Right, as critical as it is to seamlessly line up a 511/811 throat to the driver for max [smooth] HF extension, just think about a bunch of round/square/whatever throats dumping into a collector [low pass filter] that in turn adapts to the driver!
Once I learned from experience just how critical it is, I had a much greater appreciation that these huge horns/drivers could top 12 kHz at high SPL at a time when 8-9 kHz was the max available signal.
Wish I still had the pics of the super rare Jensen [32] cell/500 Hz horn; talk about attention to detail! Must have been made by pocket watch and/or 'sailing ship in bottle' craftsmen.
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One thing I've noticed is that all these [installed] wood horns have super tweeters [not to mention they are typically offered by said wood horn manufacturers as a set], so assume the throats, etc., quality are more typical of large PA horns [~ 8 kHz upper limit].
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