The answer to this question by many audiophiles would be "As many as you can afford." But for the rest of us there's an upper limit to how many pairs of headphones we want to keep around.
One way to limit and control your headphone collection is to look at headphones from a usability perspective and view them as audio tools that have been created to serve different purposes and scenarios. That pair of headphones that sounds great when you listen to it at home in a quiet room can sound horrible when you're on your regular commute on the local train.
What makes the difference you ask? Isolation, or its lack thereof.
And what does isolation mean when it comes to headphones? For those who are interested in technical aspects, a headphone's ability to isolate or reduce noise levels from the outside environment can be measured in dBs. No isolation (such as you would get from bone conduction headphones) would provide 0 dBs, while the very best in-ear monitors can deliver between 25 and 30 dB of isolation.
So why not just use over-ear closed back headphones (or in-ears) with maximum isolation and be done with it - since the best noise isolation solution would win? Because, when you lock in or seal an earphone, you now have problems with enclosure resonances and bass loss if they're not properly sealed (and sometimes too much bass pumped inside your ear canals when they are). Also sealed or enclosed headphones tend to have soundstages that feel smaller. So, although a sealed headphone will solve your isolation issues it comes with its own set of audio problems.
What do you do then?
The Solution: have at least two pairs of headphones - a sealed or well-isolated pair for environments with a lot of ambient noise, and an open backed pair for quiet private areas. And what about "noise-cancelling" headphones instead of highly isolating ones? We suggest that you go for the latter - isolation doesn't depend on batteries, neither is it as selective in blocking out sounds as the former.
If I was only able to get three headphones in total, apart from the kind mentioned above, I'd go for an in-between pair "in-between" pair that provides some degree of isolation.
This type is great for public spaces where you need to have some degree of situational awareness, such as while waiting in an airline terminal. It'll block out most of the sound, but you'll be able to hear any announcements that are made.
The final (and perhaps most important) deciding factor in any headphone or earphone choice is how well it fits. Without an optimal fit not only won't a headphone perform at its best, you won't be able to wear them for long periods comfortably.
So, there you have it - own three pairs of headphones and your personal sonic world will be completely covered for all situations. For those who own 30 pairs, it's great that you enjoy audio so much, but you don't really need them, do you?
If you liked this article, you may also like: Why 5 Guys Hanging Out with Their Headphones is a Milestone for the Indian Audiophile Community
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