Thank you for the all the information you provided about your Bluetooth speakers and all the steps you have taken. You have gone through some very good troubleshooting steps. I found an article with a few more steps you can try to assist with Bluetooth issues. You can skip any steps you have taken already. One step that stood out in the article is resetting the PRAM and VRAM:
9. Restart your computer
Sometimes a simple restart of your Mac is all it takes to get things running smoothly again. You may also want to try resetting your computer's PRAM and NVRAM.
You can find the full article here:
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I tried the "Reset NVRAM" trick and it worked perfectly
Having trouble with BT speaker / headset sound quality ? Give it a try !!!
--> Power on, and immediately -before the gray screen- press and hold "Command + Option + P + R" until the system reboots again.
So many thanks Sheila, I was getting crazy about that.
You made my day, my week, my month, and maybe my quarter