Controversy: The Single Speaker Dem Myth Page 2

Alvin Gold responds
It's not often I take up arms as a result of what I read in the hi-fi press, but there are moments. When I am told that all competently designed amplifiers used within their input/output limitations sound the same, I see red. And then there's this business about single speaker demonstrations (SSDs). . .

The reason I see red here is simple—I actually spend a lot of time listening to music using hi-fi equipment, and my ears tell me that SSDs work. BS seems content to use paper logic to prove that they don't, apparently without reference to any practical experimentation. Thought experiments conducted in ivory towers have their place, but as we are dealing with such complex, interwoven variables, it would need a computer model and a lot of data to quantify the problem adequately. Drawing conclusions comes even later in the process.

I'm not above thought experiments myself, it's just that I know their limitations. Although all objects, including walls and ceilings within a listening room, inevitably have an effect on the reproduced sound, there are different classes of interaction in volved. Some are common to all systems, those caused by the floor for example, and others tend to be there in one form or another as a result of furnishings and so on.

To a first approximation, these environmental effects are relatively linear: if they involve storage and re-radiation of the sound, they do so at very low frequencies (2–3Hz for a structure like a wall for example), or the extra path lengths involved introduce delays that tell the ear/brain that what they are hearing comes from the room, not the original sound. Alternatively, we're talking about the effects of a table or other item of furniture where resonant effects are probably very well damped.

In acoustic terms, boxes and loudspeakers cannot be directly compared. A box may have little effect for the reasons given, or it may indeed have an effect which says to the listener that "there is a box here that is modifying the sound." Big deal. With transducers, however, what we're dealing with are not linear or simple effects; but highly reactive, frequency-selective ones; that can result in a surprisingly large output from an undriven loudspeaker when measured with a voltmeter (yes, I've done it).

Presumably the loudspeaker, thus wound up, releases this energy, mostly of it near its fundamental resonance and smeared over a period of time. It's the selectivity of this mechanism to frequency and temporal aberrations that marks it out as important. Such distortions in the soundfield are undoubtedly quite difficult for the ear to sort out.

I have noticed that undriven panel loudspeakers seem to have much less of a negative effect on the sound of a system than most box speakers. This runs contrary to BS's assertion that the larger the obstacle, the greater the effect; and it reinforces the idea that it's a resonance problem, probably associated with the fundamental driver resonance when mounted in a box, that's at the root of the observations that led to SSDs. Diffraction is hardly a candidate for "severe boxiness" as Bill Sommerwerck suggests; much more likely is that the boxiness comes from the usual source of boxiness in loudspeakers—the combination of a drive-unit mounted in a box!

Some of the other points in BS's article are either spurious or just plain wrong. The one about stereo listening is a good example of the latter. We're stuck with two loudspeakers for stereo whatever happens. More to the point, loudspeakers that are in a circuit do not have the same effect on the sound as undriven one: a driven loudspeaker is effectively shorted by the amplifier, and is a much stiffer and well-damped structure. It will respond in quite different ways in a radiated soundfield than an undriven speaker. I know of one dealer who inserts a wire shorting link into all loudspeakers not in use for precisely this reason.

To say the IT ignored the stereo problem is quite fallacious. I personally heard him make a semi-ironic remark at the Chicago CES about 3–4 years ago to the effect that multi-mike recordings don't sound as good as purist ones because of the number of transducers in the recording room! He even made a similar comment about mono vs stereo. And if you want to talk about the very special qualities of some old mono recordings . . .

Far be it from me to defend IT. I haven't done so for a long while, and the last time I was up in Glasgow we spent 24 hours at each others throats about Linn's awful Index loudspeakers—yes, I've listened to them rather more thoroughly since I wrote about them in Vol.8 No.3—and other topics. But his ideas about SSDs (as I understand them) bear repeating.

The point of SSDs is simple: they are designed as a dealer aid. Now it may be argued (as James Michael Hughes has done in the UK) that they are counterproductive for 101 different reasons, or that the effects are small in absolute terms. On the latter I'll concede the point, though small differences are what hi-fi is all about. Moreover, the kind of distortion eliminated by SSDs (time-smearing distortion) is an important one.

As far as I know, no rigorous analysis has been done, but it's easy to show empirically that additional transducers in a room adversely affects the sound of a good system—be they loudspeakers, telephones, or cassette recorders. The effect tends to be particularly insidious, because it is manifested as a loss of pitch and timing integrity quite distinct from the classes of effects that arise from furnishing and room boundaries. Tonal and other more commonly anticipated effects are not usually severe, so the degradation is sometimes missed first time round by the less experienced listener.

We're talking now about quite subtle differences, but high fidelity is all about quite subtle differences. No one, not even IT, as far as I know, has suggested that all transducers other than the driven ones should be excluded from listening rooms. The very sound of an orchestra is partly determined by similar interactions between highly resonant instruments.

The point is, however, that many listeners already have listening rooms that approximate SSD environments. It's only comparator-equipped dealers that don't. So why not try and achieve the same as the home situation when a dealer demonstrates his products to the public? This way, the sound is as representative as it can reasonably be made at the point of sale, and the equipment is given a chance to do its damndest.

My personal position on this is that when reviewing it's essential to hear what the product being tested is doing, and that reviewing under SSD conditions is clearly the best and safest way to achieve this end. At best, extra transducers will have an unpredictable effect, so why not eliminate what is after all an unnecessary variable? For this reason, I have auditioned loudspeakers under SSD conditions for a number of years—but I wasn't foolish enough to subject myself to the not inconsiderable inconvenience without first establishing that the differences were not merely audible, but also musically important. You can pontificate until the cows come home, but with a good, well-optimized hi-fi system, the facts quite literally speak for themselves.

By the way, Bill Sommerwerck, grandma is quite adept at sucking eggs. Naturally, serious listening is not done with a coffee table interposed between myself and the loudspeakers. I have a wife, you see, and although she tolerated a Krell and a pair of Maggies, eventually the coffee table has had to live in the room between times. You might like to know that the room has been switched around. The loudspeakers sit just forward of the bay, and the (now round) coffee table is to one side of the hot seat.—Alvin Gold

J. Gordon Holt adds some thoughts
I agree with AG that BS shouldn't pre judge SSD until he tries it, but I also agree with BS that other speaker boxes in the room probably will have an effect, and probably a detrimental one, on the sound. But so, of course, will any other object in the room, including people. (Why not a people-less demo, for the ultimate purity?)

It appears to me that both views are partly right and partly wrong. BS, for example, overlooks the fact that an enclosed volume with a hole in it is a Helmholtz radiator, which will readily absorb energy from the surrounding air at its resonant frequency. AG reports only that the sound is better when other speakers are out of the room, without ascertaining whether this is due to the effects of their undriven cone surfaces or of reflection and refraction from the outer surfaces of their enclosures. Both, it seems to me, overlook the fact that the smaller the offending object, the less effect it is going to have on anything, and that there will be a point somewhere down the line where its effect will be too small to be detectable by even the keenest ears.

IT's stand on this appears to be based on a common misconception: namely, that vibration of an undriven speaker cone creates spurious sound waves in the room, just as though that speaker were being driven at low level by another signal source. It doesn't, because it isn't.

The amount of vibration induced in an undriven speaker cone from impinging sound waves is in fact significant, and can be easily felt with the fingertips. The amplitude of those vibrations is similar to that that would be caused by an electrical signal in the tens of millivolts range feeding that speaker, and would be clearly audible if no other speakers were playing. But the amplitude of these induced vibrations is much lower than those of the main, driven loudspeakers, because the latter are creating all the air-pressure variations in the room, while the former is being acted on by only a very small percentage of those variations.

Contrary to one's gut feeling about this, these vibrations of the undriven cone are not being re-radiated, because they represent a loss of energy from the soundfield, not a contribution to it.

That undriven cone has mass, and it takes energy to set any mass in motion, so practically none of the sound-wave pressure reaching that cone will ever leave it. Virtually all of the sound-pressure energy will have been used to move the mass of the cone. The only re-radiation that would occur from that "undriven" cone would be due to the release of stored-energy resonances from it after the cessation of air-pressure-induced motion. And in any loudspeaker we would give house room to, that stored energy should be more than an additional 50dB lower in amplitude below that of the ! cone vibrations which stored it. It is exceedingly unlikely that they would be audi ble, even to AG.

It is much more likely that the audible effects of other speakers in the room are due to reflections and refractions from the enclosures, plus their behavior as Helmholtz radiators. It is also obvious that, the smaller the volume and the smaller the hole, the less effect either is going to have; below a certain magnitude, the effects will be imperceptible.

For this reason, the idea that a telephone or a cassette recorder could affect anything at all strikes me as bizarre. Certainly, their presence is going to cause a change in the soundfield in the room, but I cannot believe that anyone could hear that change unless the object in question is suspended from wires, a foot in front of his head. But we are speaking here of common sense.

Or are we?

Incidentally, a frame-core room wall has effects far above the 2–3Hz cited by AG. Just pound on one and listen to the sustained thud it produces. That "thud" will usually be between 25 and 40Hz, and the resonance which causes it will absorb, not add to, a speaker system's LF output.

There is, it seems to me, enough justification on scientific grounds to assume that other loudspeakers in a room will affect the sound of the main ones, and to conclude that SSDs are probably a good idea. I would hesitate to assert, though, that MSDs (multi-speaker demos) have enough detrimental effect to swamp the enormous differences between competing loudspeakers, and that in-store auditions are still of value even with other loudspeakers present. But any system chosen from a MSD is likely to sound better under the more ideal SSD conditions at home.—J. Gordon Holt


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?