What is your opinion regarding electrostatics?

Sean, what an incredible post! You did a superb job of laying out the merits of horns and 'stats without becoming "partisan".

I'd like to suggest that the dipole radiation pattern of a full range electrostat is actually an asset rather than a limitation. The only significant placement issue is getting them far enough out from the wall behind them, and five to seven feet is usually adequate. You might want to treat the first reflection points with a bit of absorption or diffusion, then fine tune the toe-in angle, and you're pretty well done.

A good full-range dipole has three significant advantages over a direct radiator loudspeaker:

1. The bass is significantly less colored by the room.
2. The direct and reverberant fields are more alike.
3. The sound field more closely approximates a live event.

A dipole does not excite room modes more than a monopole speaker - in fact, it excites them far less. This is because a dipole's figure-8 radiation pattern puts 5 dB less bass out into the reverberant field than a monopole's spherical radiation pattern. True a dipole will excite the room's front-to-back standing wave modes (and so will a horn), but it will put much less energy into the side-to-side and vertical standing wave modes than a direct radiator does. The result is much better pitch definition, because the room isn't contributing nearly as much overhang to blur the decay of the bass notes.

Because a well designed dipole (such as the Maggie 3.6, 20.1, and full range Sound Labs) maintains pretty much the same radiation pattern all the way up and down the frequency range, the reverberant field will have the same tonal balance as the direct sound. This is conducive to natural timbre and to long-term listening enjoyment, because the brain expects the reverberant field to sound like the direct sound with the room superimposed on top. A direct radiator almost never gets this right because its radiation pattern changes drastically as we go up and down the frequency range. Therefore, its reverberant field cannot possibly have the same tonal balance as its on-axis sound. The result is listening fatigue over time. You can listen to a good dipole literally all day long and never get tired of it (the freedom from boxy colorations probably helps here as well).

A dipole that approximates a line source sets up a very different kind of sound field than a horn or direct radiator can (with the exception of line source direct radiators, like the Pipe Dreams - which have problems of their own). You see, sound pressure falls off with the square of distance from a point source, but linearly with distance from a line source. Okay, once again, in English: As you move farther back from a tall dipole speaker, the volume falls off much more slowly than when you move back from a horn or direct radiator speaker. The result is a vastly different "feel" than what you get from a conventional speaker. This uniform sound field feels more like a live performance, because as you listen to a live performance from forty feet away, the sound field is very uniform in volume and tonal balance.

Alas, Sean, I don't know as much about horns as you do about 'stats, so I cannot give the comparison as even-handed a treatment as you did. I certainly agree that horns do macrodynamics better, are easier to place, and are much easier to drive. So far I have yet to hear a high end hybrid horn system where the direct radiator woofer matched the clarity of the horn. But, in all fairness, I have yet to hear a high end hybrid electrostat where the direct radiator woofer matched the clarity of the panels. Just as the ultimate in electrostats is the full range panel, I would imagine that the ultimate would be a full range horn system. Besides the K-horn, does anybody make one?

Hi Sean,

Great to hear from you again! Hey by the time you and I are done, we'll have all these dynamic guys lining up for either horns or 'stats...

You are a true gentleman, and it is a pleasure exchanging ideas with you. Your ideas are worth way more than the customary $.02. I'm a dealer (see the fin on my back??), so my ideas have to be taken with so many grains of salt I oughtta buy stock in Morton...

Okay, here we go...

I gotta differ with your statement that "LOW frequencies are omnidirectional" (which, if true, would refute my assertion that dipole bass is less colored by the room). Low frequencies are only omnidirectional with a monopole direct radiator source. For example, a true low frequency horn would be just as directional over its passband as a midrange or high frequency horn.

A dipole is directional in the bass because, in the plane of the driver, the out-of-phase front and rear waves cancel. In a true anechoic chamber, you would not hear any bass if you stood exactly to the side of a dipole. But you would hear plenty of bass if you stood in front of it. In a room, what you hear to the side of a dipole is the reverberant field.

If you did an overhead graph of a dipole's radiation pattern at low frequencies, it would look like a figure-8 [see - more bass out front & to the back; less bass to the sides]. A monopole has a figure-O [omni-directional] radiation pattern in the bass.

The Stereophile 1998 "Speaker of the Year" was a dynamic dipole called the Audio Artistry Beethoven, designed by Siegfried Linkwitz. Go to this address and you will find an in-depth description of dipole bass: http://www.linkwitzlab.com/rooms.htm

You can also find an excellent but less technical discussion of dipole bass at Gradient's site (the Revolution uses dipole bass loading). Be sure to click on the link to the picture of the bass radiation pattern on the second page: http://www.gradient.fi/En/Products/Revo/Revo1.htm

Hopefully these sites will establish that a dipole is indeed directional in the bass.

Now, I'm sure you'll agree that one of the advantages of a horn is that its directional nature minimizes room-induced colorations. Well, dipoles have the same thing going on with their directional bass - they have significantly less room-induced colorations.

Mind if I try to bolster up my assertion that dipoles have similar direct and reverberant fields?

I said that with a good dipole the direct and reverberant fields sound pretty much the same. Okay, this is easy to test. Go to your Maggie or Sound Lab dealer and turn the volume up louder than normal. Walk into the next room, leaving the door open. Does it sound convincingly like live music is going on back in there? From outside the room, all you can possibly hear is the reverberant field. If it sounds realistic, then the speaker's reverberant field response is very good. By the way, Klipschorns are also very good at this, because their full-range horn loading maintains essentially the same radiation pattern at all frequencies.

As an example of the reverberant field, consider this situation: You're walking past a night club and you hear saxaphone music coming through the open door. You don't even have to look inside - you know instantly if it's live or if it's Memorex. All you can possibly hear through the open doorway is the reverberant field. With live music, the reverberant field sounds right. Over most loudspeakers, it sounds wrong. One of the most significant but most often overlooked factors in the difference between live and reproduced sound is the reverberant field. Papers published in the Journal of the Audio Engineering Society decades ago established the correlation between listener preference and good reverberant field response, but this has been all but forgotten.

I can't think of any arguments in support of my 3rd assertion in my post above, so I'll pass on that one for now.

Just for the record, many planars are indeed capable of substantial output below 100 Hz. Sound Labs and Maggie 20's go down into the mid-20's, and can shake the room, as can the dipole Beethovens mentioned above (which go down to 18 Hz). The dipole active Gradient Revolution system demo'd at the 2001 CES easily went down into the lower 20's, and had by far the most natural sounding bass I heard in any of the smaller rooms (and better than many behemoth direct radiator systems).

Frankly, I don't think placing planars in the middle of the room is necessary (or practical). Perhaps we have had different experiences?

Also, I have heard many planars that have superb imaging and do not sound the least bit "thin". Just like there are horn speakers out there that do not "honk"! I will admit that it takes more effort to get excellent imaging out of a planar, but you also get a greater sense of acoustic space and ambience. A diffuse, well-energized reverberant field is desirable in the concert hall, and in the listening room as well. Again, this from published research.

I gotta ask one clarification. I'm not clear on just what the "ONE advantage" of planars is that you concede. Hey, I gotta trumpet and celebrate any little point in our favor here!!

Hey Sean, I'm having a blast. Thanks so much for writing back. Like you, I invite reply from anyone who wishes to offer correction or a differing point of view, and I will try to offer them the same respect you have.

Kindest regards,

Duke

Point conceded, Frap - a first-class brace of 12's or 15's will indeed outslam a big panel.

I agree with you that very good results seem to come from running the panels full range and then using a low-Q sealed sub to add the ultradeep bass. This preserves all the superb pitch definition the panels have to offer. The REL's come to mind.

Sean, I have yet to hear an electrostatic or planar magnetic that can displace enough air to give you that solid chest-whump that a big dynamic can. However, a dynamic dipole (using say a dozen or so 12" woofers) can do it.

I don't blame you one bit, Sean, for wanting information on dipoles from source besides some guy selling them. And if I have come across as pushing my product, then I owe you all an apology. I believe in dipoles, and I've tried to articulate their advantages because they aren't common knowledge.

Just for the record, my background is that of an amateur speaker builder, not a salesman. I'm not blowing ad copy at you - I'm telling you things I learned over the course of 20 years of seriously studying and building loudspeakers. My intention was to one day become a manufacturer (which I almost did), but when I encountered a particular speaker I hung up my table saw and became a part-time, in-home dealer.

Sean, if you would like, I can find for you papers published in the Journal of the Audio Engineering Society that are the basis for many of the things I talk about. I didn't want to come across as some kind of name-dropper by tossing out references left and right. And frankly, unless people are really going to look them up, I'd rather not go to all the trouble to dig them out. But I understand your skepticism of claims made by a dealer, so if the references would help please let me know.

Again, I enjoy very much engaging in such dialogue. Thank you, Frap and Sean. Until next time!

Kindest regards,

Duke

Interesting thoughts, Frap. In a rectangular room I generally prefer to place the speakers along a short wall, and to sit well back away from them. To me, this sounds more like what I hear in a concert hall.

I think there's a reason for this - you see, in a concert hall, for everyone except perhaps those in the first few rows, the reverberant field dominates - that is, more sound power reaches the listener's ears via the reflections than direct from the instruments. Typically in a concert hall, the reverberant energy dominates by a huge margin - we still get our directional cues from the first-arrival sound, but the timbre is greatly enriched by the reverberant field (which also gives us the feeling of huge acoustic space). Indeed, the concert hall's feeling of velvety lushness is the product of a powerful, diffuse reverberant field. See Pisha & Bilello in the September 1987 issue of Audio magazine.

When we listen "near-field" (say a few feet from the speakers), the direct sound dominates. Proponents of nearfield listening claim that the recording itself already has all the reverberations you need, and any added by the listening room are distortions. The problem is, the ears expect for the reverberations to come from all around, not from the two points of origin of the direct sound. So while nearfield listening can give you holographic imaging (including depth), I get more of the "feel" of live music by sitting much farther back, where the reverberant field is dominant, and also where small head movements don't cause significant image shifts.

There is something of a tradeoff relationship between precise soundstaging and a rich sense of ambience - in concert halls as well as in listening rooms!

In my demo room, I have two listening positions - a single chair about 8 feet back, and then a couch about 18 feet back. The soundstaging is more holographic up front, the ambience richer in back. Probably a bit more than half of my customers prefer to listen from the chair, up close, while I usually prefer to listen from the couch - but (just to muddy the waters a bit) it does vary from recording to recording. C'est la vie.