@cd318 --
I rather suspected that my front ported Tannoy Berkeley’s didn’t go down that far despite their 15 inch drivers.
According to one site their frequency response is 35Hz - 20kHz. I strongly suspect that it barely scrapes 35Hz let alone being flat.
Come to think of it, wouldn’t FR stats be far more meaningful if they showed only the flat range, as opposed to -2db down or even worse?
Extension downwards is about the relation of bass driver size to enclosure volume (or horn path length in a bass horn) - unless we’re talking EQ’d sealed designs - and those Tannoy’s, from the looks of ’em, would seem to accommodate the response you point to - certainly in-room.
More important than extension per se is how they come about the bass that is, and I would expect it to be very satisfying here. Big paper coned woofers of at least 15" has a tuneful way with the lower frequencies that smaller units in multiples can’t replicate, and with the proper driver type (for this particular context at 15") they’re very good into the central midrange as well (though 900-1kHz is about as far as they get, I’d say), as you’ve no doubt come to experience with your Tannoy’s. Though, this would seem to go contrary to audiophile "wisdom" with the mention of beaming, cone break-ups, etc. My counter reply: try it out with actual listening, and if it isn’t one’s cup of tea - fair enough.
Regarding FR stats: Insofar the specs are trustworthy to begin with I suppose an -xdB number is meaningful in the sense of indicating the useful frequency extension, which goes beyond flat response and not least with the interaction of the listening room. I don’t really care about the bass stats of main speakers; listening will do the talking here, and in any case I’d by inclined to high-pass them in the bass, actively, for subs augmentation. Extension stats (or rather: tune/lower knee) for subs is another matter though, as this is specifically dealt with and important in the DIY designs I’m interesting in and use.
