ce577368_ight_For_The_Ground_Conditions__Double_D_Coils
Noisy or Mineralised Ground [Monoloop Coils] More sensitive to mineralisation,hot rocks and ironstone. More difficult to tune than a DD coil Can be noisier than and DD and dificult to ground balance - the larger the coil the more difficult. [Double D Coils] 
Quieter than a Monoloop coil in mineralised ground. Can be used in noisy ground where a monoloop may not function well
Metal Detector Coils Get Them Right For The Ground Conditions
Double D Coils