Well, it all has to do with system building. When you start out with a 2A3 SET amp, with its meagre output of 3 watts/channel, conventional speakers of average sensitivity do not apply. Of course, the combination will play music, as many people who use the amp with bookshelf speakers will attest, but the limitations are many. To realize the full capability of the 2A3 amp, you need speakers of sensitivity 95dB or higher.
That's horn territory! Mainstream audio speaker drivers, even so-called high end ones, come with sensitivities of about 86dB. Way short of what is needed. So, we have to go to professional audio speaker drivers for our horns.
Here, the technology changes somewhat. Bass drivers have to be large, to give high sensitivity. Cones have to be light, with inherent self damping, with paper the material of choice. Bass extension and sensitivity are opposing properties - so larger drivers just give higher sensitivity. Midrange drivers are a class apart - compression drivers that work only with a horn upfront.
Horn speakers have been around since the beginnings of audio. Lots of research has been done on them. The difference now is that computer simulation programs are available to help design them, and to scale them for domestic use.
Edit:
The above was a preamble to help explain the differences between conventional and horn speakers.
- Why go for horns? When system requirements need them - using low powered amps.
- Why use low powered amps? For clarity, and purity of tone. These amps use single output devices. Check out the popularity also of Nelson Pass's amps. High powered amps use multiple output devices, creating parallel amplification paths, recombined to a whole. Timing and phase errors creep in, creating fussy sound.
- Why is high sensitivity important? To reproduce the full dynamics of music, micro and macro-dynamics, at lower distortion that other loudspeaker systems.
- Why large horn systems? To give the sense of scale recorded in large music ensembles. To create the midbass richness inherent in music.
Viren