How is audiophile surround done?

Discussion in 'Archived Threads 2001-2004' started by Greg Smith, Feb 22, 2002.

  1. Greg Smith

    Greg Smith Extra

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    This will speak to my ignorance :b and I'm probably missuing the word "audiophile" but I'm curious as to how so-called audiophile recordings that use more than two speakers use the rear speaker to impart information like rear-wall reflections and the room ambience and such. I'm confused as to the methodology of recording, I think.

    Does the engineer put another microphone near the right wall and then that track plays from the right rear speaker? But that would also capture sound from the front also, right? This method can't be done if only two mics are used, such as when an audiophile recording uses mics placed like human ears are, or am I just missing it?

    Any help from those infinitely more educated and informed than me are greatly appreciated!
     
  2. Vic_T

    Vic_T Stunt Coordinator

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    Many of the sounds in the rear speakers are added after the fact. I'm not saying this is 100%, but it's probably pretty close. Foley work, newly recorded tracks, and phase effects are normally used to create the surround channels.
     
  3. Michael_T

    Michael_T Second Unit

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    I think Vic might be missing the point a bit. For surround sound music on either DVD-Audio or SACD, it really is specific to the actual recording.

    Older releases, such as most of the material released on DVD-Audio and SACD, utilize the multi-track master tapes (which could be 8 track, 16 track, 24 track, etc. recordings) and a totally new mix is created from the existing tracks. Nothing is added "after the fact". The information is right there on the master tapes recorded when the album was made. Sometimes the surround sound producer will utilize instrumental parts or vocals that may have not made it to the stereo mix, and add them to the surround mix. And as to speaker placement of the tracks it is totally a judgement call on the producers part.

    Where Vic might be correct is when ambience is added to older recordings for the rear channels, this may be "induced artificially" by either a digital interpolation of the front tracks, or is derived from "phasing" information that is probably included on all recorded music.

    Newer audiophile recordings, like those on the Chesky label (on either DVD-Audio or SACD) actually use a specific recording technique which allows sounds to be recorded from all directions. Depending on the placement of the mics or mic, a surround mix can be easily derived from the recorded material in a multitude of ways that I just do not have enough information to reasonably impart.

    But the main thrust of my response is that I don't really think that all rear information is added after the fact, it is actually something that is inherent in the recorded music which is merely extracted from the master tapes. I may be wrong - but I think I am close.
     
  4. Vic_T

    Vic_T Stunt Coordinator

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    You're right. I did answer too quickly. Forgot which section I was in, and was thinking more of movie soundtracks. For a new recording, yes, a sound engineer would like to place mikes in different locations to capture the sound of the room. Mixes of pre-existing music can be created with the existng multi-track masters. This can be done by re-assigning the tracks that were originally divided across two channel stereo, across 5 channel surround. Keeping the basic stereo mix and adding lower level reverb tracks to the rear speakers for ambiance (artificially creating a room sound) is the more popular method. The less you change a mix on a classic album, the less complaints you get. The center channel is usually mixed equally from the left and right front channels to help create "movement" between the speakers. The rear channels, being a "new" developement, are still played with a bit, but are mainly used to convey a sense of depth or ambiance. Elements are seldom assigned strictly to the rear speakers. The LFE, or .1, channel is created by filtering out elements of the other channels that fall below 80Hz (I believe is the cutoff point).

    But, it does really depend upon the sound engineer. I would personally love to see a 5.1 mixing board to see how they are set up.
     
  5. Greg Smith

    Greg Smith Extra

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    Thanks for the responses.

    I've not yet heard 5.1 or any of its ilk, but I surmise that a recording that uses the rear speakers to impart recording venue characteristics would be really, really cool.

    A symphony recording that when played sounded like you were sitting in a great seat at the Meyerson in Dallas would be worth getting.

    Still, how that "ambience" stuff is recorded and recorded correctly is interesting. It seems that when done correctly, a multi-speaker audiophile recording reproduction would be more "audiophile" than one reproduced in stereo only, since we actually do hear sound from all over. I'm not talking about instruments coming out of the rear speakers, but wall reflections and all the other stuff that would go towards recreating a space.

    I need to research more!!
     

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