How come Horn + woofer designs are not more popular?

@shadorne wrote:  "Horns tend to have an uneven radiation pattern with frequency."

It depends on the horn.  Many horns (such as tractrix or exponential) tend to have a wide pattern down low and a narrow pattern up high.   Often PA horns have a constant pattern in the horizontal plane but then the pattern narrows aggressively in the vertical as we go up in frequency.  But some horns have very uniform patterns across their passbands.  Radiation pattern control is actually the main reason that I use horns, but they are a specific type:  Constant-directivity, waveguide-style (the latter term signifying that they don't use diffraction or slots as part of their pattern control).   

"[Horns] can be perceived as shouty or unbalanced."

Good waveguide-style horns don't have this problem.  The "shouty" thing is often a characteristic of diffraction horns especially at high SPLs.   Most PA horns are diffraction horns, and most people's primary exposure to horns has been crappy PA systems, so most people think horns are inherently shouty, but that is not at all the case.   Horns that are shouty are ones that have been optimized for things other than sound quality. 

If any of you will be at T.H.E. Show in Long Beach in early June, stop by room 519, especially if you would describe yourself as someone who "hates horns".  We'd like to have a go at shifting your paradigm.

Duke

dealer/manufacturer

Mijostyn wrote: "there is a compromise in a two way horn system that is difficult to get around. You either have to run a woofer up into the midrange or make a very large horn to get down to where most woofers do well."

Done right, I don’t think there is any compromise to performance.

I’d like to address two myths about prosound-type woofers, such as might be found in a horn system:

First, people mistakenly think big woofers are inherently "slow" because of the cone size, when in fact a good prosound woofer has such a powerful motor that its motor-strength-to-moving-mass ratio is competitive with, and often superior to, small high-end midwoofers (5" Scan-Speak Revelator and Illuminators, for example). The 10" prosound woofer I’m working with at the moment has a motor-strength-to-moving-mass ratio competitive with a 5" Scan-Speak mid.

Second, people think a big cone cannot have a smooth response. The truth is that the accordion surrounds on prosound woofers do a better job of damping cone breakup than half-roll surrounds do, such that plus or minus 1 dB before EQ is possible up to the crossover region on a studio-quality pro woofer, and without nasty spikes in the response north of the crossover region. (For example, look at the Eminence Kappalite 3015 and imagine crossing it over a 1 kHz... the woofer Peter Noerbaek uses in the speaker linked in his post is in that same ballpark).

And here are some of the advantages of a using a good prosound woofer in a horn system:

- Because the large cone has a relatively narrow pattern in the crossover region, if the speaker designer so chooses, it is easy to match the woofer’s pattern with the horn’s in the crossover region. This is virtually impossible to accomplish with cones ’n’ domes. The result is, a good horn hybrid speaker (meaning horn + direct radiator woofer) can have an audibly seamless crossover.

- The relatively narrow pattern of a big woofer + horn system means that less off-axis energy is going into early reflections. According to researcher David Griesinger, early reflections are the ones most detrimental to clarity, so this characteristic of horn systems promotes clarity.

- If the designer chooses to use a constant-directivity horn, the reflections will have nearly the same spectral balance as the first-arrival sound, which promotes natural timbre and freedom from listening fatigue.

- Prosound type drivers are free from compression effects in a home audio application, which is not true of most moderate-efficiency high-end drivers. Musicians use dynamic contrast to convey emotion, so a good horn speaker conveys the emotion in the music better than most conventional speakers.

- Many horn speakers are compatible with specialty tube amps, such as Output TransformerLess (OTL) and Single-Ended Triode (SET) types.

- Set up properly, you can actually get a wider sweet spot with a good horn system than with any other type I am aware of.

The inevitable tradeoffs are large enclosures (lower WAF) and less low-end extension than a comparably-sized speaker of lower efficiency.

For those who think modern horn systems still have coloration issues, but are open-minded enough to do a little reading, you might google "JBL M2" or "Dutch & Dutch 8c". The speakers Peter Noerbaek linked to are essentially a hot-rodded version of the M2, and imo they are magnificent.

Duke

Pbrain wrote: "A couple years back, I had the fortunate opportunity to take part in a double-blind mono test between a Revel Salon2 (very high-end, 6-way, traditional dome-tweeter design) and JBL M2 ("master reference" horn-based 2-way design) speaker."

I recall reading about that test on another forum.  Very interesting!

This was a "mono" test, I hadn't caught that detail before... single speaker vs single speaker?  If so, I assume the speaker being evaluated was at one end of the room, a little ways in front of the wall, and in front of what would be the midpoint of that wall.  Is this correct?

"Post analysis showed that I preferred the Revel on every sample, and to my ears during the test, it was obvious which speaker was which. I just couldn't warm to that up-front, in-your-face shoutiness of what is admittedly maybe one of the best and accurate horns designs of all time."

I assume there was no audible "horn coloration" from the M2, just a more "in your face shoutiness" to the presentation, at least in comparison to the Revel.  Is that correct?  

You see, I suspect two significant differences between the M2 and Revel were in play, in addition to (and in part arising from) their obvious physical difference (horn vs cones & domes).

First, according to the measurements I've seen, the Revels have a more "continuously and gently downward-sloping" in-room response, while the M-2's sort of "plateau" off-axis from 1 kHz to 10 kHz, which would give it a more "forward" or "in your face" presentation. 

Second, again according to the measurements I've seen (and implied by their respective configurations), the Revels have a wider radiation pattern, which, while not quite as uniform as the M2s, is still very good.   This results in more spectrally-correct late-onset reverberant energy, which is beneficial to timbre and a sense of depth (less "in your face-ness") and immersion.  In general, a well-energized, spectrally-correct reverberant field tends to sound rich and relaxing. 

Now I wasn't there of course, so this is just supposition on my part - but does any of this seem consistent with what you heard?

Duke

Thank you very much pbrain for that in-depth reply.

"I think the in-your-face character of the M2 is mostly due to its higher directivity index across the audio band. That’s not atypical of horns in general."

I agree.

My study of acoustics and psychoacoustics and the implications of the size rooms we listen in at home leads me to think that all reflections should be spectrally correct; that early reflections (those arriving within the first ballpark 10 milliseconds) are likely to be detrimental; and that late reflections (those arriving after about 10 milliseconds) are likely to be beneficial. To clarify a bit about the early reflections, they have some benefits and some detriments: They can widen the soundstage and make the speaker less obvious as the sound source, but they can also degrade clarity and cause coloration. Just about everything that late reflections do is beneficial, assuming they are spectrally correct, and assuming you don’t have a significant room acoustics issue like slap echo. A sense of immersion and envelopment comes primarily from the late reflections, which come from all directions; the ear/brain system is able to pick out the ambience information already on the recording from these late-onset reflections, identifying it by its harmonic structure.

So in the shoot-out, with the single speaker far from both side walls, you had no early-onset sidewall reflections to possibly degrade the sound. Aside from the floor and ceiling bounces (which are subjectively relatively benign), all of the reflections were late-onset, and spectrally correct. So what I THINK is that the significantly greater amount of late-onset reflections for the Salon 2’s helped them to sound more natural.

With a more conventional stereo setup, left and right speakers being much closer to their respective side walls, I think the M2’s would have benefitted from their narrower radiation pattern reducing the amount of energy in those early sidewall reflections. But in all fairness, my understanding is that Toole finds these early reflections to be generally beneficial, while Geddes and Griesinger find early reflections to be generally detrimental, so there are well-informed differences of opinion on the subject.

My own somewhat unorthodox approach to horns involves fairly narrow patterns, and then additional drivers aimed such that their reflected outputs arrive "late" (more than 10 milliseconds behind the first-arrival sound). In other words, my best horns speakers might be called "polydirectionals", to use the term coined by the late great Richard Shaninian. I’m trying to minimize the amount of energy in early reflections, but then increase the amount of (spectrally-correct) energy in late-onset reflections.

It’s has not been obvious to me which is the most beneficial: Minimizing early reflections, or increasing late reflections. But the test you participated in seems to suggest that increasing the amount of energy in late reflections probably matters the most, which is something I’ve been working on. And THAT’S why I personally find this test so interesting.

By any chance will you be attending T.H.E. Show in Long Beach in two weeks? If so, I would REALLY welcome your brutally honest critique of what I’m doing. Imo your background makes you uniquely well qualified.

Duke