PBN Montana EPS loudspeaker
By Barry Willis   •   October, 1999 Most speakers don't come in heavy wooden crates—they come in cardboard cartons, two per box, light enough to be tucked under one arm and carried out to the car. Not so in HighEndLand, where the smallest minimonitor can test a healthy man's strength. There are plenty of good reasons for this cult of robustness, foremost among them structural stability and the suppression of resonances.

At 4½' tall and 154 lbs (70kg) each, PBN Audio's Montana EPS exemplifies extremism in the pursuit of solidity. Rap as hard as you will anywhere on the hexagonal cabinet—go ahead, bust your knuckles—and in response you'll get no more than a muffled thud. The massive vertical walls and heavy internal bracing guarantee that you won't. Try waltzing it into place and you'll quickly find that baby steps are easier and safer.

The theme of heavy construction continues throughout: steep-slope crossover networks packed with thick copper coils of low DC resistance; proprietary film-and-foil capacitors bigger than soup cans; and Monster Sigma M1.2 internal wiring feeding the custom-built ScanSpeak drivers.

The tweeter, a 1" fabric dome mated to a Revelator motor unit, is centered vertically between two long-throw midrange drivers, each with a 38mm fabric dome and a 4" Kevlar cone. The twin 8" woofers sport stiff, heavily doped cones and massive magnets. A flared rectangular port near the bottom of the front baffle extends the bass as low (and as linearly) as designer Peter Noerbaek can take it. Four heavy-duty binding posts are inset on the back panel; threaded inserts in the plinth accept screw-in spikes.

For all its mass, the EPS looks light on its feet, especially if finished in the flawless blond veneers of the two pairs that lived with me for months on end—one in bird's-eye maple, the other in pecan. An easily removable black grille graces the front panel's full length. Like most loudspeakers, the EPS sounds a tad more open and airy with the grille off, but more often than not I preferred to leave them on because I found the yellow Kevlar midrange cones visually distracting—they interfered with my concentration on the music.

Setup
The loudspeaker's 92dB sensitivity rating means it will play quite loudly with an amplifier in the 20–50W region. Even in a very large room, 100Wpc is totally adequate. The EPS was comfortable with everything from a 20Wpc NAD receiver to a pair of Threshold T-100 amplifiers in fully bridged monoblock mode (180W each).

When he sets his speakers up in a listening room, PBN's Noerbaek begins by placing the speakers about 2' from the back wall and about 7' apart. He then toes them in, finding the proper angle by extending the horizontal plane of the front baffle to intersect the outside rear corner of the other speaker. (This is easy to do with a length of string and a couple of pieces of tape.) Once the speakers are so positioned, they can be moved a little at a time until the optimum imaging is found.

In my room, I was able to get the Montanas relatively close to the rear wall without inducing any boominess. I found that a horizontal separation of about 6.5' between the inside front corners was optimum in my room, and 16" out from the back wall was fine. The heavy-duty spike feet are essential for getting the most out of the EPS, but shouldn't be installed until the speakers are close to their permanent positions. Once the feet are on, each speaker can be moved by tipping it back so all its weight is on one spike, then pivoting it around that point. Toe-in is critical if you want to get the best imaging from these speakers.

The EPS's vertical dispersion seemed quite good. Focus was better when I was sitting, but there was no dramatic shift in frequency balance going from sitting to standing. (I often like to stand back at a distance rather than sit in the nearfield.) The horizontal dispersion pattern was somewhat narrow, even a bit "beamy" in the upper frequencies, which meant that a few degrees of toe-in had a huge effect on soundstage width, depth, and focus. There is an ideal geometry for each room and each listening position, and it can take days of experimentation to find it. But once I'd found that geometry in my room, the Montanas let the heavens open up. Nice reward.

Music?
And music, after all, is what hi-fi is for. Though the Montanas are gorgeous as furniture—they never failed to elicit gushing praise and a few loving strokes from visitors—had they failed to deliver the musical goods, I would have bounced them back to Southern California in a hurry. But deliver they did—for many long hours, without one tiny peep of complaint. Rock, jazz, blues, country, classical, you name it—my constantly changing musical smorgasbord demanded the utmost from these speakers. They performed consistently well regardless of the material—an enduring hallmark of good design.

Like everyone else, speaker designers have musical preferences. But if they let those preferences interfere with their objectivity, they risk creating a product that also "prefers" some genres of music over others. A good loudspeaker, like a good microphone, should take itself out of the acoustic picture as much as possible, while making that picture as vivid as possible. The Montana achieves this seemingly paradoxical goal—Peter Noerbaek, a university-trained electrical engineer who has been building speakers since childhood, knows not to be deceived by his own taste. The EPS is sufficiently neutral to give itself over easily to whatever it's fed.

The speaker's most immediately apparent strength is its midrange, which seems almost prominent by comparison to the many "laid-back" designs on the market. Vocals, horns, and guitars and other stringed instruments came through with startling clarity, aided by the Revelator tweeter's silky upper octaves. The saxophones of Candy Dulfer and Richie Cole came right into the room, as did the cello of Ofra Harnoy and the voices of singers as diverse as Michelle Shocked, Paula Cole, and Isaac Hayes. Give it to me, baby—the Montanas mainlined my latest musical infatuation, Fiona Apple, whose bitter, beyond-her-years wisdom induced frequent late-night reveries. Slow like honey, heavy with mood.

But back to objectivity. The overall "flavor" of the EPS's midrange—which, spectrally, is where most of the music is—is cool rather than warm, much like the company's smaller SP (reviewed in Stereophile, Vol.20 Nos.1 and 6). This characteristic led me to favor a tube amp of relatively modest power as the best sonic match. Although Noerbaek himself favors massive solid-state amplifiers—PBN Audio has recently expanded its product line, building such amps under the Sierra Electronics label—the several transistor amps I tried with the Montana all added too much chill. I had the most trouble getting the speaker's bass output right, however, and that is best served by a stout solid-state amp. How to combine tight, powerful bass with a warm, liquid midrange?

The best of both worlds?
In triode mode, the AudioPrism Debut Mk.II provided all the midrange warmth and magic I could hope for with the Montanas, but its modest output power didn't "steer" the bass the way I wanted. The bottom octaves were a bit woolly using the tube amp full-range, so I decided to try biamping with a high-current solid-state amp on the bottom.