We are veering off-topic.
I stick to my suggestion: if Tiny Giant is to play LOUD with reasonable total-rig size, use a large (8"-12") light-cone speaker in some form of baffle/box. In today's speaker market, suitable speakers are almost all "guitar speakers" (a few PA speakers work, at higher price and less flavor).
> Perhaps you meant this as more of a semantic argument
Well, I mean that driverless cabinet efficiency is dead zero.
> for example, a horn loaded cabinet increases coupling efficiency?
OK, granted, quite true.
How many horn-loaded GUITAR amps are there?
"Coupling efficiency" is the crux. There are no good speakers. The compromise chosen for home hi-fi, TVs, car-audio speakers is smooth modest output with cheap chips to brute-force bad coupling.
Horns have their own problems. They must be big. They beam. They will not cover a large frequency range with high efficiency and useful beamwidth, so must be 2-way or 3-way, which is not a Good Thing even when necessary. Splitting the band seems to be more obvious on a single widerange instrument than on a complex full-band signal. Most practical horns have further problems.
Horns are efficient and also LARGE for their bass limit. Does it make sense to use your 20W Tiny Giant amp with a 15% efficient 150 pound 3-foot horn? No more than it would to carry a 0.1% efficient shoebox speaker and a 3,000W amp. If anybody still needs 3 acoustic watts, 1.2%+300W to 5%+75W rigs work well.
The direct radiator has a goal efficiency which it will cover over a certain bandwidth, and a fairly constant sensitivity for a few octaves more. The cabinet affects only the lowest octave of that range.
> standard guitar cabs have intense beaming and terrible off-axis
So do non-electric instruments. Trumpet is wickedly beamy. Violin/viola (or acoustic guitar!) pattern is like a mutant sunflower. Woodwinds radiate dipole different every note. Piano is wack. Nobody has a problem with that. (Except the sax-players.)
OTOH, a mis-spent youth did too much work with pure synths and hi-fi speakers. Little of it worked as "music"; it was a job. By choice, I would rather be in a dive with a Twin.
> That could be improved easily and with no drawbacks.
In music, "flawless" is boring. Writers write about "improved" and some products are available: BOSE's 'stick' stage-speakers are technically fascinating, but have not caught-on. Nobody redesigns guitars or pianos for "constant directivity". (Price and traditions are objects, but even so....)
