2018 Bluetooth Audio Codec Comparison Guide Part2: aptX HD, AAC & LDAC
SBC naturally takes a lot of abuse in marketing-copy from companies like Qualcomm, makers of premium-grade alternatives to SBC, like aptX and its new, more powerful aptX HD. For the majority of consumers looking for the convenience of wireless sound, gains in fidelity granted by aptX will be minimal or lost entirely to other chokepoints in the audio chain.
In scenarios where I’ve tested a pair of headphones with aptX (like the V-MODA Crossfade Wireless 2, for instance) and toggled between playback devices with/without aptX while using the same source files (FLAC 16/44) - the slight improvement aptX offered over SBC was not significant. Count me as calling a “maybe” there’s a difference, but I wouldn’t call it a clear step up in audio quality. Your mileage may vary and headphones specifically tuned with the aptX codec in mind may make a more substantial difference. But considering the difference in raw data-rate between SBC and aptX, it was never going to be a significant leap in sound quality.
Even if aptX alone doesn’t present a significant leap in audio quality, its arrival was a significant breakthrough for wireless headphone audio quality if only because it opened a door in demand for improved Bluetooth codecs. Headphone manufacturers willing to pay Qualcomm to license its aptX technology are making a clear statement that their product cares about wireless audio fidelity.
Qualcomm says aptX was designed to bring “CD-like” quality over Bluetooth by delivering 16-bit/48kHz sampling of your source material and streaming streaming it over a Bluetooth connection with 352-kbps throughput. So, if you’re listening to high quality source files like FLAC at 16-bit/48kHz (a popular lossless compression algorithm) where both your phone and headphones are aptX compatible, you are listening in the best-case scenario for aptX and have reached the codec’s upper limitations. Even then, aptX does introduce lossy compression, so the sound quality will be slightly compromised in-so-far as FLAC does not introduce any loss whatsoever. When adopting aptX to your wireless listening experience it’s important to keep in mind, if either side of the wireless connection doesn’t feature aptX compatibility (or another alternative codec) your Bluetooth communication will default back to SBC.
A common complaint about most Android phones is that the phone initiates the aptX handshake without notice to the user. Sure, it’s an automated convenience, but the drawback is that it’s often not possible to find any settings to prove that your phone is using aptX, leaving the listener with no method of switching between aptX and SBC. The best you can do is check your phone’s codec compatibility list and trust that it’s using aptX where available.
aptX Best Use: Qualcomm’s aptX codec can only be employed when both Bluetooth transmitter (phone) and receiver (headphones) are aptX-ready. Optimal aptX performance is engaged when your source files are encoded in a lossless format at 16-bit/44 or 48kHz, as this exceeds the capability of SBC. Because aptX is a lossy compression algorithm, compounded compression will occur when your music must be decoded from any other lossy compression algorithm such as MP3 or Ogg Vorbis (used by Spotify). But compounded compression is avoided when using lossless sources like Tidal’s Hi-Fi music stream or locally stored music in any lossless compression format (ie. FLAC)
Editorial Note about Online Music Streaming Services
Let’s take a for-instance, say your phone and headphones are both aptX-ready, but you’re streaming music from one of the many music services available, in this example I’ll use Spotify. If, in this scenario, you’re using Spotify’s “High Quality” setting, you’re streaming the equivalent of 160-kbps music files, using the Ogg Vorbis, a codec that uses a lossy compression algorithm. Spotify’s source stream is presenting a bottleneck in the audio-chain and gains from aptX are lost because the codec can’t add resolution. So, any difference in sound quality you may detect between SBC and aptX in that scenario, is simply the difference in how each of the respective codecs perform the job of lossy compression. But there are no on-paper gains in fidelity. We can only trust that the folks at Qualcomm built a better mousetrap than SBC.
New products featuring the latest version of aptX are now hitting the market for 2018. This new breed of high-end wireless headphones will join Bowers & Wilkins flagship PX wireless noise cancelling headphones that were released late last year. Qualcomm created aptX HD specifically for high resolution audio sampled at 24-bit/48kHz in Linear Pulse Code Modulation (LPCM) through its data stream that is capable of 576-kbps. Now, that’s a significant on-paper gain from either aptX or SBC. Although your options for compatible hardware is presently limited, many more were announced at CES 2018.
Whether or not high resolution audio (24-bit/48kHz or higher) presents any audible gains over the CD-quality standard of 16-bit/44kHz is a controversial topic. We won’t weigh-in on that particular minefield here, but suffice it to say, if you’ve got it - why not at least try to hear it!
aptX HD Best Use: If you’ve got a collection of high-resolution audio files at 24/48 or subscribe to a music service capable of high resolution audio, aptx HD was made for you. The only high res subscription music service available in North America at this time is Tidal Hi-Fi Master, which streams Master Quality Audio (MQA) at 24-bit / 96kHz, but this level of resolution is only available through the Tidal desktop app and exceeds the capability of aptX HD.
Tell me if you’ve heard this story before. A growing consumer electronics format gets competition from a proprietary Sony equivalent. For better or for worse, the story has lead to format wars in markets ranging from game consoles to video and high-resolution discs. The latest iteration of this recurring theme is Sony’s new high-resolution Bluetooth audio codec LDAC and can be found on Sony Xperia phones and select Sony headphones.
But this time the story is a little different than Sony simply exercising its consumer electronics and media privilege as both manufacturing giant and owner of half the world’s media. Instead of holding a death-grip on a proprietary platform as a Sony-exclusive, LDAC compatibility is now being licensed to other companies. One example is the RBH edition Prostereo H2. H2 Earphones are an excellent sounding set of wireless earbuds carrying a Swiss army knife of codecs that includes aptX, aptX HD and LDAC. Like all Bluetooth codecs, both phone and headphones must be compatible with the codec and this leads us to the best thing about LDAC - it’s going to be freely available to Android OEM phones.
In an unexpected twist, Sony has worked closely with Android to build LDAC right into the Android Open Source Project (AOSP) code of Android version 8.0 aka. Oreo. This means your next Android phone is very likely to include LDAC.
LDAC is a lossy compression algorithm that raises the bar with a throughput up to 990-kbps, nearly double that of aptX HD and triple SBC. LDAC is capable of a sample rate and bit-depth of 94-kHz at 24-bit. At the time of writing this article, it is literally the best wireless sound you can get for your lossless high-resolution audio library and comes close to matching the capability of Tidal Hi-Fi MQA.
LDAC Best Use: You guessed it! Both phone (transmitter) and headphones (receiver) must be LDAC compatible. You’ll probably see LDAC prominently displayed on the packaging for any compatible audio equipment and soon, just about any phone or tablet using Android 8, Oreo will also be compatible. You’ll acheive a near-perfect sonic replication of your high-resolution library of music files sampled at 94-kHz/24-bit. LDAC is of course a lossy compression algorithm, so your LDAC headphones won’t receive a bit-perfect copy of the music being decoded. But for today, it’s as good as it gets, and many claim that it’s better than human ears could possibly discern.
AAC Apple iOS
Unfortunately for Apple users, the aforementioned options for high-res wireless glory just isn’t for you. But, that’s not to say iOS users are left out in the cold when it comes Bluetooth audio. Apple introduces an interesting wrinkle in what might otherwise be a linear hierarchy of codecs-to-bitrates and demonstrates that higher bit-rates don’t necessarily result in better sound quality. Long story short, Apple’s simplicity and near-universal compatibility in codecs is its biggest strength.
Besides SBC, a requirement for the Bluetooth stereo A2DP spec, the iPhone is capable of streaming Apple’s preferred Advanced Audio Coding (AAC) codec. Apple keeps a tight rein on its software, so it’s no surprise iPhone codecs are limited to AAC or SBC. However, Macbook and iMac are aptX compatible, so maybe there’s future hope for additional codecs on iPhone.
The good news, is despite being slightly lower throughput, AAC is widely praised among lossy algorithms as a step up from SBC and there is a wide variety of compatible headphones. If you’re using a pair of AAC-compatible headphones, you’re theoretically getting no loss in audio quality from your stored AAC files (the iTunes standard) or streaming from the Apple Music service.
AAC Best Use: iPhone users will want a pair of headphones compatible with the AAC codec, then you want an AAC or Apple Lossless (ALAC) music library as your source. This will provide the cleanest sound quality possible, free from compounded compression your music would otherwise suffer.
Apple Music provides a native AAC stream, so it’s the next best thing to a library of AAC or ALAC files. For best results, you’ll need to pay attention that you don’t use your iPhone to stream any other lossy compression algorithms. Compression algorithms like MP3 or Spotify’s Ogg Vorbis will need to be decoded by the iPhone then encoded into another lossy algorithm (AAC) before being transmitted to your headphones.
Codecs and Bitrates Comparison
- AAC: 250 kbps
- SBC: 328 kbps
- aptX: 352 kbps
- aptX HD: 576 kbps
- LDAC: 990 kbps
Now You’re Ready for Fine Bluetooth Audio in 2018
The most important things to remember is your phone (transmitter) and receiver (headphones/speakers or Bluetooth receiver) must be compatible with the same Bluetooth codec to work. If they’re not compatible, they’re defaulting to SBC.
Generally, the bitrate between devices corresponds directly to the quality of audio you can expect. The higher the bitrate, the better possible audio quality. But it’s never that simple, because if you’re serious about sound, you also want to avoid making your phone transcode music files between different codecs, because this will result in compounded compression. So, it's usually better to get a clean transfer between lower-bit, but compatible codecs, than to have to transcode to a lossy codec from another, higher-bit lossy codec. Now, whether or not your ears can actually hear the difference in double blind a/b/x testing is up to you - the important thing is to have fun trying.
What codec are you streaming wirelessly with? Please share your experiences in the related forum thread below.
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But my rock collection like Led Zeppelin, Pink Floyd, AEROSMITH, The Grateful Dead….. Just name 4 I notice a great amount of difference for the better to what it is without LDAC.
I also have a Fiio BTR3 connected to a Yamaha old school 100 wpc stereo receiver and some 8” JBL bookshelf speakers. The player is the HiBy R3 also transmitting in Quality Priority LDAC. I can fine-tune this system to blast away all night if I want, and the sound will not penetrate a concrete wall so I am happy and so are my neighbors at 4am when I am not sleepy, at all! The Fiio BTR3 does a remarkable job. The build quality is great, the sound is great. The reception is not as good as with the EarStudio ES100. I use the EarStudio for workouts with a pair of Pioneer SE-MS5T headphones which cost a whopping $40. The Pioneer headphones and EarStudio combination, in LDAC Quality Priority, will work all over the ground floor of my densely populated home, even through walls with plumbing and electric (lots of electronic activity, air conditioners, all kinds of wi-fi, etc.). I use LDAC Quality Priority, the phones are really comfortable, sound so good I workout for 70 minutes and love every second of the experience!
I am a sucker for the Bluetooth wireless sound transmission technology ever since I discovered it can sound so good and work so well. I started with digital music in June of 2016. I started by ripping my 900 CD collection to MP3. I wasn't listening any more. It's a pain to listen to a CD collection. Digital music sounded terrible to me, but I had to start somewhere because I wasn't listening. My computer in 2016 only had variations of MP3 and one lossless program, WMA. So I re-ripped everything into WMA lossless. That sounded OK, but then the new players that I had just started collecting would not work with the WMA lossless program, so not being a computer geek, and not wanting to get stuck in the middle of a snag, I re-ripped my entire library into FLAC when I got a new computer and it had FLAC.
I am thrilled with the newer music players and those EarStudio and Fiio Bluetooth receiver/ amps.