Xiaomi’s current flagship Mi 9T, also known as the Redmi K20 in the Asian market, features an advanced wireless module that makes it easy to enjoy music without unnecessary wires. Many users face difficulties in initial pairing, not understanding why the device does not see the headset or the sound is transmitted with a delay. Proper tuning of a Bluetooth connection is not just a couple of buttons, but a whole process involving choosing the best codecs and managing device priorities.
In this article, we will take a closer look at all the stages of connectivity, from visibility activation to fine-tuning Android system settings. You will learn how to make old headsets work and how to achieve maximum sound quality through aptX HD or LDAC. Understanding these processes will allow you to fully unlock the potential of your smartphone audio system.
Before you get into specific actions, it's important to make sure your Mi 9T software is updated to the latest available version.Old security patches sometimes contain bugs in the Bluetooth stack that interfere with stable connection to new accessories.Vetting updates is the first step that is often ignored, even though it solves half of potential compatibility issues.
Preparation of the headset and activation of the pairing mode
The first and most critical step is to put your headphones into detection mode. Most users make the mistake of simply turning on the power, whereas the first connection to a new device such as the Xiaomi Mi 9T requires activating a special search mode. Usually, this requires holding the on button or a separate Bluetooth button for 5-7 seconds until the indicator starts flashing blue and red or quickly pulses white.
It’s important to understand that if the headset was previously connected to another phone, it can automatically try to connect to it, ignoring your smartphone, in which case you first need to turn off Bluetooth on the old device or reset the headphones to the factory, only after that the pairing mode will become active for external devices.
Some models, especially fully wireless (TWS), require both headphones to be removed from the case and touch touch the touchpads twice to enter the mode (pairing). Make sure the battery is sufficiently charged, as at low charge levels, some models go into energy-efficient mode and are no longer visible for scanning.
⚠️ Warning: Do not bring your headphones too close to a running microwave or router while pairing. Severe electromagnetic interference in the 2.4 GHz band can interrupt the encryption key exchange process.
Why aren't the headphones on the list?
Step-by-step instructions for connecting through Android settings
After the accessory is ready, we go directly to the interface with the MIUI operating system. The action algorithm is standard for Android, but has its own visual features in the shell from Xiaomi. Open the notification curtain with a swipe from top to bottom and find the Bluetooth icon. A long press on this icon will immediately take you to the desired menu, avoiding unnecessary transitions to settings.
In the menu that opens, make sure the activation slider is in the “On” position. Xiaomi Mi 9T will automatically start scanning the surrounding space. If your headset is in visibility mode, its name will appear in the “Available Devices” list in a few seconds. Click on the model name to initiate the mating process.
- 📱 Make sure your smartphone screen is unlocked during the search, as for security reasons MIUI may limit background scanning.
- 🔋 Check that the headphones are flashing fast indicator, signaling readiness for connection.
- 🔄 If the device is found but not connected, click “Forget the device” in the list of previously connected devices and try again.
Sometimes the system requests a pairing confirmation or input PIN-The standard code for most headsets is 0000 or 1234, but modern models often use Secure Simple Pairing, which does not require digits.
☑️ Checklist of successful connection
Customization of sound quality and selection of codecs
Xiaomi Mi 9T is based on the Snapdragon processor, which supports a wide range of audio codecs that provide high quality audio. By default, the system chooses the most compatible codec, usually SBC, which guarantees work with any device, but sacrifices detail and dynamic range. For owners of quality headphones, it is important to manually switch to more advanced compression algorithms.
To access these settings, you need to activate the developer menu. Go to Settings → About Phone and quickly click on the MIUI version seven times. Once the "You've become a developer" notification appears, go back to the main settings menu, select "Additional" and open "Developers" section.
| Codec | Bitrate (example) | Sound quality | Delay (Latency) |
|---|---|---|---|
| SBC | 328 kbps | Basic | Tall. |
| aptX | 352 kbps | Good. | Medium |
| aptX HD | 576 kbps | High (Hi-Res) | Medium |
| LDAC | 990 kbps | Maximum. | Tall. |
Choosing an LDAC or aptX HD codec is only possible if your headphones also support these standards. If you choose a codec that is not supported by the headset, the connection may not be established or the sound will be intermittent. Experiment with settings to find a balance between sound quality and connection stability in your particular case.
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For low-latency games, choose aptX Low Latency codec (if supported), and for silent music, LDAC for maximum bitrate.
Managing Connected Devices and Priorities
In the Android ecosystem, it’s common for multiple playback devices to be connected to a phone at the same time, such as smartwatches, car radios and wireless headphones. MIUI allows for flexible management of these connections, but sometimes priorities are not set right and the sound goes wrong.
To control, go to the Bluetooth menu, click on the gear next to the name of the connected device, and here you can see the status of the connection and, more importantly, the types of data being transmitted, and you can allow the device to play only media audio, leaving phone conversations on the smartphone speaker, or vice versa.
If you want to force the audio to a particular headset without turning off other devices completely, use the media control panel. When you run any audio or video content, a player widget will appear in the notification curtain or on the lock screen. Click on the audio output icon (usually looks like a triangle in a circle) and select the desired device from the drop-down list.
- 🎧 Turn off undiscovered devices in the Bluetooth menu to save battery power and the headset itself.
- 📞 Make sure that the Bluetooth profile settings activate the “Incoming Calls” and “Outgoing Calls” for full operation.
- 🔊 The volume control of the headphones and phone can be independent, check the levels in the volume mixer.
⚠️ Attention: Some cheap Bluetooth transmitters don't know how to transmit a signal of absolute volume correctly, in which case the maximum volume on the headphones can be quiet, even if the phone is twisted to the maximum.
Solving Common Connection Problems
Even with the right setup, Xiaomi Mi 9T users can experience unstable Bluetooth performance.A frequent problem is desynchronizing audio and video, especially when viewing content via YouTube or Netflix.This is often due to the system misidentifying codec latency or background processes loading the processor.
Another common problem is the spontaneous shutdown of the headset after a few minutes of operation, which can be caused by the aggressive MIUI energy saving system, which kills the background processes of the Bluetooth service. To avoid this, find the Bluetooth or Bluetooth MIDI system process in the application settings and allow it to auto-start and work in the background without restrictions.
If the sound is interrupted or wheezing appears, try clearing the Bluetooth cache. To do this, find the option “Reset Bluetooth settings” in the For Developers menu or clean up the Bluetooth application data via the application management menu. This will remove all saved pairs, but often resolves software conflicts.
adb shell pm clear com.android.bluetoothThis command, executed through a computer with ADB installed, completely clears the Bluetooth stack on the phone, use it only if the standard methods of restarting and removing devices do not help. Once you execute the command, the phone will require re-pairing with all gadgets.
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Rebooting a Bluetooth module via a developer menu or ADB often solves problems that aren’t fixed by simply turning off the phone.