The number one rule to understand when embarking on your headphone-search journey is to understand that there is no one headphone to rule them all. Like automobiles, headphones are made for different purposes. You have the supercars, roadsters, SUVs, 4x4s, sedans, to the compacts, and you chose what’s best for your day to day needs. There is no one car that can tackle snow and win races on the drag strip. The sooner you understand this fact, the more money you will save.

We run every pair through a rigorous testing process over several days or weeks. That includes playing them in all sorts of scenarios — be it on a bus, in the listening room, or at the office — and playing back from a wide array of sources. We know most people use their headphones with a smartphone, often with lower-quality MP3 resolution tracks, so we do, too.
Be sure to assess the build quality of your prospective headphones. Some earbuds and portable devices are relatively fragile, for instance. If the headphones fold up for easy storage, are the hinges robust, or will they fall apart in a month or two? Don't forget to consider that the earpads and earbuds will get extensive wear and tear over the life of the headphones.

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.
A good headphone should last 25 years. The first thing to replace is earpads usually, since wear affects the sound. Sometimes the cable will get a loose connection and need replaced. The drivers should be good forever, but in some rare cases a hair can work its way in and cause a buzz or rattle. If that happens it’s usually easy to remove an earpad and pull the hair etc. out.
The QuietComfort 20 headphones have been around for years and years; and they’re essentailly an in-ear alterative to Bose’s QuietComfort 25. They offer the same great active noise-cancellation that the company is known for, just in a traditional wired and in-ear form factor. The QuietComfort 20 can also be switched to an “Aware” (aka ambient) mode, so you can better hear the world around you.

These headphones pack about 16 hours of battery life, which ought to be enough for a whole day or more, but if not, there’s always the option of using an analog cable instead. An external switch lets you turn the noise cancellation on and off. Make no mistake, these might be aimed at kids, but the quality of construction, selection of materials, and color choices give them an appearance that will still appeal to your young charges long after they’ve outgrown their Disney phase (some of us still haven’t).

These early headphones used moving iron drivers,[7] with either single-ended or balanced armatures. The common single-ended type used voice coils wound around the poles of a permanent magnet, which were positioned close to a flexible steel diaphragm. The audio current through the coils varied the magnetic field of the magnet, exerting a varying force on the diaphragm, causing it to vibrate, creating sound waves. The requirement for high sensitivity meant that no damping was used, so the frequency response of the diaphragm had large peaks due to resonance, resulting in poor sound quality. These early models lacked padding, and were often uncomfortable to wear for long periods. Their impedance varied; headphones used in telegraph and telephone work had an impedance of 75 ohms. Those used with early wireless radio had more turns of finer wire to increase sensitivity. Impedance of 1000 to 2000 ohms was common, which suited both crystal sets and triode receivers. Some very sensitive headphones, such as those manufactured by Brandes around 1919, were commonly used for early radio work.
Due to the extremely thin and light diaphragm membrane, often only a few micrometers thick, and the complete absence of moving metalwork, the frequency response of electrostatic headphones usually extends well above the audible limit of approximately 20 kHz. The high frequency response means that the low midband distortion level is maintained to the top of the audible frequency band, which is generally not the case with moving coil drivers. Also, the frequency response peakiness regularly seen in the high frequency region with moving coil drivers is absent. Well-designed electrostatic headphones can produce significantly better sound quality than other types.[citation needed]

Earbuds have small speakers that rest on the ear canal of the wearer. These are usually much less expensive than on-ear and over-ear headphones and reproduce the sound well. However, outside sounds, such as traffic or power tools, can get past the earbuds and interfere with your enjoyment. Earbuds also don't stay in place very well if the wearer is moving much, such as exercising. These also are lower fidelity than on-ear and over-ear headphones.