Hi all, My name is Zombie_X, and I am an audiophile. I mainly listen to high end headphones and high end amplifiers. I also have more affordable headphones and can give my opinions on those. I have heard over 100 different headphones and will be hearing more. This thread serves as a place for me to give advice tot hose are looking for new headphones. I'll split this up into a few areas and hopefully this will help you find headphones that will fit your needs. I have some videos on YouTube about headphones which can be viewed here > http://www.youtube.com/user/TheZXReviews?feature=mhee PORTABLE: Firstly is the nominal impedance of the headphone. The impedance dictates the electrical resistance posed by the driver (headphone speaker) as well as estimated power requirements by the headphone. The rule is lower impedance means easier to power while higher impedance is harder to power. Portable headphones impedance's vary from 10Ohm to 60Ohm. The lower the impedance the better in most cases, but this can be counter active. Why low impedance you may ask. Well the lower the impedance the more current and less voltage your headphone will require to get to an acceptable volume. Secondly is the sensitivity. You want high sensitivity for portable use. Sensitivity is also electrical resistance of the driver. More specifically it's more about a SPL (sound pressure level) that is reached at a certain dB/mW on said headphone. The higher the sensitivity, the greater the volume you will get. Low sensitivity is anything below 96dB. So a 16Ohm headphone with a sensitivity of 102dB (many IEM's have ratings around this number) would be great for portable use. Sensitivity ratings to look for should be from 98db to 106dB or more. Third but not last, for portable use you have to consider your source, or media player. Not all media players are the same and their output power varies. Ipod's have low output power and should be used with headphones around 16Ohm's-60Ohm's. The Zune HD or Sansa Clip are a lot more powerful and can be used with stuff of upwards of 100Ohms. Lastly you have to consider if you want an open headphone or a closed headphone. When using an open headphone, sound will leak out. While using closed headphones sound will be kept in and outside noises should not creep in. Also with closed headphones you will have stronger bass while with an open design the bass will be lessened but the sound will be smoother. HOME: For home use you should pair headphones with either a dedicated headphone amplifier or a surround receiver. I recommend using high impedance headphones at home. High impedance being anything over 100Ohms. The higher the impedance the harder they are to power. A 120Ohm load with a sensitivity of 94dB would require a lot more power and a lower impedance model with the same sensitivity rating. The sensitivity rating of these should be much lower than those of portable models. This is not always the case tough. Try to get something that easier to power (higher sensitivity) if you aren't going to be using a dedicated amp. Even though 96dB sensitivity on a 120Ohm headphone looks high, the impedance counteracts the sensitivity. Higher impedance headphones require a higher voltage swing to be supplied by the amp or receiver. The higher the impedance the more voltage is required. Unlike low impedance models, that crave current, high impedance need more voltage and less current. You have to make sure you have enough voltage on tap. So a 600Ohm load with 96dB sensitivity needs a very hefty voltage swing, right around seven volts. Most portable media players may output only up to 1V and maybe a but more, so portable use is out of the question. One final thing to consider is what application you will be using this for. For movies and games I recommend an open headphone as the soundstage would be more accurate. For msuic is toss up because certain headphones designs play well with the music. This is it for now so if you have questions then don't hesitate to ask.