Convective and absolute Eckhaus instability leading to modulated waves   in a finite box
  We report experimental study of the secondary modulational instability of a one-dimensional non-linear traveling wave in a long bounded channel. Two qualitatively different instability regimes involving fronts of spatio-temporal defects are linked to the convective and absolute nature of the instability. Both transitions appear to be subcritical. The spatio-temporal defects control the global mode structure. 
Nicolas Garnier, Arnaud Chiffaudel and Francois Daviaud