I have the same model iMac as you. I use Facebook Live to do live classes for members of an organization that I’m the director of. The quality of the recording for speech is actually pretty good and I’ve given up using a lavaliere microphone. I have learned that the location made a big difference and I had to use some material to soften and deaden the room I teach from. Also, the quality can vary because of the bandwidth needed for the upload via the internet. We discovered that with many people working from home that at times the video and audio quality would suffer and through trial and error found times that minimized the impact of the limited bandwidth.
Facebook also has a setting to upload and display a higher quality video/audio recording. You need to adjust that in your Facebook account settings. When you upload in what Facebook calls HD, the initial video/audio is lower quality, but after several hours the HD version is displayed on Facebook. If you’re deleting the recording and only doing it live, you my not get benefit of the HD quality.
I find that I must constantly download the latest version of Chrome, to insure compatibility with Facebook and maintain the best quality. Lastly, I don’t think Facebook ever intended the Live feature to be near studio quality audio. Think of it more like FaceTime with the occasional lag and hiccup. If you must record and show the live version, I’d consider another platform, perhaps YouTube, which allows for much higher quality, but it comes with a subscription model pricing. If you can just use a recording, you can record to QuickTime and convert it for YouTube and share the link to Facebook.
