A/V noob question - Hi-def

[Crashoran]

Why does the center speaker in my 5.1 setup not play audio when playing my Xbox360? I'm just using the cables that came with the xbox.

I recently got the HD DVD add-on so I want to get it working.

I don't know alot about this stuff :D

[Tony-S]

We need the details. Your Xbox is connected to a receiver? How is it connected - coax, optical, discrete, something else? The center speaker should be mostly dialog - what content are you watching?

[Crashoran]

It's connected to a receiver, it's the cable at the top of this page: http://www.xbox.com/en-US/support/systemsetup/xbox360/accessories/hdavcable.htm

Doesnt produce sound when playing games or watching HD movies. Works with cable and seperate dvd player.

[Crashoran]

got it - had to change some settings in the audio receiver.

Thanks anyways

[Tony-S]

You won't get 5.1 sound from that cable. The best you'll be able to get from your media is matrix (e.g., Dolby Pro Logic). You'd be better off using the Toslink cable (optical) provided your receiver has an optical audio input. That can give you 5.1 surround.

[orisky]

got it - had to change some settings in the audio receiver.

Thanks anyways

Whatever you think you "got", it's not true 5.1 :) If your source is only providing a 2 channel stereo feed (the white and red cable from your link), then that's what should be fed back out. If you're hearing 5.1, then that means your receiver is taking the 2 channels and simulating 5.1 from it.

As Tony said, you're better off running an optical cable, or 6 individual rca cables (one for each channel, if your components support it).

[Tony-S]

Whatever you think you "got", it's not true 5.1 :) If your source is only providing a 2 channel stereo feed (the white and red cable from your link), then that's what should be fed back out. If you're hearing 5.1, then that means your receiver is taking the 2 channels and simulating 5.1 from it.

The two "stereo" channels can provide 5 channel surround, just not 5.1 surround. The LFE signal is absent.

[orisky]

But again, isn't this simulated 5 channel sound created by the receiver? If you're only feeding a L/R from the Xbox to the receiver, the source is only a L and a R channel. Am I missing something?

[Tony-S]

Orisky,

Dolby Pro Logic I (4-channel) and DPLII (5-channel) are matix-formatted analog audio. They have both R and L, but also encoded in other phases of the analog signal are C, Rr and Lr (for DPLI, Rr and Lr are mono, thus only count as one channel). If you have a receiver capable of decoding this matrix (they've been around since the late-1990s) it will separate all 5 channels and send them to the appropriate speakers. Unfortunately, there's currently no way to encode the LFE (bass) in an analog matrix, thus the '.1' is missing from such audio tracks. Another disadvantage is that there is channel leakage, such that you don't get complete separation of the 5 channels. So, even an RCA stereo cable (i.e., R and L) is capable of delivering 5-channel surround.

Since Dolby Digital and DTS (both 5.1 or more) are digital (and not analog), they provide discrete tracks (and not matrixed), thus have no channel leakage. They are also capable of delivering the LFE since it's not represented as an analog amplitude signal.

The beauty of digital audio connections (optical, coax or HDMI) is that they simply pass the audio file from the medium (e.g., BluRay disc, DVD disc, movie file) to the receiver, which is then responsible for the decoding. (The RCA cables deliver line-level analog audio only.) Since the device reading the media file (e.g., computer, DVD player, X-box) isn't responsible for decoding the audio, you can send any kind of file to the receiver or amp. Thus, if you have a 7.1 (or 9.1 or whatever might be developed) receiver, it will decode the audio for you provided it's encoded on the media. There's no need to build this functionality in the device reading the media.

[orisky]

Thanks for the explanation. Just netting it out so I'm understanding correctly. A L/R pair of RCA cables can provide 5 channel sound as long as the receiver can output prologic (which almost all can nowadays), however that 5 channel sound is not the equivalent of the 5 channels in an optical 5.1 output. And of course you're missing the .1 LFE.

Is that right? If that's right, then that's really what I meant by "simulated 5 channel sound in my prior post".

[Tony-S]

Thanks for the explanation. Just netting it out so I'm understanding correctly. A L/R pair of RCA cables can provide 5 channel sound as long as the receiver can output prologic (which almost all can nowadays), however that 5 channel sound is not the equivalent of the 5 channels in an optical 5.1 output. And of course you're missing the .1 LFE.

They are equivalent in the sense that they are the same channels, but they differ in that 5.1 (digital) has 5 discrete channels, while DPLII (analog) is matrix and subject to cross-channel contamination. The L of 5.1 is also the L of DPLII. Same is true for R, C, Rr and Lr. But they all suffer from channel leakage in DPL.

Is that right? If that's right, then that's really what I meant by "simulated 5 channel sound in my prior post".

I guess it depends on your definition of "simulated". The original audio masters are recorded as 5 (or more) channels, then encoded as the 5 channels for DPLII. Strictly speaking, it's not simulating them - they are real. It's just that there's a bit of cross-talk between channels since it's analog technology.

The difference between 5.1 discrete and 5 analog surround is noticeable, but DPLII is a pretty good method. It just doesn't have quite the spaciousness or feel as 5.1.

[orisky]

Since the OP has been silent here (maybe silently observing), I'll threadjack :)

So with my system, I have 6 individual RCA cables for each channel, outputted from a DVD/SACD player into my receiver. What's your opinion of this? Is there 5.1 discrete channels when doing it this way?

[In2Photos]

Since the OP has been silent here (maybe silently observing), I'll threadjack :)

So with my system, I have 6 individual RCA cables for each channel, outputted from a DVD/SACD player into my receiver. What's your opinion of this? Is there 5.1 discrete channels when doing it this way?
Yes. The difference here is that you are using the DVD/SACD player to decode the information rather than the receiver. There is no harm in this (as long as you use quality cables to shield interference and the line length is not too long) and is actually required for most of the older players (some units used a single cable to pass DVDA/SACD signals from a player to receiver, but they were rather expensive). My Denon setup is wired the same way (although I also ran a digital cable so I can use either the DVDA/SACD player or receiver to decode DVD Video or CDs).

[Tony-S]

I can use either the DVDA/SACD player or receiver to decode DVD Video or CDs).

Mike - I gotta ask: Do you have Pink Floyd's DSOTM on SACD?

[In2Photos]

Mike - I gotta ask: Do you have Pink Floyd's DSOTM on SACD?
Yes. I can't remember though if I have the full version or one of the free copies of Money that were given away. I also think I have two copies. Why do you ask?

[Tony-S]

Oh, I'm just jealous. I don't want to dish out the money for a SACD player, but sure would like to hear DSOTM in quadrophonic. It's too bad the CD drives on computers can't read SADC format. It'd make it easy to port the quad to discrete channels.

[In2Photos]

Oh, I'm just jealous. I don't want to dish out the money for a SACD player, but sure would like to hear DSOTM in quadrophonic. It's too bad the CD drives on computers can't read SADC format. It'd make it easy to port the quad to discrete channels.
I hear you. I got mine when I used to work for an A/V company. I think it was around $500 at the time (don't remember what I paid for it though).

It does sound rather good, especially when I used to listen to some of the stuff we had at work (like KRELL and Martin Logan or B&W). Then we got bought out and picked up lines like Vienna Accoustics and Sonus Faber. Still very nice stuff! Since my daughter was born I don't get to listen to music much like I used to, but every now and then I get to enjoy it.