I'm the bloke recommending such an idea. . . .
For many years I've been a Lowther addict. The realism of full range units with a back horn is rather good.
And for some time I developed speakers especially designed to make signals from electronic organs sound like the real pipes they were intended to reproduce and sound real.
For instance:
explores a full gamut of electronically and electroacoustically generated sound.
In the course of analysing how to reproduce sounds as real I came to the conclusion that crossovers between 500hz and 2khz split the tonality of what we hear, splitting the fundamental frequency from its aliquots, partials, harmonics. So none of the speakers on that instrument use crossovers.
This is something, on another subject, that I particularly pay attention to in tuning pianos
http://hammerwood.mistral.co.uk/tuning-seminar.pdf
When we speak or sing, we don't produce a fundamental from a big mouth and all the upper frequencies from another.
And then there's the matter of acceleration of the cone. This came home to me when assisting on a band production and the producers insisted on using standard two way studio monitors. On guttural consonants such as "k" there was a thump and a click to the sound as the two units really didn't work together.
In PA speakers this has a terrible effect. We like hearing detail in the midrange and so, with systems with confused mid, split between two units, the volume tends to be put up, so as to produce treble to tinnitus inducing levels.
Full range units, unless having very high magnetic fields, go really high evenly into the 8k-20k range. And unless horn loaded, they cannot produce bass without a lot of cone movement which then produces doppler distortion of higher frequencies.
So where we have a low efficiency 2 or 3 way speaker with two 8 inch holes, such as the Ditton 15 (and there is another Ditton similarly, I don't remember the designation, might be a 200 or something like that) or a Wharfedale Laser 120 (not tried but the B&W DM220 looks a candidate too) then one can remove the 8 inch midrange (built as a woofer rather than a midrange anyway) or Acoustic Bass Radiator inserted merely to enhance cabinet volume, and run a full range unit in its place as full range, leaving the low efficiency old woofer and tweeter to extend and smooth the extremities of the system where the full range is tailing off.
One's looking for original cabinets of around 85 to 88dB effciency and full range units from around 90 to 95 dB efficiency and the result is magic.
I sell units on ebay based on vintage JMC Audio cone design from Taiwan and I enhance these with a Lowther dimension whizzer cone extension to give the Lowther sort of emphasis. But any full range units with a whizzer will do. I like Audio Nirvana, and especially the Chinese 97dB Lowther Challenge units on ebay from Hong Kong from seller Anitaydavid, although these are a bit strong in such an application.
The result is excellent. When I did a pair of the larger Celestion speakers for an organ friend listening I almost wondered why I bothered with Lowther and horns. But the back horn gives more "air" to the sound.
Certainly as civilised size speakers, the result is great. Sons have purloined two pairs for university and I purloined one pair back for lecturing last year
where I needed top rate sound reproduction and where ordinary standard speakers just would not do.
If one has a two or three way speaker with a 6 inch hole the Fostex FE series 6 inch units are excellent. In the 8 inch size the Fostex units aren't as successful to my ears, treble tailing off and too directional.
By adopting this sort of solution you're upgrading £100 speakers to the sound of £1000 - £10,000 units.
No doubt the proud owners of expensive brand conventional speakers won't like such news, but the results obtainable are remarkable.
Best wishes
David P
