I'll make it short and sweet. I had these items for quite a few years.
I have BGVP dm7, dmg, Andromeda, Campfire and quite few other great ones.
I'll always known that these XBA are sensitive to impedance. That's said, I was looking for a high impedance adapter for another application and found an 80 ohm one at Amazon.
They didn't work for my other project, but since I had them laying around, I decided to see what would happen if I paired the adapter with the XBA 40...
Wow!
What a difference.
It totally change the signature. The sound became fuller, separation improved, mid came forward, etc... Different and much improved all around.
If you still have one of these laying around look for impedance adapters at Amazon or any electronic store (they are cheap, less than 10 bucks)
You'll be happy you did.

I've always been happy satisfied with the sound I get from my BGVP DMG, but I just made a discovery that makes them great. Looking at other BGVP iems ( just bought the DM7) on Aliexpress i came across an offer for a modified filter that claimed to tame the bass in the gold filter. I bought it and out does what it claims, great actually, it made the iem a lot more enjoyable. I used like that on and off for a while (I like to switch iems) but then I had an extra balanced cable laying around so decided to tried on to heat how they would sound, plugged them in you my DAC... and Oh My God! I could not believe the sound that came out the DMGs. Not kidding... Better than my other iems that go up to $600. Much Better than the DM7. (I still use the DM7 while commuting because of a better seal on the train) The modification consist of a tiny hole that tames the bass and opens the stage, but when you combine it with a balanced DAC... You'll be in for a big surprise. I guarantee it will keep you from spending lots of money for a while. Try it... You'll like what you hear.