Was the Snell Secret a Wide Baffle?

Yes!  Consider the Harbeth 40.2, Spendor Classic 100, Graham 5/8.

If you're interested in speaker design, Graham are now coming out with a new version of the 5/5 which is quite funky.

https://www.stereophile.com/content/graham-audio-launches-ls-55-montreal

Here’s a quote from Peter Comeau, the guy who designed the recent Lintons.

"Th[e] larger ported box, with its subsequent increased baffle size, helps solve a major problem in modern speakers, namely, the baffle step.

I grew up with large speakers with wide baffles, but, as speakers reduced in size over the years I noticed that something was missing from the sound and, when I stuck my head firmly into speaker design, I began to understand the acoustic problems caused by the baffle step.

Put simply, as the baffle size decreases, the point at which the acoustic radiation changes from hemispherical to spherical goes up in frequency. It also becomes sharper and narrower in bandwidth as the sides of the cabinet, and the walls and floor of the room, are further removed from the equation. So, this 6dB step in the power response becomes acoustically more obvious.

I believe that a thin speaker always sounds thinner throughout the midrange when directly compared to a speaker with more generous baffle width. Of course, as designers of modern, slim speakers, we compromise by adjusting for the baffle step in the crossover, but in doing so, we also compromise sensitivity. What starts out as a 90dB at 1W drive-unit often ends up as an 85dB system once we have adjusted for the power loss due to the baffle step."

Let's not forget the Sonus Faber Stradivari and Cremona Elipsa.

@prof 

Both those speaker lines seem to produce a richer/fuller-than-usual sonic presentation, where instruments have more size and sense of body.

You put into better words exactly the impression that I was trying to name when I was listening to the Classic 100's.  For my own personal shorthand I came up with "music launch", in that somehow just more of the music seemed to be arriving at the listener. But I prefer your formulation.