The option for speech/subtitle/both is ignored by the game. In the game there are always speech AND subtitle and you can not turne off one of them.
OS: Windows XP / Game-Version: DE
Best Regards Thomas
Support for the ScummVM speech/subtitles dialog is a missing feature, not a bug. Moving to the appropriate tracker
I realize you're talking about the GUI dialog, but pressing the in-game hotkeys works for me in English version