A Beginner's Guide to Audiophile

@katzkov 

The most important parameter to headphones (and speakers too) is frequency response - that is, how smoothly and perceptibly even the headphone reproduces the audible frequencies (20 Hz - 20 kHz). Everything else - driver material / type, headphone construction, etc. - can be considered 'window dressing'.

Currently, research relating frequency response to sound quality has produced the Harman Target curve. This is a frequency response for headphones that was obtained by measuring the response of sonically neutral speakers in a well-treated listening room using a head / torso simulator and further refined by listeners (trained and untrained) over a series of experiments. This would be your best shot at hearing a 'reference' or 'neutral' frequency response.

Several headphones follow the Harman curve - the AKG K371 ($149), the Mark Levinson No.5909 ($999) well as the Dan Clark Audio Stealth ($3999).  Any of these headphones can be used as a reference. Importantly, there's little correlation between sound quality and price. For example, I've owned or listened to plenty of expensive headphones from the HD 800 to the Focal Utopia, STAX SR-009 and the DCA Stealth. The headphones I use daily are the AKG K371's. They sound very close to the Revel Ultima Studios I use in my stereo.

If you don't happen to like the sound of headphones tuned to the Harman curve, use an equalizer to find which frequencies need a boost or cut. Using your adjustments along with measurements of a headphone's frequency response can give you a better idea of which headphones would be better suited to your personal taste (if you don't feel like using an equalizer is a permanent solution). This frequency chart can help you in that process - EQ Cheatsheet.

Here's some more reading on the Harman curve in case you're interested:

Headphone Measurements Explained

Where Are We At With The Harman Curve?

Are There Valid Objections to the Harman Curve?

Get Robert Harley’s book: The Complete Guide to High End Audio. I re-read it every few years. All questions will be answered.

If your interest continues,  get a subscription to Stereophile and The Absolute Sound. 

I agree that Harley’s book is probably a good place for you to learn many of the concepts and jargon that describe and embody high-end audio.  But the BEST thing you can do is go listen to as many headphones as you can with your own music, and then all these aspects of sound will become more relatable and — most importantly— you’ll start to form your own opinions on what sounds good to YOU, and in the end that is all that matters.  

Try to hear somebody playing music live, whether it be at a bar, a nite club or a musical instrument store. It doesn't matter if the musicians are good. Just try to get an inkling as to what musical instruments actually sound like. Of course, if you or somebody around you does play, so much the better. You can also try going to a mall or department store. What do the customers and salespeople sound like? Take note as to how sound varies when it comes to how far away it is, and whether the setting is echoed or "dry.". In other words, set about training your ears.

@soix and @edcyn

+1

The real learning that is required in high end audio is to be exposed to the terminology then examples of real sound, and in reproduced equipment. Over and over again.

I have been learning about sound and music / reproduction for fifty years… I continue to learn. I only got rhythm and pace down about ten years ago, although reading and listening all that time. Ok, maybe I am slow… but it is a process of reading and exposure.