I’m a big believer in physics and can’t see (or hear) how the X3s go very deep, but I failed to mention that I have a VMPS Larger sub driven by Crown K2, so deep bass is not an issue. Will try and have listen in Fla.
In my room, I estimate the -6dB point of my X3s is around 35Hz. That’s with about 3’ between the speakers rears and the wall. The X3 specs are misleading because the woofers are quoted as 4.5” units, but that’s their actual cone diameter. Most manufacturer’s claimed woofer sizes are the diameter of the entire driver to include the surround and frame. So the “4.5 inch” Børresen units would actually be considered 5.5 or 6” woofers by typical convention. For example, the “7 inch” Seas woofers in my Tyler standmounts have only a 1” larger diameter than the Borresen units. One also has to consider that a woofer can create deep, powerful bass with either surface area or cone excursion. The Børresens have a good amount of linear excursion for their size. I would say they produce at least as much bass output as a typical medium floorstander fitted with either a single 10” woofer or two 6.5” woofers. The bass extension is plenty low for most music.
Regarding your somewhat vintage 801s, they perform really well on paper, arguably better than the newest 800 series. They were certainly more linear (though linearity isn’t everything), and it seems many prefer the older 800s to the newest line. IME, it’s not uncommon for a good 25-year-old design to compete well against newer models, adjusting for inflation (and then some). I haven’t heard your speakers so cannot say whether speakers like the X3s would be a worthy upgrade if an upgrade at all. I have auditioned a couple of the D4 800 series B&Ws, compared to those, I think the X3s give them a run for the money. I think B&W’s current diamond tweeter produces a hair more extension on top, but the Børresen tweeter is completely non-fatiguing and equally “fast.” I find the midrange sounds pretty similar between the two brands. Both manage nice bass definition as well. The D4 series might be the preferable choice if wall proximity is a concern.
But truthfully, if you were to go out and audition half a dozen options between $10 and $15K/pair, and conclude you should just keep what you have, that wouldn’t surprise me at all.
