Harley: What do you consider important in music reproduction? Tiefenbrun: Oh, God. That's a great question. The cop-out answer is to say "fidelity."
Music is an international language of feeling and emotion. And all people respond to music in the same way—hard as that is to believe. To me, what's important is to communicate the emotional message. A hi-fi system above a certain threshold can begin to do that, and enable the listener to respond to the merits of a performance and the message of the composer. That's the goal.
Music does so many things, doesn't it? It's…
When J. Gordon Holt founded Stereophile in 1962, it was very much the outsider. Compared with the mass-market magazine of which he had been Technical Editor, High Fidelity, Gordon's Stereophile was the very model of an "underground" publication, with a publication schedule as irregular as its production values were inconsistent. Its writing was from the heart, however. A third of an audio century later, High Fidelity is long gone and, much to the surprise of those of us who work on it, Stereophile appears to be regarded by some as the new Establishment in audio publishing (footnote 1).…
The Model Four is the largest model in KEF's current Reference series of loudspeakers, discounting the R107/2 Raymond Cooke Special-Edition (reviewed in a follow-up in October '95). It's also the largest KEF model that uses their Uni-Q® loudspeaker configuration. When I visited the KEF factory last October with a group of audio journalists from the US, KEF emphasized the importance of Uni-Q technology to their future plans. They consider it proprietary, and intend to enforce the worldwide patents they hold on the design. One look at KEF's current line will be enough to tell you why they're…
The system
The system used in the review of the Model Four consisted of the Denon DP-S1 CD transport, Mark Levinson No.36 D/A converter (the two linked by a Kimber AGDL coaxial digital cable), and a Jeff Rowland Design Group Consummate preamp. Amplification and cables will be discussed in the review. All auditioning took place in my (approximately) 26' by 18' by 11' listening room. Listening
Because I began my auditioning of the KEFs immediately after finishing with the Wilson WITTs, I started by placing them in the same locations the WITTs had vacated, a few feet out from the…
The speakers balance remained a little up-front, but never in-your-face. Solo instruments and voices were surprisingly palpable now, helped by a tighter quality in the mid- and upper-bass. On the Fairfield Four's Standing in the Safety Zone (Warner Bros. 9 26945-2), the solo vocals still sounded a little rich and warm, but only enough to give the vocals an appealingly full-bodied character. On Gordon Lightfoot's If You Could Read My Mind (Reprise 6392-2), the same positive vocal qualities were noted, together with a guitar accompaniment which was sweet, clean, and subtly detailed. Sibilants…
Sidebar 1: Description Specifications: Four-way, six-driver loudspeaker system with coupled-cavity bass loading. Drive-units: 1" (25mm) soft-dome tweeter, 6.5" (160mm) polypropylene-cone midrange unit, 2x6.5" (160mm) polypropylene-cone lower midrange units, 2x10" (250mm) pulp-cone woofers. Crossover frequencies: 2.8kHz, 500Hz, 160Hz. Frequency response: 35Hz-20kHz ±3dB, -6dB at 32Hz. Nominal impedance: 4 ohms. Maximum spl: 118dB. Sensitivity: 92dB/W/m. Amplifier requirements: 50-400W.
Dimensions: 47.8" (1266mm) H by 11.8" (300mm) W by 15.3" (390mm) D. Weight: 108 lbs (49kg).
Serial…
Sidebar 2: Measurements JA measured the KEF Model Four using the DRA Labs MLSSA system and a calibrated B&K 4006 microphone and provided me with the results after I had completed my listening tests.
The KEF's calculated sensitivity measured a very respectable 90dB/W/m. Though this is slightly below specification, the fact that this figure is B-weighted might explain the difference. Its impedance characteristic is shown in fig.1. With a minimum impedance of 3.2 ohms at about 70Hz, and a notable increase in the phase angle below 20Hz, this is a relatively demanding load. The…
The impulse response on the tweeter axis is plotted in fig.6, the step response in fig.7. The Model Four's drivers are all connected with the same acoustic polarity, though the speaker is not time-coherent. The cumulative spectral-decay or "waterfall" plot is shown in fig.8. This is a very clean result, with noticeably less decay hash apparent across the spectrum than is usually seen. The only significant mode is associated with the on-axis rise above 10kHz.
Fig.6 KEF Reference 4, impulse response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.7…
Wood is not an engineering material. It might look pretty, but it's inconsistent and therefore unpredictable. So we smash cheap wood into sawdust and then glue it all together again to create something that can be machined. This is called medium-density fiberboard, or MDF. We then thinly slice some classy hardwood—hopefully harvested from sustainable sources—and use it to cover the ugly MDF. This might have made sense back when Chippendale was making furniture, but it seems strangely old-fashioned in our age of plastics and composites. I haven't seen wood trim on a TV set for more than a…
The tweeter is arguably the most interesting of the drivers. An original and creative variation on the dipole and tube-loaded themes, the whole assembly is roughly 9" deep and features a fat metal rod behind the diaphragm that's perforated by a logarithmic spiral of thin, differentially tuned pipes. The purpose is to create a flat acoustic impedance at the rear of the tweeter dome while also allowing through some noncoherent treble output to add air and spaciousness. The elegantly tapered rod is located within a rubber decoupling jacket and pokes some inches out through a hole in the back of…
