2018 Bluetooth Audio Codec Comparison Guide Part1: SBC & aptX

When Apple sidelined the 3.5-mm jack with the launch of last year’s iPhone 7, it looked like a bold move. But despite pockets of outrage over another clear case of planned obsolescence, it was a clear indication that the future of mobile audio is going to be wireless. The trend has officially begun with Google also abandoning the headphone jack with the launch of Pixel 2. Let’s face it, sound quality is not usually a priority for cell-phone manufacturers because it’s just not in demand from the majority of consumers. But the average phone’s 3.5 mm headphone jack was never built for sound quality. It’s a fact that has created a market for portable DAC/amplifiers, like the Oppo HA-2 SE, they use your phone’s raw digital output for an upgraded sonic experience for serious listeners that have invested in a good pair of headphones. The 3.5-mm headphone jack was never going to be missed by anyone with a serious headphone hi-fi obsession.

Cell phone makers claim that abandoning the headphone jack is necessary to save space for other, more important features inside our ever-narrowing phones. Cell phone companies are less forthcoming about the more important reason for dumping the headphone jack, planned obsolescence. There just isn’t much profit anymore in the kinds of bottom-of-the-line earbuds and headphones that satisfy the listening needs of 90% of consumers. Since the sun has long since set on the market for wired headphones, wireless turned out to be a great way to get consumers to buy something they don’t necessarily really need.

So far, it’s worked! June of 2016, when it was still only a rumor that Apple would drop the headphone jack on its upcoming iPhone 7, was the month sales revenue for wireless headphones topped wired headphones for the first time. Wireless claimed 54% of headphone dollar-sales, despite netting only 17% of unit-sales. This proved consumers are willing to pay a premium for wireless. Timing couldn’t have been more perfect for Apple to officially announce iPhone 7 in September, 2016 and substantiate rumors of the headphone jack’s demise.

Now you have the perfect excuse to buy those wireless headphones you’ve been thinking about, because sooner or later, you’ll have no choice. And let’s face it, once you’ve tasted the convenience of wireless you won’t want to go back to plugging earbuds into your phone like it was an iPod from 2003. If you’ve waited this long to go wireless, 2018 may be the perfect year to buy yourself a good pair of wireless headphones because a slew of new products have arrived with new options for enhanced wireless audio fidelity.

The latest Bluetooth codecs including aptX HD and LDAC are ushering in a new era of wireless hi-fi possibilities. But, navigating the minefield of compatibility in new wireless audio standards can be confusing, so lets separate some of the marketing hype from real-world results.

2018 – Peak Audio-Quality for Bluetooth

It’s difficult to believe it’s been almost a decade since I first wrote what has become a cliche when reviewing wireless audio: “Wireless sound quality has really come a long way since the bad old days of early Bluetooth A2DP.” In the early days, back when Bluetooth first started transmitting stereo sound, its primary goal wasn’t audio quality. Bluetooth sought to be an energy-efficient platform that’s perfect for portable, battery powered devices. But with new high-bit codecs, Bluetooth sound quality is changing for the better.

How far back does Bluetooth go? It might surprise you to know that the Bluetooth name dates way back to the Vikings, seriously. It was named after a 10th century Scandinavian king, Harald Gormsson, nicknamed “Bluetooth” for a blueish or black tooth. The Bluetooth symbol is an amalgamation of the runic characters that comprise the old king’s name.

Understanding the Audio Codecs: SBC, AAC, aptX and LDAC

To understand wireless audio, we must first understand the codec – the word is a blend of code/decode. So, it’s software that encodes and then decodes a digital data stream, in this case the digital data is audio. It’s important to note that whatever codec you wish to use, your transmitter (phone, Bluetooth transmitter etc.) must be compatible to the same codec as the receiver (headphones or wireless speaker, Bluetooth receiver etc.). So, if you got a fancy new set of headphones that feature “aptX HD”, you will need a phone that can transmit aptX HD before you’re able to hear aptX HD-quality audio from those headphones – and this is where it gets confusing.

Subband Coding – SBC

The default Bluetooth codec is Subband Coding (SBC). This is the codec that is usually blamed for the compressed sound quality that has often plagued the Bluetooth listening experience in the early days of Bluetooth audio. Like *all* the major Bluetooth codecs in use today, SBC is a lossy compression algorithm. This means that when it encodes music for playback, it literally drops pieces of music the algorithm deems low-priority, these are mostly sounds you can’t hear anyway because they’re masked by other sounds in the same frequency range at higher volume. This description of the SBC codec’s lossy compression algorithm makes it seem worse than it is in practice, and this is why the term “lossy” is often unnecessarily vilified. But, it’s certainly true that too much compression or compounded compression algorithms will often accumulate and result in a hollow or compromised sound experience.

On its own, the SBC codec is not a terrible lossy compression algo, it can provide suitable audio quality for most consumers, and it’s perfectly suited for lower quality, budget Bluetooth headphones. However, for truly discerning ears that have taken the time to store or stream high-quality music files for playback on hi-fi equipment capable of highly detailed audio quality, the limitations of SBC becomes apparent.

The priority of SBC doesn’t happen to audiophile quality sound, instead it’s designed to be efficient, using less data, less energy and low-latency. In other words, it’s never been SBC’s job to provide you with a high-end listening experience. Instead it’s designed to save bandwidth and the battery life of your wireless devices. SBC is capable of a respectable 328-kbps, that’s about the data-rate required of high-quality 320-bit MP3s. But that doesn’t mean streaming 320-bit MP3s via SBC will yield a pristine listening experience. On the contrary, both MP3 and SBC are lossy compression algorithms. Your MP3 files have already been compressed, uncompressed and then converted to another lossy compression algorithm (SBC) to travel wirelessly through Bluetooth. This is where we run headlong into compounded compression, a doubling of lossy compression algorithms. Compounded compression constitutes a significant compromise in audio quality when compared to listening to the same MP3 file over a pair of headphones that are hard-wired to your playback device.

To be perfectly honest, in real-world application using moderate to good quality wireless headphones, streaming 320-bit MP3s from your phone, you’d be hard-pressed to actually hear any discernible difference from the same source fully wired while bypassing Bluetooth SBC compression completely. But there is a difference, and higher-end headphones may illuminate SBC’s limitations.

SBC is the default Bluetooth codec. If both sides of any Bluetooth connection aren’t using a compatible alternative – you’re using SBC. While SBC is a lossy compression algorithm designed more for efficiency than hi-fi audio, things aren’t as bad as it seems. There are many more and much worse choke-points in the audio chain that could be downgrading your audio experience through Bluetooth namely, cheap headphones/earbuds or overly-compressed online streams or music files stored on your phone.

SBC Optimal Use: On-paper, the closest to hi-fi audio you can squeeze out SBC is the humble 320-bit MP3 or other compression algorithms that do not exceed SBC’s limit of 328-kbps. Although there is still that nagging matter of compounded compression you’ll get by having to transcode between two separate lossy compression algorithms such as MP3-to-SBC. These details may get under the skin of the more obsessive among us looking for the most pure audio experience possible. But, as soon as you start using lossless files, such as FLAC or lossless streams at 16-bit 44-kHz, like Tidal Hi-Fi, you’d be better served upgrading your codec from SBC.

To learn about advanced Bluetooth audio codecs like aptX and more, click over to Page 2 of the Bluetooth Audio Guide for 2018.