Hi-res audio is perhaps the biggest hype in the audio world. But what exactly is it, and why is it so exciting? In this article we will discuss all the basic concepts and the most important ins and outs of High-Resolution Audio, including the difference between 16 and 24-bit and the added value of audio playback in true high resolution.
Hi-res audio in short
You can explain exactly what high-resolution audio is in two ways. Very elaborate, or very short. Let’s start with the last: High-Resolution Audio is anything that sounds better than CD quality. Incidentally, the exact name can often differ; high-resolution audio, hi-res audio, high-res audio, and high-resolution audio are commonly used terms.
Technical specifications
Hi-res audio actually refers to a technical specification, such as horsepower for cars, for example. It does not say that the music is necessarily going to sound good or is of a higher quality, because that has to do with other things – such as the quality of the recording and all the preconditions in the studio. So let’s start with the definition of ‘CD quality’ first. This refers to audio files of 44.1 kHz and 16-bit. Two related properties that could of course use some extra explanation.
From 44.1 kHz
The 44.1 kHz is the sampling frequency. It indicates how many times each second of the analog signal – the recording – has been sampled in the conversion to digital. After all, the music in the studio, played analog, has to be translated to the ones and zeros of the digital domain. This conversion takes place in pieces, or samples. 44.1 kHz or 44,100 Hertz indicates that 44,100 samples per second (!) Are taken. 44.1 kHz is not an arbitrary number, but a standard adopted by Sony and Philips in the development of the compact disc.
Specifically, 44.1 is based on the Nyquist-Shannon sampling theory, named after electronic engineers Harry Nyquist and Claude Shannon. Without really diving into the technology, we can say that you have to take twice the number of samples per second to reach a certain frequency. A sampling frequency of 44.1 kHz ensures that you are good for just over 22,000 Hertz. To make an unnecessarily long story short for now: because our hearing can at best perceive up to 20 kHz, analog signals are converted with a sampling frequency of 44.1 kHz to realize at least double that. With a little extra play of about ten percent, to be precise. Hi-res is basically anything higher than 44.1 kHz, CD quality. For example, nowadays you will find high resolution files with 96kHz and 192kHz.
From 16-bit
As mentioned, there is a second element to be explained: 16-bit, a reference to the depth of the signal. 16-bit, or 2-to-the-power-16 or 65,536, indicates how many pieces of information are hidden in each sample. The more information, the greater your dynamic range. Compact discs work with 16 bits per sample, media such as DVD-Audio, digital high-resolution audio files and Blu-ray go up to 24-bit and thus enter the hi-res domain. Nowadays you already have a large number of high resolution audio files of 192kHz and 24-bit for example.
The meaning of hi-res
But wait a minute. If our hearing does not exceed 20,000 Hertz and a sampling rate of 44.1 kHz more than compensates for that, what is the use of an even higher frequency? For starters, the extra space above the audible range allows the studio to better edit the recording. A larger dynamic range means that all those digital tricks, master operations and the errors that can arise are pushed away into frequencies that we cannot perceive. You could say that there is some waste in the signal, which is stored in a room that our hearing cannot reach.
Hi-res in the living room
The above mainly relates to the editing in the recording studio itself. Of course, this also influences the route from the microphone in the studio to the speaker in your listening room. Ambassadors of hi-res (read: anything above CD quality) argue that the production of hi-res audio leaves more usable from the original analog signal than just what you can perceive. The conversion of the analog signal to the digital domain in the sampling frequency of the CD is therefore not sufficient in their view.
What’s up with that? Advocates of High-Resolution Audio argue that more information “lives” in the recording studio than what happens in the audible domain. The sound of any music fragment, be it a voice or the touch of a violin string, is made up of both audible and inaudible tones. With the latter you can think of the harmonic tones of each instrument that echo as it were after striking the musical note in a frequency that we cannot perceive, but which are indeed part of the so-called total sound. Hi-res in that sense is richer and more detailed. Where science and experience meet, the actual added value is something that every pair of ears must determine for themselves.
Digital high resolution files
You can use various digital file formats to listen to High-res audio;
- DSD – Files that you find on SACDs and are slowly becoming more loose digital files. Not all devices play these files.
- WAV – Audio file developed for Windows that can be played by most equipment. WAV files are large due to no use of compression, but are supported by many devices and support metadata.
- AIFF – Audio format developed for Mac computers and which can also be played by many audio equipment. Meta-data is supported and the files are quite large as with WAV.
- FLAC – Currently the most widely used audio format for high resolution audio due to wide equipment support (except iTunes), ‘open source’ usage and ‘losless compression’. The latter means that the data is compressed (made smaller) but can be restored (unpacked) in its original state, so that no quality is lost.
- ALAC – Audio format developed by Apple and also known as ‘Apple Lossless’. This format also uses ‘losless compression’. This can be compared to extracting a ZIP file with which all files in the folder are restored to their original state.
A DSD, WAV or AIFF file in the highest possible quality (24-bits at 192kHz) can easily run into the hundreds of Mbs per song. A FLAC or ALAC file that uses ‘losless compression’ averages 50Mb to 100Mb per song. So you do need the space for it.
Incidentally, a new audio format called MQA has recently been introduced. This audio file does not have its own extension, but must offer an optimal reproduction of high-resolution audio through smart algorithms and compression.
Where to get it and how to play it?
Hi-res audio is quite widely available these days. In addition to the well-known Super Audio CD, which has a sampling frequency above 44.1 kHz, you can download digital high-resolution files with numerous parties. This concerns files in, for example, 88kHz / 24-bit, 96kHz / 24-bit, 176kHz / 24-bit, or 192kHz / 24-bit quality. Examples are HDtracks , ProStudioMasters and NativeDSD.com . In addition, there are various streaming music services that offer hi-res subscriptions, including Qobuz and Tidal .
To play hi-res audio, you obviously need the right equipment. Think of a receiver, amplifier or digital-analog converter that can handle hi-res files. There are also dedicated mobile players from brands such as Sony, Fiio and Astell & Kern that are suitable for playing the larger audio files. Note: an investment in High-Resolution Audio also means an investment in speakers that make the best use of the music files.
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