Boy, it's a long and rocky road testing cheap headphones. Manufacturers have to make a lot of compromises to build product at this low price, and you will have to be a bit careful when spending your money here to make sure it goes to things that are personally important. Let's see if we can sort through it all ... [caption id="" align="alignright" width="298" caption="Frequency response of the four sub-$40 in-ear headphones."][/caption]Of the first four sub-$40 headphones I really like the Skullcandy Smokin' Buds for young kids up through Jr. High school. The ergonomics are good for smaller heads; they'll like all the bright colors; and the rolled off high frequencies will be gentler on their ears when they inevitably turn it up too loud. (On that note, I regularly check how loud my daughter plays her music and remind her that if she wants to enjoy music long into her life she needs to keep the volume low. You too might want to do that.) The Skullcandy Titans while a bit zippy in the high frequencies have huge bass and come in some really cool color schemes. The aluminum construction of these headphones may make them well suited to older kids who are likely to beat them up by running them over with a skateboard or some similar thoughtless act. Careful if they'll wear them under a beanie though as the hard edges may be uncomfortable. The iHarmonix Pro ev with only two ear tips of roughly the same size is adults only, and only if your budget won't let you spend the $5 more to get the Sonys. The sound quality winner of the sub-$40 group is the Sony MDR-EX56LP. They are a little tricky to get seated in your ears, but it's well worth the effort. And like all the above headphones, only more so, they'll sound great when compared to the standard ear buds that came with your portable player. [caption id="" align="alignleft" width="298" caption="Frequency response graphs for the $50 in-ear headphones."][/caption]You can see the frequency response graphs of the $50 in-ear headphones are bunched more closely together as one would expect as the headphones get better sounding. All three of these cans are better sounding than the lower priced headphones in this review, and each has merit in its own way. The Klipsch Image S2 is a really cool looking headphone --- yes, I'm rather old school. Their long slender body and unique oval tip allow these headphones to slip farther into your ear (more comfortably too) than the other cans reviewed here and provide terrific isolation for outside noise. In noisy planes and trains their better isolation probably makes the slightly uneven sound compared to the next two a worthwhile trade-off. The Denon AH-C360 is almost as good sounding as the Sennheiser, but the ergonomics are superior in my view. The angled tip seemed to fit most better, and the ability to route the cable up and over the ears, and around to the back of the neck where the sliding keeper snugs them up will work much better for those using the headphones for exercise and other physical activities. Which brings us to the surprisingly good sounding Sennheiser CX 300-II, a very good general purpose in-ear headphone. A strong bass, well behaved mid-range, and tasty highs make this a fun headphone to hear. Sure I gripe about the unequal earpiece cable lengths of the "J-cord" but for most day-to-day purposes it works quite well. Believe me, with sound this good, I'm not going to complain much. Thanks for reading along and hearing my thoughts on low-cost in-ear headphones. What about you? What are your favorite low-cost in-ear headphones, and why?