Faking a 5 channel signal with 2 channel audio?

By Pheryllt ยท 5 replies
May 21, 2009
  1. I have the X-Fi SupremeFX PCIe card that comes with the Asus Rampage II Extreme. Its hooked up via Digital Coaxial to a 5.1 HTS Receiver.

    I don't have any issues with 5.1ch Dolby Digital when watching DVDs that support it. But all my other audio only comes out the 2 front channels as PCM. On my older computer with a Sound Blaster Audigy card, I was able to get 5 channel stereo through PCM by hooking up through the digital out mini jack and out again through a Digital coaxial cable into the Receiver.

    Is there any way to be able to send the 2ch audio to the surround speakers using the SupremeFX card cabled directly to my receiver?

    Thanks for any input.
  2. captaincranky

    captaincranky TechSpot Addict Posts: 12,992   +2,527

    Dolby Pro logic supposedly responds to the directionality of a signal, and that's how it synthesizes(or perhaps extracts) the 5 channel info. Well that's great, but I have found that it sounds like s*** on a 2 channel music source, So, I just use the surround modes and allow myself to be entertained with rear channel surround. If the front channel speakers are imaging correctly, there is no need whatsoever for a center channel with music.

    Plan "B" is obviously a brand new receiver with discreet 5 or 7 channel inputs. And that pins you to 1 specific listening position, or the effect is lost.
  3. jobeard

    jobeard TS Ambassador Posts: 11,138   +985

    very old radio technology: Cross over networks.

    A composite speaker system (one with Bass, midrange and tweeters in the same box),
    have cross over networks to segregate one source into three frequency ranges.

    sure isn't surround, but it beats mono :)

    here's the ideas

    A butterfly filter circuit
  4. captaincranky

    captaincranky TechSpot Addict Posts: 12,992   +2,527

    I'm gonna stick with the digital delay of my 5 channel receiver. That's true stereo with ambiance faked.

    Did you know that you can wire the rear channel speakers in series across the 2 positive leads of the receiver's "B" speaker terminal, and all they will reproduce is the differential signal, which I think amounts to the reverse phase information contained in the stereo source. Sound reverses phase when it hits the back wall.

    What you get though, is what you get. There's no level control or such.
  5. Pheryllt

    Pheryllt TS Member Topic Starter Posts: 50

    To be honest I'm not really clear on what you guys mean, I can only get PCM Stereo through my receiver when listing to music, videos and internet media. My receiver supports DD PLII but it never goes to that, plus I'm only looking to get my rear surround speakers to copy the audio from my front 2 speakers to give my audio a more omnidirectional sound rather than always from the front.

    On my older system all my audio came through as 5ch Stereo PCM with the option to switch it to just stereo PCM. That system didnt have a Coaxial Output on the card so I used the mini jack Digital out with the Creative I/O modual and used that to connect the coaxial cable to my Receiver.

    What I really don't understand is why I was able to get that 5ch audio through PCM on the older system and not through the new one with a coaxial-out connected straight to the coaxial-in on my receiver?

    I'm not very skilled with audio equipment or how to get them working to my advantage. So if there is something im missing about the difference between the 2 systems I'm just not seeing it.
  6. captaincranky

    captaincranky TechSpot Addict Posts: 12,992   +2,527

    I have an older receiver (Pioneer), which has whast they call "5D theater". What it mostly, is digital delay with reverb that simulates the various size and acoustics of different rooms.
    When I listen to just music I stuff it in that mode. When I watch movies I use the "Pro Logic". This is an old receiver that doesn't have "Dolby Digital as such.

    So, if your receiver doesn't have this feature, I suppose you could buy an external Digital delay unit, then drive it's output to a second stereo amplifier, and connect that to the rear speakers.

    Alternatively just hook the rears up to the "B" speaker terminals, and make the best of it. Put the best pair up front.

    Plan "C" put the back speakers somewhere else in the house, and let the building provide the "ambience".

    Dolby Digital from a home DVD player is connected via a stereo pair of line cords anyway, and you get 5 channels (plus sub) out of that.

    As I said before 5 channels are actually contraindicated in most music reproduction. If a CD (or whatever) is recorded correctly, then you won't need to have a center channel speaker. The mix automatically places the vocalist front and center.The center channel in home theater is used primarily to localize the voices of talking characters at the screen, without activating the music and LFE channels. You don't really need a subwoofer to reproduce Minnie Mouse speaking, now do you!
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