What are the best earbud headphones?

What is it that changes the bass response in different models of earbud headphones?

• I needed a new pair of headphones today and checked the details on the packaging of a wide range of headphones in the local shop, finally buying a pair with a 5Hz-23kHz range.  They sound excellent, and they weren't expensive, but in the past I've had some terrible earbud 'phones - tinny sounding even when crammed right into my lugholes.  The designs all look pretty much identical to me though, so what component is it that makes such a huge difference, and why would manufacturers make versions with such a poor range?

• Answer:

  How well the in-ear earbuds seal to your auditory canal is one important difference, though even a lot of the cheap buds often include 3 different sizes which you should always compare for best fit. Also the wires differ a lot, and are sometimes microphonic (you can hear movement of the wires through the buds), which is a bad thing. But the REAL difference is what's inside those buds, which you can't see. And forget the frequency response specs as any useful basis for comparison, the smoothness of the response is a much harder goal to achieve than the extremes that even the cheapest models claim. In general, I'd look to known brands first, the Sony Fontopia series is excellent value, also Sennheisers if your budget allows. The only useful spec is sensitivity; some MP3 players have brawnier amps than others, and if you're looking for high SPL (sound pressure levels) with a tiny amp, more sensitivity will help. 103dB or better is a good indicator that they'll get plenty loud (if not good) - also if the impedance is indicated that can make a difference; they range from 8 ohms to 32 ohms and higher. These days most players are happy with either end of the range, but a lower impedance unit should get louder, all things being equal. Still, the quality of the actual driver inside is what you're paying for, and only listening for yourself in a store or, failing that, looking at other users' reviews can point you towards a well-designed earbud that's easy on the ears with a wide range of music and at the levels you want... as to why they'd make bad ones, same thing applies, most people buy them based on either price or packaging and never get to listen to them until they're home, so manufacturers can get away with cheap materials and a short warranty (and they know hardly anyone ever makes warranty claims on cheap buds, they just go buy a different model.