The second point, relative inefficiency, is potentially a more serious concern.
Orthodynamic ‘phones tend, as a general rule, to be low in sensitivity. The power hungry HE-5LE, for example, carried a low-ish sensitivity rating of 87.5 dB (1 mW input)—a sensitivity rating much lower than ratings for typical top-tier headphones that use conventional dynamic drivers. The HE-6, in turn, quotes an even lower sensitivity rating of 83.5 dB (1 mW/input), despite the fact that it is equipped with a “super efficient magnetic circuit,” which means it’s not an easy headphone to drive.
In practical terms, there are several things prospective owners should understand about the HE-6. First, the HE-6 cannot be driven directly from an iPod, iPhone or any other low-powered digital device. As New Yorkers might say, “fuhgeddaboutit.” Second, while the HE-6 can be a phenomenally good-sounding headphone, it absolutely requires an adequately powerful, high-resolution headphone amp to give of its best. Lesser amps can, of course, get the HE-6 to product sound, but the fact is that they cannot and typically do not reveal the terrific sonic subtlety and nuance of which the HE-6 is capable.
But take comfort in this: once you invest in an appropriately good headphone amp, the HE-6 will deliver heightened levels of performance that are well and truly breathtaking. In fact, the HE-6 stretches the sonic performance envelope even further than the HE-5LE does, which is saying a mouthful. In the process the HE-6 establishes itself as one of the finest headphones now available at any price.
Consider this headphone if: you want a headphone that offers five powerful benefits: ultra wide-range frequency response, accurate tonal balance, blindingly fast transient speeds, extraordinary resolution of low-level sonic details, and serious dynamic clout (provided, of course, that you’ve brought a good enough headphone amp to the party). Let me put it this way; even if you’re familiar with the sound of great, five- or even six-figure loudspeakers, there’s a good chance the HE-6 will unveil elements of familiar recordings that you’ve never heard before. It’s that good. Once you get used to these ‘phones, you may have the unnerving sense that almost all other headphones are guilty of leaving valuable musical information “on the table.”
Look further if: you favor light, compact, and relatively easy-to-drive headphones. The HE-6 is comfortable, but also large and quite heavy (about 100 grams heavier than the already hefty HE-5LE). Also look further if you require a headphone that offers good isolation from external noises; the HE-6 is an open-back design that lets room noises through, and that can faintly be heard from the outside when it is playing. Finally, look further if you’re not prepared to spring for a high-powered, high-resolution headphone amp. If you’re committed to using low-powered headphone amps, be aware that there are other good headphones that are much easier to drive.
Ratings (relative to comparably priced headphones):
• Tonal Balance: 10
• Frequency Extremes: 10
• Clarity: 10
• Dynamics: 10 (note: performance in this area is highly amplifier dependant)
• Comfort/Fit: 8.5
• Sensitivity: 2
• Value: 10 (though certainly not cheap, the HE-6 is priced below most—though not all—of its legitimate competitors)
At the outset, let me say that the HE-6 basically builds upon the strengths of the already very good HE-5LE. Specifically, the HE-6 offer improved extension and definition at both frequency extremes and conveys a significantly greater sense of top-to-bottom clarity and coherency—almost as if you are listening to an HE-5LE whose power, focus, and resolution have been dialed up to “12.”
Tonal balance between the two HiFiMAN models is similar, but not identical, with the HE-6 offering slightly more prominent low bass, and somewhat more forward-sounding upper mids and highs—differences that many listeners interpret as giving the HE-6’s a greater sense of transparency and openness. Other listeners, however, tend to perceive the HE-6 as sounding slightly bright or “analytical,” so that while acknowledging the flagship’s sharply focused and finely resolved sound, they ultimately gravitate back toward the HE-5LE’s warmer, more midrange-centric and admittedly more forgiving presentation.