Unfortunately, I haven't had a chance to hear the famous Tannoy horns. I'd love to compare them with the Hawthorne Audio drivers custom built by Eminence for open baffle use.
Here's a like to Hawthorne Audio.http://hawthorneaudio.com/
If memory serves, the Tannoy's are a bit more efficient than the Hawthorne's. Because the Tannoy's are made for a rear loaded horn and the Hawthorne's are made for open baffle, the two drivers are not interchangeable, so you wouldn't want to build a Tannoy horn for a Hawthorne driver. (wasn't there some Tannoy bass reflex speakers also?)
So far, I can't find anything to complain about with the Hawthorne Audio Silver Iris speakers. They do need some bass augmentation when used on a reasonable sized baffle, but even if you buy the matching bass driver, it's still cheaper than Tannoys, and the open baffle type enclosure is far easier and cheaper than a Tannoy horn enclosure.
Also, the horn high frequency drivers on these sound very detailed and no noticable horn "nasties", at least as far up as I can hear (admittedly not all that high anymore). The highs sound much nicer than the highs in a pair of Klipsch Heresy-1's I recently sold which had EV T-35 horns.
Crossover is at 3.5 kHz and is well made.
Mids sound very natural.
Dave