This set is not compatible with the XDrum DD-650, because it comes with a second crash cymbal, which is connected to one of the two external inputs on the module.
As a result, only a fourth tompad can be added to the XDrum DD-650.
Under the following link you will find the suitable Add-On-Set:
https://www.kirstein.de/en/E-Drum-Modules-Pads/XDrum-DD-650-Add-on-Set-10-Mesh-Tom-Klemme-L-Rod-Kabel.html