However, the Bose 700 earphones have a much slimmer profile when folded up, and they have a few updated elements, including more integration with digital assistants, touch controls, and sensors for Bose’s “augmented reality” apps. Bose has kept some of the best-loved features from its older models as well, such as adjustable levels of noise cancellation, a monitoring mode to let in sound from your environment, and an advertised 20-hour battery life. According to Bose, call quality is improved as well, though CR doesn’t test call quality in headphones.
The fit isn’t always an easy thing to be sure of when you can’t try before buying, since some ear pads will not have a satisfactory fit to some ears. Power requirements aren’t a simple matter of looking at the impedance, since efficiency or sensitivity doesn’t always track directly with impedance. Another issue indirectly related to power requirements are whether the headphone has the option for ‘balanced’ use or some other connection that isn’t a 3.5 mm or 6.35 mm jack and plug.
There’s a lot of debate in the headphone world about wireless audio. Wireless standards like Bluetooth are capable of making music sound great, but because Bluetooth relies on data compression, it will never sound quite as good as a wired connection. The big question is, with the improvements in Bluetooth, can anyone tell the difference anymore between Bluetooth audio and wired audio? We’re skeptical that the difference is meaningful, so here’s our best advice: if you’re an audiophile who cares about hearing music in high fidelity, you’ll probably be better off with a set of wired headphones; if you need everything to sound great but prefer the convenience of wireless connections, go for a pair of Bluetooth headphones.
Sensitivity is a measure of how effectively an earpiece converts an incoming electrical signal into an audible sound. It thus indicates how loud the headphones are for a given electrical drive level. It can be measured in decibels of sound pressure level per milliwatt (dB (SPL)/mW) or decibels of sound pressure level per volt (dB (SPL) / V). Unfortunately, both definitions are widely used, often interchangeably. As the output voltage (but not power) of a headphone amplifier is essentially constant for most common headphones, dB/mW is often more useful if converted into dB/V using Ohm's law:
Although some headphones available are wired, many more are available that are wireless, and use Bluetooth to enable your music to be heard, even if the stereo or other device is several feet or even a few rooms away. Wired headphones deliver superior sound quality to wireless and Bluetooth because there's no chance of picking up interference from other devices, which sometimes happens with wireless headphones. In addition, wired headphones have no batteries to power them, so there's no chance of interruption should the batteries wear out.