Jitter
As described in the January 1993 Stereophile (Vol.16 No.1), we are now able to assess the level of word-clock jitter in digital processors and CD players, measured where it matters: at the pins of the DAC. The technique uses the LIM Detector designed by Ed Meitner of Museatex. I won't go into the details here—they're in the aforementioned Stereophile article—but the procedure produces an overall measurement of the jitter (expressed in picoseconds), and also shows the spectral content of that jitter (figs.15 and 16). There's a good correlation between jitter and sound quality in…
search
SIDEBAR 1: Decibels
The term decibel (dB) appears repeatedly in specifications and measurements, yet it's often misunderstood. In addition, there seem to be all kinds of dB: dBm, dBR, dBV, dBFS, dBW, and dB SPL, to name a few. What do they all mean?
The term decibel (dB) appears repeatedly in specifications and measurements, yet it's often misunderstood. In addition, there seem to be all kinds of dB: dBm, dBR, dBV, dBFS, dBW, and dB SPL, to name a few. What do they all mean?
The most important thing to realize is that the decibel doesn't express an absolute value—it expresses a ratio between two values. When we say that a particular CD player has a 2.5dB higher output voltage than another CD player, we're expressing the difference in output voltages between the players. In the case of our CD players, it's the…
SIDEBAR 2: The Audio Precision System One
Most of the measurements Stereophile makes on review products are performed with the Audio Precision System One, a computer-based audio test system. This instrument, introduced in 1985, has so revolutionized audio testing that it's hard to imagine life without one.
Most of the measurements Stereophile makes on review products are performed with the Audio Precision System One, a computer-based audio test system. This instrument, introduced in 1985, has so revolutionized audio testing that it's hard to imagine life without one.
The System One is a large box that interfaces to an IBM-compatible personal computer through a custom board in the computer. The box contains analog signal generators and analyzers controlled by commands from the personal computer. Instead of adjusting front-panel knobs on an array…
SIDEBAR 3: Output Impedance
In the perfect world of mathematical abstraction, an electrical device such as a CD player or amplifier would deliver its signal in a manner completely unaffected by what it's hooked up to. In the real world, however, there's an interaction defined by the impedance of the load—the "load" or "input impedance"—and that of the source component—the "source" or "output impedance."
In the perfect world of mathematical abstraction, an electrical device such as a CD player or amplifier would deliver its signal in a manner completely unaffected by what it's hooked up to. In the real world, however, there's an interaction defined by the impedance of the load—the "load" or "input impedance"—and that of the source component—the "source" or "output impedance."
The output circuit, or stage, of a component can be mathematically modeled as a perfect, loss-less AC-voltage generator coupled to the outside world through a series resistor (fig.1…
SIDEBAR 4: Capacitors & Capacitance
Capacitance is associated with "capacitive reactance," which can be thought of as frequency-dependent resistance. As frequency increases, the capacitance produces less and less "reactance," or resistance to current flow. The higher the frequency, the lower the opposition to current flow produced by the capacitance.
Capacitance is associated with "capacitive reactance," which can be thought of as frequency-dependent resistance. As frequency increases, the capacitance produces less and less "reactance," or resistance to current flow. The higher the frequency, the lower the opposition to current flow produced by the capacitance.
A cable's capacitive reactance can be thought of as a resistor in parallel with the load. As frequency increases (and the capacitive reactance decreases), more and more of the drive signal is dropped across the cable's capacitance,…
This compact, $1600/pair monitor employs many of the same design features found in the company's highly rated Matrix 801 system. Although the price is high for a two-way minimonitor, the 805 fits right into a growing high-end marketplace for such designs, one which emphasizes high quality in a small enclosure which will fit into most living-room environments without calling much attention to itself.
There are two versions of the 805: the vertical version reviewed here, and a model whose external tweeter is mounted on its long side so the speakers can be laid lengthwise on a bookshelf, or…
The wonderfully rhythmic quality of the 805s was best heard on The Commitments soundtrack (MCA MCAD-10286). Catch the raspiness of Andrew Strong's voice belting out "Guess you got to put your flat feet on the ground" in the chorus of "Mustang Sally." The 805s kept Strong's great lungs at the forefront, never allowing them to be drowned out by the band's tight drums, horns, and piano work. Everything integrated with a tight, driving rhythm. The 805s performed the same magic for my favorite classical LP, Shostakovich's Symphony 6 and The Age of Gold Suite, both with Leopold Stokowski and the…
Sidebar 1: Specifications
Description: Two-way, stand-mounted reflex dynamic loudspeaker. Drive-units: 1" (26mm) metal-dome ferrofluid-cooled tweeter, 165mm (6.5") Kevlar-cone woofer with 3" voice-coil. Crossover frequency: 2.7kHz. Frequency response: 35Hz-22kHz ±6dB. Sensitivity: 87dB/W/m (2.83V). Nominal impedance: 4 ohms. Amplifier requirements: 50W minimum, 120W maximum.
Dimensions: 12.75" (323mm) H by 13.6" (347mm) W by 8.9" (236mm) D. Weight: 18.7 lbs (8.5kg) each.
Finishes: natural oak, rosewood, walnut, or black ash.
Serial numbers of units auditioned: 002421/002422.
…
Sidebar 2: Reference System
My main listening room has served as my standard listening space for the past 15 years. It's 26' long, 13' wide, and, with its 12' semi-cathedral ceiling, constitutes a voluminous, sparsely upholstered space. An 8' by 4' doorway at the back of the room opens into our kitchen, which adds another 25' by 15' space. I set up the speakers at the narrow end of the room, and listened from two positions: 8' away for nearfield, and then my favorite spot, another 10' back. The speakers were also auditioned in a 15' by 10' study. Upholstered with a wall-to-wall carpet,…
Sidebar 3: Measurements
The 805's B-weighted sensitivity measured to specification at around 87dB/W/m, while its impedance plot (fig.1) revealed it to be a relatively easy load for an amplifier to drive. The cursor shows the minimum magnitude to be 5.2 ohms at just under 11kHz. The port is tuned to 40Hz, the frequency of the saddle between the two bass peaks, and the basic alignment is a little overdamped, this appropriate in view of the intended use of an electronic equalizer to flatten and extend the speaker's low-frequency response. The correction applied by this equalizer is mild, as…