the Troy Pro's or Killer B Wasp which are the two I have been using for quite some time now.
As a rule, having a good broad decibel range helps, but I have found that some of the best headphones to produce a clear and crisp audio response are those with an impedance of 100 ohms or more.
Most of the better headphones on the market today for the serious detectorist use speakers that are rated in the 100 to 150 ohm range. keep in mind that our detectors are not operating in stereo and the nominal impedance (due to detector design) is in the 50 to 75 ohm range.
Compare that with typical budget headphones which are rated at 8 ohm to 16 or 32 ohm, and when in use on our mono-operation detectors have a nominal impedance of only 4, 8 or 16 ohms.
Shop for headphones that are not only using a high-impedance speaker, but are also very comfortable for long periods of comfort, and are of quality construction. They are the most important accessory item you can own, with the only exception being a smaller-than-stock coil.
Monte