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I estimated the Montana SP's B-weighted sensitivity at 89dB/W/m, almost exactly to specification. As BW noted, it doesn't take many amplifier watts to drive this speaker to satisfying levels. Its impedance (fig.1) is moderately demanding, dropping to 4 ohms through the lower midrange. It remains above 8 ohms for almost all frequencies above 800Hz, however. In the bass, the saddle in the magnitude curve centered on 30Hz reveals the tuning of the large 2" port.

Fig.1 PBN Montana SP, electrical impedance (solid) and phase (dashed) (2 ohms/vertical…

PBN engineer and chief executive Peter Noerbaek has made some improvements to the design of his model SP loudspeaker, reviewed by me in the January 1997 issue (p.225). The new production model, designated the Series 2, retains the same drivers, crossover network, and front-baffle dimensions, but differs from the original in that its cabinet is 2" deeper, increasing its internal volume by 844 cubic inches, or 17%. A foam pad added inside the cabinet just below the lower woofer is said to act as an acoustic low-…

It's astonishing to realize that it's been more than six years since I reviewed PBN Audio's original Montana SP loudspeaker, for the January and June 1997 issues of Stereophile. The march of progress has been generally beneficial—for me, for Stereophile (whose website nears its own sixth anniversary), and for PBN founder and chief engineer Peter Noerbaek, whose product line in that period has grown from three speaker models to eight. Corporate PBN now includes Sierra Electronics, manufacturer of three…

That 80/20 ratio corresponds to Vilfredo Pareto's principle that for many systems (he was thinking of economies and societies rather than stereo systems), 80% of the consequences flow from 20% of the causes (footnote 1). For the purposes of this exercise, I'd peg a more-ambitious-than-usual…

Both speakers are sturdily built and have high-quality biwire terminals, cleverly arranged so that it's less likely that the jumper plates will be mis-installed so as…

"Do you want to hear an even more amazing coincidence?" he continued. "The president of Sound Lab (the other American maker of ESLs) is Roger West. My first name is Roger.…

My listening room is a lightly damped, rectangular, 5400ft3 area 26' long by 13' wide by 12' high, with a 12' semi-cathedral ceiling. The far…

The Eros Mk.III took first place in transparency and imaging. This was surprising, given its highly variable in-room frequency response. Somehow, simply tuning by ear, I had found this speaker's most felicitous—if perhaps not its…

Description: Hybrid electrostatic/moving-coil loudspeaker system with remote-control active crossover/bass amplifier module. Drive-units: 41" by 11.5" flat electrostatic midrange/HF transducer; transmission line-loaded, 10" fiber-cone woofer. Crossover frequency: 360Hz. Crossover filters: fourth-order (24dB/octave, Linkwitz-Reilly). Frequency response: 24Hz-27kHz, ±2dB. Sensitivity: 98dB/2.83V/m. Electrostatic impedance: 112 ohms at 500Hz, falling to 2 ohms at 20kHz. Woofer impedance: 4 ohms. Recommended panel amplifier power: 80-300W. Amplifier/crossover…

Analog source: Linn Sondek LP12/Lingo turntable, Linn Ittok tonearm, Spectral moving-coil cartridge.
Digital sources: Krell KRC-28 CD transport, Sony SCD-C555ES multichannel SACD player.
FM tuners: Day-Sequerra FM Reference Classic, Rotel RH-10, Fanfare FT-1A, Magnum Dynalab MD-102, with Model 205 Sleuth RF amplifier.
Preamplification: Krell KCT, Sony TA-P9000ES, Mark Levinson ML-7A with L-2 phono section, Conrad-Johnson Premier 18LS, Margulis phono preamplifier, Duntech MX 10 moving-coil amplifier.
Power amplifiers: Mark Levinson No.334, Krell…