Magnetostriction headphones, sometimes sold under the label Bonephones, work by vibrating against the side of head, transmitting sound via bone conduction. This is particularly helpful in situations where the ears must be unobstructed, or for people who are deaf for reasons that don't affect the nervous apparatus of hearing. Magnetostriction headphones though, are limited in their fidelity compared to conventional headphones that rely on the normal workings of the ear. Additionally, in the early 1990s, a French company called Plasmasonics tried to market a plasma-ionisation headphone. There are no known functioning examples left.
The iPhone will drive the headphone fine and make a very nice sound, but the amp will make a big improvement in harmonic extension and soundstage. Use the amp whenever possible. Both Headfonia and I concur that the E07k is a great amp, and probably the best thing you can get for up to twice the price. I’m familiar only with the E07k, the E17, and the E12. I think the E07k beats the E17 (and both are also USB DACs), while the E12 is just an amp, and has a darker sound but with more power for inefficient headphones. The Philips is not inefficient.

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).[12] 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:
At the heart of the WH-1000xM3 is outstanding wireless sound. Sony’s LDAC technology delivers a wireless signal at what the company claims is three times the quality of standard Bluetooth streaming, and the headphones also support the latest aptX HD codec (with supported devices). The 1000xM3 even “upscale” wireless music from high-resolution audio devices using a special chip, helping to make music sound dynamic and beautiful, with authoritative bass and clear treble response held together by a well-rounded midrange.
They’re among the best-performing wireless home/studio-style headphones in our ratings, and though the price fluctuates, you can often find them for as little as $150. That’s less than half of what you’d pay for some comparable models. If you want over-ear headphones with the convenience of Bluetooth, this pair is a steal. It comes with a detachable audio cable so that you can use your headphones without draining the battery, and the ear cups fold in for easy storage and travel.
The Bose QuietComfort 35 II is arguably still the most comfortable pair of noise-canceling headphones you can buy. Released in the summer of 2018, you can think of the QuietComfort 35 II as simplified, less sophisticated and more affordable version of the new Headphones 700. The lack the transparency mode, superior call quality, USB-C charging port and on-ear gesture controls, but they still boast really impressive noise-canceling skills. The also have the tradional foldable design — it folds more compactly — that many travelers really like.
What I’m saying here is that it’s better to own three $100 headphones than one $300 headphone. Or three $300 headphones than one $900 headphone. Why? Because most people don’t limit their playlist to strictly one genre. And following the logic from Rule #2, the right headphone-music pairing is going to be better than one expensive headphone paired to the wrong music.
Over-ear and on-ear headphones effectively block out outside sounds, allowing you to hear your music or whatever else you're listening to crisply and without distraction. Over-ear headphones are sometimes known as full-size headphones because they completely envelop the wearer's ear. This results in what's known as passive noise reduction, which makes these some of the most-preferred headphones available. The only drawback is that your ears and the skin around your ears can get warm and sweaty. These are usually the heaviest type of headphones.