What is special about horn loaded drivers?

[Defcon]

I've noticed a lot of highly regarded HT speaker brands such as JTR, Danley, JBL use the same basic design - horn loaded compression drivers and big woofers.

What are the pros and cons of this? I can see they play very loud due to high sensitivity which is due to a horn design, but what does the CD do that's different from a normal tweeter? And how do they differ from normal hifi speakers which have smaller woofer and dome tweeter?

 

[Steve81]

I've noticed a lot of highly regarded HT speaker brands such as JTR, Danley, JBL use the same basic design - horn loaded compression drivers and big woofers.

As you noted, that particular combination is used to achieve high sensitivity and high output. In addition, the horn will control dispersion; done right, that leads to an off axis response that declines smoothly as the frequency goes up. As far as cons go, there's obviously the matter of size. One also has to be careful as resonances in the horn can color the sound.

 

[TLS Guy]

I've noticed a lot of highly regarded HT speaker brands such as JTR, Danley, JBL use the same basic design - horn loaded compression drivers and big woofers.

What are the pros and cons of this? I can see they play very loud due to high sensitivity which is due to a horn design, but what does the CD do that's different from a normal tweeter? And how do they differ from normal hifi speakers which have smaller woofer and dome tweeter?

Basically those speaker you mention are for boring a hole in your head. That type of speaker design is for blasting pop music, and they are never "civilized" speakers.

 

[ski2xblack]

Doc, while it's true that there are more uncivilized, head-hole boring, pop blasters out there, you are wrong to characterize all horn speakers as such. I strongly suspect you would actually appreciate Danley Synergy horns and find them quite civilized.

 

[TLS Guy]

Doc, while it's true that there are more uncivilized, head-hole boring, pop blasters out there, you are wrong to characterize all horn speakers as such. I strongly suspect you would actually appreciate Danley Synergy horns and find them quite civilized.

I actually doubt I would like them under domestic conditions. They might be alright in an auditorium or church. Sectoral horns just do not have the right dispersion pattern and smoothness for home installations. You really need to put significant distance between speaker and listener.

I have done large hall installations and used large drivers crossed to big sectoral horns, and they have worked well for speech and bands. However the best installation I did used 15" drivers in an exponential back loaded horns, and a long distributed line of eight very high quality drivers as a line source, crossed at 500 Hz bi-amped. That was beautiful, you could have sworn there was an orchestra on the stage.

For the music I listen to, those type of designs you are talking about, will just not fit the bill. I can tell you I would never design a system like that for my personal use.

I will say for the record that the dispersion pattern of those designs is not correct. You do not want to control dispersion as frequency rises.

One of my objections to those designs, is that the sound of string,s especially violins, is far from pleasant or natural. You see a stringed instrument is an omnidirectional radiator. Strings sound best on systems with the widest dispersion, especially at the highest frequencies. The brass sections, those type of speakers can often reproduce well. On the other hand the dispersion patterns I favor also reproduce brass very well. It is the string sound that is always the big Achilles heel of those large horn loaded top ends.

 

[Swerd]

While Danley Synergy horns (haven't heard them) may be the exception to the rule, the rule still is that horn speakers are made to be VERY LOUD in large auditoriums or outdoors, conditions where standard home use speakers cannot play loud enough. They accomplish this loudness at the expense of sound quality.

I have encountered many audiophools at audio shows who seem to have swallowed the Kool Aid on this subject. The horn speakers they adore, have all (with one exception) sounded awful to me. That exception was a Klipsch La Scalla clone, the name of which I forget. It costs over $17,000 and I am certain I won't be buying it.

As far as I understand things, an important feature of loud speakers is that they disperse sound as widely as possible in a room. This allows two speakers in stereo to create a realistic sound image that exists outside the speaker cabinets. Horn speakers are designed to direct all their sound energy in a narrow pattern to project sound to great distances. In a theater where these distances might easily be 200 feet or greater, their dispersion will approach the dispersion achieved by non-horn speakers in smaller rooms found in homes. I understand how Constant Dispersion (or is it Controlled Dispersion?) can work in a large auditorium, but it can't be of any benefit in normal sized rooms.

 

[Steve81]

As far as I understand things, an important feature of loud speakers is that they disperse sound as widely as possible in a room.....I understand how Constant Dispersion (or is it Controlled Dispersion?) can work in a large auditorium, but it can't be of any benefit in normal sized rooms.

Not necessarily so. As I understand it, the most important thing with the off axis response is that its reasonably even/smooth, without any big flares or dips. What controlled dispersion does for you is help reduce room to room variability, simply because the speaker is interacting less with the room. You can see this philosophy in Harman designs ranging from low end Infinities to high priced Revels and their M2 Master Reference Monitor. This is also the reasoning behind the KEF UniQ, including the LS50.

 

[Swerd]

Not necessarily so. As I understand it, the most important thing with the off axis response is that its reasonably even/smooth, without any big flares or dips. What controlled dispersion does for you is help reduce room to room variability, simply because the speaker is interacting less with the room. You can see this philosophy in Harman designs ranging from low end Infinities to high priced Revels and their M2 Master Reference Monitor. This is also the reasoning behind the KEF UniQ, including the LS50.

Just how does a manufacturer of Controlled Dispersion speakers know where an owner will place his speakers? No one makes speakers with user-assigned variable dispersion. That might address the problem, but a fixed and limited dispersion pattern only limits how an owner may locate his speakers.

I've heard this idea before, and I don't understand it. I have never listened to speakers and thought, "these sound nice, but if they only had narrower dispersion, they might sound wonderful".

 

[TLS Guy]

Not necessarily so. As I understand it, the most important thing with the off axis response is that its reasonably even/smooth, without any big flares or dips. What controlled dispersion does for you is help reduce room to room variability, simply because the speaker is interacting less with the room. You can see this philosophy in Harman designs ranging from low end Infinities to high priced Revels and their M2 Master Reference Monitor. This is also the reasoning behind the KEF UniQ, including the LS50.

I don't agree with that entirely. We are getting into the classical/pop divide here.

The two most difficult things to reproduce are the stings, especially the violins and the human voice. The latter, especially the voice not close miked, like the opera stage.

I can assure you for this, you just can't have too much dispersion. In fact the ideal speaker actually would be an omni directional point source radiator. I emphasize point source as pointing a bunch of cone drovers to all point of the compass is a total mess. For classical music you want the room live with a dominance of reflected sound. I am uncertain if that holds entirely in the pop domain.

Now I believe the controlled directivity of speakers like the KEF UniQ is only advantageous for a center speaker, were I believe you need to limit the interaction with the mains. That is why my center speaker uses a coaxial driver and the mains do not. My ears and living about 10 years with my system leads me to believe I am correct.

All this is a reason I design my own speakers. I don't like pop music, with close miked singers and amplified instruments. I basically have no interest in reproducing it all and never do for myself. Although the funny thing is that engineers from the pop world have been finding their way to my studio, to check and adjust mixes. I tolerate this under forebearance. So I am now unsure if the classical/pop divide actually exists.

However if a speaker can not do a really good job of solo strings, massed strings, the human voice and all else besides, then it won't stay in my home. My experience and research lead me to the conclusion this impossible with the speakers under discussion.

 

[Swerd]

The OP, Defcon, asked a question about horn loaded speakers. It may help to separate his question into two separate questions.

1. What about big loud high sensitivity speakers?
   and
2. What about speakers with limited dispersion, the so-called controlled dispersion speakers?

The answer to #1 is clear. These speakers sacrifice sound quality for quantity. They are good for large auditoriums, but not in homes.

The answer to #2 is, at best, controversial. I fail to understand why it would be better to deliberately limit dispersion.

 

[KEW]

I've noticed a lot of highly regarded HT speaker brands such as JTR, Danley, JBL use the same basic design - horn loaded compression drivers and big woofers.

What are the pros and cons of this? I can see they play very loud due to high sensitivity which is due to a horn design, but what does the CD do that's different from a normal tweeter? And how do they differ from normal hifi speakers which have smaller woofer and dome tweeter?

I just wanted to add an aspect that comes with the efficiency, in addition to playing loudly, it also makes for a very dynamic speaker. In my experience, this type of design provides a fast transient or good impact on the attack of sudden sounds.

I do believe you can get equivalent attacks out of a more traditional driver, but a $300 speaker with horn hits harder than a traditional $300 speaker.

Every horn I have ever heard in a residential setting colors the sound, but I have never heard any of the premium speakers with horns.

 

[ski2xblack]

Swerd, in answer to #2, it depends on the room and intended goals. I'll post this link again. I'm with Bill Waslo in his suspicions that few that have heard controlled directivity speakers have heard them implemented properly. (Pardon the seeming crudity of the piece, but it's founded on quite a bit of actual research over the years from the likes of JBL/Harmon, Earl Geddes, etc.)

 

[Steve81]

Just how does a manufacturer of Controlled Dispersion speakers know where an owner will place his speakers?...

They don't, and that's rather the point. As I said before, a controlled dispersion design introduces less room to room variability because it interacts less with the room. That means in addition to the physical walls of the room, it's interacting less with the furnishings within it. That would tend to make it less sensitive to where it's placed. As long as the dispersion is still reasonably wide, ala KEF, Revel, et al., the overall performance doesn't have to suffer for it either.

I don't agree with that entirely. We are getting into the classical/pop divide here....In fact the ideal speaker actually would be an omni directional point source radiator.

It's not so much a matter of the classical/pop divide so much as the question of what makes an ideal loudspeaker. In one sense, you're correct that an omni-directional point source would be ideal. On the other hand, that ignores the real world issue of the room/speaker interface. The sound of such a speaker would vary widely depending on the room. That is to say, while such a speaker could sound very good under the correct circumstances, it could also sound awful under the wrong ones. That's not necessarily desirable from a manufacturer's perspective, at least not one who wants to deliver a consistently good performance in any room, thus reaching the widest audience. Removing the variability in the room/speaker interface is also useful as a whole to the industry simply because it becomes more feasible to achieve some semblance of a reference standard.

 

[TLS Guy]

They don't, and that's rather the point. As I said before, a controlled dispersion design introduces less room to room variability because it interacts less with the room. That means in addition to the physical walls of the room, it's interacting less with the furnishings within it. That would tend to make it less sensitive to where it's placed. As long as the dispersion is still reasonably wide, ala KEF, Revel, et al., the overall performance doesn't have to suffer for it either.



It's not so much a matter of the classical/pop divide so much as the question of what makes an ideal loudspeaker. In one sense, you're correct that an omni-directional point source would be ideal. On the other hand, that ignores the real world issue of the room/speaker interface. The sound of such a speaker would vary widely depending on the room. That is to say, while such a speaker could sound very good under the correct circumstances, it could also sound awful under the wrong ones. That's not necessarily desirable from a manufacturer's perspective, at least not one who wants to deliver a consistently good performance in any room, thus reaching the widest audience. Removing the variability in the room/speaker interface is also useful as a whole to the industry simply because it becomes more feasible to achieve some semblance of a reference standard.

That is totally contrary to my experience. I made recordings with monitors of my own design over a quarter century or so. I had my speakers in a huge variety of listening rooms, yet I could always trust the monitors and they sounded very similar were ever they were.

Reflections form any room are in general a very good thing, and the more the merrier.

My first level listening room has tons of reflections and a pronounced echoes. The room sounds absolutely wonderful and I enjoy listening in it immensely.

This is an area of audio, where there is far more bunk than fact. What I do know is that there are far too many lousy speakers around, and that is what really generates these discussions.

All I can tell you the better the speaker the less fussy it is about were it is placed.

I will say categorically a finicky speaker is a bad speaker.

 

[Steve81]

That is totally contrary to my experience. I made recordings with monitors of my own design over a quarter century or so. I had my speakers in a huge variety of listening rooms, yet I could always trust the monitors and they sounded very similar were ever they were.

I don't doubt that. A wide dispersion speaker can sound very good in a wide variety of settings if its off-axis performance is free from major aberrations. The Philharmonic 3 is a good example of this, which I've heard in Dennis' relatively open living room as well as in a hotel room.

This is an area of audio, where there is far more bunk than fact.

True enough, but this is generally based on the research and musings of Floyd Toole, Sean Olive, et al, from papers like this one, which is aptly subtitled:

Part 2 – Making a good loudspeaker -
Imaging, space and great sound in rooms.
Loudspeakers can be designed to be “room
friendly” so that they can sound good in a
variety of different rooms. Controlling
reflections can optimize imaging and spatial
effects.

 

[AcuDefTechGuy]

There are always exceptions to every rule, but I think the general consensus is that higher efficiency speakers (horns, CD, Pro-style speakers) are great for loudness and dynamics, but may not be so great for accuracy (speaker measurements).

Personally, I use horn/CD/pro speakers for outdoor events and karaoke.

But some people love to use these speakers for everything. There is no right or wrong. Everyone is different.

 

[Swerd]

In my opinion, this controversy comes from a misunderstanding of wave behavior. Sound can behave as particles or waves depending on the wavelength and the distances between reflective boundaries (ie. room walls, ceiling, and floor). Most of us can intuitively imagine how particles bounce off boundaries, as if they were ping pong balls. But waves aren't so easy to characterize. Waves of short enough wavelength, higher frequency, for all intents and purposes act as if they were ping pong balls.

As the wavelength gets longer, approaching the size of the speaker cabinet width, or the dimensions of a room, much different things happen. Waves can propagate, bend, reflect and diffract in non-intuitive ways. And wave phase begins to matter greatly. We don't have to think of phase angle when ping pong balls bounce.

When wavelengths are in the same order of magnitude as room dimensions there is a rough dividing point, called the Schraeder Frequency. In many rooms in our homes, the Schraeder Frequency is roughly 250 Hz. Waves with shorter wavelength act more like ping pong balls, and wave with longer wavelength behave in more difficult ways to understand, especially if you prefer to imagine them as acting like ping pong balls. Below the Schraeder Frequency, waves reflected off of room boundaries have a major effect on sound. Above it, much less so. The controlled dispersion idea seems to assume that all wavelengths behave as do the waves longer than a rooms Schraeder Frequency. Maybe it helps to think of room dimensions in terms of wavelengths and not feet. Sound travels at 1126 feet/second. Sound at 100 Hz (100 cycles/second) has a wavelength of 1126/100 = 11.26 feet. So a room with walls 22 feet apart are 2 wavelengths apart for sound at 100 Hz. For other wavelengths… you do the math.

I think the controlled dispersion idea may have some merit for frequencies below a room's Schraeder Frequency. Above that, not so much. But most or all of the horn speakers claiming controlled dispersion benefits, control the dispersion of the tweeter and not the bass driver.

The proper way to increase the dispersion of a woofer is to lower it's crossover frequency. If you run it too high, it's dispersion gets narrow and narrower. The lower range of a tweeter will disperse sound over a very wide angle. If a woofer is crossed over too high, there will be large and audible discrepancy between its dispersion and the tweeter's. So the controlled dispersion idea argues to limit the dispersion of the tweeter in order to avoid this dispersion discrepancy. I would rather avoid this problem by crossing over the woofer at a lower frequency. This may require a more expensive tweeter, but it sounds much better to have dispersion as wide as possible.

The effects of reflected sound at wavelengths shorter than a room's Schraeder Frequency just don't matter like they do at longer wavelengths.

Where is Floyd Toole when you really need him?

 

[Steve81]

Where is Floyd Toole when you really need him?

Not sure, but he is the author of the paper I linked in my last post, which includes tidbits like these:

Nowadays, we know enough about horn design to be able to make
them sound really good, and take advantage of their directional
control. The days of horns that are just loud and sound like
megaphones are past – for good engineers at least.
If the room is acoustically live (the way many interior decorators like
them), then the only option is to use horns, or waveguides, to control
the radiation from the loudspeakers. This way the energy is focused
on the listeners, and kept away from the reflecting surfaces,
improving the intelligibility and directional effects.

Movies, especially, are designed for listeners in a strong direct sound
field. Some people use wide-dispersion loudspeakers, and then cover
the walls with sound absorbing material. This gets the job done, but
in doing so it makes the entire system work harder, first to create the
sound, and then turning it into heat in absorbers. The result, dynamic
range is sacrificed. Not necessarily a good tradeoff.
Acoustically dead rooms are also not very pleasant places in which to
spend time, conversing or anything else. Some custom home theaters
are like this. It is not a recommended solution.

In the Real World The room is the final audio component, and it is not under control!

Reflections alter both Sound Quality and Imaging; Reflected sounds can be controlled by:
(a) controlled-directivity loudspeakers, (b) absorbing or diffusing objects on reflecting surfaces in the room, (c) the shape of the room, (d) some of each.

NARROW DISPERSION FOCUSES SOUND ON LISTENERS, MINIMIZING WALL REFLECTIONS,
MAXIMIZING CLARITY AND INTIMACY AS INTENDED IN MOVIES.

WIDE DISPERSION “ILLUMINATES’ THE ROOM, CREATING MANY REFLECTIONS WHICH ADD
SPACIOUSNESS, EVEN IN SCENES WHERE IT IS NOT APPROPRIATE.

 

[Swerd]

Don't quote theories that disagree with my theories .

"In theory, there is no difference with practice and theory. In practice, there almost always is."

Floyd Toole has said both at different times, that room reflections at shorter wavelengths than a room's Schrader Frequency don't matter nearly so much as they do at longer wavelengths. And he also wrote the long quote you cited.

Like I said, where is FET when you really need him.

All this thinking of wavelengths and phase angles has me spinning .

 

[ski2xblack]

The effects of reflected sound at wavelengths shorter than a room's Schraeder Frequency just don't matter like they do at longer wavelengths.

That all depends on the timing of the reflected sound. Controlled directivity allows one to sidestep early reflections and preserve later, more attenuated far reflections.