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On the minus side, the resistor must be capable of dissipating considerable power. Assuming a 200W power handling for the speaker and a worst-case 10dB peak:mean program dynamic range ratio, a 200W, 8 ohm delivery translates to 40V peak, or 26.4V mean. In theory, up to 20V of program energy applied to the power resistor results in a possible flat-out dissipation of 20W. Taking no chances, Sonus Faber has chosen a high-quality, metal-clad power resistor of the type which may be bolted to a heatsink for optimum heat release. (The latter is the small finned metal structure visible on the back…
A number of fine, recommendable speakers can only scale the audiophile heights when their idiosyncrasies have been pandered to. They are sufficiently flawed as to need great care taken with placement, height, separation from boundaries, and angling, as well as being very sensitive to the complementary sounds of cables, power and control amplifiers, even to CD sources and moving-coil cartridges. They might have suspect bass and require the most careful positioning of both speaker and listener to involve the room acoustic in some kind of bass equalization. The result may still be more than…
The facility for the user to adjust the bass power in the 35Hz-70Hz octave, centered on 45Hz, was most useful not just for correct alignment in the optimum room position (to give the best stereo image, low coloration, bass uniformity, and extension), but also for some measure of program tuning. The adjustment was fine enough for surprisingly critical adjustment.
For example, I preferred the damping set higher for loud, fast rock material; for older, drier classical recordings played at more modest levels, a judicious reduction in ABR damping helped fill out thinner recorded balances.…
Sidebar 1: Specifications
Description: Two-way, ABR-loaded, stand-mounted loudspeaker. Drive-units: 1.2" (28mm) soft-dome tweeter, 7.5" (190mm) mineral-loaded polypropylene-cone woofer, KEF B139 or TDL 3021GT03 bass unit used as an ABR (Auxiliary Bass Radiator). Crossover frequency: 2kHz. Crossover slopes: first-order, 6dB/octave. Frequency response: 35Hz-18kHz ±3dB. Sensitivity: 88dB/W/m (2.83V). Nominal impedance: 4 ohms. Amplifier requirements: 200W maximum.
Dimensions: 18.1" (460mm) H by 10.7" (270mm) W by 21.7" (550mm) D. Enclosure volume: 20 liters. Weight: 88 lbs (40kg) each.…
Sidebar 2: the Listening Station
The main amplification consisted of a Krell KSA-150 or a pair of Meridian 605 monoblocks. A second pair of 605s allowed for passive bi-amping (footnote 1), which gave significant gains in definition, focus, and clarity. Supplemental listening included a Motif 200, while early indications were that tubed amplifiers under 150W/8 ohms rated would not deliver sufficient raw power for a good dynamic range with the Extremas.
Preamplification majored with the fine Audio Research LS2 line stage plus phono stage, supplemented by a phono-stage-fitted Krell…
Sidebar 3: Measurements
As far as possible, my tests conform to established Stereophile practice, DRA Labs' MLSSA being the main analytical tool. The 88dB/W (8 ohm, 2.83V) sensitivity claim was met within 0.5dB, using broad averaging over the axial reference response. This above-average sensitivity, in conjunction with the 200W maximum program input, will provide up to 111dB at 1m, or a typical value of 106dBA maximum for a stereo pair in a typical 80m3 listening volume. While not deafening, this level is well above the norm for compact two-way systems. The BBC LS3/5a sticks at 95dBA,…
One of the characteristic traits, I have found, that defines the loudspeaker designer is that they are loners—they seem to avoid one another's company as if on purpose. But if ever you sit down with a designer, all you need to do to open him up is to ask him what he feels to be important in loudspeaker performance.
Such was the case with John Dunlavy of Dunlavy Audio Labs. I was driving up to Colorado Springs to measure his 530-lb Signature SC-VI loudspeaker—reviewed in the August 1996 by Steven Stone—so it seemed an ideal opportunity to sit down with John and ask him what he felt to be…
Atkinson: The perfect on-axis impulse response will also give you a perfectly flat amplitude response on that axis. But with most loudspeakers in the world, even if they have perfect, flat amplitude responses, that doesn't mean they have perfect impulse responses?
Dunlavy: That's right. You can go one way but not the other. Flat on-axis response provides very poor correlation, in general, with what you hear. On the other hand, if you have near-perfect impulse and step responses, it follows that you must also then have from that a near-perfect frequency response on-axis. And using a first…
Atkinson: I do wonder that with designers who haven't thought through the fundamentals of what they're trying to achieve in loudspeaker design, a lot of the tweaking or "voicing" that they do with their speakers is balancing problems in the on-axis response, say, with those in the power response, or vice versa. Let's imagine that someone is using an 8" midrange unit that beams quite narrowly at the top of its passband, crossing over to a 1" tweeter that has very wide dispersion at the bottom of its passband. That speaker will tend to sound bright. So what the designer then does is to pull…
Dunlavy: It depends on the music you're listening to. If the music you're listening to has a great deal of low frequencies, the answer is probably yes—although the ear is an amazing device in terms of having a very effective built-in equalizer. When we enter a room, assuming that we're a sighted person, something between our ears and this computer we've got in our head calculates what the room ought to sound like. It does it subconsciously. Especially after we've been in the room and listened briefly. And I'm sure a lot of your readers have experienced that—when you first enter and start…