In the beginning, Bluetooth audio was lousy—the connection standard simply wasn’t capable of accurately transmitting sound the way a pair of wired headphones could via a 3.5mm connection. But the situation has improved dramatically since those days, likely accelerated in part when Apple (and subsequently most Android phone manufacturers) removed the headphone jack from its phones several years ago. Wireless earphones and headphones are now the norm, and we hardly ever even review wired models any longer.
Audio quality improvements over Bluetooth are mostly because of the development of far superior codecs that enable near-lossless streaming. Before we run through the basics of each of these codecs below, the main thing to understand is that they largely determine the quality of your streaming audio. Also keep in mind that in order to use a codec, both your source device (phone, PC, or tablet) and headphones must support the same one.
Understanding Bluetooth Technology: It’s Like Delivering a Package
Understanding codecs first requires understanding how Bluetooth technology works.
Bluetooth 5.2 is the current standard for the wireless technology, and defines how devices like phones and headphones connect to each other. Each new version adds capabilities or features, with more recent Bluetooth iterations enabling faster connections, better performance over longer ranges, and more. Older devices might have previous Bluetooth versions like 5.1 or 4.2, and since these versions are backward compatible, you’re able to connect your Bluetooth 4.2-equipped iPhone 6 to your shiny new 5.1-equipped Bose QuietComfort 45 headphones (though performance and sound quality might not be as good as with a new phone). Think of the Bluetooth version as the road a delivery truck is driving down, and the higher the number means the road is smoother and wider, with a higher speed limit.
While the Bluetooth version determines how devices connect to each other, it doesn’t define the type of data that is sent between them—that’s what profiles are for. Bluetooth profiles are the standards and protocols for transmitting stereo audio, phone calls, photos, printer jobs, and even faxes over Bluetooth. A2DP, the Advanced Audio Distribution Profile, is the specification for sending high-quality sound over Bluetooth. Think of the Bluetooth profile as the truck itself, which is driving down the road of the Bluetooth connection.
The Most Common Bluetooth Codecs
Codecs encode and decode audio using different types of file compression to send as much information as possible using the available speed and bandwidth. Much of what distinguishes a codec comes down to bit depth (bits), bitrate (Kbps), and sampling rate (kHz), with higher numbers indicating higher quality in nearly all scenarios.
Even if you store the highest-quality files on your device, how they sound through your Bluetooth headphones depends in part on the transmission codec. In most, cases, the bitrate is what holds back even the high-end codecs from reaching CD quality (16-bit; 44.1kHz; 1,411Kbps) or better. Higher-end audio codecs like LDAC can support up to 32-bit and 96kHz sound, but even they can only hit about two-thirds the bitrate at best (LDAC is 990Kbps), which means that less data is coming through.
In brief, SBC is the most basic codec with the lowest bitrate and, therefore, the lowest sound quality. AAC and AptX are both steps up from SBC and are generally mainstream, though different devices might support either or both (AAC is most common on Apple phones and tablets, while AptX is the preferred standard for Android).
LDAC and LHDC enable even higher quality sound than those codecs, and are currently the only ones to which the Japan Audio Society extends its Hi-Res Audio Wireless certification (that’s the gold and black Hi-Fi logo you see on high-end audio products).
Below are all the codecs you may encounter (in order of prevalence) when streaming audio over Bluetooth. We mention a couple of emerging codecs in this article, but you likely don’t need to worry too much about them unless you seek out devices and headphones that specifically support them.
Note that the specs we list are those that apply to mainline applications; variations of each codec may be capable of different specs, but the implementation ultimately depends on the manufacturer.
SBC
- Bit depth:16-bit
- Sampling Rate: Up to 48kHz
- Bitrate: 328Kbps
SBC doesn’t stand for Sorta Basic Codec, but maybe it should. SBC, or subband codec, is the default (and only) codec most lower-cost audio gear supports, and what devices often fall back on when higher-quality codecs aren’t available. SBC isn;t terrible—it’s capable of better-than-CD quality audio in terms of bit depth and sampling rate (16-bit and 48kHz, respectively), but that’s only under the most ideal circumstances. Latency with SBC is also high, which means the codec isn’t very suitable for gaming. All Bluetooth devices must at least support SBC.
On good headphones and with good source material, you can likely easily hear the difference between playing audio over SBC and a higher-end codec, so we recommend that you use SBC only when you have no other choice.
The codec itself isn’t necessarily the limitation here, but rather how it’s usually implemented. A deep dive from the Lineage OS Project details how the combination of SBC’s Dual Channel mode and eXtreme quality profile (SBC XQ) can produce results that rival AptX HD. A successor to SBC, LC3 (Low Complexity Communication Codec), is also in development, and promises to be more efficient, support more bit depths (up to 32-bit), and work at a broader range of bitrates.
AAC
- Bit depth: Up to 24-bit
- Sampling Rate: 44.1kHz
- Bitrate: Up to 320Kbps
AAC (Advanced Audio Codec) is a Bluetooth codec Apple uses, but confusingly, it’s also the name of the file compression scheme Apple uses for transmitting audio between its products and for storing music files as an alternative to MP3s.
SBC offers a (slightly) better sampling rate and maximum bitrate than AAC, though it performs worse, especially on Apple devices. This is because AAC uses a superior compression algorithm, and Apple’s phones, tablets, and headphones can run this potentially battery-guzzling codec so efficiently. As a result, AAC sounds less lossy than SBC. It isn’t particularly low-latency, though, so like SBC it’s not ideal for gaming.
You can use AAC on Android phones, but that OS doesn’t process it as effectively, which leads to a loss in audio quality.
AptX
- Bit depth:16-bit (AptX); Up to 24 bits (AptX HD)
- Sampling Rate: 48kHz (AptX); 48kHz (AptX HD)
- Bitrate: Up to 384Kbps (AptX); 576Kbps (AptX HD)
Qualcomm’s AptX codec is actually a number of codecs with different purposes. There’s standard AptX, AptX LL (low latency) for gaming, AptX HD for high-quality audio, and AptX Adaptive, which uses adaptive bitrate to offer a combination of lower latency and higher quality. AptX HD is the best option for audiophiles out of the bunch, because its bitrate locks in at a high level.
Another AptX variant to keep an eye on is AptX Lossless, because it combines some of the best qualities of AptX Adaptive and AptX HD. It uses an adaptive bitrate that scales from 140Kbps up to 1Mbps, which is even higher than LDAC. We don’t know when headphones that support that technology will hit the market, however.
Qualcomm has a helpful resource for finding various products that support each of these standards, though AptX Lossless is not currently an option in the drop-down menu.
LDAC
- Bit depth: Up to 24-bit
- Sampling Rate: Up to 96kHz
- Bitrate: Up to 990Kbps
If you want to max out specs while streaming over Bluetooth, Sony’s LDAC codec offers gaudy capabilities. It streams at up to 990Kbps, with a sampling rate of up to 96kHz. It enables some of the highest-quality audio when it’s at its best, but its fallback modes are pretty much in line with the other codecs, as low as 16-bit and 330Kbps. You can force LDAC to always play at the highest bitrate (we explain how in a later section), but doing so can affect playback if streaming conditions aren’t ideal. In contrast, AptX HD stays at a constant bitrate, so it might provide more consistency to your listening experience.
Apple’s iOS devices don’t support LDAC, but because it’s part of the Android Open Source Project (AOSP), the vast majority of Android devices should. And, like most other codecs on this list, latency is also an issue on LDAC, so once again it’s not suitable for gaming.
LHDC
- Bit-depth: Up to 24-bit
- Sampling Rate: Up to 96kHz
- Bitrate: Up to 900Kbps
LHDC is a relatively new codec from Savitech and supported by Huawei, and primarily competes with LDAC. The codec appears to, like LDAC, scale dynamically between bitrates, but the maximum rate is just a bit lower than LDAC at its best. An additional variant called LLAC offers better latency, but limits audio quality to 24-bit, 48kHz, and 600Kbps. Details about LHDC and LLAC are scarce and not easy to confirm, so these specs may not be exact.
The codec benefits from Huawei’s adoption, and you can search for devices and headphones that support it on the codec’s website. LHDC is a part of the AOSP, too.
Matching Phones, Tablets, and Computers With Codec Support
AAC is the highest-quality codec that Apple products support, but they default to transmitting over SBC when paired headphones don’t support that codec. So if you use an iPhone (or just about any Bluetooth-capable Apple product), you should make sure your headphones support AAC. You can often (but not always) find this information on the product’s specs page or on the box itself, and we strive to provide this information in our reviews. For reference, AAC also seems to be the most common codec that headphones support apart from SBC based on those we have reviewed.
Android users need to pay even closer attention to codec support on headphones; if they only have AAC and SBC, they won’t provide the best audio quality possible, but that’s just the start. Look for at least aptX, but you should also consider whether your headphones use aptX HD, LDAC, and LHDC as well, depending on what your phone supports.
While Android phones aren’t usually capable of efficient AAC playback, they can work with different combinations of SBC, AptX (in various forms), LDAC, and LHDC, depending on both the processor in the device and whims of the manufacturer. For example, the Snapdragon 8 Gen 1 chip is one of the few so far that supports the AptX Lossless codec, and should enable all other AptX formats, though the Samsung Galaxy S22+ has that chip and only supports AptX, not even AptX HD
Meanwhile, while LDAC and LHDC are technically part of AOSP, individual manufacturers can still choose whether to enable them on their devices, and LDAC seems to be supported more broadly than LHDC.
You can change the Bluetooth codec in the Settings menu of your Android phone (tap System > Developer Options > Bluetooth Audio Codec). With the LDAC codec specifically, you can specify a streaming preference: Optimized for Audio Quality; Balanced Audio and Connection Quality; or Optimized for Connection Quality. That first option gets you to the highest 990Kbps bitrate. You can further control the codec, and prevent your choice from resetting to the default Best Effort setting, by downloading the Sony Music Center app. In the app, open the three-dot menu and tap Music Center Settings > Bluetooth Output Settings > LDAC Playback Quality, and select the Priority on Sound Quality option.
Some manufacturers helpfully equip headphones and speakers with both AAC and AptX or LDAC, which saves you from having to think about sticking with a single platform for listening to music. But you still may need to manually switch between the two codecs in an app, your phone’s settings menu, or on your computer depending on your sound source.
Even if your device doesn’t support a specific codec, some software or hardware workaround likely exists. For example, it’s possible with some Macs to stream via AptX instead of AAC, but you have to manually set this up and the process is more involved than we have room to describe here. Similarly, you can buy external gear that you can use with iPhones and iPads to force support for other codecs, but again, this isn’t an ideal (or Apple-approved) solution. Windows 11 devices support AAC, but you must turn to alternative methods to use any of the other high-end codecs.
What About Apple Lossless and Other High-Res Streaming Audio?
Apple and other streaming services have joined Tidal to offer lossless streaming, but if you’re listening via Bluetooth, you’re not hearing it. Virtually all Bluetooth codecs are lossy, which means some data is lost in the compression and decompression process that lets the audio be transmitted wirelessly. In fact, the only lossless Bluetooth codec, aptX lossless, is less than a year old and hasn’t actually been implemented in anything yet. That means the sound you get through your Bluetooth headphones won’t technically have as much detail as if you used a wired pair of headphones or a different wireless connection that’s fast and wide enough to send all of that data without encoding.
Apple Music uses the company’s own lossless audio compression technology, called Apple Lossless Audio Codec (ALAC). So what happens when you listen to ALAC over Bluetooth headphones that only support AAC or SBC? The short answer is that you eliminate the lossless quality—the source device encodes the ALAC files to the AAC codec before transmission. Even on AirPods.
This isn’t really Apple’s fault, and is more a result of the current limitations of Bluetooth. For instance, the most popular non-Apple lossless compression codec, Free Lossless Audio Codec (FLAC), still loses some data when sent over Bluetooth, at least until aptX Lossless becomes readily available. Apple Lossless being unavailable (at its highest fidelity, at least) on AirPods is somewhat ironic, but until Bluetooth upgrades to truly hi-res specs, no Bluetooth headphones or speakers can output ALAC or FLAC at its best.
This goes for every music streaming service out there, Apple or otherwise—no matter how “lossless” the stream may be, it becomes lossy once the source encodes the stream for Bluetooth transmission. Exactly how lossy depends on the codec.
When Codecs Don’t Matter (as Much)
Let’s be reasonable: The goal of a budget-friendly pair of headphones isn’t to produce superb audio. Most of these models stick with the SBC codec, and that’s fine because most of the drivers in these models are unable to produce crystal-clear, audiophile-grade audio anyway. This holds true for most headphones and speakers under about $100. Manufacturers also have to pay to license AAC or AptX support on their devices, which likely contributes to the decision to omit the codecs.
Bluetooth speakers are even less generous with high-end codec support—plenty of portable models that cost over $200 (and that we recommend enthusiastically) support only SBC. The reality is that pristine audio quality often takes a backseat to a list of other features in this category, like booming bass or a waterproof design. That doesn’t mean you can’t find quality codec support in Bluetooth speakers, but SBC-only portable speakers are the most common.
There’s Still a Long Way to Go to Lossless
When televisions made the leap from CRT to flat-panel, letterbox-shaped screens, it was pure magic. But if you were to go back and watch a Blu-ray on an early LCD TV, you might find the resolution lacking and the color-banding problematic. Once you get used to something good (4K resolution, for example), it’s easier to see the flaws in older gear.
Bluetooth codecs are like that—they enable far better sound than early Bluetooth technologies, but there is still room for improvement. Latency remains an issue with most codecs, some of the better ones aren’t very energy efficient, and frequency response can vary greatly. And, of course, all are lossy to a degree.
Even if you load your phone with lossless uncompressed WAV files, no Bluetooth codec can currently transmit them without some level of compression. Until truly lossless codecs become the norm, you need to pay close attention to which ones your source device and headphones support—it’s a matter of ensuring that you get the least compressed audio quality possible.
Of couse, you can also consider using one of our favorite pairs of audiophile headphones with a DAC/AMP combo, and bypass the whole issue of not having a headphone jack.
