Hi, Chris
Thanks for the advice. I thought about feedback. Before I started switching domes and my user experience profile in the fitting software, I watched the ReSound video offered through Audiology Online on the theory and practice of using their DFS Ultra II feedback profiler. The video was a bit unhelpful in not really mentioning much about what circumstances merited running the feedback profiler again, seemed mainly to be called for in the advice given if the user was having a problem with feedback, if I remember correctly.
Since the feedback analysis was run for me while wearing open, vented domes and all the domes I’m trying beyond that are more closed, I shouldn’t have any increased problems with feedback going to a more closed dome - and that’s been my experience on trying each of the different ones that I mention for several days each.
I also did worry about changes in gain with changes in closeness of dome fitting as I mention in a post above in replying to MDB but in rerunning the ReSound Smart Fit 1.3 software and switching the hardware configuration between open domes and the closed power domes, the software did not refit me to any gain changes whereas if I changed my user experience profile, the software decidedly changes the amount of gain applied at various frequencies.
Below is a screen capture of my right ear fit showing the amount of gain applied with 50, 65, and 80 dB SPL of input (higher and higher series of red squares) for the OUTDOOR program, the one where gain applied most closely matches the fit prescribed for me by ReSound’s Audiogram+ fitting algorithm based on NAL-NL2. The darker gray inverse peak is the feedback danger region for me. The lighter gray region is the “Outside of Safe Fit” region and the red/pink region is “Outside of Instrument Capability” region" - so the diagram goes along with my experience - I have to try very hard to get any sort of feedback out of my instruments - I managed to get some the other day in switching back to the looser fitting smaller ReSound Power Domes, wearing closed over-the-ear headphones, and rubbing one headphone cup against my shoulder - perhaps the closed headphone efficiently traps sound exiting my ear in the vicinity of the HA mics and increases the chances for feedback?
So as mentioned in a post above, I’ve decided to go with the ReSound Small Power Domes. They are almost an occlusive fit but very comfortable. Speech clarity is pretty good. They are easy to insert and remove. After a lot of experience with these, I’ll worry about whether it’s worth the hassle and expense of a custom-fitted mold and maybe a decrease in hearing ability with (hopefully) further ageing will drive me in that direction anyway. The 2006 Widex paper analyzing an open fit vs. a closed fit purports to show from word recognition tests performed on a number of users that word recognition is just as good on a very slightly open fit as compared to a closed fit, declining by 25% to 33% with more and more open fits. So hopefully I’m still right in that sweet spot that seems to be offered by a little bit of openness. See figure from that technical article copied into my post in the “Article on Open Fit vs. Closed Fit” thread started by MDB back in 2017.