Unusually, I found the CS.5 to be a little more sensitive than its specification suggests, at about 89dB/2.83V/m (B-weighted). Its impedance, however, is, as with all Thiels, quite demanding, as can be seen by taking a gander at fig.1. Remaining below 6 ohms pretty much throughout the bass and midrange, it drops to a minimum value of 3.3 ohms at 200Hz. It does stay higher in the treble, however, and the electrical phase angle (dotted trace in fig.1) is generally lowish. But "8 ohm-rated" A/V receivers should still be shunned by Thiel owners if "cheap-amplifier…
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Fig.4 shows a similar set of dispersion curves, this time in the horizontal plane. The '.5's output is maintained across the band to about 20 degrees off-axis. Beyond that angle, a cancellation notch appears in the low treble, and the high treble falls off more rapidly than is usually seen with a 1" dome tweeter. It is difficult to predict the subjective effect of such behavior. I suspect that in all but very dead rooms, the mid-treble flare at the bottom of the tweeter's passband will to some extent compensate for what might otherwise be too polite a tonal balance.
Fig.4 Thiel CS…
In the fall of 1982, I had just become the Editor of the English magazine Hi-Fi News & Record Review. Hi-fi was in a state of flux. The Compact Disc had just made its debut in Japan, but the British and American launches were six months and a year away, respectively. The Linn orthodoxy prevailed about the role of the source in system performance, but there was no agreement about what was and was not important when it came to enhancing the musical experience. "Objectivists" insisted that amplifiers and even loudspeakers had pretty much reached a design plateau where no further improvement…
Compared with the Stereophile-owned pair of Mark Levinson No.20.6es that reside in my listening room, the Krell '50S had a noticeably less extended, weighty bass. This is hardly surprising, considering the Levinson monoblocks have fully regulated output-stage power supplies and cost five times as much. What did surprise me was that the KSA-50S had a more liquid-sounding midrange. Eric Clapton's rather dead-sounding vocal on "Motherless Child," from From the Cradle (Reprise 45735-2), was more palpable, more solid. The difference was analogous to that between, say, Kodak Tri-X film and Ilford…
Sidebar 1: Specifications
Description: Solid-state stereo power amplifier. Specified output power: 50W into 8 ohms (17dBW), doubles with each halving of load impedance down to 1 ohm. Maximum output voltage: 75.8V peak to peak, 26.8V RMS. Maximum output current: 60A. Frequency response: not specified. Distortion: 0.018% at 1kHz; 0.18% at 20kHz, full power. Signal/noise ratio: >100dB. Input sensitivity: 1.34V RMS. Gain: 26dB. Input impedance: 47k ohms.
Dimensions: 19" W by 14.25" D by 8.5" H. Weight: 52 lbs (net).
Serial number of unit reviewed: 31-10530.
Price: $3300.…
Sidebar 2: System
My digital front-end consisted of a Mark Levinson No.31 CD transport and an Aiwa portable DAT recorder, both driving an HDCD-equipped Mark Levinson No.30.5 via either a Sonic Frontiers UltraJitterbug or an Audio Alchemy DTI•Pro (original Star DSP version with v2.7 software) (footnote 1). My real-world digital source was a Parts Connection Assemblage DAC-1 processor. Digital datalinks included Madrigal, AudioQuest, and Illuminati AES/EBU cables and ASM Labs Mamba ST optical fiber.
The phono front-end consisted of a Linn Lingo'd LP12 fitted with an Ekos arm and…
Sidebar 3: Measurements
I primarily measured the Krell KSA-50S in its balanced mode. Unusually but gratifyingly, Krell provided a full set of Audio Precision measurements for the review sample. (I wish more manufacturers did this!) The '50S's two bias LEDs came on at 8 ohm output power levels of 765mW (red) and 25.2W (blue). Though the KSA-50S's heatsinks were hot following the 1/3-power, one-hour preconditioning test, I could still keep my hand on them.
The KSA-50S's input impedance measured 49k ohms unbalanced, the same for each leg of the balanced input; its output impedance…
Sidebar 4: Follow-up from September 1995 (Vol.18 No.9)
In my review of the $3300 Krell KSA-50S stereo power amplifier last month (Vol.18 No.8, p.165), an obvious point of sonic comparison would have been the $3495 Conrad-Johnson Premier Eleven A that Wes Phillips wrote about in the same issue (p.195). Time constraints, however, prevented that from being possible, hence the appearance of this Follow-Up.
For details of the system used, see my review of the AR 303 loudspeaker. The main loudspeaker used in the comparison was the B&W Silver Signature, although I also used the AR…
I must confess to a certain sentimental affection for Magnepan products. An early version of the Tympani did more to rekindle my interest in audio than any other speaker I can think of. In a world which seemed doomed to finding out just how small and dull it could make acoustic suspension boxes, the Magnepans reminded me that speakers could produce a large open soundstage, real dynamics, and musical life.
Both box speakers and electrostatics have gotten far better since that time, but Magnepan has continued to steadily improve its planar speakers. It also has introduced some superb ribbon…
There were very slight problems apparent in the transition from ribbon tweeter to planar midrange. They were far less apparent than with all but a handful of cone speakers, and compensated for by very wide dispersion, and a midrange sound which was open and live without making the listener feel the usher had just dragged him into the front row. The overall timbre was excellent, with no change from the midrange up to the limits of my hearing (and that of assorted family females).
Getting the best transition from midrange to bass, and overall bass energy levels, required careful amplifier…