Most people who now listen to tube amplifiers began with a transistor amp, and know from experience that a tube amp of a given measured power output sounds louder than its nominally identical transistorized equivalent. The unofficial consensus is that you need two to four times the transistor power to achieve the same loudness as you would using tubes. In other words, given the (subjectively) undistorted sound level a 25W (footnote 1) tube amplifier can provide, if you want the same loudness from solid-state technology you would have to replace it with at least a 50W transistor amp (footnote 2).
One of the challenges I faced in optimizing the performance of the Thiel CS7.2 loudspeakers that I reviewed in February 2000 was controlling and tuning their interaction with my listening room. Intuition, experience, trial and error—all came into play, as did several of the procedures and calculations covered by Jonathan Scull in his "Fine Tunes" column.
This series of articles is based on a paper presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint, "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, www.aes.org, offers a secure transaction page for credit-card orders.
This series of articles was initially written (in slightly different form), as a paper presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint, "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, www.aes.org, offers a secure transaction page for credit-card orders.
This series of articles was initially written (in slightly different form), as a paper presented at the 103rd Audio Engineering Society Convention, New York, September 1997. The preprint, "Loudspeakers: What Measurements Can Tell Us—And What They Can't Tell Us!," AES Preprint 4608, is available from the AES, 60 East 42nd Street, Room 2520, New York, NY 10165-0075. The AES internet site, offers a secure transaction page for credit-card orders.
Because I'm suspicious of just twiddling knobs to make the sound "nice," I didn't rely solely on my ears when I used the Z-Systems rdp-1 that I review elsewhere in this issue for speaker and room contouring. Instead, I used the ETF speaker/room-analysis software from Acoustisoft to help me manipulate the equalizer properly. This program can measure the first-arrival, on-axis speaker response, as well as the room response with its early and late reflections and its resonances.
Over the years as a reviewer, I have tracked the swings of opinion and popularity of various audio ideas and technologies. Amid a sea of advanced designs that achieve powerful technical performance and laudable specifications, I'm reminded of a major blind listening test of 18 power amplifiers that I set up for the long-since-defunct UK magazine Hi-Fi for Pleasure back in 1975. We had "advanced technology" then: the transistor amplifier had matured and was well accepted by audiophiles. Prices of the review samples ranged from $300 to $3000 (equivalent to $1000-$10,000 in today's dollars). The auditioning sessions were graced by the presence of many industry leaders, among them the late Spencer Hughes of Spendor, Julian Vereker of Naim, Philip Swift then of Audiolab, Alan Harris then of retailer Audio T., Bob Stuart of Meridian, and John Wright of IMF (now TDL in the UK).
High-quality digital audio systems require that all digital interfaces in the signal path exhibit signal transparency. The widely adopted AES/EBU and S/PDIF interfaces have been criticized for a lack of signal transparency; here we (footnote 1) address possible problems with such interfaces and present methods for improving the interface standard.
A thorough exploration in a magazine article of such a pervasive and complex topic as vibration control in audio systems is next to impossible; vibration and sound are so intimately bonded that it would be very easy to extend this discussion to just about any area of interest in audio. My intention here is simply to lay a foundation for understanding the basic mechanical forces affecting our quest for improved sonic fidelity, and in the process provide the tools for anyone to achieve good, practical vibration control in his or her system.
Editor's Note: The matter of whether—and if so, how—speaker cables and interconnects can affect the sound of an audio system has vexed the audiophile community since Jean Hiraga, Robert Fulton, and others first made us aware of the subject in the mid-1970s. Most of the arguments since then have involved a great deal of heat but not much light. Back in August 1985, Professor Malcolm Omar Hawksford Ph.D (of the UK's University of Essex and a Fellow of the Audio Engineering Society) wrote an article for the British magazine Hi-Fi News & Record Review, of which I was then Editor, in which he examined AC signal transmission from first principles. Among his conclusions was the indication that there is an optimal conductor diameter for audio-signal transmission, something that I imagined might lead to something of a conciliation between the two sides in the debate. Or at least when a skeptic proclaimed that "The Laws of Physics" don't allow for cables to affect audio performance, it could be gently pointed out to him or her that "The Laws of Physics" predict exactly the opposite.
As mentioned by two readers in this month's "Letters," amplifiers are used to drive loudspeakers but are almost exclusively measured into resistive loads. The reasons for this are twofold: 1) real loudspeakers both produce neighbor-annoying sound levels and tend to break when driven with typical amplifier test signals; and 2) the question as to which "standard" loudspeaker should be used is impossible to answer---at least the conventional resistive loads are consistent and repeatable.
If you read Stereophile regularly, you already know that all audio equipment does not sound the same. But did you know that a given piece of gear can sound better or worse depending upon how it's set up and used? With a few simple tweaks, you can bring out the best in your audio system.
Although I still haven't been able to listen to the Cary Audio Design 805 single-ended tube monoblocks that Stereophile praised so highly a year ago (Vol.17 No.1, p.104), I've recently auditioned many other tubed single-ended designs. Undeniably, a good SE design has a distinctive quality of harmony and atmosphere in the midrange that reaches well beyond the average attainment of its solid-state brethren.
Time to 'fess up: How many of you actually read the "Measurements" sections of Stereophile's equipment reports and understand what's being measured, and why? I suspect that many readers skip over the technical assessment of the reviewed product and make a dash for the "Conclusion."