Looking to buy a logitech z906 5.1 surround sound system. Don't really want to buy a receiver and 5.1 system speakers it's quite expensive.
My pc rig contains an ASUS Rampage IV Extreme mobo which so called supports 7.1 surround sound. Which means no authentic Dolby live surround compatibility etc.
So should I invest into a decent sound card such as the (Sound Blaster X-Fi Titanium Fatal1ty Professional Series) or (Asustek Xonar DX/XD PCI-E Low Profile Sound Card) to hook up with the z906 surround. Would like to spend from £50-80 if it will ridiculously improve the quality of surround sound from the logitech speakers or just stick with the inboard mobo sound capabilities?
I actually did a fair amount of research on this last week. The short answer is no, you don't need an additional sound card. Your mboard has 8-channel audio outs divided into four 3.5mm jacks ( green, black, red, and orange, two channels per output. ) Just connect the green ( front L-R ) , black ( center & sub ) and orange ( rear L-R ) outputs to the 906 sub and it should work just fine. However, you likely won't be able to get Dolby or DTS from your fiber optic S/PDIF connection for games ( but you can for movies. ) If you want to know more about this, read below.
A lot of this centers on audio compression, coding, and decoding, specifically something called Dolby Digital Live ( and DTS Connect. ) Dolby Digital Live isn't so much a codec/format as a technology that encodes all outgoing sound into a Dolby Digital 5.1 format ( DTS Connect does the same thing for the DTS format. ) You may ask yourself, "If my computer can output movie DD and DTS audio over the S/PDIF, then why can't it output those formats for games?" It can, however games themselves don't output DD or DTS, even though their boxes and cases say they do.
Games don't natively encode their output audio to any specific format. It seems they just use PCM on specific channels. This gets passed straight to your on-board audio. Your on-board knows how to read this multi-channel signal, it just normally doesn't have the ability to encode it into another format. So your on-board audio can successfully output multi-channel audio, it just has to do it over the multiple analog outputs rather than the single S/PDIF.
So in short, your on-board audio can read and output lot of audio formats, it just isn't receiving a DD or DTS signal from the game in the first place. That's where DDL and DTS Connect come into play. They'll take those PCM signals from a game and encode them on the fly into DD 5.1 or DTS that goes to the S/PDIF.
My confusion came because my old first-gen PS3 can output DD and DTS in games. So why then could a 2006 piece of hardware do something better than my far newer 2011 mboard? It's because the PS3 and 360 both have DDL and DTS Connect hardware so they can encode the game audio on the fly ( even though my PS3 only has DD and DTS logos stamped on it but no DDL or DTS Connect logo, again leading to my confusion. )
Add-on cards, like the Sound Blaster and Xonar, have the DDL abilities to give you compressed surround sound over the S/PDIF. The reason that people use them is because they want emulated surround sound in their headphones. Most gaming mixamps have fiber S/PDIF, but not a multi-channel input, so they need a compressed digital signal instead of the pure PCM coming over the analog jacks.