Horns used to be the only way to get any sound out of the feeble power amplifiers available in the 1920's. They were used in large spaces like movie theaters to make a few watts of power fill an auditorium. And, of course, they were used on acoustic phonographs to get any sound at all!

Is there an advantage in using them now? Well, let's see.

They are still used in movie theaters, stadiums, concert halls and any other place where the sound has to be very loud, and fill a large space. One of their chief advantages is that because of their sensitivity and efficiency, they can easily take the wide dynamic range of motion picture soundtracks, live music, etc. If you tried to push any all-direct radiator speaker to the sound presure levels encountered in filling a movie theater, it would self-distruct in no time. Also, horns can be made to any directional characteristic needed. They can be made to fill a very specific area of an auditorium, with no sound wasted from being directed where it's not needed.

None of the above advantages have anything per se to do with home theater, or sound quality in general. In fact, the above systems sound pretty darn bad by hi-fidelity standards!

Now, Paul Klipsch of Klipsch Loudspeaker fame recognized the advantages of horns for home use in the late 1940's and created the Klipschorn. He championed one unique advantage to horns that does have a direct bearing on sound quality. That is low amounts of doppler and harmonic distortion. Simply put, doppler distortion arises whenever the source of sound moves, relative to a fixed point (the listener in this instance). What is moving? Picture the cone of a 15" speaker moving back and forth by 1/2" as it reproduces a 30Hz tone at a loud volume. Now superimpose another tone of 1000Hz on top of that 30Hz tone. The speaker cone is now moving that 1000Hz tone nearer and farther from you at a rate of 30Hz! The effect is exactly as that of a car passing you by while honking it's horn. In that speaker, it will make the 1000Hz tone sound like it's 'underwater', or 'gurgly'. You are literally frequency modulating that 1000Hz tone, and creating distortion sidebands in the process.

Paul Klipsch reasoned that since a horn is very efficient, it's moving parts (the diaphram of the horn) needed to move very small distances in order to create healthy sound pressure levels. Because of this, his horn speakers produced dramatically reduced levels of doppler distortion (and also lower levels of harmonic distortion, for the same reason). They sounded cleaner than what was available at the time.

This is still true today, and is one of the chief advantages of horn speakers.

Of course, speaker technology has marched forward since that time, and today's speakers are much better than they were in 1950. BUT - take any speaker system today with direct radiators and play a loud continous bass tone that the speaker can reproduce, and add another pure tone that will be reproduced by that same driver (that has not been crossed over to the mid-range speaker by the crossover network), and you will hear doppler distortion if the level is increased enough.

Does this still matter today? People who make horn speakers (like Klipsch) think so.

When hi-fidelity meant only two speakers and music only, all this was somewhat a non issue to all but a few crazies like myself. Now, with the advent of home theater, with it's requirement to reproduce all manner of explosions, gunfire and other acts of violence, maybe it does matter. There's no denying that horns reproduce movie soundtracks with more 'punch' than direct radiators do. Those of you who have Klipsch speakers probably purchased them because they sounded good with movies. But does this make horns better?

That is a personal question. Any good speaker can sound wonderful. Speaker manufacturing technology has evolved tremendously, and today's consumer speakers sound WAY better than they did 20 years ago. But here are a couple points:

As discussed above, horns reduce forms of distortion like doppler, and also harmonic and intermodulation distortion because the moving parts have to move so little to create high sound pressure levels.

Because horns can have a very well defined directional pattern, they are very adaptable to the principles espoused by certification entities like THX. It is much harder to control directivity with direct radiators. The sound can be controlled and kept off walls, floors and ceilings to a greater extent before it reaches the listener. This has become important in home theater.

With a all-horn system (like mine) it is possible, by nature of the length of a horn, to achieve precise time alignment between the low and high frequency drivers by simply moving them in relation to each other, forward and back. Moving their relative position while looking at the reproduction of a square wave is a good way to achieve precise time alignment. This is not possible with direct radiator speakers, when the drivers are all mounted on one flat baffle. This limitation can be overcome however by slanting the baffle, or having stepped mounting surfaces for each driver.

Then, there is the characteristic 'horn sound'. This can be absolutely wonderful and 'alive' sounding if the horn system is executed well. Horns can also have a unique way of imaging the soundstage. They can image well behind the speakers (in stereo) as most conventional designs can, but they also have the ability to image the performers well into the room and all around you, way beyond the confines of the speakers. I've yet to hear a non-horn system that can do that as effectively.

Horns are unfortunately not executed well a good deal of the time, and the resulting horns sound simply "honky". Horn systems such as these, and horns used for PA applications have given them a bad reputation for some people.

And, as I have outlined in my previous posts, as horn coverage of the audio spectrum is widened, it becomes increasingly important to use tube amplification. This is because of the uniquely wide "class 'A' window" these amplifiers afford.

Horns are used mainly for tweeters in consumer systems today. It is very expensive to make a horn. In fact, most all horns today do not make use of a very important component that complements the horn: THE COMPRESSION DRIVER. Most horns today could be more accurately described as horn-loaded tweeters. They use a conventional speaker driver with a horn in front of it. A compression driver has a diaphram that fires through a 'donut' shaped magnetic structure. But before it reaches the throat of the driver, the sound passes through a 'phasing plug' which corrects the phase of the signals that enter the throat from the various parts of the diaphram. Thus there is no phase cancellation from say , the sound coming from the edge of the diaphram and that coming from the center. The problem with compression drivers is that they are extremely expensive to make. They require machining of precision parts, and this makes them cost prohibitive for consumer use.

The makers of today's horn speakers have done an excellent job of working around some problems arising from the lack of a true compression driver. Some of the phase problems resulting from direct loading of a conventional driver remain, however.

As home theater has come into being, there has been a gradual shift upwards in the sensitivity of speakers. This is probably for two reasons. More sensitive speakers (especially horns) are more able to take the abuse of sound effects that exist in modern motion picture soundtracks. This is simply because the speaker elements do not have to move as much to generate a particular sound pressure level. Thus less likelyhood of damage to the drivers. Another reason is that higher sensitivity speakers makes it possible to lower the power requirements of the power amps that power them. This was not much of an issue when amplifiers only had two channels, but gets to be a very big issue when as much as seven channels are put into a single amplifier chassis. 7 times 1000 watts? Get 'outta town!!

Would I purchase horns now, knowing what I do? You bet!

Should YOU? Well, that is a question only you can answer. Shop around and give the various horn designs a listen. There are only a couple firms that market all horn speaker systems currently, most systems having horn tweeters. Therefore, for better or worse, your selection, and therefore how crazy you can get with it, is somewhat limited. That is, unless you go with professional speakers....

[This message has been edited by soundhound (edited January 27, 2003).]