I have to be honest Dave, I have not had the same exsperiance.
I was a modulus endorser years ago and several Basses with Bart’s. The passive VJs for instance sounded good but very low output.
I an personally attest to that because I had 3 of them.
We also played around with some active passive switching (not standard) on a Q5 with dual coil soapbars and that was on the mellow side as well.
Its around that time that led me to Nordstrand which have more output in general than Bart’s (based on my own experience) and Nordstrands not done in series will still not have enough output for what I’m looking for.
Granted I have tried everything of course...Lol BUT I have only found 2 passive pickups that have the same output as Big Singles wired in series and still using a Pre.
-Dimarzio (Model P and J are just shy of it and perfectly acceptable, but it’s only for 4 strings)
-Lull T Bird humbuckers (same ballpark, but they are big humbuckers)
I’m measuring the gain reduction on my compressor, I can see what coming in, between that and a DB meter.
Cheers