Every headphone has two key specifications: impedance (measured in ohms, Ω) and sensitivity (measured in dB per milliwatt). Together they tell you how hard an amplifier has to work. High impedance means high voltage is needed. Low sensitivity means more power is needed. A 300Ω headphone at 91.8 dB/mW — the Sennheiser HD 600 — needs 6.6 mW and 1.4 volts for a 100 dB peak, which is more voltage than a weak phone output has. A 32Ω headphone at 110 dB/mW needs 0.01 mW and 18 millivolts for the same peak, and runs from anything. Impedance sets the voltage you need; sensitivity sets how much of it.
Probably not a separate DAC. Modern motherboard audio and smartphone DACs are genuinely good. The component that makes the biggest difference for hard-to-drive headphones is the amplifier — specifically, one with enough voltage swing for your impedance load. A $100 dedicated headphone amp will usually have more voltage swing than the 3.5 mm socket on a $1,000 phone, and voltage swing is what 300Ω headphones need. A good USB-C dongle closes most of that gap, which is why the honest answer is "check the numbers" rather than "buy an amp".
Consumer headphones are tuned to a target curve — usually a variation of the Harman curve — which controlled, level-matched listening tests find most listeners prefer, trained and untrained alike. It emphasises bass and softens the upper midrange. Studio models are generally tuned to a different balance — less bass shelf, more upper treble — which is not the same thing as flat: the DT 990, a studio staple, has one of the larger treble peaks on the market. Neither target is objectively correct, and neither hands you the recording unfiltered, because a headphone that measures flat at the eardrum does not sound like the recording — which is the whole reason target curves exist. The question is which target you prefer.
A headphone does not have a power requirement. It has a sensitivity, and you pick a loudness; the power follows. Every figure on this site is quoted at 100 dB SPL, which is not a listening level — it is a peak level. Most people listen between 75 and 85 dB, and music has short peaks ten to fifteen decibels above its average. Designing for 100 dB means the loud moments arrive intact instead of squashed, while the volume you actually sit at stays somewhere safe. If an amplifier clears that bar with 10 dB to spare, more power buys you nothing you can hear.
Four traps, in the order they cost people money. The unit. Sensitivity comes per milliwatt or per volt, the two differ by 10 × log10(1000/Z), and a bare “dB” settles nothing — the word in front of it does not settle it either, because makers who print per-milliwatt figures still label the line “Sensitivity”. The load. A power figure with no ohm value next to it is not a specification; two watts into 32Ω and two watts into 300Ω are different amplifiers. The output. Balanced and single-ended jacks on the same box can be rated four times apart, and plenty of makers print one number without saying which socket it belongs to. The mode. Gain and boost switches change the rating, so a headline figure may be the one you only get with a switch flipped.
An amplifier's own output impedance forms a voltage divider with the headphone, and because a headphone's impedance changes with frequency, that divider changes the frequency response. The working rule is that the source should sit under an eighth of the headphone's impedance. Above that, the amplifier starts tuning the headphone for you — often by more than an EQ preset would, and always without telling you. It is the reason a tube amplifier can make the same headphone sound different from a solid-state one while both measure fine on distortion, and it matters most for exactly the headphones people buy most: low-impedance in-ears.
Power answers whether an amplifier can get loud enough. It says nothing about what you hear when the music stops. A source has a noise floor; a sensitive in-ear turns that noise floor into audible hiss, and the more efficient the headphone the worse it gets. Sensitive in-ears and powerful desktop amplifiers are the bad combination, which is the opposite of the usual advice to buy the most powerful thing you can afford. The awkward part is that most makers do not publish a noise figure at all, so for a lot of gear there is nothing to calculate from — and this site says so instead of filling the gap with a guess.
"Endgame" is the audiophile term for the purchase that ends the search. In practice, endgame gear tends to reveal the limitations of your other components, which triggers another round of upgrades. The only genuine endgame is deciding what you actually want from audio and buying the tool that does that job — even if that tool costs $300 and comes in a cardboard box with no unboxing experience.
The Abyss 1266 TC is a remarkable headphone. So is the ZMF Verite Closed. So is the Chord Dave. They are also subject to diminishing returns so steep that the incremental improvement per dollar spent becomes vanishingly small above a certain level. That level is lower than most audiophile forums will admit. My own estimate, from having bought my way up the ladder and back down again, is that roughly $500–800 for headphones and something similar for source gear gets you most of the way — and that everything past it is a long, expensive road for the remainder. That is a judgement, not a measurement, and the endgame calculator states it as one.
Most of this site is a calculator answering one question at a time. These 11 tables are the opposite: the same arithmetic run over the whole database at once, printed in full. Each one lists only figures the makers published themselves, and adds a column no spec sheet contains.
None of them is a ranking of sound quality, and a product missing from one of them is missing because a number is missing from its documentation — not because it failed anything. Each table says so where it stands.