Are you first pulling the stream into the EMS? The EMS cannot handle Speex, and so if you pull it into the EMS first, the audio will be trimmed. The proper chain should be:
source -> evo-avconv -> EMS -> wide-world-of-devices-and-players
the URI you are using to pull the stream into the EMS can be used in the -i section of your evo-avconv command.