AudioQuest NightHawk: Do No Harm
In creating our first headphone, AudioQuest and NightHawk designer Skylar Gray had large, ambitious goals. We knew that NightHawk had to be something special—not just another ordinary headphone—but, beyond that, we strove to liberate headphone design from decades of misinformation and neglect, most specifically characterized by the pervasive use of Mylar-based driver diaphragms, the misapplication of well-intentioned but ultimately ineffective correction curves, and an array of other cost-saving measures that too often permeate the consumer electronics industry.
With that in mind, Gray began from the ground and worked his way up, reevaluating and reimaging every aspect of headphone design. His mandate, as issued by AudioQuest founder William E. Low, was to follow his passion, to take all the time necessary—while, of course, working efficiently—to design a product that meets AudioQuest’s (and his own) highest standards: unsurpassed love, appreciation, and respect for the source signal.
NightHawk is the result of over two years of development—a product that uses sustainable engineering, high-quality materials, and creative thinking to minimize waste and excess while maximizing performance and value. A product designed to build stronger emotional and intellectual connections with music, movies, and games. A product designed to successfully bridge the gap between two of hi-fi’s most enduring and seemingly disparate pursuits: the pursuit of unbridled pleasure and the pursuit of unprocessed truth. A product designed to inspire: music lovers and headphone enthusiasts, as well as thinkers, builders, engineers, and creators of all sorts. A product designed, like all AudioQuest products, to minimize distortion and to do no harm.
Distortion Mechanisms in Typical Headphone Design
Just as there is no perfect loudspeaker, no perfect cable, no perfect source component, no perfect amplifier, etc., there is no perfect headphone. There are, however, various degrees of compromise toward lowering distortion and enabling a more immersive, emotionally compelling, non-fatiguing listening experience.
For far too long, typical headphone design has been victim to a number of distortion mechanisms that impede the listening experience.
Various factors contribute to the most general of these distortion mechanisms and include: driver suspensions that exhibit non-linear or asymmetric compliance; primitive motor designs, marked by asymmetric magnetic fields, high inductance, high levels of motion-induced inductance variation, and overhung voice-coils; mild to severe magnetic flux modulation; fixed-edge diaphragm termination, causing vibrational reflections along the diaphragm surface; and—perhaps the worst offenders—parts and materials selected for inexpensive manufacturing or high profit margins, rather than high performance.
Ten distortion mechanisms common in most of today's headphone drivers:
(1) Mylar diaphragms that deform and break-up at upper mid and high frequencies.
(2) Fixed-edge construction with no surrounds result in non-pistonic motion and vibration reflection through the surface of the diaphragms.
(3) Lack of voice-coil formers which necessitates...
(4) long, overhung voice-coils that are...
(5) asymmetrically positioned within the magnetic gap and exhibit...
(6) high inductance due to the many windings of small-diameter wire.
(7) Smaller magnets and motors create weaker fields, constraining and thus compromising material options and diaphragm / voice-coil construction.
(8) Short magnetic gaps cause the voice-coils to be constantly immersed in extended fringe fields (areas of high non-linearity) throughout their travel.
(9) Sharp vent corners create turbulent airflow which contributes to high-frequency noise.
(10) Damping membranes made from materials with patterned organization (such as metal or nylon woven mesh) produce higher distortion compared to organic non-woven fabrics.
Common distortion mechanisms directly related to low-frequency performance include: asymmetric airflow venting; voice-coil deformation and voice-coil rocking modes made possible by the absence of a true voice-coil former; and decreasing magnetic-field strength with increasing excursion.
Common distortion mechanisms directly related to high-frequency performance include: turbulent airflow within driver cavities; diaphragm breakup characterized or caused by non-pistonic motion; and various levels of adverse coloration due to diaphragm material.
While none of these distortion mechanisms are necessarily easy to overcome, there is much that can be done to counteract or minimize the effects of distortion in headphones.
NightHawk: Designed for Low Distortion and Maximum Performance
The current state of the headphone art is ripe for improvement and advancements. Designed for low distortion and maximum performance, NightHawk represents a number of alternatives to typical headphone design.
NightHawk's rigid bio-cellulose driver diaphragm with rubber surround (left) compared to a typical diaphragm (right) made from inherently unstable Mylar plastic with no surround.
NightHawk’s bio-cellulose driver diaphragm is equipped with a compliant rubber surround, enabling pistonic motion and anechoic termination: As the voice-coil moves, the diaphragm moves—not adversely, but sympathetically—thus carefully controlling and preserving the coherence of timing information.
NightHawk's voice-coil assembly (left) includes a stiff former. Typical driver designs (right) leave the voice-coil unsupported and unpositionable, forcing the use of motor configurations with higher distortion.
NightHawk’s voice-coil is carefully wound on a small cylinder of kraft paper, selected for its combination of low weight and stiffness—perfect for retaining the voice-coil’s shape—enabling productive motion, while preventing adverse flexion. Moreover, the voice-coil is wound at a very specific location on the former, precisely positioned at its zero resting point within the magnetic gap, thus providing the ideal symmetry of motion for the accurate reproduction of high frequencies.
NightHawk's driver baskets (left) are fully ventilated around the perimeter of the diaphragm area for reduced distortion. Typical driver baskets (right) have blocked vent sections that cause the diaphragm and voice-coil to rock, increasing low-frequency distortion.
Unlike most headphone driver baskets, NightHawk’s basket is intelligently designed for perfectly even distribution of its air vents, thus avoiding adverse rocking of the voice-coil. Free from the resultant distortion, low frequencies are better controlled and, therefore, sound cleaner and clearer, with more natural impact and extension.
NightHawk's equitangential corners (left) enable smooth airflow. Sharp corners of typical drivers (right) lead to turbulence and eddy current buildup around vents and internal cavities.
In NightHawk, airflow is further optimized through the use of equitangential curves. Rather than forcing air through vents whose edges are sharp, we allow air to take its natural course, thus counteracting high-frequency chuffing.
The Solution: NightHawk
NightHawk does not exaggerate high frequencies in order to create the false perception of greater detail.
Unlike headphones that exhibit significant boosts (+5dB or more) at frequencies from about 2–8kHz, NightHawk’s frequency response is perceptually balanced based on research in the fields of room acoustics, head-related transfer functions, auditory physiology, and modern measurement techniques. In fact, NightHawk exhibits greater extension and better linearity at both low- and high-frequency extremes than most headphones at any price. (NB: Above 8kHz, there is no good way to accurately measure frequency response 16. See “Notes on Headphone Measurements” below.)
The high-frequency boost of so many other headphones is due in large part to free-field or diffuse-field equalization, discussed above. Because so many other headphones are boosted by +5dB or more at high frequencies, a listener who is accustomed to that sound may initially perceive NightHawk as having recessed highs. However, NightHawk’s response is actually more naturally detailed and extended at upper-mid and high frequencies—a fact to be revealed through extended listening. We recommend that listeners put up to 150 hours of active playing time on NightHawk headphones before making serious attempts at assessing its sound quality. This will provide ample time for NightHawk’s biocellulose driver diaphragms and rubber surrounds to break in, and will also give certain listeners the time they need to adjust to NightHawk’s uncommonly low distortion.
Impedance: 25 ohms
Power Handling: 1.5W
Driver: 50mm Dynamic | Biocellulose Diaphragm | 1.2T Split-Gap Motor
Frequency Response & Distortion Measurements
Length: 8’ (2.4m)
Conductors: Solid Perfect-Surface Copper+ (PSC+)
Geometry: Symmetric Star-Quad
NDS: Noise-Dissipation System
Terminations: 3.5mm Stereo > Dual 2.5mm Mono | Direct-Silver Plated Copper
Why does NightHawk sound so different from most headphones?
Notwithstanding the various driver technologies (Dynamic, Planar Magnetic, or Electrostatic) available to headphone designers, the majority of today’s headphones exhibit frequency responses that are plainly characterized by an upward tilt. That is, in contrast to their midrange and bass frequencies, their upper midrange and high frequencies are unduly emphasized. This situation is made worse by the unavoidable nature of Mylar, a pervasively used diaphragm material, whose high-frequency instability can be characterized by increased distortion at breakup frequencies.
NightHawk is designed for near-zero distortion and a much more natural frequency response. Unlike headphones that exhibit significant boosts (+5dB or more) at frequencies from about 2–8kHz, NightHawk’s frequency response is perceptually balanced based on research in the fields of room acoustics, head-related transfer functions, auditory physiology, and modern measurement techniques. In fact, NightHawk exhibits greater extension and better linearity at both low- and high-frequency extremes than most headphones at any price. Further, it employs a carefully constructed bio-cellulose diaphragm with a true voice-coil former and compliant rubber surround to help achieve this extension, balance, and ultra-low distortion.
NightHawk does not exaggerate high frequencies in order to create the false perception of greater detail.
Does NightHawk require a break-in period? If so, how long will it take? And how should it be accomplished?
Yes. NightHawk, like all mechanical devices—loudspeakers, phono cartridges, automobiles, etc.—will require some amount of “break-in” before reaching optimal performance. Results will vary from user to user, but, as a general rule, we suggest 150 hours of playback.
Break-in can be achieved without listening by connecting NightHawk to a system and playing a wide-band audio signal (such as the white- or pink-noise tracks commonly found on test discs) or music that features excellent dynamic range and tonal variation (such as large-scale classical). However, we recommend you achieve break-in through listening to music, at safe volumes, as you normally would.
NightHawk’s cable will also require time before reaching its peak performance. With cables, however, the term “break-in” is a misnomer. The more accurate term is “burn-in.”
What’s really happening is that the insulation, or dielectric, is being “formed.” When a signal is present (i.e., when current is flowing), the dielectric absorbs energy from the conductor, which causes the molecules in the dielectric to be gradually rearranged from a random order into a uniform order. The process may take up to two weeks.
Once the molecules are fully rearranged, the cable is “burned-in.” The dielectric will now absorb less energy from the conductor, causing less harm, and improving performance. To ensure that the cable stays “burned-in,” there must be a signal present in the cable at all times. While it’s impractical to have your system playing constantly, you can leave the components powered on. Even when there is no music playing, there is an electric potential present. This will ensure that your cable (as well as your components) remain at their peak performance. However, if there is no signal present in the cable at all (i.e., if all the components are switched off, or if the cable is disconnected), the molecules will gradually rearrange themselves back into their original random order. Over a period of about two weeks, the cable will become almost like new again.
The ideal burn-in time is essentially the same for all cables. However, the apparent need for burn-in varies wildly. Human perception is more sensitive to the existence of a distortion than its quantity. Therefore, a superior cable or component, when new, will sometimes sound worse than inferior alternatives: the obvious distortions that have not yet been defeated by adequate break-in or burn-in will not be ameliorated by other gentler distortions. As with amplifiers and other components, the better the cable, the less distortion it has, and therefore the less there is to conceal the obvious distortion associated with simply being new.
What is Liquid Wood?
Liquid Wood is the material used to form NightHawk’s sophisticated earcup enclosures. Made from 100% renewable raw materials, its principal component is lignin—a byproduct in the cellulose pulping and papermaking process—whose annual production exceeds 50 million tons.
Whereas the production (and disposal) of plastic—a much more commonly used earcup material—is known to present environmental hazards, the production of Liquid Wood has minimal impact on the ecosystem. Lignin is combined with natural fibers, resins, and waxes, then treated in such a way that it can be injection molded.
Compared to ordinary plastic or wood, Liquid Wood has far superior acoustic properties and provides a vast array of geometric possibilities. In NightHawk, Liquid Wood is used to shape the earcups to more closely resemble the human ear, thereby providing a more complete and comfortable fit, reducing stress on the listener’s head and ears. (For more information, see Sustainability and Acoustics.)