God is in the Nuances Page 11
Another aspect of old loudspeakers that seems important to me is the drivers they employ. Old loudspeakers are all about pneumatic coupling. When a loudspeaker chassis' membrane is propelled forward by voltage and/or current applied to the voice-coil, the air in front is pushed away. Depending on membrane size and the length and speed of the excursion, the air in front of the loudspeaker will react more or less willingly to the input (the technical term is acoustic impedance). There is a fairly precise point when the air will more or less fail to be impressed by the driver's stimulus, with an inverse ratio between frequency and loudness on one hand and membrane size on the other hand. (Loudness is a function of the air you move; to achieve a greater loudness level, you have to increase either the surface or the excursion of the membrane.)
Put simply, to reproduce a bass tone loudly, you need a fairly large membrane; for a treble tone, a much smaller surface will suffice (in case you wondered why your tweeter is smaller than your woofer). Above a certain frequency, the air will effectively follow the membrane's movements, vibrating forward and backward. Below that point, the air's inertia is too great to be influenced by the driver---compare the effect of waving your hand with waving a ping-pong bat. There is also a point where excursion cannot be substituted for membrane size, because the air will no longer couple efficiently to the driver.
This acoustic impedance stuff is one of the reasons why horns were once so popular. A horn can be seen as an acoustic impedance transformer: The air in front of the driver cannot escape to the sides when stimulated by the membrane, but will faithfully follow the stimulus. By gently broadening the canal through which the sound waves travel, these air movements will be imposed on an ever greater amount of air, until you come to the end of the horn. In a certain sense, the air that is present at the horn's outlet can be seen as the effective driving surface of the horn driver, because it is this air that couples to the rest of the room. The larger the surface, the less excursion is needed to play at a certain loudness level; and in speakers, the less excursion, the better.
A large bass driver needs a large cabinet behind it, which makes it impractical for many people. I think it's no coincidence that the small infinite-baffle speaker was invented when stereo became available. One big enclosure, for mono, can be tolerable enough, but two such behemoths are beyond what most people will tolerate in their living rooms. Fine, I say. Just be aware that there is a sonic price you pay for the small woofer.
There's one other component of the hi-fi chain I want to comment on: the phono cartridge, for those of us who still listen to vinyl. Some time ago I reviewed (for a German magazine) the latest iteration of the EMT cartridge, a design that started out in the early '60s. Listening to this cartridge after a spate of newer designs made me realize anew that certain classic designs (whose number includes the Denon DL 103 and the Ortofon SPU series) have an emotional rightness that speaks powerfully to the heart and soul of the listener, even if his head can discern some not-very-subtle deviations from linearity. The EMT has a much more colored sound than many modern cartridges do. Yet it is a heck of a lot more fun to listen to than those modern, oh-so-flat, tread-carefully designs. When was the last time you read that a cartridge could really get down and boogie?
Yes, I'll listen to the future
Please don't think that I'm anti-progress, anti-technology, anti-digital, or whatever. Far from it. I hate the expense and complication I have to go to to obtain good sound---which to me means satisfying sound: the rigors of speaker placement (a surprisingly accurate first approximation for speaker placement is to put them where they do the most visual damage to a room; that's probably where they'll sound their best), cables that positively invite you to trip over them, the seemingly unstoppable proliferation of small or not-so-small electronics boxes, and so on. My ideal hi-fi rig consists of a small and preferably inexpensive appliance that sits quietly and unobtrusively in some corner of the room, but fills the room with sweet music. Now that's what I'd call progress.
I'm also not saying that triodes are the only way to go. I remain unattached to any specific technology. I would like to see more single-ended transistor amplifiers. These should provide quite respectable specs, a low output impedance, a flat amplitude and phase response, and so on. Judging from my experiences with tube designs, I would caution against the use of parallel transistors in the quest for higher power outputs. Anyway, the compromises inherent in this technology tend to show up much more clearly in single-ended topologies than in circuits that split the signal.
Single-ended designs are necessarily class-A, so they'll never be as energy efficient as I'd like my hi-fi to be. It could be argued that it doesn't matter much on a global scale. I don't yet see a Japanese electronics giant bringing out inexpensive single-ended integrateds, so for the foreseeable future this exciting technology will remain the expensive preserve of the dedicated few. But I have to say that I'd be happier if all of humanity could follow my path to audio truth without vaporizing the polar ice caps. This aspect truly troubles me.
I also have great hopes for the Super Audio CD and DVD-Audio formats. The present CD format, after all, was laid down in the late 1970s and relied on technology that was then cost-efficient to manufacture. If you compare a present-day computer to its late-'70s counterpart, the latter appears to be a relic of the Neolithic. The CD standard seems just as antediluvian when compared with the new digital technologies.
A change in direction?
I'm sure that I've raised more questions in readers' minds with this article than I have provided answers. However, I hope to ignite a discussion that may lead to a better understanding of how sound influences emotion, and how equipment that doesn't get in the way of the emotion can be designed. The High End has become too technocratic, too sure of itself, maybe even a little arrogant. In my estimation, we have only scratched the surface of this whole matter of music reproduction in the home. Some humility would give a more accurate perception of our achievements in this worthwhile field. Personally, I'm usually very unhappy when someone tells what I should and shouldn't enjoy.
In lieu of a conclusion, I offer this observation: There is a paradigm shift underway in the world of music reproduction. For the last 40 years or so, the High End's aim could be summed up in Quad's famous motto: "the closest approach to the original sound." But there is a growing movement underfoot that refuses to adhere to this motto, creating its own instead: the closest approach to the original emotion.