOU NEED TO KNOW
For a period of more than 40 years, from its introduction right through to the mid-2010s, the CD was regarded as the gold standard for digital audio quality. It was only knocked off its pinnacle by the introduction of high-resolution audio. But why? The following guide tells you exactly what hi-res audio is, what its advantages and disadvantages are, and everything else you need to know about it.
TABLE OF CONTENTS
What is high-resolution audio?
The term hi-res audio or high-resolution audio is generally used for digital audio files or formats that boast a higher quality than an audio CD. The first high-resolution formats were Super Audio CD (SACD) and DVD Audio. Both formats arrived on the market within months of each other in the year 2000. They used proprietary digital formats that could only be listened to on a small number of extremely expensive playback devices.
Neither of these formats attracted a large number of fans outside the die-hard high-end community. When describing these formats, the audio sector at the time tended to use the terms like HD audio and high-resolution audio interchangeably, leading to an understandable confusion among consumers.
What determines the quality of audio files?
The quality of audio files is determined by two factors – the sample rate and the bit depth. These two terms are explained in the following sections.
What is bit depth?
When a digital recording is made of analogue signals, so-called samples are created. Samples are small and precisely delimited sections of the analogue signal. With the aid of a digital-analogue converter, the original analogue signal can later be reconstructed from these sections, and output via a loudspeaker, for example. The reconstruction process is impacted by the number of bits used to describe each sample, known as the bit depth (or resolution).
The bit depth of a digital sample is an important benchmark for the quality of the digital signal. Depth is decisive in terms of the accuracy with which the analogue signal is “sampled” during digital recordings, determining the dynamic range of the signal: the greater the bit depth, the greater precision with which the analogue signal is digitally described, and can later be reproduced.
A bit depth of 16 bits means that 65,536 quantization steps can be calculated and reconstructed by a DAC (216 = 65,536). With a bit depth of 24 bits, this increases to 16,777,216 steps (224 = 16.7 million). These number show that greater bit depth permits finer and more detailed resolution of the music signal.
16 and 24 bits – the most common bit depths
Theoretically, any technically feasible bit depth could be used for audio recordings. However, a wide range of different bit depths would be impractical. The most important bit depths for audio recordings are:
As we described above, a bit depth of 24 bits means that each sample contains 65,536 quantization steps for calculating the original, analogue signal on playback. A CD has a bit depth of 16 bits.
A bit depth of 24 bits or higher is used in music studios for recording audio files.
The bit depth is sometimes referred to as the sampling depth, but this should not be confused with the sampling rate.
The sampling rate: What is an audio sampling rate?
Audio sampling is the process of converting an analogue music source to a digital file. During a digital recording, a sample of the source sound wave is captured at regular intervals. The more samples gathered per period of time (i.e. the sample rate), the closer the quality of the digital file to the original analogue sound. As a rule, a higher sample rate leads to a better quality of playback.
The sample rate is a measure of the samples of an analogue system taken per second. It determines the frequency range captured in digital audio. On most DAWs (Digital Audio Workstation), the sample rate for recordings can be adjusted in the audio settings. Sample rates for digital recordings are normally measured in kilohertz (kHz). CDs, for example, are recorded at 44.1 kHz, which means that 44,100 samples are taken per second.
Hi-res audio channel coding – uncompressed, loss-free and compressed audio files
Digital audio signals can be stored and transmitted in various file formats. In the same way that images can vary greatly in terms of quality and clarity, audio files also differ depending how large they are, how much information they contain, and what function they fulfil.
The three categories audio files can be classified into, depending on their format, are as follows:
- uncompressed audio data
- loss-free compressed audio data
- lossy compressed audio data
Uncompressed files
Although it’s the exception that proves the rule, uncompressed files contain the most information and therefore have the highest bit rate. Uncompressed audio files are therefore extremely large and contain all the information an audio device is capable of identifying. Uncompressed audio formats store the original information on a one-to-one basis. Uncompressed audio formats include the following:
- WAV – in several different versions
- AIFF – the Audio Interchange File Format is Apple’s WAV
DSF and DFF for DSD signals (Direct Stream Digital)
Loss-free compressed files
These files are compressed, but no information is lost due to compression. As a rule, loss-free compressed files are larger than lossy compressed files with the same contents, but smaller than uncompressed files with the same contents. As the name indicates, loss-free compressed files can be used to reconstruct original files with no loss involved. Loss-free compressed files include the following:
- Free Lossless Audio Codec – FLAC
- Apple Lossless Audio Codec – ALAC, Apple’s FLAC version
- Windows Media Audio Lossless – WMA Lossless, Microsoft’s proprietary audio codec
Lossy compressed files
The third category is made up of the lossy compressed files. These are usually the smallest files, requiring the least storage space. During compression, any information not regarded as absolutely necessary is removed from these files, causing them to shrink in size. Popular lossy file formats include the following:
- MP3 – including codings with varying data rates in which the quality can differ widely.
- AAC – the Advanced Audio Coding format is superior to MP3 in terms of efficiency
The advantages of hi-res audio
Does hi-res audio actually sound better? One thing is certain, hi-res audio contains more information than, for example, a CD. But whether this also brings a significantly superior listening experience is something audiophiles have been arguing about for years. Some say hi-res audio is a rip-off, others maintain that it eliminates the constraints imposed by the sample rate of a CD. It should be capable of delivering a superior listening experience. In the case of quiet passages, particularly in classical music, extremely high-resolution audio files can have clearly audible advantages compared to conventional CDs. How clearly this superiority can actually be heard, however, depends on numerous factors connected with the recording and the playback device.
What are the disadvantages of hi-res audio?
High-resolution audio files have one disadvantage – the file size. A high-resolution file can be as large as several dozen megabytes. Depending on how much storage space is available, a few hi-res files can quickly fill up available resources. This problem, however, occurs less frequently than it used to. Over the past few years, storage space has become considerably cheaper, and a sufficient amount is now available in most cases. The large file size may also mean that wi-fi or mobile network speeds are too slow to stream the files without delays or interruptions. Such problems can really spoil the listening experience.
What is the role of playback devices with hi-res audio?
A genuine high-resolution listening experience requires several factors to come together. Obviously, the audio file needs to have a high resolution. The playback device must also be capable of supporting high-resolution formats.
And the same applies to the other devices in the audio chain, such as wireless loudspeakers or headphones. In the case of wireless Bluetooth® headphones, high-resolution enjoyment is only possible when the headphones and the transmitter on the playback device use the same hi-res codec. The conventional Bluetooth® codec compresses files, therefore degrading the quality during transmission.
In order to enjoy high-resolution audio, iPhone users require connection of a digital-analogue converter between a Lightning-to-USB adapter and hi-res-compatible headphones.
What do the Hi Res AUDIO und Hi Res AUDIO WIRELESS logos indicate?
The Hi-Res AUDIO and Hi-Res AUDIO WIRELESS logos are seals of quality issued by Japan Audio Society. Products bearing these logos need to fulfil certain requirements. For example, amplifiers and headphones with this logo need to have an analogue frequency range of 40 kHz and above. Furthermore, DACs with the Hi-Res AUDIO label must be able to process resolutions of 96 kHz/24 bits and above. Devices enabling wireless high-resolution audio via Bluetooth® or wi-fi can display the Hi-Res AUDIO WIRELESS logo.
How can I obtain high-resolution music and in which quality?
There are now numerous sources for downloading or streaming hi-res audio. Listed below are the names of some of the recommended sources for downloading and streaming hi-res audio files.
High-resolution music
for downloading
Popular platforms where you can download high-resolution audio:
HDtracks
ProStudio Masters
iTrax
Native DSD Music and Beyond
High-resolution music
for streaming
You can enjoy music on the go by using platforms that permit streaming of hi-res audio. Examples of such platforms:
Amazon Music HD
Apple Music
Qobuz
Tidal
Suitable headphons for hi-res sound
Are you on the lookout for headphones that permit you to fully enjoy music in hi-res quality? Whether you’re looking for in-ear or over-ear, wireless or wired, you’ll find we have exactly the right headphones for you.
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