If you still do not know what Hi-Res sound is, we will update you with a comparison that is easy to understand. Suppose we watch a video on YouTube in 480p resolution, that is the basic resolution and what we are used to on mobile phones. When we go up in screen size, the lack of resolution is noticeable and we see pixels and lack of sharpness.
That is when the high definition modes 720p, 1080p, 1440p or 4K come in. They require a greater bandwidth (data that is transmitted) and show much more detail in the image, avoiding that pixelation, something that is obvious to the naked eye.
With the Hi-Res sound we have the equivalent effect but in sound. To get an idea, we find a 44.1 kHz sampling rate and 16-bit depth on CDs and most streaming services.
Digital Sound Basics
Sampling rate (Hz)
Sounds are captured just like video in chunks of data. The sampling rate could be compared to the images per second of a video. In audio it is measured in Hertz, that is, the number of samples per second.
A minimum of two samples per cycle are needed to represent any frequency, which is why 44.1 kHz was chosen for the CD (it is estimated that the human ear can reach 20 kHz).
High-resolution sounds (Hi-Res audio) are considered to be 96 kHz or higher. The higher the sample rate, the larger the file, the more samples it has for the same audio time.
Bit depth (bit)
Each audio sample has a size and is what determines this number. Are the bits used to capture each samplewe could compare this figure with the resolution in pixels of each frame of a video.
CD quality is 16 bit, Hi-Res files are 24 bit. At higher bit depths, the size of the audio file also increases for the same given time.
Bit rate (kbps)
This figure is the necessary bandwidth to transfer the audio in question. It is calculated by multiplying the sampling rate by the bit depth and gives us a figure in kbps / Mbps which is the amount of data that is emitted per second.
In summary, it is, therefore, the minimum speed that we need in a connection so that the audio can be reproduced without cuts and as it is the original.
Re-compression via Bluetooth and popular Hi-Res codecs
Well, suppose that we listen to Spotify as a sound source and that we have some files that are downloaded in real time on our mobile. Those files are compressed in AAC/MP3 format, lossy formats. That is, the sound that reaches our mobile already has fractions of the original audio discarded.
There are alternatives and subscriptions on the market such as Tidal or Apple Music that offer the option of LossLess (lossless), that is, we do not have this initial compression, so the audio reaches our mobile with all possible quality. Each song takes up much more, and by far we’re saying a factor of up to 30 or 40 times the file size.
However, the majority of uses on the Internet, by saving bandwidth and data spent on mobile rates, use quality formats with loss, mostly AAC. That format and codec is free and offers a good compromise between quality and size.
What if you want to hear that audio with your true-wireless headphones?
This is where additional compression comes in because the available bandwidth between the bluetooth connection of your mobile and your mobile can reach around 1-2 Mbps in optimal conditions, but usable by removing connection instability on a day-to-day basis. It is close to, below, 1 Mbps.
The mobile connects to the headphones via Bluetooth and to transmit the audio it is done through the common connection standard between the headphones and the mobile. An agreement is reached during pairing and from then on, your mobile compresses the audio that is sent and the headphones become decompressors and audio players.
This audio compression and decompression is done using different codecs, here are the most popular:
- SBC: It is the most basic and mandatory standard in A2DP Bluetooth devices. It is the one with the lowest bandwidth, although it can reach up to 328 Kbps, up to 44.1 kHz and 16 bits.
- CAA: is the default format in use on the Internet, for example YouTube or Spotify. It is a more modern compression algorithm and achieves more quality. It can go up to 24-bit, 44.1 kHz, and 320 kbps.
- aptX: It is a proprietary Qualcomm codec that has different subversions and can reach up to 24bit, 48kHz and 576kbps in its aptX HD version.
- LDAC: It is a proprietary codec from Sony and has a high bandwidth when the connection and device allow it. It can reach up to 990 kbps 24bit and 96kHz, although if the connection varies, the quality drops to 16 bits and 330kbps, as we see in the line of the most basic codecs. You need stable bluetooth connection to be able to enjoy the maximum quality.
- LHDC: This codec is open and allows to reproduce sound with very high quality, 24-bit, up to 96kHz and up to 900 kbps. It has a low latency version that halves the sampling rate and the bandwidth to 600 kbps.
|SBC||up to 48kHz||16 bit||328kbps||No|
|aptX||up to 48kHz||16 bit | 24 bit (HD)||384kbps | 576kbps(HD)||No|
|CAA||Up to 44.1kHz||Up to 24 bit||320kbps||No|
|LDAC||Up to 192kHz||Up to 24 bit||990kbps||Yeah|
|LHDC||Up to 192kHz||Up to 24 bit||900kbps||Yeah|
The only ones Codecs capable of handling Hi-Res sample rates are LDAC and LHDC. As you read, no Apple headset is capable of reproducing Hi-Res sound, although lossless sound is possible thanks to Apple’s proprietary ALAC codec in the source, the headset would arrive in recompressed AAC.
It is something that the company makes clear on its website, and that is that, although they offer Lossless sound on their Apple Music platform, their headphones use the AAC standard and can reproduce 24-bit 44.1 kHz sound at most.
And, yes, here comes the great dizziness of formats and connectivity and the Tinder between mobile and headphones.
Looking for the Match between headphones and your mobile if you want Hi-Res
As we can see, there are different types of connectivity that supports Hi-Res audio via Bluetooth. The most popular are LDAC and LHDC.
That is why you have to see that your mobile is compatible with one of these formats and buy headphones that use that Hi-Res codec.
That is, not all Hi-Res headphones will work in this mode with all mobile phones. In our tests of the Enco X2 we saw how the headphones could work in LHDC mode but could only reproduce Hi-Res sound through the LDAC codec depending on which mobiles.
The latest and just released Nothing Ear (2) also use LHDC 5.0 codec as standard to transmit Hi-Res audio via bluetooth. I had to try several mobiles until I found one that supported and allowed headphones to be connected with that format. In fact, it was with the Redmi Note 12 Pro+. Not even high-end phones like the Oppo Find X3 worked.
So It is not an easy or simple task to choose a headset that works with your mobile if you want Hi-Res sound.. They will work, but based on a small quality drop in the last link of the audio chain.
There are applications such as Bluetooth Codec Changer in the Play Store that allow us to see what codec our mobile is capable of using if it has headphones connected and also what codecs those headphones are.
In my personal experience, I have found more probability of Hi-Res connection between headset and mobile if both are LDACbut, as I say, each case is a world.
If you have doubts, you can always use wired headphones if it has a minijack and skip this last conversion or get a small DAC USB-C to minijack with Hi-Res support.
I also want to comment in closing, that the difference in sound quality is noticeable, but you need to be in a quiet environment for it to be noticeable. So if your main use is in the subway, or in the middle of the street, don’t be obsessed with Hi-Res Audio either.
I bet a coffee that not even the most knowledgeable music lovers or sound engineers would be able to tell the difference between Hi-Res and non-Hi-Res in those situations.