Please check how the earphones fit, because it's necessary to fit earphones appropriately as the elements for best Sound Quality. Then, you can customize the sound using the Technics Audio Connect app, such as 5 Preset Sound mode and 3 Equalizer settings.
1. Fit the earphones firmly as per the illustration.
2. If you need to replace earpiece, please follow below instruction to select appropriate one for you.
3. Customize Sound setting at Apps, such as 5 Preset Sound mode and Equalizer settings below.