In the last two or three months, I have dabbled in headphones and earphones a bit. I have read a bit, and listened to a few devices which I could lay hands on. Here is my personal story, for what it's worth.

Why headphones at all?

I design and build speakers, and I love the feel of room-filling sound. Why then did I lean the headphone way?

Answer: privacy. I am sensitive to the presence of others when listening to music, and I live in an apartment where people (not necessarily family members) keep walking through the main living room where we keep our music system. With the coming of my (absolutely adorable) little boy, this has increased. I now do not get the chance to listen to music the way I would like.

I realised one fine day that I have practically stopped listening to music. This cannot be a good thing. Listening to any kind of music on any kind of system is better than not listening at all. Clicking any kind of pictures using any kind of camera is better than not clicking any photographs at all. (In both cases, the caveat is that you must enjoy doing it, therefore you need to set things up for at least a minimum level of quality.)

My thoughts turned towards portable music listening. I live and work in Bombay, and I sometimes visit clients 20 km away. This can be a two-hour drive each way. A chauffeur drives the car; I'd love to be able to sit back and listen to music during such rides. I also realised that I could sit in one corner of my home and listen to music on headphones or earphones with much more privacy than the main audio system in the living room.

For the source, I began wondering whether one needs to buy a dedicated MP3 player. Will a good cellphone do? A month ago, I lost my trusted Treo 650 in a sad accident, and upgraded to a high-end Android phone (the HTC Desire HD, if you must know). These phones all come with good analog headphone outputs and can be used as music players. I decided I will see how far this sort of rig can deliver good music. That's the starting point of my exploration of headphones.

Some basics learned

WARNING! All this is knowledge gathered by reading, not experiencing.

Here's some basic information I gathered while mucking around on the Internet:

• Morphology: Headphones come in all shapes and sizes (I include earphones here). Broadly, they can be classified into "big" and "small". Each category can be further subdivided:
  • "Big" thingies: the headphones:
    • Circumaural: they are like cups which surround your ears, enclosing them completely. One of the most glamorous of these designs is probably the one from Bowers and Wilkins.
    • Supraaural: these are like discs which sit on top of your ears, not surrounding them
  • "Small" thingies: the earphones:
    • Earbuds: the small circular things, like swollen coins, which sort-of sit at the entrance of your ears. These are the designs most commonly bundled with cellphones, music players, etc
    • In-ear phones: these things go inside your ear canal. Some go in only a bit, others quite a lot.
• Open and closed: The earbuds and in-ear monitors are all sealed at the outer end (their backs), and only have an opening towards your ear. The larger headphones, on the other hand, come in levels of openness. Some are completely sealed back. Others are completely open-back, allowing as much sound to escape from the rear as into your ear. And yet others are partly open-back, allowing some sound leakage to the outside.
• Headset or not headset: Some phones come with a microphone and controls, to allow you to use them as hands-free kits with a cellphone. These are called "headsets". Others are purely one-way street, for music listening.
• Impedance: Headphones and earphones vary in their electrical impedance. There are low-impedance models (32 Ohms or less) which are easy to drive from low-powered portable devices. There are medium-impedance models (250 to 300 Ohms), and then there are the seriously high-impedance headphones (600 Ohms). The higher the impedance, the more power you need to drive the devices. 600 Ohm devices simply cannot be used directly from a computer's headphone jack or a portable player's output.
• "Rich" and "dynamic" sound: These terms are often used by polite reviewers when talking about headphones and earphones which "enhance" the sound. If you, like me, want accurate reproduction, keep away from these models like you keep away from, well, spam emails, Justin Bieber, Britney Spears' music, ... you get the idea. In speaker design lingo, we call them "boom-tizz" designs, which carry a U-shaped SPL curve (frequency response). If you want the other type of headphone, look for reviews which use words like "natural", "accurate", and "clean".

  There is a huge market for "dynamic" earphones, connected to portable music players, used to pump bass straight into the brain, in a modern-day equivalent of intravenous drug abuse. Eyes of abusers will have the same glassy look in both cases, and both communities twitch involuntarily while in the throes of these psychedelic experiences. Both may show permanent brain damage. Keep away.

None of this, of course, has any impact on sound quality. That part comes later.

Let us glance at some samples of various shapes and sizes before we move on.

• The Bowers and Wilkins P5: these chaps are famous for making excellent speakers, and have just entered the headphone arena with this model. It is a supraaural closed-back low-impedance design. It's a sign of the times that B&W's first headphone model is designed for connecting to smartphones and MP3 players.

  Selling on Amazon right now (July 2011) for US$299.
  

• The Etymotic HF2: Etymotic are famous for in-ear monitors of very high quality. Their HF2 is a low-impedance IEM. IEMs are light, small, and usually very popular for portable music listening, because of their tight fit inside the ear canal (while jogging or gymming), light weight, and low impedance. The HF2 has two siblings, the HF3 and HF5. The HF2 has a mic and one-button control, which works for most smartphones. The HF3 has a mic and a three-button control unit, which works with the proprietary iPhone interface. And the HF5 has no microphones at all -- it is a pure earphone, not a headset.

  Selling on Amazon right now (July 2011) for US$99.
  

• The Beyerdynamic DT 990: This company is one of
  the most reputed headphone makers, and their DT 990 is designed for very high sound quality. It is available in three impedance ratings: low, medium and high, and prices of these three versions differ. This is a circumaural open-back design, which means the earcups completely encase the ears on all sides, but outside sounds will reach your ears, and headphone output will be audible to the guy in the next seat. This model has amazingly low distortion and is designed for critical listening or studio monitoring.

  Selling on Amazon for US$289 for the 32-Ohm version, US$299 for the 250-Ohm version, and US$304 for the 600-Ohm version. As in July 2011.
  

This was a sampler, not an industry survey. It was heavily non-representative -- it featured three models I found remarkable. It ignored about five dozen models I would not be caught dead using. It didn't even cover the most expensive or the most hot-selling models. The best place to read up about headphone models is probably Headroom. Very knowledgeable, frank guys.

What about sound quality?

Now I will humbly submit before your esteemed selves what I've learned about headphones and high quality audio reproduction. Once again, most of this learning is from the Internet.

• Price doesn't correlate with quality. There are $99 in-ear phones which can easily surpass headphones costing four times as much. (Duh!)
• Open-back headphones. If you want headphones (the big thingies), not earphones, then you may want to look at open-back models. It is particularly difficult to get a flat frequency curve and low distortion in a sealed-back model, because of internal resonances within the earcup enclosures. Therefore, the Beyerdynamic DT880 and DT990, the AKG K702, etc, all are open-back. (Well, the DT880 is semi-open.)
• Earphones. In this category, earbuds are almost always of poor quality. Discard them. After them come the second category: the boom-tizz earphones. Most of these are slightly in-ear designs -- they enter your ear canal just a little and fit there. The Denon AH-C260 and most models from Skull Candy, Monster and Dr.Dre are in this category. And after them come the IEM and high-quality earphones. These can be excellent for accurate music reproduction.
• A case of impedance. It seems that it's more difficult to manufacture really high-quality headphones with low impedance. Therefore, the top-end headphones (we're talking the absolute top end) are largely high-impedance -- 250 Ohms or higher. This means they can't be plugged in to your iPhone if you want to experience what the fuss is about. However, earphones and IEMs seem to be able to work very well with low impedance designs.
• SPL and distortion curves. This bit is common sense. If you want to know what a particular headphone model is like, SPL curves and distortion curves are very useful. Headroom is one of the very few places which makes available such data.
• IEM and the 7KHz itch. It seems that many in-ear monitors may have a peak in the frequency response at about 7 KHz. This may be due to resonances of the ear canal chamber where the IEM fits. The net result is a shrill edge to the sound. As often happens, I got rare insight from Dr Linkwitz. I looked up Reference Earphones on his site, and he talks about the uneven SPL curves of in-ear monitors. Watch out for this squiggle, and try to select an IEM which does not have this problem.
• Headphone amps. These are essential for mid- and high-impedance headphones or earphones. They add some value for low-impedance ones, depending on the quality of your basic player. Some of these headphone amps also include DACs. If you like listening to your music from your laptop, then one of these DAC+amp combinations may give you serious quality improvement, because they do a better job of D-to-A conversion of the USB sound than the laptop's internal circuits can.

My experiences

When I bought my cellphone, I got a wired headset with it (mic and earphones). The sound of those earphones was strictly so-so.

Chapter 1: the Philips earphones. I decided to buy an inexpensive pair of earphones which would go into the ear at least a little bit, just to see whether I got better sound. So I started flipping through offerings at Reliance Digital, Croma, and similar stores. It's very hard to find something which does not claim to give you thumping and heart-pounding bass. After flipping through a dozen models, mostly by Panasonic, Sony and Philips, I picked up a pale blue coloured set for Rs.400 or so (US$ 10). They were the "lightly in-ear" kind, with rugby ball shaped soft plastic tips (see picture of another brand's tips of the same shape). The set came with three sizes of these replacement tips -- the smallest of them seemed to work well for me.

Initial impressions in the first fifteen minutes were very gratifying -- I was hearing detail I'd never heard before, and thus the music was very engaging, attention grabbing. I was thrilled. After a couple of days, I began to feel that the sound had a harsh edge. So I kept it in a drawer at home all day and night one weekend, plugged into my laptop and playing BB King in an infinite loop at fairly loud volumes. The sound improved quite a bit on Monday. Break-in actually works.

Mechanically, these earphones are "made to a price" -- their low price is visible in the fit and finish and quality of, say, the cable and connector. I'm not complaining here -- I'm just saying that costlier earphones I've seen are visibly better built.

After a week or two, I began to notice that some music (specially the brighter ones, e.g. most things by Billy Joel) would sound too loud at "normal" volumes. If I cut the volume, then those pieces would sound right but anything not that bright would sound too soft. So I noticed that I was constantly pushing the volume setting up and down a notch or two between songs. Initially I thought that this volume sensitivity is par for the course with earphones, specially "revealing ones" like mine. Then I began to wonder whether there was indeed something wrong with the sound.

Chapter 2: the 7KHz itch. At that time, I browsed around, spoke with friends, and chanced upon Linkwitz' page on Reference Earphones (link given earlier in this page). I read his remark about how he found that more than one pair of in-ear phones has this peak in its SPL curve at about 7-8 KHz. I began to wonder. I downloaded PowerAMP, an Android music player which among other things, plays back gapless tracks correctly and has a 10-band graphic equaliser. I usually keep very far away from equalisers, but this time, I decided to try cutting the gain at the 8KHz channel. My earphones immediately became much more listenable.

It's quite a strange experience. You would think that cutting an entire octave-wide band sharply in an equaliser will make a big difference. You would expect that pieces of music would go missing -- cymbals would sound dull, saxophones would sound like they've caught a cold. Nothing like that happened. But my listening fatigue largely disappeared. Now I could listen to bright pieces and softer pieces without having to fiddle with the volume control between songs.

One mystery had been solved. It was clear that my cheap Philips had non-linearities in its SPL curve and was adding a harsh edge at certain frequencies.

Chapter 3: The Etymotic HF2. After these experiments, I was ready to buy a decent pair of earphones, plonking some non-trivial (for me) cash. So I did my online reading and concluded that Etymotic seemed to be a "safe" brand to make friends with. Other brands, including many very high-quality ones, seemed to like some "personality" or "colour" in the sound of their earphones, even their high-end models. But Etymotic seemed to be happy just giving you the sound as accurately as possible. My kind of guys.

So I compared their models:

• The ER range: their most expensive ones
• The HF range: HF2/HF3/HF5, all costing US$100 or more
• The MC range: MC3/MC5: their entry-level models

I decided to opt for the HF range, since they were much less expensive than the ER range and fit in my budget. They seemed to have pretty much identical sound, but the HF2 had a mic and single-button control, thus acting as a headset in case I needed to take calls on my cellphone. (The HF3 had three-button controls for iPhones, and the HF5 was pure earphone.)

I bought the phones from Amazon, and ordered extra eartips for them. One never knows whether the standard set of tips would fit right -- and ordering from the US into India is always a major project.

The sound. It's beautiful. It's hard to say what's so great about it, because there's nothing breathtaking or dramatic about the sound. It sounds neither dull, nor "revealing" nor "rich". It just sounds right.

With the earlier Philips phones, I used to be lulled into sleep (literally) if the volume was a notch lower than optimal. I don't know what this indicates. But with these phones, the music remains very engaging at the right volume.

It's an amazing experience for me to hear sound reproduced "just right". I can hear more details than I have ever heard on any kind of system. (Yes, this is my first experience with good earphones/headphones.) If I have to describe the sound I get, the best description is that it is extremely "balanced". Everything is in the right place, in the right proportion, and without either extra detail or extra oomph. And music sounds so bloody good. :D

Two more points. No break-in was required for the HF2: it sounded this good from the first minute. And I encountered no problems with the fit in my ears: their standard triple-flange tips which were fitted when I got them are perfect for me.

The MC5. A friend bought the Etymotic MC5 soon after I got my HF2, so I got a chance to compare them. The MC5 costs almost half as much as the HF2. The sound quality is so close that only an A-to-B comparison session shows up differences. The basic "nature" of the sound of both these models is the same. The only difference I can see is a slight loss of resolving power, the finest levels of detail, in the MC5 -- you can "see into the music" a bit more with the HF2. So, as things stand, the MC5 is a great budget alternative to the HF-series.

The issue of SPL. Cellphones may have different levels of sound at their headphone outputs -- beware. If you are the kind that needs slightly louder sound to hear the music right, then some cellphones may disappoint you. I have tried listening to music on the Samsung Galaxy S and my HTC Desire HD. I have used the same earphones and the same music files (copied into both phones from the same computer). The Samsung cellphone's max volume is similar to what I get from the HTC at about 4-5 notches lower than max. This difference is quite a lot -- one friend has problems enjoying music from the Samsung phone because of the SPL being too low.

The issue of quality. People say that MP3 files cannot sound good. People say that an inexpensive cellphone and earphone, without headphone amps, cannot sound good. All of this may be true. But I am hearing clearer, more accurate, more enjoyable music with my current rig than I have heard from anything else I've heard in the past. (I've spent one evening listening to a US$30,000 2-channel audio system with Balanced Audio Technology CD player and amp and Dunlavy speakers. I've also heard many other very high-end systems.) Therefore I'm inclined to believe that others may be able to hear the limitations of my current rig -- but for me, with my limited hearing ability, this is a great setup.

Lossy digital music encoding: a comment

All my exploration into music listening through earphones from laptops and cellphones has taught me one interesting thing: MP3 encoding done well can sound indistinguishable from lossless digital audio (WAV or FLAC). Most of the MP3 I see on the Internet is atrocious quality (96 and 128 Kbits/sec). The MP3 I download from Amazon seems to be mediocre. The only MP3 I can trust is the one I have encoded myself. I use

   lame --preset extreme

to encode MP3 from WAV files. This generates VBR MP3 with bitrates varying widely, from 32 Kbits/sec in the quiet leader/trailer passages going up to 256 and 320 Kbits/sec in the other parts. I cannot hear any differences between these MP3 files and their WAV originals. I have often heard distortions in songs when listening to the MP3 versions, and each time that I've checked against the FLAC version of the file, I have heard exactly the same distortion. So it's in the recording, not in the MP3 encoding. However, your mileage may vary.

All in all, music is back in my life. :D