Thank you Jim for adding some sanity to this discussion. The Quad 63
series is indeed a phased array intended to mimic a point source at an
assumed distance. At least that's how Peter Walker described it to me
back in 1979.

If you want more bass output, buy a 989 or 9805 instead of this silly
stacked arrangement of 63s. It keeps the point source mimicry with
greater SPL and lower frequency output. That was the point in making
them, after all.

As an aside, the following paragraph is perhaps the silliest things
ever written about Quads:

"Put a single ESL63 or derivative -- minimum case, yeah? one speaker
only, okay? -- in the middle of an empty room. Play music. Stand in
front of the speaker. Hear the point source. Walk around the music.
Hear the point source on the other side of the speaker. So what do
you
have? One speaker, two point sources."

Apparently Andre never learned the definition of a point in middle
school.

Of course even that would be a pointless discussion...

Remember Zappa's Law: There are two constants in the universe:
hydrogen and stupidity.