The iPhone 6 is one of the best phones in the market, considering its audio output quality. It has a mono stereo speaker with noise cancellation and spatial audio features. It has a speaker Grill in the bottom part of the phone. It should be kept in mind that, the speaker grill is there to catch audio inputs for your voice calls and Siri. The two speakers of the iPhone 6 are located on the bottom of the phone. The top speaker also serves its purpose as an ear speaker when in calls. 

However, some users have reported a lot of different audio issues. The most common audio issues faced by iPhone 6 users are:

No sound in voice calls

No sound in audio playback

Phone stuck in Headphone mode

Distorted sound/Low sound on the speakers

Audio not working or audio levels low after an update.

Ringer Switch not working/ Audio level increases or decreases automatically/ Physical audio level buttons not working.