The Bluetooth codec your headphones use significantly affects the sound quality. Unfortunately, macOS sometimes uses the SBC codec subpar instead of the aptX or AAC superior codecs. So here we explain how to force macOS to use one of them.
What is a Bluetooth codec?
The word «codec» is the abbreviation for «codec-decoder», which is precisely what a codec does. In this case, the codec is used to compress the audio file at one end (encode) and decompress it at the other (decode). This allows the file to be transmitted quickly. Some codecs are better than others to compress audio without reducing its quality, so it is essential to choose the right one.
SBC is the codec that macOS sometimes uses by default, while aptX and AAC offer better sound quality. The three codecs compress the audio before sending it to their headphones, but aptX and AAC do so without a dramatic impact on the overall audio quality.
Thus, SBC was designed to be efficient and ensure compatibility instead of offering the best possible sound quality. Latency is also a consideration with SBC and audio delay is noticeable when you watch some video content. Neither aptX nor AAC exhibit this behavior.
In summary, aptX promises a "CD-like" sound quality, which is something that SBC cannot offer. Similarly, AAC's improved compression algorithms allow for better sound quality, despite its lower maximum bit rate of 250 Kbps compared to SBC's 328 Kbps. However, the aptX codec exceeds both at 352 Kbps.
Unfortunately, not all Bluetooth headphones are compatible with aptX or AAC codecs, although most recent models do. If you force your Mac to use any of the codecs, but your headphones don't support them, don't worry, instead it will automatically switch to SBC.
How to verify which codec is in use?
So you can see what codec is in use, connect your Bluetooth headphones to your Mac and play some audio. You must press and hold the Option key and click on the "Bluetooth" icon in the menu bar.
Highlight your headphones and observe the active codec.
This is the codec that is currently in use. You're already fine if it's aptX or AAC; otherwise, you have to keep reading.
How to force aptX or AAC
Download additional tools for Xcode from the Apple developer site. You must create a free Apple developer account to do so. Once it has been downloaded, double-click on the DMG file "Additional Tools" to mount it.
Double-click on "Additional Tools" on your desktop.
Now, double click on the "Hardware" folder.
Drag «Bluetooth Explorer.app» to your applications folder.
Then, double-click on the "Bluetooth Explorer" application and then click on "Tools and Audio Options" in the menu bar.
Check the “Force use of aptX” and “Enable AAC” boxes. Here you must make sure that the “Disable AAC” and “Disable aptX” boxes are unchecked. For some reason, the application will allow you to check the "enable" and "disable" boxes.
Click on the "Close" button to save the changes.
Disconnect and reconnect your headphones and then confirm that they are now using the aptX or AAC codecs as described above. If so, you should notice an improvement in sound quality. Otherwise, it might be time to enjoy new headphones.