Recently, I assessed four disparate room-correction systems based on digital signal processing (DSP): Copland DRC205, Lyngdorf Audio RoomPerfect, Velodyne SMS-1, and Meridian DRC. I concluded that Meridian's approach—which applies IIR (Infinite Impulse Response) "anti-resonance" filters to suppress room resonant modes, if only partially—was, in many respects, the best. What I particularly like about Meridian DRC is that, unlike the Copland and Lyngdorf processors, its approach to system tonal balance is largely hands-off. Yes, it lightens up the extreme bass a little, as you'd expect, but it doesn't recast the system balance in any way that might prove undesirable. If you like your system's tonal character as it is, Meridian DRC behaves just as you'd want a room-correction system to behave: it quells room resonance effects while leaving the system's essential sound well alone.
As Chester Rice, co-inventor of the moving-coil loudspeaker, once ruefully observed: "The ancients have stolen our inventions." So often, what is painted as new and innovative turns out to be something someone thought of long before. We have a habit of forgetting, and that applies not only to inventions, but to knowledge of other kinds as well.
Headphones get pretty short shrift in much of the hi-fi press, which is puzzlingthe headphone market is burgeoning. I don't know what the equivalent US figures are, but in recent years the UK headphone market has increased by an annual 1520% in both units sold and overall revenue. It's easy to dismiss this as a natural byproduct of the Apple iPod phenomenon, but 20% of the market value is now accounted for by headphones costing over $120; a significant subset of consumers would seem to be looking for quality. When you also consider that many people's first exposure to higher-quality audio comes via headphones, there is ample reason for treating them more seriously.
Bob Stuart, chairman and co-founder of Meridian, will deliver a lecture on active loudspeakers to the UK Section of the Audio Engineering Society in London on Tuesday, July 11. Although Bob has been a champion of active speakers for 30 years, he has, surprisingly, delivered only one previous paper on the subject, at the AES UK Conference earlier this year. In this lecture he will expand on that presentation and be able to discuss the topic more fully with the audience.
If there is one thing I've learned in almost 28 years (ouch) of audio writing, it's that audience reaction is fickle. Sometimes readers will swallow the most contentious pronouncements without indigestion, only to choke on throwaway lines you've invested with little importance. It just goes to confirm that human communication involves senders and receivers, and they aren't always in synchrony.
Until the Recording Industry Association of America hit the headlines in recent years with its antipiracy campaign, the initials RIAA meant one thing to seasoned audiophiles: the vinyl-disc equalization characteristic introduced in the 1950s to standardize what had previously been an anarchy of different EQs. Three decades later, as CD gained ascendance, a large proportion of audiophiles still knew what RIAA equalization was, and a good number of them had some idea or better of what the RIAA EQ curve looked like, and why it was applied.
If anyone ever thinks to compile a list of the 100 seminal audio papers that should be found in every tech-aware audiophile's filing cabinet, Harry Olson's "Direct Radiator Loudspeaker Enclosures" deserves to feature in it. Originally presented at the second Audio Engineering Society Convention, in October 1950, it was published in Audio Engineering in 1951. In 1969—in a rare and certain acknowledgement of its classic status—the AES republished it in its Journal (footnote 1).
In 1977, just as I was about to take my first faltering steps in hi-fi journalism, the UK's Hi-Fi News ran two articles, translated from French originals by Jean Hiraga, that seemed to me and many others to turn the audio world we knew upside down. The second of them, "Can We Hear Connecting Wires?" was published in the August issue and is the better remembered because it introduced many English-speaking audiophiles to the contention that cables can sound different. The earlier article, published in the March issue, was less earthshaking but still an eyebrow-raiser of considerable force. Simply titled "Amplifier Musicality," it was a response to the word musicality being increasingly used in subjectivist circles to describe the perceived performance of amplifiers and other audio components. It was implicit that musicality was a quality not captured by conventional measurement procedures—a lack of correlation that Hiraga's article sought to address.
Why, in loudspeaker reviews, is impedance measured (assuming that the magazine in question bothers to measure anything)? Generally, for one principal reason only: to establish whether the speaker presents an "easy" or a "difficult" load to its partnering amplifier. In the design context, much more information can be extracted from a graph of speaker impedance vs frequency—such as details of the bass alignment, and indications of internal or structural resonances that can be difficult to identify by acoustical measurements. But for a magazine audience, the principal interest in a loudspeaker's load impedance lies in gaining some indication of its compatibility with a given amplifier.
As Hans Christian Oersted, the Danish physicist and founder of electrodynamics, discovered in 1819, an electric current passed through a wire generates a magnetic field. Place that wire close to a permanent magnet and the interaction of the two fields will generate a force. That, in two sentences, summarizes the operating principle of the motor that energizes every moving-coil drive-unit in millions of loudspeakers worldwide. It sounds simple, but—like everything in audio—it isn't.