Drop 2 IV

The Drop 2 IV voicing of Db6 stacks F, Bb, Db and Ab from the bottom up: the major 3rd, 6th, root and 5th of the chord.

It's one of the Drop 2 voicings: four-note chords in close position with the second note from the top dropped an octave, played over the root. The others for Db6 are Drop 2 I, Drop 2 II and Drop 2 III.