God is in the Nuances Page 10
"Which explains, by the way, why certain old loudspeakers with a very high sensitivity and thus a very high precision in the rendition of dynamics, especially of very small signals---just like certain tube amplifiers with very simple circuits---and despite more or less obvious colorations and the omission of an octave or two, manage to reproduce with disturbing fidelity all the emotional intensity of an interpretation. Which should give our designers something to think about, and convince them that the musically more important kind of dynamics is that which loses itself in silence (footnote 14), not the kind that turns into noise."
Learning from our ancestors
I think it is no coincidence that Jean-Marie Piel would turn to "old" technology for inspiration. Some old gear can still hold up surprisingly well today. The American press, with the occasional exception from Sound Practices, has concentrated so far on triode amplifiers as "the new thing." Loudspeakers receive a lot less attention. I have given my opinion on triode amps and their qualities in this magazine (footnote 15), and of late there have been a number of articles on single-ended triodes. Instead of further amplifying this addiction to triode amps (which, contrary to what you may have been led to believe, are no panacea; if we have to talk about amps, I'd prefer to emphasize the role of the preamp), let me concentrate first on another piece of the hi-fi chain in need of a reevaluation: the loudspeaker.
Let's start with an unexpected item of old technology: vintage tube radios. Those of the 1940s to 1960s often have an astonishingly good sound quality. The frequency range of their single driver is severely restricted, but they have a magical coherence that more than compensates. All the really good ones seem to have a single-ended tube, not necessarily a triode; an EL86 pentode can sound wonderful in a single-ended topology. (By the way, Jean-Constant Verdier, designer of the best turntable I have ever had the pleasure to hear, has a huge collection of old tube radios.)
One of the more intriguing facts about old tube radios is the way they make use of their enclosures. These are not designed to be as acoustically inert as possible, as are most modern speakers, but are allowed to resonate with the music, a character trait shared with many old loudspeakers. The wood panels' size and density are judged so that those inevitable resonances are consonant with the music. Music seems to pass through them unscathed. If you listen to the output of modern speaker cabinets (using an ear pressed to the box; or, for a more dignified approach, a stethoscope), most sound horrible. The sounds emitted by an Altec Voice of the Theatre's cabinet can be much less objectionable (footnote 16).
Another facet of this phenomenon is the way the room is energized by a loudspeaker using a noninert enclosure. Sound, especially the lower frequencies, is radiated from the entire surface of the box, not just the chassis. This seems to accomplish much the same thing as using multiple drivers or dipoles. One of the most convincing loudspeakers I have ever heard is built according to principles having more to do with the making of musical instruments than with orthodox hi-fi loudspeakers.
Another aspect of old loudspeakers is that they tend to have dimension ratios diametrically opposed to those of modern speakers. Modern speakers typically have very narrow fronts, the enclosed space needed for a reasonable bass-driver alignment being found by making speakers tall and deep. By comparison, old loudspeakers tended to be wide but shallow. This has profound consequences for sound dispersion. Once the baffle is narrower than the wavelength of a tone emitted by one of its chassis, the emitted sound is no longer reflected by the baffle and projected by the speaker toward the listener, assuming the listener sits in front of the speakers; instead it will travel around the speaker and radiate to all sides.
Typically, low and middle frequencies are dispersed quite evenly in the room, while high frequencies are projected in a narrow angle. Thus the energy concentration at the listener's point in the room is tipped toward the high frequencies. Many designers compensate for this by introducing a slight clockward tilt in the speaker's frequency response, a gentle fall from low to high frequencies. The indirect sound, which in nondead listening rooms makes up an important part of the overall gestalt of the sound, the perceived tonal balance, will then be perceived as lacking in high-frequency energy. The speaker sounds dull. To prevent this, there will often be an on-axis rise in the tweeter's top octave. Unfortunately, two wrongs don't make a right. Old loudspeakers, which have wider baffles, project more energy at lower frequencies toward the listener and have a more natural balance between mid and high frequencies without that tilt in the frequency response.
Footnote 14: To quote Keith Jarrett (Stereophile, April 1994, Vol.17 No.4, p.59): "Silence is where music comes from." Jarrett meant this from an artistic point of view, not from a sonic one, but the parallel is striking.
Footnote 15: Stereophile July 1994, Vol.17 No.7, p.19.
Footnote 16: Depending on the specific model and the execution of the cabinet. There are bad ones and good ones.