The K-81 would be nice if it weren't for their outrageous bass. As it goes, they have excellent diaphragm travel, deep space, deep dynamics, but the bass is plain nauseating (with a headphone amp anyway). Now, "portable" headphones aren't those that are foldable, "portable" is anything that doesn't require an AC/DC adapter and doesn't weigh 1 KG (or more). Has anyone ever seen someone fold their "portable" headphones anyway? Most of the time they just hang on the neck. CAL/Denon AH-D1001 are great street headphones. So, what this comes to. Please, more circumaurals in the review, and not just foldable. In short: if it can be powered by a player and is lightweight and comfortable, it's good for outdoors. JVC HA-RX700 sounds interesting. Yamaha RH5MA sounds interesting (and cheapish).