Horn based loudspeakers why the controversy?

 Everybody has horror stories about hearing horn's. I remember the first time I went to addition a pair of model nineteens. The owner had them hooked up to a solid-state Mac and proceeded to turn them up so they were playing at about 120 DB steady. He looked at me with a big smile  and said see how clear they are? He didn't even have them set up properly, had  them facing one another across the room. I couldn't get out of there fast enough. Thankfully down the line I had some reasonable experiences  and grew to appreciate horns greatly. 

 Regarding Altec A7's I had a pair for a while and after quite a few mods they can sound quite good.  

 You cannot get the same dynamic range with inefficient speakers. You can apply as much power as you want but you will not get as great a range between the quiet and the loud as you will with a more efficient speaker. 
That is why typically efficient speakers will sound more realistic at lower volumes.

Kosst  it's all a matter of mathematics. Thanks it in these terms. You have a speaker that is 100 db efficient.  The source music goes from 10 DB to 30DB.  You multiply the two numbers together to get your final levels.  You are going from 1000 to 3000. Now take the efficiency of the speaker and substitute in a figure of 80db efficiency.  The source music still goes from 10 to 30. Do your multiplication and you get 80 to 240.  In the second scenario spread is much smaller than the first scenario.  That represents the dynamic range.Obviously this is a huge oversimplification  as the decible scale is logarithmic, but I think it serves to illustrate what I'm talking about. Increasing the power of the amplifier which can bring you to the same peak  levels will not give you nearly the same range. People continue to confuse dynamic range with ability to play loud and they are two different things. 
 So if you call continuing to try to correct misinformation not taking no for an answer, I am guilty as charged. 
Kosst  about 5 to 10 years ago I used to think just like you. I thought all vintage stuff must have been massively superseded by today's offerings.  I believed the magazines with all their reviews and advertising drivel.   Then I met a few friends who were older than me and had been into Audio since they were in their teens. They'd collectively pretty much owned everything at some point or another,  The one guy had made a lot of money flipping gear just prior to the Internet and in the beginning years of the Internet.   At one of their houses I heard Vitavox horns with SET amplification.  That's basically gear who's technology predates  the stereo era.  Granted it was set up with a top-of-the-line clear Audio table and Goldfinger cartridge.  Upon hearing that I realized that the best today's mega dollar offerings can hope for is to approach equalling it. In fact all of today's mega dollar offerings I've ever heard did not even come close, but I'm giving it the benefit of the doubt because I haven't heard all of it.  
The other funny thing is that with all of their collective experience, none of these gentleman ever, ever, ever participate in forums anymore.   In fact the one gentleman was a leading expert in the electronics and telecommunications fields for 30 years.   He holds numerous patents in his name. He has scratch built his whole system and it too is better than any modern commercial offerings I've ever heard. When I asked why, they explained that because when they try to correct the miss information they basically get shouted down and treated like idiots. I totally see what they mean. 

 Yes many of the horns are not damped well enough including a lot of the vintage stuff. The pair of vitavox that I keep going on about were mounted in a wooden box with Sand poured around them. He said that made a big difference and took away some of the edge. I noticed  that as well with the pair of the voice of the theatres that I had. I poured lead shot over top of the horns and damped the bottom with a sticky butimen pad. Big difference!  Another point to consider is that with a pair of Vitavox or klipschhorns they need to be pushed right back in the corner of the room. So they actually end up being less obtrusive then your run-of-the-mill Monkey coffin that needs to be pulled out 5 feet from each wall. 

 Just regarding the OP's a post I think Horns are really polarizing because they are like a microscope on the entire chain that lies before them. So if there's anything bad in the chain it really really highlights it. But if everything is good and the horns are good it's really good. 

 Also just regarding atmospheres comments about SET amps and distortion. It's true that they have higher distortion when they are run at anywhere near the rated power but they also have vanishing low distortion if they are run at about 10% of full power. So when you hear them coupled with  horns usually you're not hearing the amps distort.   Solid-state is the opposite at about 10% of its full power it will have quite a bit higher distortion  then the SET amp at 10%. And many people have bass their opinion on horns from the 70s and 80s with crappy higher powered solid-state amps. I don't know why anybody would use that combo but unfortunately lots of people did.

Boy unsound really  doesn't have a clue, does he? 

Oddiofyl  I believe that is when Altec  was no longer Altec