How to improve headphone sound quality in iOS 14 for iPhone, iPad, and iPod touch

Open the Settings app . Note: The Settings app icon may appear in a different place on your home screen than shown in our example, below.
In the Settings app, scroll down and select Accessibility from the list.
On the Accessibility screen, scroll down and select Audio/Visual.
On the Audio Visual screen, select Headphone Accommodations.
On the next screen, set the toggle switch for Headphone Accommodations to On.
You can tune the audio by selecting one of the pre-sets shown under Tune Audio For - Balanced Tone, Vocal Range, or Brightness - or you can use Custom Audio Setup to determine which of these pre-sets is best for you.
If you choose Custom Audio Setup you will be given a series of tests which ask you to choose between different sound adjustments.
Next, choose how much you want to boost soft sounds, choose between Slight, Moderate and Strong.
To hear how your custom settings sound, select Play Sample.
At the bottom of the page, you can choose whether your customs settings are applied to Phone, Media, or both.
When you are happy with your settings, you can return to the home screen page of apps by:
- On devices with Face ID: Swipe up from the bottom of the screen.
- On all other devices: Press the home button once.