What information do I need on headsets or headphones to accuratly compare audio quality?

Question

I would like to know which of the following details I should take into consideration when attempting to judge audio quality:

• Often comparisons of headphones only show the frequency range. However frequency range alone does not at all guarantee a good audio quality. I should always aim for about 20Hz to 20kHz correct? Is it worth to go for headphones which reach ever so slightly over 20kHz or below 20Hz?
• I have also heard of graphs showing the frequency response of a headphone. Can I ask for these at most stores?
• Also the impedance seems to be relevant, to judge whether a headphone needs an amplifier to work properly. But is there a good reason to choose for headphones which require amplification? Isn't low impedance always the best impedance?
• Some headphones offer noise cancelling. Is it only noise insulation or is it also an electronic component of a headphone which actively reduces noise?
• Do open headphones have a better audio quality than closed headphones?
• How relevant is the size of the driver?
• Does it matter what kind of magnet is used?
• And can wireless headphones compete with the audio quality of wired headphones?
• Maybe there are other relevant details I didn't list here.

I would like to be able to separate relevant information from commercial 'mumbo jumbo' next time I walk into a store. Of course good audio is in the ear of the beholder, but I would like to know how I can compare the specifications of headphones to make the search easier.

(This question is limited to quality of the audio, not the headset or headphones as a whole.)

So which of these specifications do I really need to know?

Let's assume I want the very best audio quality.

Answer 1

"Audio quality" is typically a function of the induced change in the signal. As quality goes up, the amount of change goes down. The best quality is the one that plays back the signal with no changes (there's no difference between the input and output).

With that in mind, you should be interested in the measurement of those changes. Look for a flat frequency response, and a very small total harmonic distortion. The frequency response alone will give you a very good idea of how the headphones behave, if you know how to interpret it.

Often comparisons of headphones only show the frequency range. However frequency range alone does not at all guarantee a good audio quality.

That's correct.

I have also heard of graphs showing the frequency response of a headphone. Can I ask for these at most stores?

In most stores they'll give you a weird look and ask what the hell are you talking about. Frequency response is sometimes visible in the box, sometimes included in the documentation. You'll have better luck doing that research through the internet than attempting it in the store. Any decent headphones should have that info available in the official site.

Also the impedance seems to be relevant, to judge whether a headphone needs an amplifier to work properly.

Correct, and if you need an amplifier you are interested in the specifications of the amplifier as well.

Some headphones offer noise cancelling. Is it only noise insulation or is it also an electronic component of a headphone which actively reduces noise?

It typically refers to isolation. The specifics of the implementation vary between headphones.

Do open headphones have a better audio quality than closed headphones?

Open headphones tend to have a better quality by themselves, but they are also terrible for noisy environments (in which they tend to perform worse than closed headphones).

The comparison depends on the context.

How relevant is the size of the driver?

As a consumer, sonically and not aesthetically, it shouldn't be of concern. Bigger drivers tend to reproduce lows easier, and smaller drivers tend to reproduce highs easier (think woofers vs twitters), but the acoustics and mechanics involved are not that simple, so the diameter itself tells us little to nothing. A huge drive can have awful lows, and a small drive can have good lows.

Does it matter what kind of magnet is used?

Every little design detail matters, but you already have the information you want from that system (the headphones) condensed in the frequency response. As a consumer it shouldn't matter, unless you are looking for a specific feature that a specific magnet offers.

And can wireless headphones compete with the audio quality of wired headphones?

Yes.

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In short, all you should need is the frequency response. If you want to use them in noisy environments (outdoors, a room next to a busy street, work, etc), go for closed headphones.

Don't over-think it though. Frequency response will give you a good idea of what to expect, but you should try the headphones with some material you are very familiar with (your favorite songs) before making a decision. Flatter is not always better.