Owners of Xiaomi Redmi 9 often face the question: why does the sound in headphones or speakers seem muffled despite the maximum volume? The reason lies in the default HD Audio mode, a technology that expands the frequency range and improves the detail of sound. In this article, we will not just show how to turn on HD Audio, but also explain what codecs your smartphone supports, how to check the functionality and avoid typical errors in configuration.
It’s important to understand that HD Audio is not a marketing stunt, but a real technology feature embedded in the Qualcomm Snapdragon hardware platform on which the Redmi 9 is built. However, the manufacturer often turns it off “out of the box” to save battery power or compatibility with budget accessories. Our instructions will help activate the feature without risk to the device – with explanations for users of any level of training.
What is HD Audio and why it is not on Redmi 9
The term HD Audio (or High-Definition Audio) refers to high-bit (up to 24 bits) and sampling (up to 192 kHz) audio technology. For comparison, standard sound in smartphones is usually limited to 16 bits and 44.1 kHz. The difference is especially noticeable when listening to music in FLAC, WAV or ALAC formats through high-quality headphones.
The Xiaomi Redmi 9 is disabled for three key reasons:
- 🔋 Battery savings: processing HD-Sound requires more Snapdragon 662 processor resources, which reduces battery life by 5-10%.
- 🎧 Accessory Compatibility: Many budget headphones don’t support high frequencies, so include HD Audio can lead to distortions.
- 📱 Optimization MIUI: The default firmware is focused on the “average” user, who is satisfied with the basic sound quality.
Critical detail: on the Redmi 9 HD Audio only works through wired headphones with a 3.5 mm connector or USB-C (with an adapter). Wireless headphones via Bluetooth use separate codecs (for example, aptX or LDAC), which are independent of this setting.
Preparation of the smartphone: checking the version of MIUI and compatibility
Before you turn on HD Audio, make sure your device supports this feature. On Redmi 9 (model M2003J15SC), it is only available on MIUI 12.0.3.0 and later.
- Open the settings → About the phone → version of MIUI.
- Compare the number to the table below.
| MIUI version | Support for HD Audio | Notes |
|---|---|---|
| 12.0.1.0–12.0.2.0 | ❌ No. | Update required |
| 12.0.3.0–12.5.x | ✅ Yes. | The function is hidden in the engineering menu |
| 13.0 and newer | ✅ Yes. | Available in standard sound settings |
If your version is outdated, update your firmware through Settings → System Update. Don’t use informal firmware – it can block access to hardware features, including HD Audio.
⚠️ Note: Some regional versions of Redmi 9 (e.g. India or Europe) have an option HD Audio can be locked at the core level, in which case it can only be activated by unlocking the bootloader and installing a custom recavator, a procedure that voids the warranty.
How to turn HD Audio on Redmi 9
There are two ways to activate the function: through the engineering menu (for MIUI 12) and through the standard settings (for MIUI 13+).
Method 1: Through the Engineering Menu (MIUI 12.0.3.0–12.5.x)
This method requires entering a special code in the phone application:
- Open the Phone app.
- Enter the combination: ##36446337##
- Select Hardware Testing → Audio → Headset Mode.
- Find the Hi-Fi Audio setting and set the Enabled value.
- Save the settings and restart the smartphone.
Important: If the sound is lost or distorted after the reboot, go back to the engineering menu and turn off the option. HD-regime.
Check version MIUI| Connect compatible headphones | Battery charge > 30%| Make backup of settings-->
Method 2: Through sound settings (MIUI 13+)
In the new versions of the firmware, the option is made available to the public:
- Go to Settings → Sound and vibration → Sound quality.
- Activate the HD Audio switch.
- Select a sound profile: 🎵 Balanced – Optimal for most tracks. 🎧 Detailed – High and low frequency. 🔊 Loud – increases volume but reduces quality.
After activation, check the sound through headphones with impedance of at least 32 ohms – only they are able to reproduce the entire frequency range of HD Audio.
💡
If the HD Audio sound is quieter after you turn on, try turning off the Adaptive Sound function in the same settings. It automatically lowers the volume to protect the speakers.
Checking the performance: tests and diagnostics
How do you know if HD Audio really works?
Testing through apps
- 📱 Audio Test (Play Market): Checks frequency range and distortion.
- 🎛️ Wavelet: Shows the current bitrate and codec.
- 🔊 SoundAbout: Analyzes the routing of sound.
In Wavelet, look at the Audio format bar, and if it shows 24-bit/192kHz, HD Audio is activated successfully.
Manual check
Turn on the track in FLAC 24/96 format (e.g. from 2L.no) and compare the sound before and after activation of the function.
- 🔍 Detailing: Are previously invisible instruments heard (e.g., musician’s breathing or guitar echoes).
- 🎚️ Dynamics: the difference between quiet and loud fragments became more noticeable.
- 🌀 Scene: The sound became "volume" as if the sources were located around you.
⚠️ Attention: If, after activation, HD Audio earbuds have background noise (hisping), which means that their resistance is too low (less than 16 ohms). Use headphones with impedance from 32 ohms or connect an external UHF.
What to do if HD Audio is not turned on?
Common Problems and Their Solutions
Even after successful activation, users face difficulties, and let's look at typical scenarios:
| Problem. | Reason. | Decision |
|---|---|---|
| The sound's quieter. | Volume limit activated in settings | Turn off the Safe Volume Level in Settings → Sound |
| There's been distortion. | Incompatible headphones or damaged cable | Check the headphones on another device |
| The function disappears after restarting | Resetting the settings of the engineering menu | Reactivate or update MIUI |
| It doesn't work via Bluetooth. | HD Audio is only available over the wire | Use LDAC or aptX HD codecs for wireless headphones |
If the problem is not solved, try resetting the sound settings to the factory:
- Go to Settings → Applications → Application Management.
- Find the sound settings and click Storage → Clear the data.
💡
HD Audio on Redmi 9 works only with wired headphones. For wireless devices, use LDAC (for Sony) or aptX Adaptive (for Qualcomm).
Alternative ways to improve sound without HD Audio
If your version of MIUI does not support HD Audio or you use wireless headphones, use these methods:
1. Equalizer adjustment
The MIUI has a 10-band equalizer:
- Open Settings → Sound and vibration → Equator.
- Choose Preset Classic or Jazz for better detail.
- Manually lift the sliders to 60 Hz (for bass) and 10 kHz (for high frequencies).
2. Sound enhancement applications
- 🎛️ Wavelet: Supports codecs LDAC and aptX, has a built-in equalizer.
- 🔊 ViPER4Android: requires root rights, but gives maximum control over sound.
- 🎧 Poweramp: player with support for Hi-Res audio and own audio settings.
Important: When using third-party apps, disable the MIUI system equalizer to avoid conflicts.
Hardware solutions
If the software methods do not work, consider:
- 🎧 Buying headphones with support for Hi-Res Audio (for example, Sony) MDR-1AM2 or Audio-Technica ATH-M50x).
- 🔌 Use of external DAC (digital-analog converter) through USB-C.