Transducer technologies employed much less commonly for headphones include the Heil Air Motion Transformer (AMT); Piezoelectric film; Ribbon planar magnetic; Magnetostriction and Plasma-ionisation. The first Heil AMT headphone was marketed by ESS Laboratories and was essentially an ESS AMT tweeter from one of the company's speakers being driven at full range. Since the turn of the century, only Precide of Switzerland have manufactured an AMT headphone. Piezoelectric film headphones were first developed by Pioneer, their two models used a flat sheet of film that limited the maximum volume of air movement. Currently, TakeT produces a piezoelectric film headphone shaped similarly to an AMT transducer but, which like the Precide driver, has a variation in the size of transducer folds over the diaphragm. It additionally incorporates a two way design by its inclusion of a dedicated tweeter/supertweeter panel. The folded shape of a diaphragm allows a transducer with a larger surface area to fit within smaller space constraints. This increases the total volume of air that can be moved on each excursion of the transducer given that radiating area.
Impedance: Generally speaking, the lower the headphones' electrical impedance (aka resistance), the easier it is to get higher volume. But here again, the low impedance is no guarantee of high volume capability; other factors can still limit loudness potential. Since many MP3 players have feeble power output -- the iPod is a notable exception -- smart shoppers should check the loudness before purchasing any pair of headphones. To be sure, listen with your player.
Pairing high sensitivity headphones with power amplifiers can produce dangerously high volumes and damage headphones. The maximum sound pressure level is a matter of preference, with some sources recommending no higher than 110 to 120 dB. In contrast, the American Occupational Safety and Health Administration recommends an average SPL of no more than 85 dB(A) to avoid long-term hearing loss, while the European Union standard EN 50332-1:2013 recommends that volumes above 85 dB(A) include a warning, with an absolute maximum volume (defined using 40–4000 Hz noise) of no more than 100 dB to avoid accidental hearing damage. Using this standard, headphones with sensitivities of 90, 100 and 110 dB (SPL)/V should be driven by an amplifier capable of no more than 3.162, 1.0 and 0.3162 RMS volts at maximum volume setting, respectively to reduce the risk of hearing damage.
Will Greenwald has been covering consumer technology for a decade, and has served on the editorial staffs of CNET.com, Sound & Vision, and Maximum PC. His work and analysis has been seen in GamePro, Tested.com, Geek.com, and several other publications. He currently covers consumer electronics in the PC Labs as the in-house home entertainment expert, reviewing TVs, media hubs, speakers, headphones, and gaming accessories. Will is also an ISF Level II-certified TV calibrator, which ensures the thoroughness and accuracy of all PCMag TV reviews.
If you’ve been on an airplane in the last few years, you’ve probably seen the Bose QuietComfort noise-cancelling headphones before: they’re a favorite of regular travelers because they’re so good at keeping outside noise out. They’re comfortable, they sound incredible, and the noise cancellation is so impressive that you feel like you’re in your own personal bubble. These headphones are not cheap, but they’re definitely worth the money.
Case in point: the Koss PortaPro headphones first hit the market in 1984 and have become such a favorite with audiophiles that the company leaves the design (and the price tag) untouched. You can still pick one up for less than $50, and they come with a lifetime warranty, no receipt necessary. Check out our favorite budget headphones for more selections.
Communication headsets are used for two-way communication and typically consist of a headphone and attached microphone. Such headsets are used in a variety of professions as aviation, military, sports, music, and many service-oriented sectors. They come in all shapes and sizes, depending on use, required noise attenuation, and fidelity of communication needed.
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