LDAC, AAC and SBC: which Bluetooth codec your phone uses
What a codec is
Bluetooth cannot send music exactly as it is in the file, so it compresses it. The codec is how that compression is done. The phone and the earbuds must both support the same codec to use it.
SBC and AAC
SBC is the basic codec every Bluetooth device has. AAC is used by iPhones and many Android phones and usually sounds better than SBC at the same rate. All TESNA earbuds support SBC and AAC.
LDAC
LDAC sends more data and allows Hi-Res sound, with near-wired detail. It works on many Android phones, but not on iPhone: there the earbuds use AAC. The TESNA Ultra and the TESNA Pods Ultra over-ear headphones support LDAC.
LC3
LC3 is a newer codec designed to sound good at low power. The TESNA S7 and TESNA Open2 support LC3, alongside SBC and AAC, for phones that have it.
Why there are several codecs
Bluetooth cannot send music as it is stored, because the radio link has little bandwidth. The phone compresses it with a codec, sends it, and the buds decompress it. Each codec strikes a different balance between quality, stability, latency and power use.
SBC is the basic codec, required in every Bluetooth audio device: it works everywhere but is not the finest. AAC is the codec Apple prefers; on iPhone, iPad and Mac it sounds very good. LDAC, created by Sony, can carry far more data, up to 990 kbps, and is found on many Android phones. LC3 is the codec of the new Bluetooth LE Audio standard: good quality at lower power.
What to choose by phone
If you have an iPhone, AAC is the best codec you will use: iPhone does not support LDAC. Any TESNA bud with AAC sounds as good as it can on an iPhone.
If you have Android, check whether your phone supports LDAC; most Android phones from version 8 on have it. With the Ultra or the Pods Ultra, both with LDAC, you can listen to Hi-Res music from services that offer it.
If you have a new phone with Bluetooth LE Audio, buds with LC3, such as the S7 and the Open2, can use that codec at lower power.
Quality or stability
LDAC usually has three settings: quality, balanced and connection. At top quality it sends the most data, but the link is more fragile: in a crowded metro station or with the phone in a back pocket, the sound may cut out.
If it drops, choose the balanced setting or leave the phone on automatic. For podcasts and calls you will not hear the codec; it matters mostly for music listened to in a quiet place.
The source matters just as much
A good codec does not fix a poor source. If you stream at reduced quality to save mobile data, LDAC has nothing to add. Check the quality setting for streaming and downloads in your music app.
Files downloaded at high quality and a stable connection get the most out of the headphones.
How to check on your phone
On Android, the codec usually shows in the device’s Bluetooth settings or in developer options. On iPhone there is nothing to choose: it uses AAC.
The codec for calls
On calls the buds do not use the music codecs but a separate mode for voice, in both directions. That is why your voice on a call sounds different from music, whatever the codec.
If you listen to music and turn the microphone on, for example in a game or a meeting, some phones switch to the voice mode automatically, and the music suddenly sounds poorer. That is normal: it comes back when the microphone is off.
What Hi-Res means
"Hi-Res" or high-resolution audio means music stored with more detail than a CD: more bits and a higher sampling rate. You find it on some streaming services and in digital music stores.
For it to reach you, every link has to support it: the file, the app, the phone and the headphones. Over Bluetooth, LDAC is the codec that carries most of that detail; the Ultra and Pods Ultra have it. You hear the difference best in a quiet place, with a good recording.
Every model is in the shop, under noise cancelling earbuds and over-ear headphones.