Array-averaged NEFD as a function of the line-of-sight opacity τ/ sin(δ). Black dots (resp. red squares) refer to the 1.25 mm array (resp. 2.14 mm) for the 2012 observation campaign, during which the trend at 2.14 mm is compatible with a exp(τ/ sin(δ)) behavior (as shown with the red curve), while a departure from this behavior is observed at 1.25 mm. The latter can be attributed to the degradation of the KID resonance quality factor with increasing power load. Open circles (resp. open squares) refer to the 1.25 mm array (resp. 2.14 mm) for the 2013 observation campaign. Very few points have been measured, but the achieved sensivities are much better and do follow an expected exponential trend.