Modern Redmi Note 9 smartphones feature advanced Bluetooth modules that allow high-quality audio to be transmitted without delay. However, the initial pairing process for new users can raise questions, especially when working with different codec protocols. Proper connection settings ensure not only stable sound, but also optimal power consumption of the device.
Xiaomi owners often face the need to switch between multiple headsets or eliminate audio desynchronization in video. Standard connection procedure takes less than a minute if the basic requirements for both devices are met. In this article, we will discuss in detail all the stages of configuration, from activating the search mode to fine-tuning the parameters in the engineering menu.
It's worth noting that the MIUI shell interface has its own features of visualizing connected devices, and understanding these nuances will help you avoid common mistakes when the phone "sees" the headphones, but the sound is not transmitted. Let's look at a step-by-step algorithm for successful synchronization.
Equipment Preparation and Bluetooth Activation
Before you start looking for devices, make sure both gadgets are ready to go. On the Redmi Note 9, the wireless module can be turned off to save charge or be in a state of failure. Check the charge level of your headset, as at low voltage, some models go into power saving mode and cease to be visible to external devices.
To activate the module on your smartphone, swipe the notification curtain from top to bottom. Find the Bluetooth icon and press it to turn blue. The alternative is through system settings: go to Settings → Bluetooth. Here you will see a switch at the top of the screen that you need to activate.
If the icon is missing or not activated, there may be a failure of system services, in which case the smartphone will help to restart, after activation, the system will automatically start the necessary drivers for the operation of wireless interfaces, and also make sure that the system does not hang on the screen notifications for critical hardware errors.
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Keep your headphones and smartphone at a distance of no more than 1-2 meters during the pairing process to ensure a stable signal.
It's important to understand that a Bluetooth adapter in the background can consume CPU resources. If you don't plan to use the headset anytime soon, it's better to turn off the module. This also increases the security of your data, preventing unauthorized connections to your device in crowded places.
Mode of pairing on headphones of various brands
The most critical step is to put the headset in visibility mode, and many users mistakenly believe that simply turning on the headphones is enough to detect the phone. It's not: the device must be in a pairing mode, which is often different from normal on.
For models with a separate control button (often marked with a power icon or Bluetooth), you need to press this button for 5-7 seconds. The indicator will flash red and blue (or white, depending on the model), This is a signal that the module broadcasts a detection signal.
- 🎧 TWS-Cases: often require the removal of headphones from the case and prolonged clamping of the touch zone or physical button on the case of the charging case.
- 🎧 Head models: usually have a separate slider or button that must be held until the indicator flashes quickly.
- 🎧 Sports clips: may require simultaneous clamping of the volume buttons "Plus" and "Minus" for 5 seconds.
If the indicator is on a straight light or flashes slowly (once every few seconds), the device is not ready to connect. In this case, the Xiaomi Redmi Note 9 will not be able to find the headset in the list of available. Carefully study the instructions for your particular model, as the login algorithms may differ even from one manufacturer.
Search and Connection Process in MIUI
Once the headset is in search mode, pick up your smartphone. Open the Bluetooth menu, where the Redmi Note 9 should already scan the air. If the list of devices is empty or has not been updated in a long time, click the "Search for devices" button or the update icon in the corner of the screen.
In the list of "Available devices" will appear the name of your headset, it may be the same as the brand (for example, JBL, Sony, Samsung, or be a model number. Click on the name. The system can request a pairing confirmation or input. PIN-99% of the time, the code is standard: 0000 or 1234, or the confirmation is automatic without entering the digits.
When you connect, you may see a pop-up requesting access to contacts and call logs. If you plan to use the headset for conversations, you need to allow access. For listening to music, this is not critical, but the functionality will be limited to media audio.
☑️ Checklist of successful connection
Once synchronized successfully, status will change to Connected, and you can now run any audio player or video to check. If the sound is still going through the phone's speaker, tap the speaker icon in the notification curtain or in the Music app and select your headset manually.
Setup of profiles and audio codecs
Xiaomi owners need to know that the system supports different audio profiles, using A2DP for music and HFP/HSP for calls by default, but the sound quality depends on the codecs supported: SBC, AAC, aptX or LDAC.
To check or change your settings, go to the Bluetooth menu, click the arrow next to the name of the connected device, and you can set individual settings here, such as turning off the audio of media files, leaving only phone calls, or vice versa, and here you can see the battery level of the headset, if the protocol allows this information to be transmitted.
For advanced users, you can access a hidden developer menu where you can force the codec to be selected. You need to click on the MIUI version 7 times in the About Phone section, then go to Advanced Settings → For developers. In the Bluetooth Audio Codec section, select the desired option (for example, aptX HD), if your headset supports it.
| Codec | Sound quality | Delay (MS) | Compatibility |
|---|---|---|---|
| SBC | Basic | 200-250 | All devices. |
| AAC | Good. | 150-200 | iOS, Android |
| aptX | High. | 40-70 | Qualcomm chips |
| LDAC | Hi-Res | 150-200 | Sony, flagships |
What is Latency (Sound Delay)?
Managing Multiple Devices and Memory
The Redmi Note 9 can remember up to a few dozen previously connected devices, but it can only transmit audio to one pair of headphones at a time (unless it uses dual audio mode, which depends on the Bluetooth version and firmware), and if the phone stops seeing the new headset, the cache list may be full.
In the Bluetooth list, click on the gear icon or arrow next to the unwanted gadget and select "Cancel pairing" or "Forget device" to delete the encryption keys and clear the module's memory. Then try to search again.
There is also a “double connection” function for some. TWS-If you have conflicts (sound from one device or another), try to turn off Bluetooth on the second phone or break the connection in its settings.
⚠️ Note: When you reset your network settings to Xiaomi, all stored Wi-Fi passwords and Bluetooth devices are deleted. Use this feature only if other methods do not help.
Solution: If the sound is interrupted or absent
It's not uncommon to have a connection but no sound. First, check the volume of the media track. Xiaomi has a separate volume control for calls, media and alarm clocks. Press the volume buttons and make sure that the slider is raised to play music or video.
If the sound wheezes or is interrupted, it may be that the 2.4GHz Wi-Fi signal is interfering, because Bluetooth is running at the same frequency. Try to switch the router to 5GHz or move away from the signal source.
In some cases, clearing the Bluetooth service cache helps. To do this, go to Settings → Apps → All apps, click three dots in the corner, select Show System Processes, find Blueetooth and click Clear Cache. Don't confuse it with Clear Data, it can knock down all settings.
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Rebooting both devices (smartphone and headphones) solves 80% of problems with unstable connection and sound desynchronization.
If the problem persists in only one particular app (like YouTube), check the settings of the app itself. Some video players have a separate selection of audio output device. Make sure your Bluetooth headset is selected there, not Phone Dynamics.
Additional sound settings in MIUI
The MIUI shell offers advanced features for audiophiles. In the Sound and Vibration section → Sound Quality and Effects section, you can activate the visualizer, adjust the equalizer or enable the Mi Sound function. For headphones, it is recommended to choose Headphones or Hi-Fi mode if available.
And you also have to pay attention to the Mono-audio feature, which, if it's on, mixes the stereo into one channel, which is good for people with hearing impairments, but for normal music listening, you'd better turn it off to keep the spatial sound.
Some users have noted that after updating the firmware, the equalizer settings may reset, so after each major update, the MIUI recommends rechecking the sound profile. This will take a minute, but return the usual playback quality.
⚠️ Attention: Using third-party equalizer apps may conflict with Xiaomi's system settings, causing distortion or no sound at all.