In this article we present beamix, an audio engine and its graphical user interface which allow one to produce directional audio effects (FX), that is, sound transformations localized in certain areas of space. These effects (such as equalizer, compressor, etc.) are applied to an Ambisonics-encoded sound scene, which was previously decomposed by a spatial filter bank. The latter, based on the state of the art, applies beamforming with virtual microphones (a process analogous to a plane-wave decomposition of the sound field) so as to partition the 3D or 2D sound field into a set of angular sectors. A chain of audio effects can be inserted into each of these sectors, allowing fine manipulation of the soundscape. The approach thus proposed offers more flexibility than transformations applied in the spherical harmonics domain, in particular for the realization of non-linear effects. The tool is typically useful for production or post-production of Ambisonics scenes, but can also be used for editing directional room impulse responses (DRIR).