According to the manufacturer of the SpeaKa Professional HDMI Audio Extractor with Toslink and 6 Channel (5.1) RCA Output:
"Supported HDMI audio formats: DTS-HD / Dolby TrueHD / LPCM 2 / 5.1 / 7.1 CH / DTS / Dolby-AC3 / DSD"
"Audio decoder.....................................Dolby Digital (AC3), DTS, LPCM 2CH"
"Sampling rate......................................32 - 96 kHz"
So if you are playing a 4 channel file and only getting 2 ch out from it, it appears to be an issue with your computer/laptop feeding the wrong signal to its HDMI output. Something perhaps is converting all out sources to 2 channel before it even reaches the SpeaKa. Obviously first make sure that foobar is not doing that. (foobar> Preferences>Playback>DSP Manager> left window should contain NO DSP plugins. ). After that , make sure your soundcard's HDMI drivers actually support surround output. If not , update the driver.
The switch on the front of the SpeaKa tells the playback device what audio track to provide. '5.1' should have worked but also try 'PASS'
If you are using foobar, you can also try using the
WASAPI output plugin to bypass the Windows mixer. In that case .wav files will be passed unadulterated as PCM, and .dts as raw DTS, .ac3 as raw Dolby (DTS and Dolby will be decoded by the SpeaKa).