I'm very pleased to hear there's an explanation Mark

I've been working with sub augmentation for several years, regardless of the bass ability of the main pair. I totally agree with you that reproducing the lowest frequencies does something for the complete spectrum in terms of soundstage, presence, clarity, dynamics - well, just three steps further towards reality as opposed to reproduction and I wouldn't be without a sub now (never had two).

Just realised that BK are in my home town