RE my previous post, yes, my sources have all indicated that the "QUAD" loudspeaker I mentioned does appear to be extinct; a carcass or two might be found in an English attic.
I found a review of this "Corner Ribbon Loudspeaker" in "Wireless World", December 1950 issue, page 29. From the article I have concluded that all of these (I believe) magnificent loudspeakers have been 'incinerated' by the advent of more powerful, double digit Watt amplifiers.
Short of a human sacrifice, I do not believe I will get my wish for a pair, much less one, of these beauties. Amazingly priced at £83, including installation! Of course 1950 £83 translates, based on the 1950 £ to $ conversion rate and the inflation factor, to only a mere $1,100. Nothing of this caliber could be produced today for anything close to 10X this price, considering stunning finish (even the hidden sides) and complex interior bass acoustic filter structure.
Thanks for everyone's advice on my X-12 question; I appreciate the replies. Will try the absorption pad . . . a cheap option.