The Beyerdynamic DT 990 Pro and the Beyerdynamic DT 770 Pro are two of the most popular models of Beyerdynamic. Both headphones are known for their great sound quality and comfort. However, there are some differences between the two models that you should keep in mind before making a purchase. The Beyerdynamic DT 990 Pro is an open-back headphone while the Beyerdynamic DT 770 Pro is a closed-back headphone. This means that the Beyerdynamic DT 990 Pro will have a more spacious sound while the Beyerdynamic DT 770 Pro will have a more focused sound. Beyerdynamic DT 990 Pro is mostly used by Music producers for mixing purposes while DT 770 Pro is more common for recording vocals, and is a good headphone for podcast recording.