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Anti-Node: Active Room-Acoustics Correction

Recently, I assessed four disparate room-correction systems based on digital signal processing (DSP): Copland DRC205, Lyngdorf Audio RoomPerfect, Velodyne">http://www.stereophile.com/musicintheround/1105mitr">Velodyne SMS-1, and Meridian">http://www.stereophile.com/musicintheround/706mitr">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.

Heavy Load: How Loudspeakers Torture Amplifiers

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.

Hot Stuff: Loudspeaker Voice-Coil Temperatures

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.

Wayward Down Deep

The audio diaspora is split on the subject of bass. Some audiophiles—surely the majority—consider the reproduction of low frequencies purely in terms of the weight and drama it adds to sounds with significant bass content. Others—the generalists—take a much wider view of the significance of extended bass response, noting that an audio system's ubiquitous high-pass filters are unusual in Nature and suggesting that this is one of the factors that separate, at the fundamental level, live sound from its poorer reproduced cousin. When John Atkinson wrote on this subject more than 10 years ago (Stereophile, November 1995, "As">http://www.stereophile.com/asweseeit/75">As We See It"), he quoted a memorable line by Kal Rubinson that encapsulates this latter view: "Something in Nature abhors a capacitor."

Euphonic Distortion: Naughty but Nice?

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.

Measuring With MLSSA

Wouldn't you just know it. As soon as I decide on a formal regime of measurements to accompany Stereophile's loudspeaker reviews—see Vol.12 No.10, October 1989, p.166—along comes some hot new technology that changes everything. Robert Harley reported in last month's "Industry Update" column how impressed he and I were with the new MLSSA measurement system from DRA Laboratories.

Copying and Sharing Recorded Music (The Dos and Don'ts of Copyright Law)

The introduction in 1982 of the compact disc ushered in the age of digital audio. Audiophiles now have lots of new digital toys and technologies at their disposal, including SACD, DVD-Audio, MP3 players, hard-drive–based CD players, and digital equalization and room correction, to name a few. Videophiles have similarly benefited from digital technology, with an armamentarium that includes high-definition television, DVD-Video, Blu-ray, HD DVD (the latter two still on the horizon), DLP, LCoS, and D-ILA, among others. Action-based films have also benefited from breathtaking, digitally enhanced special effects. Even those of us who still prefer LPs must acknowledge—reluctantly, perhaps—the incredible impact that digital has had on our hobby (footnote 1).

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