Sidebar 3: Measurements
Unless otherwise noted, all measurements were made at level settings that resulted in a 1W output with an input of 100mV. This was approximately 1:30 on the Manley Stingray's volume control, at which position the voltage gain into 8 ohms was 29dB. The Stingray's gain at the maximum setting of the volume control was 39.5B.
After one hour of operation at 1/3 power the Stingray was running no hotter than is typical of tube amplifiers. The Manley's input impedance measured a comfortably high 47.2k ohms. The output impedance, however, was also high, ranging from…
If you've read Stereophile regularly over the past decade, you know that ProAc Audio's Stewart Tyler has a winning formula for designing loudspeakers. In review after review, this magazine's writers have celebrated the sonic profile he has created for ProAc speakers: a spacious soundstage with a big, coherent image; a clean, grain-free midrange; extended highs that don't intrude on the music; and tight, tuneful bass response. Jack English found both the $6500/pair Response Three (Stereophile, September 1991, Vol.14 No.9) and the $18,000/pair Response Four (March 1994, Vol.17 No.3; May…
Setup
My listening room is 26' long, 13' wide, and 12' high, with a semi-cathedral ceiling. One long wall is covered with bookshelves, while the other has a bay window. The Response 3.8s faced the full length of this narrow room, the opposite end of which opens into a 25' by 15' kitchen through an 8' by 4' doorway. I placed the Response 3.8s where the Revel Salons (March '99) had sounded best: 63" from the rear wall and 36" from the side walls, sitting on a circular area rug, their offset tweeters were positioned toward the speakers' inside edges, closer to a point midway between the…
The other CD that illustrated the Response 3.8s' spaciousness was Diana Krall's Love Scenes (Impulse! IMPD-233). This recording features a much more intimate acoustic, best revealed in Krall's rendition of the well-known Gibbons-Dyrenforth standard, "Garden in the Rain." While this track lacks the cavernous depth of soundstage heard on Rutter's Requiem, there is an effortless openness and spaciousness, especially for a studio recording. Krall's piano is spread from speaker to speaker, with Russell Malone's soft, amplified guitar to the left and Christian McBride's bass dead center. Krall's…
While the Response 3.8 had the same effortless dynamic range other reviewers found in other ProAc speakers, it did not share the exceptional freedom from compression of more expensive loudspeakers, such as the $15,000 Revel Salon. Signs of compression were evident when I drove the 3.8s with the Electrocompaniet Nemo monoblocks in my large listening room: David Hudson's didgeridoo lost some its raw, throbbing edge on "Rainforest Wonder" (Didgeridoo Spirit, Indigenous Australia IA2003 D); the timbales' explosive snap on Tito, from Arturo Sandoval's Hothouse (N2K-10023), was smoothed; and the…
Sidebar 1: Specifications Description: Three-way, floorstanding, reflex-loaded dynamic loudspeaker. Drive-units: 1" (25mm) soft-dome tweeter, two 7" (175mm) carbon-fiber bass/mid units (each with 1.25" voice-coil). Crossover frequencies: 500Hz, 3kHz. Crossover slopes: 12dB/octave, 18dB/octave, 18dB/octave. Frequency response: 40Hz-25kHz, ±3dB. Sensitivity: 88dB/2.83V/m. Nominal impedance: 8 ohms. Amplifier requirements: 50W minimum, 250W maximum.
Dimensions: 49" (1244mm) H by 9.25" (235mm) W by 13.5" (343mm) D. Plinth & spikes add 1" to height. Weight: 85 lbs (38kg).
Finishes:…
Sidebar 2: Associated Equipment Analog sources: Linn Sondek LP12 turntable, Lingo power supply, Ittok tonearm; Spectral moving-coil cartridge.
Digital source: Krell MD-1 CD transport, Adcom GDA-700 D/A processor.
Tuners: Day-Sequerra FM Reference Classic; Rotel RH-10; Magnum Dynalab MD-102, 205 Sleuth RF amplifier.
Preamplification: Krell KBL, Mark Levinson ML-7A with L-2 phono section, Margulis and Duntech MX-10 moving-coil preamplifiers.
Power amplifiers: Mark Levinson No.331.5 and No.334, Bryston 7B-ST monoblocks and 9B-ST 5-channel, Electrocompaniet Nemo monoblocks.
…
Sidebar 3: Measurements Larry Greenhill observed that the ProAc 3.8 didn't sound as sensitive as he was expecting from its 88dB sensitivity specification and my own (B-weighted) estimate of 84.5dB/2.83V/m. While this is below average, the 3.8's impedance plot (fig.1) revealed it to be an easy load for the partnering amplifier to drive. The amplitude drops below 8 ohms only briefly in the upper bass and mid-treble, and the electrical phase angle is also low.
Fig.1 ProAc Response 3.8, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)
Note,…
Fig.5 shows the 3.8's horizontal dispersion, referenced to the tweeter axis. (The off-axis behavior on the tweeter side of the asymmetrical baffle is shown at the front of this graph.) The narrow directivity in the top audio octave can be seen in fig.5 as well, as can a narrow off-axis notch on the tweeter edge of the baffle. There's actually an excess of energy off of the other (badge) edge of the baffle in this region, which will make the speaker sound too bright if the room's side walls are close and reflective. In the vertical plane (fig.6), the drive-units' polarities have sensibly been…
History teaches us that the full flowering of any social phenomenon takes place after the seeds of its destruction have been sown. That tourist magnet, London's Buckingham Palace, for example, was built decades after the English Revolution and the Restoration had redefined the role of the British monarchy as being merely titular, and made the elected Parliament the real seat of power.
The same forces can be seen happening in the High End, where large advances in LP playback technology took place after the mass market had embraced CD. Similarly, it is only now, when DVD-Video has…
