Poor/Muffled Microphone, Speaker Works Great — Why?

Yo,

My microphone quality was awful. I purchased a replacement microphone/charge port and installed it with no issues. However, the quality is still terrible both in phone calls and utilizing a voice-recording application.

Despite this my voice quality while using the ‘speaker phone’ during calls is excellent.

What’s up with that?

Anyone got any ideas on how I’d go about fixing this?

Thanks.