Description: Four-way, seven-drive-unit, floorstanding, reflex-loaded loudspeaker system. Drive-units: 1" (25mm), ferrofluid-cooled, inverted titanium-dome tweeter; two 6.5" (170mm) plastic-cone midrange units; 12" glass-fiber-reinforced pulp-cone upper woofer; 15" pulp-cone lower woofer; two rear-firing 1" metal-dome tweeters. Crossover frequencies: 120Hz, 3kHz, 12kHz (rear tweeters). Electrical crossover slopes: first-order, 6dB/octave woofer/midrange; second-order, 12dB/octave, midrange/tweeter. Frequency response: 19Hz-22kHz ±3dB. Low-frequency extension:…
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Sidebar 1: Specifications
Sidebar 2: Wilson Audio Specialties
During discussions with Dave Wilson when he was setting up the X-1/Grand SLAMMs in my room, I wondered aloud how someone without formal training as a speaker designer could possibly produce the sophisticated and uncompromising products for which his company is renowned. Wilson's own background is based in years of research in the medical engineering field, where reliability and safety standards are second to none. However, when I learned that he was also an enthusiastic audiophile of many years, standing as well as a self-taught recording engineer and…
Sidebar 3: Measurements
Incorporated in this speaker's title is the term "Super Linear," which implies low distortion. It certainly sounded as if it should have low distortion, but would the X-1/Grand SLAMM really measure better than typical moving-coil designs? Characteristic distortion measurements in loudspeaker reviews are often made at more than one sound-power level: 86dB at 1m is a typical midrange sound level on music and natural speech; 96dB is quite loud—loud enough for most purposes, in practice; 100dB is quite often the upper working limit for miniature speakers; while 106dB…
My inner engineer keeps whispering that flat curves must sound better; but it ain't necessarily so. Judgment of the semi-anechoic laboratory frequency response of a loudspeaker must be tempered by assessment of the performance over a range of forward axes. You need to judge the energy uniformity seen in the forward solid angle which encompasses the listener and the relevant reflective boundaries. The overall energy response as reflected in the Room Averaged Response is also most useful.
A loudspeaker's single axial response cannot, therefore, fully reflect its perceived "sound." Yet…
Okay, back to equipment racks and resonance tuning.
Let's say your components are snugged into one of those ubiquitous Target racks I used to use myself, or a similar round- or square-section hollow-tube rack with MDF shelves supported at their corners by tabs or push-in paddles. Shut your system down, remove the component on the top shelf, and rap the shelf with your knuckles. Not very reassuring, is it? Not only is the shelf resonant, but being supported at only its four corners makes it rattle'n'jump when you rap it.
Back in February's "Fine Tunes," I suggested making your own…
When I reviewed VTL's MB-750 monoblock amplifier in the December 1997 Stereophile (Vol.20 No.12), it was a transitional time for the company. Luke Manley had recently taken it over, and he and his wife and partner, Bea Lam, were aggressively retooling. They introduced new business systems, including rigorous inventory and quality control; rebuilt VTL's dealer network around top-rank dealers; and systematically upgraded the products themselves to improve their consistency, reliability, manufacturability, and performance. VTL's goal, Luke explained to me at the time, was to build amplifiers…
"But the biggest thing is the precision regulated power supply. Along with maintaining correct bias, the way to keep tubes at their optimum operating point is by regulating the high tension power supply. Normally, the voltage begins to sag as power is pulled out of the supply, and B+ voltage might drop by as much as 10%. The S-400's supply never varies by more than 0.1% or 0.2%.
"The S-400's supply is essentially a power amp in itself. The regulation requires six 3300µF capacitors and five 800V, 30A MOSFETs. They've got tremendous transconductance, so when the caps dump, the regulation…
Sidebar 1: Specifications
Description: Tubed stereo power amplifier. Inputs: 1 pair unbalanced (RCA), 1 pair balanced (XLR). Outputs: 2 pairs binding posts. Tube complement: two 12AT7, two 6350, twelve 6550C (KT88). Rated power output at <3% distortion: 300W into 8 ohms (24.8dBW), 400Wpc into 4 ohms, tetrode (23dBW); 150Wpc into 8 ohms (21.8dBW), 200W into 4 ohms (20dBW), triode. Frequency response: 10Hz–125kHz, +0/–3dB. Output impedance: ca 1–1.5 ohms. Input impedance: 57k ohms. Input sensitivity: 2.2V for full output. Power consumption: 480W at idle, 2500W at full power.
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Sidebar 2: Associated Equipment
Digital Sources: Burmester 001, Cary CD300/303 CD players.
Analog Source: VPI TNT HR-X turntable & tonearm, Lyra Titan cartridge; Sutherland PhD, Ensemble Fonobrio phono stages.
Preamplification: VTL TL-7.5, Sutherland Director, Placette active line stages; Placette Remote Volume Control, Sonic Euphoria PLC passive line stages.
Power Amplifiers: VTL Ichiban, Simaudio Moon Rock, Mark Levinson No.20.6 (all monoblocks).
Loudspeakers: Thiel CS6.
Cables: Interconnects and speaker: Nirvana S-X Ltd., Audience Au24, Nordost Valhalla, Silversmith…
Sidebar 3: Measurements
For logistical reasons, I measured a different sample of the S-400 to the one BD auditioned. My sample had been used at the Home Entertainment Show last May and came to me following the Show, before its return to New York dealer Sound By Singer.
With its choices of unbalanced and balanced inputs, and triode or tetrode output-stage operation, VTL's S-400 is four amplifiers in one. To make measuring its performance feasible, I carried out complete sets of tests for both triode and tetrode operation in balanced mode, spot-checking some measurements via the…