1. Patch the navcore with one of the tools discussed in the tools subforum.
2. Grab the VocalizerTTS folder discussed in the Vocalizer topic by Megalos in this subforum.
Do not install two vocalizer voices at one time on your device, as this may result in no working voice.
Vocalizer has two advantages: it is lighter than Loquendo and it does not need patching.