Look how large a K Horn midrange horn has to be just to get down to 500 Hz were it crosses to a 15 inch woofer. This is one area were that ESLs have a major advantage over both horns and dynamic speakers. You can easily design a speaker that is One Way all the way down to 100 Hz as long as you can live with the size.@mijostyn The Classic Audio Loudspeakers model T-1 employs a machined horn that is crossed over at 250Hz. This is an easy speaker to google images. The trick to getting horns to go this low (500Hz is easy) is to use a modern surround like Kapton for the compression driver. This was solves one of the more serious issues facing old school drivers- breakups resulting from inability to deal with excursion could make older drivers somewhat painful and screechy. OTOH, crossing over a 15" woofer at only 500Hz is pretty easy- most of them can go considerably higher than that without breakups.
Admittedly the T-1 is a speaker that has been too large for my listening rooms but CAL also makes a version of the same idea that is taller rather than wider (the T-3) and that does fit. One advantage horns can have is that they can be a bit easier to place. My speakers are only 3" from the wall behind them yet they play soundstage width and depth with ease.
IMO/IME a lot of people that are down on horns really haven't been paying attention to how far horns have progressed since computer power has become so ubiquitous. Duke's loudspeakers (Audiokinesis) are also a good example of that and Duke is also a master at crossover designs that really blend seamlessly. Understanding how the horn is to be used (a PA horn is often not ideal in the home for example) can eliminate entirely that 'horn sound' to which so many audiophiles object.