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Horn Speakers - Is it me or.......
- Thread starter March Audio
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Keith_W
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Tim Link
Addicted to Fun and Learning
When evaluating whether a horn is "honking" or not, I think it's important to listen to and measure the horn by itself. It's not unkown for a horn tweeter to get blamed for a problem that really belongs to the woofer it's crossed over to. A wide dispersion horn is least likely to make offensive noises. Try a long throat horn with an undersized mouth and no roundover if you want to make something resonant.
I suspect that honk is a severe amplitude peak in the mid frequency range. Is that something that could be EQed out?
'HOM' or high order modulation. Earl geddes has spent half a lifetime on the subject if you want to Google the threads on DiY Audio.
The Oblate Spheroid Constant Directivity (OS) wave guide is the mathematically optimum shape of horn to reduce the effect.
You can reduce HOM further with a $0.50 bit of pond filter foam in the throat of the horn.
I tried the filter and measured notably smoother FR on a large format JBL 2452SL 300hz JMLC horn.
I haven't read this entire thread, and this may already have been mentioned. I have probably heard as many lousy horn loudspeakers as anyone on this forum, honky, shrill, nasal, you name it. Long throat horns that identify their principal axis with a distinctive very high frequency sizzle. But, now there are better designs and this one got my attention, and has my respect. It will be mentioned in the 4th edition of my book now being written, and was on the cover of the 3rd edition.
The JBL Professional M2 Master Reference Monitor. This is an active loudspeaker, with a dedicated outboard power amplifier/equalizer. The 15-inch woofer is crossed over to a 120° Horizontal by 100° Vertical horn of unconventional shallow design. The crossover frequency is 800 Hz. It is rated at 117 dB continuous, 123 dB peak at 1 m. 108 dB peak at 8 m distance.
This is an example of competent engineering. It is a high-power, high-sound-quality loudspeaker intended for control-room monitoring, high-end home theaters, and the like. It is expensive, large, heavy, somewhat “industrial” looking, but it can play louder than humans can safely enjoy and compete in double-blind listening tests with highly rated neutral cone and dome loudspeakers in terms of sound quality.
There are smaller siblings.
The JBL Professional M2 Master Reference Monitor. This is an active loudspeaker, with a dedicated outboard power amplifier/equalizer. The 15-inch woofer is crossed over to a 120° Horizontal by 100° Vertical horn of unconventional shallow design. The crossover frequency is 800 Hz. It is rated at 117 dB continuous, 123 dB peak at 1 m. 108 dB peak at 8 m distance.
This is an example of competent engineering. It is a high-power, high-sound-quality loudspeaker intended for control-room monitoring, high-end home theaters, and the like. It is expensive, large, heavy, somewhat “industrial” looking, but it can play louder than humans can safely enjoy and compete in double-blind listening tests with highly rated neutral cone and dome loudspeakers in terms of sound quality.
There are smaller siblings.
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Sometimes. I was once tasked with "fixing the horn honk" on a loudspeaker. A notch filter on the woofer cured it.
The resonances caused by reflections at the horn mouth (which propagate back down to the diaphragm and then reflects back up to the mouth and so continue) are standing waves. You can compensate for them with EQ but ONLY at a specific point in space (presumably where the measurement microphone is), and you can probably make an improvement near that location, but you CANNOT correct that sort of problem GLOBALLY (that is, throughout the horn's coverage pattern). The solution is, a better horn design, in my opinion anyway.
Imo getting the mouth of the horn RIGHT matters a great deal. Not that the mouth is the only thing that "matters a great deal", but if the mouth is wrong imo the rest doesn't much matter, if very high sound quality is the goal. Unfortunately a lot of horn designs trade off a generous mouth round-over for an effectively larger horn. Click on the image of the JBL M2 in @Floyd Toole's post just above and notice how much of that big horn's frontal area is arguably "mouth round-over". A horn with the same outer dimensions but with a skimpy mouth round-over would go deeper, but it would not be as free from colorations.
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"Honk," exists in the frequency range of 450Hz to, maybe, 950Hz, according to this chart:
I have had several horn speakers and heard others. Most were in a large treated room with diffusors and absorbers, plus carpeting on the floor. I usually heard them at about 13 feet. I heard "Honk" only on a cheapie Magnavox horn console my parents had, and with a couple of coaxes made in the '60s. I have never heard a "Honk" from an Altec A5 (in a 70mm theater), an Altec A7 (came close to honking, though), the JBL 4355, a JBL Paragon, the Klipschorn, the Belle Klipsch, etc. I sure would go listen to some of the hi-end horns, but: 1) I can't afford them, and 2) nobody in my area has them set up to listen to.
I suspect the popularity of the term came from dealers who did not carry horns, but kindly demonstrated their alleged "Honk" by cupping their hands around their mouths and speaking, or, worse, singing.
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With the M2 and serveral other JBL waveguides, JBL basically has traded an improved on-axis response in exchange for en inferior off-axis response. The old JBL horns measured much better off-axis, but in return had issues on-axis.
While the polar of the M2 isn't terrible, it's very far for being SOTA.
While the polar of the M2 isn't terrible, it's very far for being SOTA.
It doesn't beat the Revel salon 2 in blind tests though. All other things being equal, this would likely be due to the narrower pattern width.
It isn't possible to make a horn play significantly wider than the M2 without losing vertical pattern width, so Charlie did a phenomenal job with the M2 given the constraints, especially in the time it was designed.
The next advancement of interest is wide pattern coax. There isn't any technical factor stopping one of the big manufacturers from making one. I guess KEF has too many of the patents?
I don't have the funds or inclination to do a project like this myself. What I don't understand is why hasn't anyone else?
That's an impressive narrowing of the dispersion from at 150-200Hz where the bass has already drop - 6dB at the rear. How does it achieve that?
It seems like even a 15" driver isn't enough to beam at those frequencies, and the port reinforcement would be lower?
What other tests besides Speaker Shootout - two of the most accurate and well reviewed speakers ever made?
Pro audio people like to talk of "polars", tradition from the old 1/3-octave days. Related to audience coverage, which is the essence of public address systems. For sound reproduction in small rooms the perspective has to change. Measurements like the spinirama attempt to predict the sound that arrives at a listener rather than the sound that leaves the loudspeaker. When measurements of that kind are correlated with subjective responses from double-blind tests one finds that the important information in the off-axis data is evidence of resonances, the dominant source of coloration in loudspeakers. Bumps that show up in on and off-axis curves indicate resonances. So all curves being smooth, and off axis curves gradually changing (for forward firing loudspeakers) are key factors. The on axis response- direct sound - is the prime determinant of sound quality, so if that is wrong, the rest is relatively unimportant. Anechoic data and dedicated EQ can help.
A good cone and dome speaker is designed for timbral neutrality and playing loud is a bonus. Pro loudspeakers are designed to play loud, and not break, and timbral neutrality is the bonus. When we get to high-power monitor loudspeakers the two worlds blend. The M2 is a good blend of both approaches. It was inspired and the design driven by two talented consumer group engineers who believed in double-blind listening, collaborating with talented Pro guys, which explains it.
Traditional horn monitor loudspeakers were often dreadful pieces of misery - see evidence in Chapter 18 of the 3rd edition of my book. It is absolutely amazing that decent music survived - but it was the music and musicianship, and talented recording engineers, not the loudspeakers that made it happen. Today Genelec is a leader in pro monitoring, and Ilpo followed the developing NRC science from the outset. No compression-driver horns but lots of waveguides. The spinoramas tell the tale.
No publicly available ones I'm afraid. Others do exist though.
The M2 and the Revel Salon 2 were close enough in my listening to it in the speaker shuffler room at Harman, and in the reference listening room that I debated about having it in my home theater that was being renovated at the time. The Revel won the visual aesthetics contest hands down, but it isn't perfect either. In listening tests it was a close race, mostly a statistical tie. Program is the moment-by-moment determining factor. Revel also had a meticulous end-of-line QA process. They were all very much alike - something one pays for, and they could play plenty loud for my old ears - trying to preserve what is left
They are also remarkably short. Only a couple of inches deep measured from the mounting plate to the outside edge.
Rob
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Thank you for once again articulating a distinction that is easily overlooked but which offers valuable insight. If I understand correctly, what matters more in home audio is not necessarily the radiation pattern shape in and of itself, but its effect, which (imo) is ideally the best presentation of direct + reflected sound to the listener's ears.
I suspect the "polars" along the diagonals of the M2's horn look different from the horizontal and vertical polars, but the net spectral balance of the reflection field remains correct.
That makes sense. Wide-pattern horns tend to be short, based on simple geometry. My understanding is that by traditional horn thinking a horn has to be long in order to go deep, but if the compression driver is up to the task, a wide-pattern short horn can also go deep, as shown by the M2's 800 Hz ballpark crossover. Of course it uses a rather exceptional compression driver which actually has two diaphragms and therefore twice the "cone area" of a conventional counterpart.
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Vertical walls are the dominant reflecting surfaces so far as ears in the horizontal plane are concerned - what happens at other angles is less important because of longer path lengths, inverse square law and air attenuation.
Thank you. It makes sense that the horizontal reflections are the ones which matter most, and that getting them right takes priority. Normally the first same-sidewall reflections also arrive fairly early, and if I understand correctly, that contributes to their perceptual significance.
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