I have had a BF-2 since highschool, it's a green bottom taiwan version and is still ACA. I did tweak with the trim pots when I was a kid, but pretty sure I got it back to "normal" or pretty close. I used it for guitar back then.
While the BF2 works fine for bass, the low end does get a little muddy, not a total drop out, but the BF-2b bass flanger does let the fundamental come through a bit more solidly. I currently use it set for a fast vibrato like effect for "spiders" in a system of a down tribute, and it sounds exactly like the album. I use a CE-2b chorus as well, which gets turned on more than the flanger, which is just for one song. If I needed a more traditional jet sounding flange for something else, and spiders was in the set, I would just use my bf-2 for the other setting. They are similar, same controls and everything, but I believe the difference is the BF2-b applies the effect only to the upper register, not sure where the cutoff freq is, but probably around 100hz or so. In fact the warble effect was a little stronger on the bf2 because it flanges the whole range. Still I found the bf-2b to be the better choice.
While the BF2 works fine for bass, the low end does get a little muddy, not a total drop out, but the BF-2b bass flanger does let the fundamental come through a bit more solidly. I currently use it set for a fast vibrato like effect for "spiders" in a system of a down tribute, and it sounds exactly like the album. I use a CE-2b chorus as well, which gets turned on more than the flanger, which is just for one song. If I needed a more traditional jet sounding flange for something else, and spiders was in the set, I would just use my bf-2 for the other setting. They are similar, same controls and everything, but I believe the difference is the BF2-b applies the effect only to the upper register, not sure where the cutoff freq is, but probably around 100hz or so. In fact the warble effect was a little stronger on the bf2 because it flanges the whole range. Still I found the bf-2b to be the better choice.