Sound quality is also very subjective for everyone. Therefore, going to the physical store and listening to the display earphones in the store is very helpful for purchasing. Play a few music you like, listen carefully and pay special attention to the overall balance, to avoid the earphones obviously distorting the original song, or the sound is too dull or too bright.
Simply put, the higher the sensitivity, the louder the earphones will be at any given volume setting; the lower the sensitivity, the softer the sound will be. You can find the sensitivity/efficiency level of the headset in the product specifications, expressed in “dB/mW” or “dB/V”.
Speaking of it, we should buy the loudest earphones, but this will easily be overloaded. If you connect them to a powerful amplifier, it may directly damage the earphones. If you buy headphones mainly for listening to portable listening devices such as smartphones (usually equipped with low-power amplifiers), then you can buy headphones with relatively high sensitivity (100 dB / mW or higher). Conversely, you can choose a model with a lower sensitivity, which is more adaptable in a wider listening environment.