Controversy: The Single Speaker Dem Myth

Bill Sommerwerck: The more intelligent you are, the less you know. I don't mean just the obvious use of "know," where one rigidly holds certain beliefs as absolute. I'm also suggesting that the properly disciplined mind replaces a lot of specific facts with a few generalities.

The inductive process (reasoning from general observations to specific principles) has obvious application to math and science and is just as applicable to such studies as economics or history. And once one understands enough basic rules, deductive reasoning allows one to predict the outcome of a particular set of conditions from a general principle. The predictive quality of scientific and engineering principles gives them their power.

Deductive reasoning can also be used to test the plausibility of observations. For example, if listener L claims that turning the channel selector on her TV to an in-between position improves the sound of her stereo, even with the TV off, listener S may object to that observation as wrong-headed because he cannot think of any mechanism that would change the sound of a stereo coincident with a change in TV channel-selector position.

Most people intuitively understand in ductive and deductive reasoning without knowing their names. They apply these principles to their work, and, as time goes on, their systematic understanding increases. There are exceptions, however, the most obvious one in hi-fi being Ivor Tiefenbrun of Linn Products.

IT (as he is known in the UK) has a reputation in some quarters for citing observations (right or wrong) and following them up with a lot of apparently ill-drawn conclusions. I want to set one of his most serious errors straight, and then show why it is not always a good idea for equipment reviewers to publicly parade their devotion to someone of doubtful authority.

The issue is this business of "single-speaker" listening and demonstration, which has become fashionable in the UK.

The premise: bringing a second pair of loudspeakers into your auditioning room upsets the sound of the pair you're listening so badly that the first speaker's ability to correctly reproduce the timbre of musical instruments is destroyed. This observation is almost surely correct. But IT and his coworkers are so devoid of any real understanding of mathematics or acoustics that they draw invalid conclusions. In fact, they miss the real significance of their observations.

There is no question that adding another speaker does alter the sound. But what conclusion are we to draw from this observation? The one drawn by IT, et al, is that no additional speakers, of any kind, are allowed. This includes any tympanic surface, including microphones, and the transmitters and receivers in telephones!

I cannot recreate IT's line of reasoning, but, given the conclusion, I can make a stab. If another speaker upsets the sound, what distinguishes the speaker from any other object? Easy; it has a vibrating surface. Ergo, all vibrating surfaces are banished from the room. (As Linn puts it, "all transducers, no matter how small".) Does this include phono pickups, the motor in a Polaroid SX-70 camera, and electric lights?)

As most readers will have already seen, this reasoning is incomplete because it ignores a broader principle: how does anything in the room, speaker or otherwise, affect the sound? The sound arriving at our ears is a combination of the direct sound from the speaker, plus sound reflected from and diffracted by other surfaces. Generally speaking, the larger an object and the closer it is to the speakers, the more it affects what we hear. One cannot single out the effects of a speaker's driver diaphragm, while conveniently ignoring everything else in the room!

Imagine a totally absorptive room, containing only a pair of speakers and the listener. Now position a wood box, about the size of a shoe box, a few feet in front of the listener, above his head and to the right. What effects will it have?

At low frequencies (those whose wavelengths are much longer than the dimensions of the box) nothing will happen; sound simply passes around the box as if it weren't there. At high frequencies (wavelengths much shorter than the box), the box both reflects and diffracts sound. (Diffraction occurs when wave motion en counters an obstacle that is comparable in dimension to its wavelength. The wave re-radiates from the edge of the obstacle as if the edge itself were a source of sound.) At intermediate frequencies, there is some combination of reflection, diffraction, and passing-around.

These sounds, of course, reach the listener after the direct sound from the speaker. The delay introduces varying phase shifts between the direct and reflected sound, increasing the amplitude where they are in-phase, and reducing it where they are anti-phase. This upsets the frequency bal ance and changes the phase relationships among the harmonics of musical sounds.

These effects are audible! The change in spectral balance introduces colorations. In fact, our hypothetical wooden box should be audible as an obstruction in the sound field. With music playing, I'm certain that any of our readers could walk blindfolded into this imaginary room and describe the approximate size and position of the box.

Of course, I've picked a deliberately exaggerated example. How about something simpler, such as putting the box in the plane of the listener's ears, and a few feet to the side? That, too, would certainly be audible as a slight change in balance and timbre, and a minor degradation of the image.

In short, it is possible to predict all the effects heard by Ivor Tiefenbrun et al, not by introducing a second speaker, but merely a second speaker box. Is there any significant difference if the box contains a driver? I think not. Some of the incident sound will reflect from the driver just as if it were the surface of the box.

The driver will also be set into motion, re-radiating some of the sound. The spectral balance and phase of the re-radiation will be altered by the mechanical characteristics of the driver. However, most drivers are small compared to the wavelengths they reproduce, so they make a poor impedance match to the air. This means that the incident sound will move the diaphragm little, and that even less energy will be returned to the air. In short, the driver has far less effect on the sound field it is immersed in than the box which holds it.

Besides: Who listens to a single speaker?! Almost everyone has stereo. If bringing a third speaker into the room degrades the sound, then why doesn't the second speaker of a stereo pair foul up the sound produced by the first speaker?

In fact, the speakers in a stereo pair do mutually interfere. Visiting your friendly neighborhood audio saloon you probably see three to five pairs of speakers arranged in a single row. If you play a pair with whose sound you're familiar, you should notice that it is suddenly afflicted with severe boxiness and noticeable colorations. Why?

It has been known for 40 years that the edge of a loudspeaker enclosure does a great job of diffracting the sound produced by the drivers. One way to minimize this diffraction is to make the front panel of the speaker as narrow as possible, which tends to keep diffraction effects out of the passband of the driver. When a speaker system is set flush with a half-dozen other systems, the front panel suddenly becomes very wide, and the diffraction effects move down into the midrange. Getting the pair as far as possible away from any other surface produces the best sound.

Although the effects are not as pronounced, exactly the same thing happens between...the two speakers of your stereo pair. The larger the speakers, the worse the interaction.

The side-effects of this interaction can be minimized by covering the speaker with acoustically absorbent material. Several firms, notably Infinity and Acoustic Research, have layered their front panels with felt or polyfoam, with the intent of reducing diffraction and re-radiation effects. It may have not occurred to them that this would also reduce coloration caused by sounds emanating from the other speaker.

I said earlier that we would examine what happens when reviewers endorse the principles of dubious authorities. I'm thinking specifically of the article in the March 1984 issue of Hi-Fi News & Record Review, which shows the listening set-ups of their reviewers. One in particular says ". . . this room is a 'single speaker' room—television sets have been banished elsewhere, and the telephone is unplugged and removed when I am listening."

In a sketch of the room in the article, you can note the "low table" in front of the listening position. Egad! The speaker's output will reflect from the table, combining with the direct sound to chop holes in the response, particularly in the midrange! How can one take this reviewer's opinions seriously when he doesn't recognize the fidelity-destroying character of his own setup? His obeisance to the principle of "single-speaker" listening, while allowing a coffee table to corrupt the sound of his system, is a classic example of straining at gnats and swallowing camels.—Bill Sommerwerck

Footnote 1: Nevertheless, if listener L somehow establishes that sonic changes do take place with a change in channel-selector position—we'll leave to another discussion how L might do so—it simply indicates that S is ignorant of the mechanism at work. The history of audio is filled with examples of audible results from impossible or non-existent mechanisms.—Larry Archibald

tonykaz's picture

They sell much better when there isn't any Competition nearby, especially Pro-Ac Tablets or Magnapan or Thiel CS3s.

LINN Kanns were the best sellers ( by far ).

LINN Sara was dismal.

LINN Isobaric ( we called em Isobarbarics ) were poor sellers.

Of course, I'm talking USA sales ( not to Brits who have tiny listening rooms ).

Ivor was a "hoot" to be around, ( especially at Winter or Summer CES Shows ) where he'd have the rooms "stripped" of all kinds of stuff.

I also sold tons of those LINN Sondek LP12s, pre Valhalla Mod. ( 33 only ). It's a very nice table but don't have Wooden Floors, it'll skip like mad. Wood floors need the big heavy VPI ( which has better Bass ).

LINN and Ivor, the Good ole Days!

I saw Ivor giving a 30 minute Talk at an Engineering Event ( a couple of years ago ), he's still going strong and still making the LP12, going-on 50 years now. I promised him that I'd buy something LINN from Overture Audio in Ann Arbor, Mi. ( I haven't yet )-hmm.

Tony in Michigan

ps. I hope for Linn to make a Headphone

volvic's picture

Met him here in NYC a few years ago, told him I still love my Kans which I do, and my Kremlin, Kairn, Ikemi, Klout, Numerik, Majik and Klout. What though made him especially happy was that I still enjoyed my LP-12. I have since purchased a newer one and sold my VPI. Didn't have the heart to tell him that I was considering an SME though. Have come full circle on the LP12, I think it is not perfect, but great for enjoying music and is to the SME.

dalethorn's picture

In the early 70s I had Advents, courtesy of the rave Stereophile review. The sound was quite neutral. In a fairly crowded medium-size showroom in my local town, I heard the Bose 901 for the first time, and was impressed with how close it matched the tonality of the Advents (their other speakers weren't close at all). Sometime later in a large showroom in Cleveland, I had a listen to the Klipschorns, and again was impressed with their neutrality. I had the distinct impression that a properly designed speaker, playing in an appropriate setting (size, furnishings etc.) should sound very much like it will at home. When the showroom setting varies greatly from home, I'd expect it to sound very different.



tonykaz's picture

Good one !

I'll even demo them "one pair at a time" .

Tony in Michigan

tonykaz's picture

....that if we can get the "Source" right the rest of the system will having something good to work with. "Garbage in, Garbage out"

Now-a-days, I'm kinda in the Meridian MQA Boat of getting the Source right. For me, Vinyl has become the Garbage Source ( short of throwing $50,000 at a good Vinyl Source )

Tony in Michigan

volvic's picture

Enjoy your MQA. Listening to Gieseking, Furtwangler and Walter through my new vinyl rigs has rediscovered my record collection, and through smart purchases both rigs cost less than $8500 combined. Plenty of money left for pristine used vinyl. Doubt any streaming offers what I need anyway. Vinyl is resilient.

Gorm's picture

Surely we all know that everything in a listening room makes a difference, the question is which ones are an improvement and which ones must we live with. When I switched the Beethoven Head sculpture I had between my speakers ( I know, a real cliche) and installed a lovely (same sized) wooden Buddha head, the sound was substantially degraded; my wife immediately nixed the Buddha.

Some years ago I heard a demonstration of a speaker pair with,and without, a second unconnected identical set in the room. We all heard a subtle but distinct difference but not in the amount of bass, level of mid range or extension in the treble. After a while we nailed it: the Jazz band we were listening to simply sounded more together, as if they had practiced their craft more. Their overall timing was better sort of like early Linn Sondek 'tables were compared to the rest.

Anton's picture

Everything matters, except for having other speakers in the room.

Everything but that.

A piece of gear's sound is affected by its enclosure, unless it's a piece of Oppo gear crammed into a Lexicon chassis. Then, it makes no sonic difference at all.

Just wait, solo speaker demo rooms will matter again during the next audiophile cycle.

tonykaz's picture

I have a single pair demo room in my home, don't I ?,

don't we all ?

Tony in Michigan

scottsol's picture

All of discussions miss what is, perhaps, the most important fact. Even with many speakers in a room, nobody would have any problem identify the sound of a real voice or instrument in the room compared to the playback of a recording.

gsnorris's picture

This is the only comment on this thread that addresses the music. So much focus on equipment and personalities - a chronic audiophile affliction dating back more than a half century. Why?

Trevor_Bartram's picture

In the late 70s I remember going to a hotel demo of a well renowned direct drive turntable vs the LP12, everything else being equal, the LP12 was clearly far superior. I lusted after that LP12 but being a student, finances dictated I settle for a Dual (still in use til ten years ago). In the 70s and 80s Linn and Naim were synonymous with great British HiFi, despite their eccentricities. IT was the man.

tonykaz's picture

I think you have it right, the LP12 was the beginning of HighEnd Home Audio.

Still, the LP12 was a refinement of the AR Turntable ( which was rather junky by comparison ) which we could up-grade by careful rebuilding.

The LP12 is still worth owning, if only for historical reasons.

Tony in Michigan

austinstereo's picture

Linn Sondek no doubt blazed some trails. Especially in terms of turntables. In decades past, they were ahead of most in suggesting that enjoying music was more important that watts or other specs.

Sure, having other speakers in the room has some effect in terms of resonant ringing. I have long thought that the "single speaker" thing was just dumb. Among other things, if you mono the source, you end up cancelling out some of the ambience, and in many recordings, part of the actual music.

We have had numerous Linn speakers in our shops. Frankly, they would be at the end of a long list of speakers I would consider.

johnebli's picture

The input terminals of a second unused loudspeaker in the room should be shorted together to prevent the diaphram(s) from becoming passive radiator. ;)

James Romeyn's picture

Mr. Sommerwerck,
Suppose three pairs of unused speakers are located in the sound room, but far enough from the listener and speakers in use that the unused boxes do not disturb performance. Suppose the room is otherwise superb, symmetrical, lightly but well treated, and the system is highly refined.

Do you suspect you might hear a difference between unused speaker inputs open vs. shorted, and if so, to what degree?