Your setup approach is not the best if you want the best out of this projector. As some people have already indicated the proper approach is to make use of an AV receiver but you need to make sure that this is capable of receiving and passing through a 3D signal at 1080p. Most should but its best to check this.
In order to get the best picture and sound quality you need to maintain a HDMI cable setup right throughout and DONT rely on video out or optical or anything other than HDMI.
My setup involves a Samsung Bluray player and this is connected to the BD/DVD HDMI input of the AV receiver. The output from the AV receiver is also HDMI and this is then connected to the HDMI 1 input to the HD131X projector.
Some very important notes:
1. Make sure that in the GUI setup within your AV AMP receiver that the HDMI audio is only set to AMP and NOT AMP+TV! otherwise the Samsung player will downgrade your audio quality to PCM 48 as it is trying to play the audio via your projector. Setting the HDMI audio to restrict to the AMP only setting will play your sound as uncompressed DTS Master Audio.
2. Ensure that your bluray player audio is set to uncompressed audio
3. Dont buy cheap DLP 3D glasses such as SainSonic as they do not work with this projector. In the end I had to purchase the official Optoma 3D Glasses: ZD301 (available on Amazon) and they never lose sync and the colour rendition is just like in the cinema! Yes these glasses arent cheap but they work extremely well and avoid temptation on trying to save some cash by buying cheaper nasty glasses - you are wasting your money.
4. If your setup involves passing through HDMI cables through a HDMI switcher box i.e. to swap between Sky or Apple TV be careful as cheaper ones wont support the 1.4a standard and you will end up having problems. Ideally you should always maintain a good robust link from the BD player to your AMP and back out to your projector.
HDMI cables!! - Amazon stock code: ASIN: B0036BD0K2
You need high grade HDMI cables. Those articles which state you can use a cheap and nasty one is simply rubbish! These DONT work with 1080p signals in 3D especially when you try to run these cables via a 7.1 AV receiver!!
Make sure that you are using proper HDMI v1.4a cables which are shielded and have at least 15GB's throughput capacity otherwise the cable gets overloaded and will not properly work in 1080p 3D. There are a few on Amazon which claim to work but I had big problems. 2D at 1080p worked fine but then 3D 1080p was a big headache until I found these cables on Amazon:
You can search for ASIN: B0036BD0K2. These cables are highly recommended and are very high quality and at a reasonable price!!