The proper header should read, "the likely effects of dual-mono amplification on headphones for which balanced drive is a prerequisite". The benefits of dual-mono speaker drive are well documented. Dedicated power supplies improve channel separation which improves imaging precision. They also improve overall stability because challenging bass transients appearing in just one channel won't affect the other channel. The benefits of four times more power should be self-evident when it comes to dynamic headroom and bass grip. Lower distortion is another benefit. From all this it seems fair to suspect that for today's experiment, dual-mono drive would be the prime attraction, balanced drive merely its enabler or mandatory condition. After all, one needs separate leads to feed two amplifiers in the first place. It's certainly what distinguishes this scheme from a standard 'balanced' headphone output.

HifiMan HE1000 mano-i-mono. For my formal review of these $2'995 flagship planarmagnetics, click here. Nicely, stock delivery includes three leashes which on the headphone side all terminate in two 2.5mm plugs to be super easy to swap. On the amp ends we get a 3.5mm right-angle plug—incidentally perfect for my Eversound Essence powered computer speakers with switchable 3.5mm output—a standard 6.3mm plug and a 4-pin XLR. All are based on the same conductor/dielectric recipe to eliminate disparate cable flavours from today's equation. For this test, preceding the Questyle station was my usual music iMac with the most current PureMusic player and AIFF files; and the COS Engineering D1 with its volume control bypassed to work as just a fixed-gain USB converter.

The first thing to notice because it was most obvious? The size of the occipital pillow aka headstage wrapping around the back and through the skull extended farther and more away from the ears. The result was as immersive or enveloping as headfi can possibly get. To whittle it down to a bullet point, think soundstage expander. If that kidney-shaped headfi stage around the base and back of the skull were inflatable, dual mono was a size larger and even more pressurized. Tied to that effect but also separate was LF weight. It's well known that proper infrasonic subwoofers, set up correctly, enhance depth of field, contrast and overall scale even on material that's apparently devoid of low bass. The usual floating air balloon of the imaging field gets anchored way down deep. As a result, the balloon appears bigger and rounder. Though having nothing in common with boom trucks of adolescent excess, think of this effect as the bassifier aka scaler. It's not a tonal imbalance but greater bottom-end visibility and intelligibility tied to greater weight and impact.

The third aspect should be called the explicicator to once again default to Pidgin English. An obvious area that's most explicit is hardcore pornography. It's a perfect example. Nothing more needs saying. How does it relate to musical playback? Having played the classical clarinet in chamber music and orchestral settings, I'll put it this way: nobody but the actual musician hears and perceives their playing as they do. What's more, the interaction with the instrument adds physical dimensions. A clarinet's mouth piece interfaces with the teeth, the reed with the lips. Player vibrations transfer to the skull and, via the lungs, to the rest of the body. No listener shares that sensation. It's a unique perspective. Yet microphones may come close, especially if, in the clarinet's case, the pickup sits inside the barrel. Anything in the violin family would use the bridge. A piano's mic will hover directly above its strings and so forth. Like porn does with cameras and eyes, the typical music studio production puts mics where no human ear would ever be. This has the potential for hardcore hifi. Translated it means more separation, more image specificity, more extreme nearfield attributes than occur naturally in any one listening position no matter how close to stage. Not even the conductor hears an orchestra in that way.

In speaker systems, room effects, cabinet talk and environmental noise all are mellowing agents. They undermine the most explicit reading. Select a more purist production using far fewer microphones in mid to far positions. Their perspective becomes more natural still. Because headphones eliminate the room, they not only do away with the ambient field of reflections. They also eliminate room noise and bass issues. By that virtue alone, they're more explicit already. They relate more of what's actually recorded, not how it happens to interact with your personal acoustics. Within that generally higher headfi explicitness are tiers of transducer quality, recording type/quality and ancillaries. In German, the term 'perspicacity' translates to Scharfsinn. Translated back verbatim, it becomes Sharpsense like a Red Indian brave in a Karl May novel. It's an excellent phrase for dual-mono headfi. We must only declaw the sharp bit to not mean needly, biting or edgy. The desired meaning is heightened perception like a friend once described an outdoor peyote trip. In it he saw the forest asleep, then the day's first bird call travel through the air, bounce like a billiard ball from tree to tree and thus awaken them all in the very early morning. In audio terms, the resultant detail density is immense. If the peculiar headstage were a grid, each little square of it would pulsate at the same intensity. There'd be no area less filled or present. Like a conductor confronting his players, our awareness either absorbs all of it in its totality; or selects at will any tiny 'box' to inspect its contents. Not only was this aspect greater with two amps, the actual grid map was bigger, too. This hardware would make for an ultimate mastering/mixing tool. Its ultra explicitness isn't a function of spot-lit HF. It's not undue brightness or faux resolution. It's a higher-power magnifying glass which works not in the mostly two dimensions of a jeweler's loup but in fully developed three axes inside your head. Quality recordings benefit most. They've not been mastered for wall-of-sound homogeneity at maximum loudness but for sophistication and multi-layer interest. To wrap up my first trial, dual-mono'ing the HE1000 acted as soundstage expander, bass/scale enhancer and larger magnification power for heightened detail density. I would call the sum total extreme explicitness; or the conductor's immersive intimate perspective.