Said about horns...

"...But when you get a horn system set up right, the sound quality is amazing. The most obvious advantage is in the dynamic range and transient response of the horns. For me, the emotional impact of recorded music is in the dynamics. Most speakers just do not produce realistic dynamic constrasts. Horns do, and they do so with ease. They also excel in low distortion. The sound seems unusually clean even at high levels..."
"One of the major challenges in setting up a horn system is finding an amplifier which will work with the horns. High power solid state amplifiers sound best when mated to inefficient speakers. With horn speakers they tend to sound really awful. The efficiency of horns is so high that your average big hog solid state amp never really gets turned on. Likewise, big tube amps using banks of 6550s just don't sound that clean when operated in the milliwatt power range. Horns work best with low power tube amps."
Greg Boynton, "What about horns", Sound Practices Vol.1, #1

"At equal acoustic outputs, as compared to conventional dynamic or electrostatic loudspeakers, horns offer a dramatic increase in dynamic capability, image size, and presence. Harmonic distortion drops to a quarter of the value found in audiophile direct radiator systems. In contrast, most direct radiators severely compress dynamic contrasts and reduce image size to the proportions of a symphony on a table-top. These are bothsevere distortions for which there are no measurements. More importantly, these are distortions which reduce the fun and excitement of music.
When reproduced music lacks weight and body, when sudden transients fail to startle, and the lead singer is only two feet tall, what's left? Detail? Transparency? Tonal balance?
People often say that most horns "sound like horns" and are therefore "disqualified from audiophile consideration". To me, a 90% reduction in image size is a gross distortion, but owners of minimonitors talk endlessly about imaging and transient response. But without weight and body, the transients fail to startle and lose most of their emotional power.
A system capable of reproducing an enormous soundstage, that showcases dynamic contrasts, and presents music with realistic presence, weight and body will never fail to excite and arouse. These are the traits that the triode/horn systems use to communicate. These are the traits that stimulate our body and unconscious mind..."

Herbert E. Reichert, "The Science of Beauty: Audio Culture in the Nineties", Positive Feedback (The Journal of the Oregon Triode Society) Vol.5, #1

"...If you have only heard nasty horns, you might find it hard to believe that a good horn system can be the best speaker PERIOD."
Herbert E. Reichert, "Casual Reactions", Sound Practices, Vol.1, #4

"...If you don't think a speaker can have explosive dynamics, wall-to-wall imaging, a seamless midrange that just won't quit, incredibly low distortion, a sweet, airy top end, and do all this without a hint of strain, you just haven't driven a good horn system lately!"
Jeff Markwart and John Tucker, "Altec Voice of the Theater speakers for Hi-Fi", Sound Practices Vol.1, #4

"...Once horn speakers get in your blood nothing else will do. They put you IN the music in a way other types of speakers rarely do."
Paul Eizik, letter to "Readers' Forum", Sound Practices Vol.2, #1

"...Horns have a very forward presentation. Back in the Seventies, "too forward" was a common criticism of speakers. What people were looking for was that backward sound, I guess.
The illusion horns provide is a "they are here" sound rather than the old "you are there" illusion. That is, the sound is so dynamic and alive that it sounds like the music is going on IN YOUR ROOM."

Joe Roberts, "Reconsider Baby - The Promise of Horns in the Contemporary Situation", Sound Practices Vol.2, #3

"The higher the efficiency of a loudspeaker, the lower the distortion. In the absence of weight-loading, the distortion may be expected to be inversely as the square of the efficiency. In the case of weighted diaphragms, the major penalties are the power required to accelerate the extra weight and the resulting looseness of coupling between the electrical power and the air being moved. Transient response has to do with peak power output available with linearity (freedom from amplitude distortion) and the ability of the speaker to produce sound pressures proportional to applied instantaneous power.
Much effort has been expended to reduce weight of moving parts such as the diaphragm, and so forth - even to the extent of using aluminum ribbon voice coils instead of copper. There is seen to be a premium placed on high efficiency. This significantly applies not only to speakers but to amplifiers.
High efficiency results in reduced distortion in the speaker and less demand on the amplifier."
Paul W. Klipsch, "Speaker Power", Audio, October 1961

"The existence of subharmonics in direct radiator loudspeakers is well known. However, in horn loudspeakers the diaphragms are relatively small and quite rigid. Consequently, the conditions for the production of subharmonics is not particularly favorable."
Harry F. Olson, "Elements of Acoustical Engineering", Chapter 7 - "Horn Loudspeakers"

"As far as the ear can tell, consistently clean and spacious bass can be reproduced only by a driver unit coupled to a horn-type acoustic transformer..."
"Toneburst", "Low-cost Horn Loudspeaker System - Details of successful experiments", Wireless World, May 1974

"Although full-range horn systems are used today only by a small number of enthusiasts, most experts are unanimous in acclaiming their virtues as loudspeaker enclosures, especially their high degree of realism and "presence".
Jack Dinsdale, "Horn Loudspeaker Design", Part I, Wireless World, March 1974

"The advantages of horn-loaded systems lie in the fact that it is possible in such systems to obtain relatively distortion-free output at the low frequencies because of the small motions of the diaphragm even when large amounts of acoustic power are realized. Secondly, the high efficiency of the horn-loaded systems means, of course, that for a given power output the system does not have to be driven as hard electrically as the direct radiator baffle. This naturally results in more conservative use of amplifier power with consequently reduced amplifier distortion and better linearity of response during peak bursts of power."
Abraham B. Cohen, "Hi-Fi Loudspeakers and Enclosures", Chapter 11 "Horn-Type Enclosures"

"In every case - woofer, squawker, tweeter - the horn offers "cleaner" sound at all practical levels of sound pressure output. Indeed the horn is about the only means for delivering extremely high sound pressure levels with reasonably low distortion."
"A crude analogy of the direct radiator loudspeaker would be a "baffled" piston on the surface of a lake. It could agitate the waters but it would not be much of a pump. But put a cylinder around the piston, and it becomes capable of lifting the water. This is analogous to the driver unit coupled to a horn. The cone is forced to work at higher pressures with lower velocity.
Another analogy is the gear ratio of the automobile which transforms the "low impedance" engine - low torque, high speed - to the "high impedance" drive wheels - high torque, low speed. The direct radiator speaker is a low impedance device - low pressure, high velocity. The gear box is an impedance transformer. The horn acts as a transformer to increase the pressure and reduce the motion of the driving system."
"Modulation distortion is directly affected by the amplitude of diaphragm motion, and would thus be greatly reduced by horn loading."
Paul W. Klipsch, "Loudspeaker Performance", Wireless World, February 1970

"...Another great advantage of horn loading is that it results in heavy damping of the cone movement and consequent elimination of resonances."
H.J.F. Crabbe, "Design for a Folded Corner Horn", Wireless World, February 1958

"A small diaphragm may be designed to be extremely rigid and to move as a piston up to frequencies much higher than can be achieved with a large paper cone; as a result, the variations in sound output over the frequency range will be much reduced. A properly designed horn presents a resistive load to the diaphragm that is high and constant over a wide frequency range and down to a much lower frequency than is possible with a direct radiator speaker. Transient oscillations of the diaphragm are thus largely damped, and this gives the reproduction from a properly designed horn a solidity and body unequalled by any type of direct radiator speaker."
James Moir, "High Quality Sound Reproduction"

"These speakers' high efficiency and dynamic range provide an impact and realism to percussive sounds I haven't heard in many nonhorn systems."
Rick Steiner, "A Back-Loaded Wall-Horn Speaker", Speaker Builder 4/91

"...The model proved highly successful and gave good correlation with measured results, which used a Community M4 as a signal source (capable of producing signals with less than 1% harmonic distortion, even at 150 dB).
Philip Newell and Keith Holland, "Round the Horn", Studio Sound, March 1994

"The use of horn-loading provides, I believe, the best acoustic coupling yet devised, with superior transient response, smoother frequency response, and high efficiency, while the configuration improves the polar response of the unit."
James Nicholson, "A High Efficiency Mid & High Range Horn", The Audio Amateur

"I first became acquainted with horns when I heard a fellow engineer's home built system in 1977. I was literally blown away by the realistic dynamics of the system and set about learning all I could about horn design..."
Dr. Bruce Edgar, letter to "Readers' Forum", Sound Practices, Vol.1, #2