Related -- how waterproof are 406x? I've never gotten mine wet -- though have run them in the rain. I assume given their application they're at least resistant to sweat-level moisture, but have never really done much research to find out...
Very. I've no concerns about rain damaging them. DPA's recommended cleaning procedure is to immerse and swizzle them around in distilled water. Of more concern is any residual contamination left behind from evaporation- salt, oils, mineral deposits. Only real concern for me in rain are direct-droplet-impact "bomb noises", waterlogged windscreens can sound muffled, and possibly a temporarily muted mic if a giant tropical droplet were to score a rare direct hit that happened to fill the grid housing.
Amusing anecdote-
I used to be far more concerned about moisture protection with them because I'd had standard externally polarized condenser mic which were either moisture-sensitive or became outright damaged. The wide 3' to 6' spacing I use precludes the use of a single mic umbrella, so at one point I experimented with sealing them in condoms - placed either under or over the windscreens or without windscreens - to accommodate the often unpredictable FL weather turns at the Suwanee Music Park, where a tropical deluge can seemingly come out of nowhere. I made these sound tests on a weather-threatened day set up in the amphitheater, and had left on a run back to camp, returning through heavy rain to find that prior to the deluge the single adamantly non-taper-friendly act of the fest had refused to take the stage until all mic-stands had been lowered. Fellow tapers and sound guy lowered the stands of all tapers not present, and in doing, also lowered the hinged telescopic antennas with the 4061 at the ends in condoms so that the extended arms hung down parallel to the stand, preventing damage to them, instead of leaving them extended out to either side with the stand lowered to just over chair-back level. I didn't foresee this possibility, and as a result, copious rain water ran directly down the telescopic arms and into the gaff-tape-sealed condoms, filling them like tiny water balloons with the mics swimming around inside. After that set I removed the condoms, spun the stand around a few times to sling water out of the mics and recorded the following sets, figuring at least the center mics would at least remain functional, protected under an umbrella.
Back at taper-camp later that night we all had a cringe and a laugh as I packed the mics in desiccant to ready them for the following day. I then pulled up the recording and listened over headphones.
Sounds of PA announcement of artist's stipulation.. sounds of taper section discussion.. sounds of other rigs being lowered.. sounds of mine being lowered (stereo image collapse and expected handling noise).. sound of the band taking the stage and beginning to play.. sounds of the storm moving in.. band continues to play.. heavy storm sounds.. band continues to play.. set ends. Unbelievably, other than the obvious imaging and height issues from the mics being lowered, there was no impact on the sound from total and complete immersion of the mics in water. Not while they were being slowly inundated, not while completely submerged, and not afterwards for the following sets. We were all dumbfounded, no one could hear a difference!
Granted, these mics are tiny. Small enough that they are in that water-tension realm where the housings may not have become saturated even though completely submerged. Water-bug flotation and all that being what it is. Still, it was an impressive accidental demonstration. After that I never bothered to try and rain protect them, and only once have I had a direct droplet impact which did fill the housing and mute the mic until it was "spun out", upon which the mic worked fine again. I was sure to do a distilled water swizzle on it when I got home to make certain there was no evaporation residuals. That was like 6 or 7 years ago and those mics are still going strong in my outdoor rig.
If anything, the B3 may be somewhat even more rain resistant.. at least without any grid mounted on it. That's because it has a stainless steel diaphragm flush with the front face of the capsule and without a grid there is no place for water to get mechanically trapped at all.
To my way of thinking, the salty, greasy sweat that these tiny lav-omnis are designed to handle poses more of a long-term concern, and I suspect full submersion to a significant depth would damage either of these mics, as they must have a tiny atmospheric pressure equalization hole somewhere (maybe cable entry?), but I've no worries with rain.