I used a Hitachi speaker for a while with the DNLA/Media Renderer app and driver. Originally it wouldn't speak with the built-in TTS and I has to use an external TTS service. @cybrmage tracked down the issues and I had native TTS working before I decided to stop using the speaker. Here's a link to the post detailing the changes and a link to his code.
DLNA Player and Media Render warning message
Good luck!
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