Ever since I purchased the AirPods a month ago, they demonstrate extremely poor quality while activating the AirPod Mic, whilst they are connected to a Mac. When activating the Mic to record audio, it seems that both the recording quality AND audio playback quality severely drops to a substandard level (Mono 8.0 kHz).
For example, if I invoke Siri (on the Mac directly, or by double-tapping on AirPod), whatever is being said and recorded by me, AND the Siri/Mac/AirPod audio response will be in poor quality. After the recording is done, audio playback quality usually goes back to normal1. Any mic audio recorded to a file will however be in the poor quality; which is why I interpret the issue to affect both recording and playback qualities.
The issue appears to be identical to the one discussed in this Apple Support Forum thread. The thread offers possible explanations but no definitive solution or suggested course of action.
I have a Late-2013 MacBook Pro Retina. I don't have this problem when using the AirPods with an iPhone 6s. I have tried resetting the Mac Bluetooth interface, tried resetting the AirPods, and so forth.
AirPod model: A1523. Firmware: 3.5.1. Hardware version: 1.0.0
FYI: Using the macOS native application Audio MIDI Setup, I attempted to observe what's happening when AirPod recording is activated. Output quality drops from the standard 2 ch 24-bit Integer 44.1 kHz → 1 ch 16-bit Integer 8.0 kHz.
1It has happened that the Mac has been permanently stuck in low quality until system reboot, and even whenever the AirPods are reconnected afterwards. I had to try AirPod unpair/re-pair, and even AirPod charging case reset to fix the latter situation.