Since in-ear headphones sit in or near the ear canal, they don't interact with the pinna, the bends and curves of the outer ear that direct sound to the ear canal. The pinna also serves as an acoustic filter, enhancing the frequency range of human speech, and it also supplies directional cues, so we can localize where sound is coming from. That's how our ears and brains process sound in real life, but in-ear headphones don't interact with the pinna, so they can't sound as realistic as full-size headphones or speakers. In-ears can still sound great, but they definitely sound different than full-size headphones. To test how they differ, I first compared the C5 ($179) in-ear with the P3 ($199) on-ear headphones. Both are made by Bower & Wilkins.
I selected those two because they were probably designed by the same team, so it seemed like a great way to zero in on the differences between the two types of headphones. The C5 in-ear model has tight punchy bass and excellent midrange detail, while the P3 on-ear set has a warmer, richer tonal balance, so it's less articulate and more laid back. Vocals sound more natural, and the P3's dynamic punch outshines the C5's. Turned up loud, the P3 is easier to listen to than the C5. The P3's stereo imaging was slightly more open than the C5's. I also found the P3 more comfortable to wear over extending listening sessions; like most universal-fit headphones, the C5's eartips' fit wasn't totally secure, so they would occasionally fall out of my ears or lose the seal and bass response would plummet. Full-size headphones don't have those problems. The P3 wins Round One.
I next selected two of my favorite $100 headphones, the Thinksound ts02 in-ears, and compared it with the Audio Technica ATH WS55 full-size headphones. This little one had full bass and good overall sound, but the ATH WS55s still trounced it, first because it had a broader, more accurate tonal balance, and the expansive stereo imaging sounded more natural. The ts02 headphones are so light and comfy that it was easy to forget they were in my ears. Full-size wins again for sound.
To finish the in-ear vs. full-size shootout, I brought out the big guns: the custom-molded Jerry Harvey JH-13 headphones ($1,099), plugged into an ALO Rx MK3B portable headphone amplifier ($649) and a Cypher Labs AlgoRhythm Solo digital-to-analog converter ($579). The sound was just as good as I remembered it from a few weeks ago. For full-size headphones I used Audeze LCD-2 headphones ($995), matched with the Red Wine Audio Corvina ($1,000) home amplifier (and the AudioQuest DragonFly ($250 digital converter, review in the works). Again, the sound was stunning.
The JH-13/ALO/Cypher Labs system resolves detail and the very texture of sound with a beguiling ease. Listening on the subway or bus to sound this good, it's hard not to have a big, fat smile plastered across your face. In NYC, that makes people stare at you. The following comparisons were done at home, and when I switched over to the Audeze/Red Wine/AudioQuest combo, the sound field expanded outside my skull; the in-ear headphone kept more of the sound in my noggin. Playing the Simon and Garfunkel "Live '69" album, the sound really did sound live; it was more like being there. The spatial quality of the full-size headphones tipped the balance for me, but I have to admit the in-ears more intimate perspective was enjoyable in its own right.
Radiohead's dynamics kicked harder over the big headphones; the weight of the bass made me feel more connected to the music. The JH-13/ALO/Cypher Labs setup was a marvel, but the Audeze combo came out on top, so it's three for three for big headphones. Size, even for headphones, still matters. Neither set of headphones scores high for comfort, but I'd give the nod to the JH-13s.
I prefer full-size headphones' sound, but never use them on the go; I will continue with in-ears for those occasions. If you're on a limited budget and only going to buy one type of headphones, put some thought into how and where you're going to use them before you buy them.