This was a one-off crossover fix that we did because my first set of 801 series two speakers did not sound as good as they should of. My EE analyzed the crossover and located the crossover layout issue. The largest inductor in the bass section was located in line with the largest inductor in the midrange section.
This was causing nearly 100 percent cross coupling at 200 Hz. The mid driver was seeing the bass signal, the woofer was seeing the midrange signal. This screwed the frequency response and raised distortion in both.
B&W knew they had a problem but never found the issue. They tried to fix it by supplying a bass equalizer active box (shades of Bose). After our fix, the bass boost box was redundant. We told B&W about it as we were a dealer then. They fixed the issue in their next generation series 3 version. Our thanks, we were dropped as a dealer.
Again, the fix is available as a free .pdf file from us. Just email us for it.
Frank
Frank