At Debussy, we do not want to make any compromise on quality. This is why we are integrating 4G and WIFI in our headphones to offer you a unique experience that you will not find in any other nomad audio device. The entire audio chain is built directly inside the ear-cups, from the source to the audio transducer, and it is a true advantage and a guarantee of excellence.
But we do listen to what you have to say - we understood from your early feedbacks that it is important for you to be able to use your Prélude the way you’re used to: over Bluetooth with your smartphone.
That’s why our devices also support music playback over Bluetooth.
As you may know, a BT connection is limited and audio broadcast means most of the time a loss of audio quality. Since the bandwidth dedicated for the audio signal is much smaller than the raw audio signal, a compression algorithm is applied. The audio signal is coded at the source (audio player) level and decoded at sink (receiver) level; this is why this processing is called CODEC (for coder/decoder). It is important to know that all codecs are not equal in term of compression rate and audio quality.
"what occurs once my audio stream is compressed with loss?".
BT codecs have to lighten the audio signal to avoid any cut in the transmission and most of the time the audio restitution lacks definition in the whole spectrum with a poor soundstage, a bad dynamic and a less immersive experience.
Bluetooth protocol for audio transmission (A2DP for Advanced Audio Distribution Profile) has been created with one single codec (SBC) but is evolving and several codecs can now be used depending of their availability on the sink and the source. For example, Android 8 devices supports the following codecs: SBC, AAC, aptX, aptX HD and LDAC.
SBC CODECFirst of all, the very basic Bluetooth codec is SBC (Sub Band Coding). SBC delivers low-end audio quality because of its old coding algorithm. Independently from the codec quality, the original audio file has to be decoded then encoded through SBC to be broadcasted. SBC encoding is deleting some audio information (high frequencies mostly) reducing the signal to a specific bitrate before it can be transmitted. This bitrate is 345 kbps max for a stereo file. It is almost 4 times lower than CD normal bitrate (1 411 kbps).
For example, whatever the original quality of the audio source (e.g. a 256 kbps mp3 or a hi-res FLAC), the SBC codec will end up being the bottleneck, leading to poor audio performance.
AAC CODECAAC (Advance Audio Coding) is a Bluetooth codec (used by Apple). Typically, bitrate is between 256 and 320 kbps and is made with more complex psycho-acoustical models, but it still doesn't reach frequencies high enough to match CD quality.
We could imagine that one advantage of AAC codec is when used within apple environment as both file format and BT codec is AAC. This is seldom the case, and most of the time the audio file is decoded to be mixed and then re-encoded with the BT encoder, leading to a loss of information.
Note that AAC encoder is pretty complex and power consuming; this could explain why on many (android) phones the encoding quality used is not optimal.
aptX and aptX HD CODECQualcomm developed a couple of new gen codecs: aptX then aptX HD. Because aptX didn't reach the expected audio quality, Qualcomm launched aptX HD in 2017.
Supposed to deliver a Hi-Res audio experience, it can handle Hi-Res files (24 bits / 96 kHz resolution) but with respectively 352 kbps and 576 kbps, it can only deliver a lossy rendering.
LDAC CODECSony codec is the first to propose a "CD quality" via Bluetooth, promising bitrate up to 990 kbps (48 and 96 kHz sampling frequencies files) and 909 kbps (44.1 and 88.2 kHz) and strong coding-decoding algorithms. Nonetheless, there are still strong limitations with true lossless Hi-Res audio file (24 bits / 96 kHz requests a very minimum of 2 000 kbps with good compression ratio algorithms). As stated in interviews, they are quite far from truly Hi-Res performances.
LDAC is a proprietary solution and so far, only Sony’s devices support LDAC decoding. LDAC is by default enabled on Sony’s device but if you have a poor BT connection or if you decide to activate specific audio effect (like audio EQ for instance) you do not have any other choice than using the SBC codec.
Talking about competitors, Bose headphones (QC35 II or headphones 700) only supports SBC and AAC, no recent BT codecs are available.
Prélude is APT-X HD compatible.Prélude will support AAC, aptX and aptX HD and appropriate sound enhancements, designed by the awarded sound engineer Antoine Chabert, will be automatically applied.
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