One of the main shortcomings of the Sonos system was its lack of Hi-Res audio support. Congratulations, Sonos users and fans. Sonos now support Hi-Res audio with the S2 software upgrade, all S2 supported models can now play Hi-Res musics with some limitations.
Followings are S2 compatible devices.
Hi-Res Audio Definition
The short, succinct definition is a digital audio format those used higher bit depth and/or sampling rate than CD (16 bit/44.1 kHz). Most Hi-Res music currently have 24 bit/48kHz, 24 bit/96kHz or 24bit/192 kHz.
High resolution audio is a digital audio format those used bit depth and/or higher sampling rate than CD (16 bit/44.1 kHz).
So what do bit depth and sampling rate mean?
Bit Depth
This is the 24 bits part of Hi-Res. Conceptually, a bit depth can be thought of as how many different types of sound can be allocated within the file. Let’s do a little analogy. Imagine you got an ancient black and white TV or perhaps you are a radiologist looking at X-rays. If the picture is built with 1 bit system i.e. you have only 0 or 1, that system only have either full white or full black.
In contrast, 6 bit systems have 2^6 = 64 options. So you can have multiple grays in between.
So the difference here is 2^16 = 65536 vs. 2^24 = 16777216. The number difference is huge but clearly you won’t hear that much of difference in sound quality. Let’s go back to the visual analogy. This time we are adding just one more bit but that makes twice more amount of gradients.
First of all, 6 and 7 bits grey pallets are not real bit calculated gradient, but two are indeed about twice difference in their gradient scale so should corresponds to about 1 extra bit difference.
Can you identify different grays that you can only find in 7 bit pallet but not in the 6 bit? Well technically, half of the grays should be that but our eyes can’t tell the difference Even if you can tell the difference, it is so subtle does it really matter? If it was color palette you may say, I can tell the difference easier. It is true between 64 vs. 128 colors but what about 1024 vs 2048? How about 4096 vs. 8192? There will be a point, human eyes can’t tell. The sound is also the same.
If threshold was 16 bit or lower, then 24 bit may not matter. However, if it was above, then extra 8 bit may contain subtly intricacy of the music that you could never hear with CD. In fact, Hi-Res supporters often make an argument that bit depth may be more important part of Hi-Res than the sample frequency.
Sampling Frequency
This is 48kHz, 96 kHz etc. part. In layman’s term, this is simply how often do you take a sample. The real world sound is an analog i.e. everything is continuous/infinite. Digital world have finite values. So Analog audio is converted by taking samples of a given time i.e. digitized. Then digital data is used to reconstruct analog audio by interpolating the data in between. Let’s take a look at example.
Right: 3 sample converted back to analog
The above example took 3 samples of original continuous graph. If the 3 sample points were used to restore analog signal, you can see we will miss the dip between last two sample points and the increase after the third sample point i.e. not a good restoration of original graph.
Let’s increase sampling frequency to twice i.e. 6 samples.
Right: 6 sample converted back to analog
We can see this time original graph is recovered. This is the importance of sampling frequency.
Similar to bit depth, human ear can only hear so much of frequency. Whether 44.1 kHz on CD has been enough or not is one question. But now, Sonos users may need to argue 48 kHz vs. 96 kHz vs. 192 kHz. Because Sonos only supports 48 kHz.
Hi-Res Audio Controversy
There are many articles on the internet talking about Hi-Res audio. There is almost always those who take it on blind faith and complete rejectors. As with anything else, the truth lies in between. In fact, auditory sensory and music preference are very subjective. Especially, some believe sampling frequency beyond 44.1 kHz may not be audible to human.
48kHz Limit
Sonos support 24 bit 48 kHz audio format, which is undoubtedly a real Hi-Res audio given both numbers are over the CD quality. However, competitors often support even higher sampling rate such as 96 kHz and 192 kHz. Here is a quick comparison of what other Wi-Fi speakers support.
Sonos elected to hold off on the sampling rate. Between bit depth and sampling rate, most would agree bit depth is more important for Hi-Res, so in that regard Sonos made a right decision. I believe with the decision of 48 kHz sampling rate; however, the controversy will continue amongst Sonos users with likely those insists on saying beyond 48 kHz, Hi-Res won’t matter. It would be interesting how many of those people actually said Hi-Res won’t matter at all until recent Sonos support.
Local File Only
Hi-Res formats are loss-less i.e. FLAC, ALAC, AIFF, and WAV. As we see on the table above, these file formats are currently only supported locally and not via streaming service. As Hi-Res audio files cost substantially more than regular/CD quality audio format, dominant portion of Hi-Res adopted audiophiles have at least one of Hi-Res streaming service such as Tidal, Qobuz, Amazon Music HD etc. Therefore, lack of Hi-Res streaming support is a disappointment to many.
Conclusion
Sonos has finally added Hi-Res audio support; however, it turned out there are relatively significant limitations. One is sampling frequency limit of 48 kHz. The other, more important for more users, is the Hi-Res support is only limited to the local music.
Having said this, we have a hope. Unlike many other manufactures, Sonos are well-known to be a truly evolving platform. Recent, Hi-Res support is one such great example. Even though it took a long time, some of the devices on the compatible device list are released over 7 years ago. Most manufactures usually require updated hardware for any significant added feature. Therefore, I strongly believe that this is just a very first step and almost certainly Hi-Res audio stream support to arrive in the Sonos platform eventually. If time comes perhaps higher sampling rate may also arrive. For the competitors, addition of Hi-Res support in the Sonos has made much harder to dethrone the king of multi-room Wi-Fi speaker ecosystem. As a consumer, competition will be no longer just having Hi-Res support or not, it is now de facto standard. So this will hopefully lead to more feature, sound quality and price competition that in the end benefits and gives choice to us, consumers. Let’s welcome Sonos to the world of Hi-Res.