PBN Montana EPS loudspeaker Page 2

But I'm too cautious to try something like this without setting it up on the test bench first—if you've ever accidentally smoked an amplifier by misconnecting its output, you'll know why. In biamping with two unlike amplifiers, you can't be sure that their outputs are in phase with each other, or if they "track" in a similar fashion—that is, produce equal output voltages for equal inputs. My test procedure was to put the AudioPrism and the Parasound HCA-1000A I intended to use side by side and feed them the same frequencies (from a Leader sinewave generator) while monitoring their outputs into 8 ohm loads with a dual-channel oscilloscope.

The Parasound, which has parallel pairs of input jacks for each channel, makes this easy. After adjusting its level controls so that the outputs from both amplifiers were equal with a 1V input at 300Hz (the Montana's lower crossover point), I "swung" the frequency between 20Hz and 1kHz. The amplifier outputs remained in phase throughout. Then I varied the input level between 1V and 3V to see if the amps tracked each other, and they did—except that the AudioPrism hit the clipping point at about 25W and the Parasound was clean to about 165W. Biamping looked like a promising possibility.

The amps went back in the rack, the AudioPrism connected via 10' lengths of Nordost SPM to the Montanas' upper-frequency inputs, and the Parasound connected by a double 10' run of Straight Wire Rhapsody II to the lower ones. Again I set the generator to 300Hz, and connected the 'scope probes to the speakers' binding posts, slightly adjusting the Parasound's level once again. Thus, the crossover-frequency voltage appearing at the speaker terminals was in phase and equal in amplitude—just as it would be if driven by a single amplifier. But the tubes would now supply the mids and highs, the transistors the bass. Thus configured, each amp could now do what it does best.

Both amps were running full-range, with their outputs "shaped" by the Montanas' crossover networks. A steep-slope electronic crossover ahead of the power amps would probably be more kosher, but this hookup worked wonderfully well: magically lucid midrange, gossamer highs, and visceral bass—audiophile nirvana.

Listening
I was so taken by the Montana and its ability to do justice to every kind of music that I kept returning to it as a reference (also the reason I hung onto these samples far longer than I should have) as other loudspeakers came and went—among them, the System Audio 2070 and Tannoy Churchill.

The Montana EPS consistently kicked celestial ass, and did likewise at the home of my cycling buddy and fellow audiodweeb Marc Meisner, where we compared them against his Green Mountain Diamantes. The smaller (and less expensive) Diamantes got the nod from both of us for their sense of intimacy, but the Montanas easily swept the competition in terms of dynamics, power handling, image size and depth, and frequency extension. Marc's system—Cary 805c monoblocks, Cary SLP 94P preamp, Museatex Melior CD transport/Theta DS Pro Basic III DAC, and Well Tempered Reference turntable with Sumiko SHO cartridge, linked primarily by Straight Wire Virtuoso—could not have been more different from mine, but the Montanas adapted to the new environment like stray kittens.

Ultra-low bass, the very bottom of the bottom octave, wasn't the EPS's strong suit. The loudspeaker's low end rolled off gradually—a wise choice on the part of Peter Noerbaek, I feel. Rather than boost the bass to give the music some artificial impact (and thereby muddy the midrange), he prefers to let the drivers perform as "naturally" as they can. Result: the Montana made music with an effortless quality that made prolonged listening sessions an unquestioned necessity. With Marc's Velodyne ULD 18 Series III subwoofer in charge of floor-shaking and earthquaking, the Montana's performance was within a few millimeters of world-class. It never screeched when driven hard but simply got louder, maintaining the same reliable acoustic character at every level. Marc's long-suffering wife, Amanda, is to be commended for her patience and fortitude in enduring our audio excesses. Thanks, Mandy; Lisa Astor would love to hear your war stories.

Near the end of my prolonged experiment with the EPS, Noerbaek called to say he'd made a slight production change to the speaker—routing out the midrange enclosure by ¼"—that he claimed gave a smoother midrange response. During a visit to Northern California a few weeks later, he picked up the original pair (destined for legendary European amplifier designer Erno Borbeli) and dropped off the new ones. Sure enough, the mids were smoother. The man knows his speakers.

But the bass was now a tad anemic—these woofers hadn't had hundreds of hours of playing to break them in. It was a few weeks before they exhibited the slam and impact I'd grown so accustomed to. A long break-in period is the only real flaw in the EPS's list of merits and demerits.

Conclusions
Here's the audiophile scorecard:

Visual Design: excellent
Construction: excellent
Fit and Finish: excellent
Sound (overall): excellent
Treble extension: excellent
Treble smoothness: very good
Midrange clarity: excellent
Bass extension: good
Sensitivity: very good
Power Handling: excellent
Macrodynamics: excellent
Microdynamics: excellent
Imaging: very good
Compatibility with varied equipment: very good
Durability: appears excellent
Performance per dollar: excellent
Break-in time: long
Portability: poor

While the Montanas were here, I went to some trade shows, visited some manufacturers, and hung out with audiophiles. During that time I heard plenty of good systems and lots of good-sounding loudspeakers, but apart from Sonus Faber's $18,000/pair Amati Homage, none filled me with raging lust. I liked the EPS enough that when it came time to ship them out to Santa Fe for measurement, I inquired about buying a pair—the ultimate endorsement. With an overwhelming preponderance of "excellent"s and few scores even as low as "very good," the Montana's $8000/pair price tag makes it not merely a good deal, but a freaking bargain.

I was ready to write the check, but then didn't buy them—only because I've gone instead into long-term debt for a pair of Montana KAS speakers, the EPS's larger sibling. Deficit financing in the pursuit of a reference audio system: further evidence of an incurable obsession. We'll save that story for another time.

COMPANY INFO
PBN
1015 La Mesa Avenue
Spring Valley, CA 91977
(619) 465-6450
ARTICLE CONTENTS
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