Nice points Jim, good discussion here. I was fitted with open domes, but in asking, Collin (HIS at Costco) gave me extras of open, tulip, and closed/bass/power domes to try. I asked if changing domes required refitting the HAs, and he stated usually that made no difference. He did warn me to make sure I got them attached well so they did not come off in my canal!
At first I liked the closed ones better for better music especially bass. He even gave me one larger size of closed domes to try. Yes they make music better streaming the HAs, but I miss sounds when listening to my stereo or TV speakers. I’ve been back to open domes for a few weeks now. I’m still trying to find a solution of better music when out walking, over ear headphones gave feedback, none of my earbuds work with the aids.
Now I need to try the closed domes again to see if I get the “processor noise” with them.