The chassis of the NAD C370 was hot after the usual one-hour preconditioning period at 1/3 power into 8 ohms, but, at around 55 degrees C, well within the bounds of safety. (The internal heatsinks were much hotter, of course, but these cannot be reached by inquisitive fingers.) The amplifier didn't invert signal polarity, and the maximum voltage gain (into 8 ohms) was a high 39.4dB. Input impedance at 1kHz was 300k ohms and the output impedance across most of the audioband a moderate 0.16 ohm, this rising slightly to 0.19 ohm at 20kHz. This is equivalent to a…
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This can be seen in figs.7 and 8, which show FFT-derived spectra of the NAD's output while it reproduced a 50Hz tone at 1W and 10W, respectively, into 8 ohms. At the lower power level, an entire series of odd harmonics can be seen that effectively disappear at the higher level. Yes, even at 1W, the third harmonic—the highest in level—lies at -80dB (0.01%), with most of the other harmonics at or below -90dB (0.003%). But this still suggests a somewhat inadequate output-stage bias current.
Fig.7 NAD C370, spectrum of 50Hz sinewave, DC-1kHz, at 1W into 8 ohms (linear frequency…
Genesis Advanced Technologies was formed in 1991 to manufacture loudspeakers designed by industry veteran Arnie Nudell, who was responsible, with Cary Christie, for some of high-end audio's highest-performing models when both were at Infinity Systems. The company was acquired a few years back by Gary Leonard Koh and some of his friends, but Nudell remains with the company as Chief Scientist and the company has offices and a production facility in Seattle.
The last Genesis design reviewed in Stereophile was the 500 (in May 1999), which then sold for $11,500/pair. Kalman Rubinson…
Sidebar 1: Specifications
Description: Four-way, floorstanding loudspeaker with powered woofer section. Drive-units: two 1" (25mm) circular aluminum-ribbon tweeters, 4.5" (115mm) titanium upper-midrange cone, two 6.5" (165mm) aluminum lower-midrange cones ("midbass couplers"), three 8" (200mm) aluminum woofer cones. Inputs: speaker level on 4mm terminals, line-level on balanced XLR, LFE line-level on XLR. Output: LFE pass-through on XLR. Frequency response: 20Hz–36kHz, ±3dB. Crossover frequencies: 71–135Hz, 300Hz, 3.6kHz. Nominal impedance: 4 ohms. Sensitivity: 90dB/2.83V/m. Maximum…
Sidebar 2: Associated Equipment
Digital Sources: Ayre C5-xe universal player, Olive Symphony media server; Mark Levinson No.30.6, Benchmark DAC 1, Grace m902 D/A processors.
Preamplifiers: Mark Levinson No.326S, No.32 Reference; NHT Passive Volume Control.
Power Amplifiers: Mark Levinson No.33H monoblocks, Musical Fidelity kW750.
Cables: Digital: Kimber Illuminations Orchid AES/EBU, AudioQuest SVD-4 S/PDIF. Interconnect: AudioQuest Cheetah, Madrigal CZ Gel-1, Ayre Signature Series, Crystalconnect, Canare (balanced); DiMarzio, Canare (unbalanced). Speaker: AudioQuest Kilimanjaro…
Sidebar 3: Measurements
I estimated the Genesis 5.2's voltage sensitivity as 89.2dB/2.83V/m, which is within experimental error of the specified 90dB figure. However, as can be seen from the plot of its impedance magnitude and phase (fig.1), the speaker demands a lot of current from the partnering amplifier. With the tone controls set to their maximum positions (bottom trace), the impedance drops below 2 ohms for most of the lower midrange and briefly in the mid-treble, where the minimum impedance is a low 1.4 ohms at 7.8kHz. More problematic, the phase angle is highly capacitive in the…
In the audio field, the British have traditionally thought "small," scoring hits both with their compact loudspeakers and with medium-priced amplifiers. The continued growth of the audiophile speaker market in the US, however, which favors larger loudspeakers, has at the same time stimulated the research and design of more powerful, excellent quality amplifiers. In their turn, these have placed increased demands on the speakers they drive.
Until 1986, nearly all UK speaker companies shied away from competing head-on with the bigger US loudspeakers, but two models launched last year…
With the electronic crossover—which connects either in the preamplifier tape loop or between pre- and power amplifiers—set to 100Hz, the bass section can be adjusted for absolute level and the best extension in the nominal 20-70Hz range, with a constant Q of approximately 0.4. The 24dB/octave, 4th-order Butterworth crossover slopes are complementary, being obtained by substitution; ie, the low-pass output is obtained by subtracting the high-pass output from the input, and the crossover is DC-coupled throughout, this (unusually) including the high-pass section, which has no series capacitors…
Subjectively, the frequency response stretched from 25Hz to 15kHz, lacking some upper treble sparkle; compared with most big speakers, it was a little too dry in the final bass octave (just as the KEF seemed a little too rich in the same region).
Coloration levels were low, with no perceptible box effects, and just a mild, cone-type, "nasal" thickening in the upper mid. A hint of "sibilance" was also present in the treble. Taken overall, however, the treble was very fine, with high resolution, transparency, and neutrality, free from grain or "zizz." Only if the subwoofer level were set…
Sidebar 1: Specifications
Celestion SL600: two-way, sealed-box loudspeaker with Aerolam (aluminum-honeycomb) enclosure. Drive-units: 1.25" copper-dome tweeter, 6.5" Kobex-cone (PVC) woofer. Crossover frequency: 2.3kHz, second-order, 12dB/octave slopes. Frequency response: 60Hz-20kHz ±3dB, low-end, -6dB at 60Hz in free-space conditions. Sensitivity: 82dB/W/m. Nominal impedance: 8 ohms. Amplifier requirements: up to 120W on program.
Dimensions: 14.5" (368mm) H by 7.75" (197mm) W by 9.25" (235mm) D. Enclosure volume: 12 litres (0.4 cubic feet).
Weight: 11.25 lbs (5.1kg) each.
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