Asus Zenfone 5 ZE620KL low volume

[Kuis_Kiske]

I hope after this Asus can provide firmware to improve the volume sound of Asus Zenfone 5 ZE620KL which is too slow. Volume has lost by 50% after I upgraded to android Q and remains slow even though I have upgraded to android P again.
I bought Asus because of its sound quality.
Hope Asus cares about this.
Thank you.

[Christine_ASUS]

Hi Kuis Kiske
Thank you for your asking. We apologize for any inconvenience caused and your valuable advice will be included in future design and optimization considerations.

If the function is in urgent need for you, please refer to the guide below as 10 to 9 downgrade steps.
1. Download "Version Android 10 downgrade to P" and then put the image file into the root directory of the MicroSD card.
https://www.asus.com/Phone/ZenFone-5-ZE620KL/HelpDesk_BIOS/
2. Insert MicroSD card into phone and then power off the device.
3. Long press with "Power" key and "Volume Down" key together and stop after feel the vibration to enter Recovery Mode
4. Use "Volume Down/Up" key and press "Power" key to choose "Apply update from external storage"
5. Select the downgrade file
6. When the updating process is done, Choose "Wipe data/factory reset" and tap"Yes" to perform the master clear.
7. "Wipe cache partition" > "Yes"
8. "Reboot system now" 
#Android 10 to Android 9 Guide 
https://www.asus.com/support/FAQ/1042349

[Kuis_Kiske]

Ok, I have downgraded the firmware from Android 10 to Android 9 but the sound is still slow.

[Christine_ASUS]

Hi Kuis Kiske
Thank you for your reply. If the volume sounds the same in both firmware version, please check
1. Sound settings
Settings>Sound & vibration
2. SMMI test 
Calculator> type ".12345+=">SMMI TEST>Single Test>Speaker Test/Receiver Test/Headset Test
If any of the SMMI tests fails, indicating high possibility of faulty hardware, kindly bring your device to the nearest ASUS repair center for device checking: https://www.asus.com/support/Service-Center-All-Countries/
If it is impossible to access the service center during Covid-19 period, please try Call us: https://www.asus.com/support/CallUs
3. Also, please try "the Factory Reset" 
Settings>System>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.

[Kuis_Kiske]

I think the problem of music sound is not strong on earphones due to the audiowizard application not working properly.