From downunder on another forum:-

Lately there are more and more postings with a question about the same problem...
The new 9.4xx Navcore (and some older V9 as well) will cause many XL models to go silent when computer voices are used,
a few won't even play recoreded voices anymore.
There is a very simply check that you should perform if you think you are affected:
Make a full backup using the Windows Explorer (safety first!),
connect to TT Home and check if you can download any computer voice for your device - you might have to log in to your account for that.
If Home does not offer you any computer voice it means that your device has no offical support for TTS.

The new Navcore perform a check on the device and if the model is incompatible the TTS system will be disabled.
Also the newer XL models have a similar check hardware based that will cause most Navcores, patched the normal way or SE, to fail to provide TTS support.
For older NC's only the so called model ID was used, for example 25 for the X30 series,
newer NC's now also utilise the sound model ID, usually it will match the model ID but if an emulation is used the sound model won't change,

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this results in a mismatch of sound model ID and model ID, effectively disabling the TTS system.
It is quite obvious that behind all that is a simple marketing strategy...
XL models offer a big screen for low money, since the hardware is often still good enough TT had to find a way to block the normal ways of enabling the TTS system.
Really old TT devices like the 300, 500 or even the normal ONE are not affected as the hardware is based on entirely different platfroms.

Footnote, this hasn't helped orgal so more help/suggestions welcome

biggerdave Reviewed by biggerdave on 11th November 2012. XL IQ Routes Edition computer voice Hi there, I have a TomTom XL IQ Routes Edition 340 - 2GB: 4EM0.001.01 with 64mb ram and no sd card, (It is the the non-TTS XL IQ Routes / 340 - 2GB version) so tts is dissabled ... I am running 9465 navcore and 900.4602 uk & ri maps works well but TTS is dissabled...would still like to get kate Loquendo voice working on it I have tried a few different se and dsa navcores including downunder's 9.485 with hardwired sound navcore but can not get loquendo to work on it, a bit anoying as the Rating: 5