4D sound is a proprietary technology using proprietary software and is based on columns of omnidirectional speakers. With 4D sound composers must create content using these proprietary tools, and they'll only ever be able to reproduce it on a specific 4D system.
ENVELOP uses Ambisonics, which is fundamentally different mathematically. The content is portable across other Ambisonic systems (not just ENVELOP), and can also provide a binaural mix that allows you to hear 3D sound with normal headphones. We are aiming to make this technology accessible to many people outside of the ENVELOP system in SF.
Comparing 4D sound to ENVELOP is a bit like comparing apples to oranges. However, we are just excited that there is more interest in live spatialized sound, and the more installations that are out there in the world, the more it has the potential to catch on with listeners and content producers.