Defintion of RMS/encoding/decoding and how they apply...

Discussion in 'Archived Threads 2001-2004' started by Brad Craig, Feb 7, 2002.

  1. Brad Craig

    Brad Craig Stunt Coordinator

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    I see this terminology alot when others are talking about receivers, dvd players, speakers, etc...
    Could someone explain in layman terms what these things mean and how they apply to the above components and speakers...
    [​IMG]
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Brad: there is a big jump between some of those concepts. Can you phrase it in less general terms what you want to know?

    For example: RMS has nothing to do with encoding or speakers. It's a funny term that basically means "Average Power". Receiver manufacturers (honest ones) tend to report something like:

    "80 watts per channel RMS"

    Encoding: I could tell you all about different types of encoding, but I would quickly loose you. Why do you want to know?

    It looks like you are shopping for a receiver. If so, ask us specific questions and we will try to answer them, rather than flood you with useless theory.
     
  3. Brad Craig

    Brad Craig Stunt Coordinator

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    Well I guess I'm wanting in laymans terms the process of the dvd player sending out the audio signal and it being decoded in the receiver... IS it decoding it or encoding it and what is the difference???

    I could or sworn I've seen speakers rated in RMS watts, am i wrong on this completely???
     
  4. Adam Barratt

    Adam Barratt Cinematographer

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    Audio encoding takes place at the production stage of a disc, while decoding is at the playback stage (ie. in your home).

    When you listen to a DVD soundtrack at home, your DVD player or receiver is decoding the data that was encoded by the disc content's producers and recorded onto the disc.

    Speakers are often rated for maximum prolonged input in Watts, but as long as the minimum required input is met it's not a particularly useful figure.

    Adam
     
  5. Ken Shiring

    Ken Shiring Agent

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    Brad, Adam's comments are correct. However, for the sake of diversity, I will add my own comments too [​IMG] .
    Encoding : The most common contexts for this term is in describing the data on a DVD. Video as well as audio is encoded. It is a relly simple term that just means that there is a compact representation for all of those hours of A/V on that little shiny disc [​IMG] . Video encoding can mean several things, but usually refers to the "aspect ratio" of the video material. That has been well described in other threads, do a search and you should find all you need to know.
    Audio has its own encoding. By far the most common methods are Dolby Digital (DD) and Digital Theater System (DTS). These are the only two audio formats DVD supports.
    Decoding : The process of taking the information stored on the DVD (or other formats, like HDTV broadcasts) and converting back into visual/audible form. This either happens at the DVD player or at your receiver, depeding on your equipment and your connection style.
    RMS : This is an engineering term. It stands for Root Mean Square. It only has meaning when stated with a power measurement suffix, i.e. watts. It is a way of specifying how "strong" a signal is, even when that signal is a complex looking wave that has no apparent structure to it (e.g. music). Higher RMS watt values mean the signal has more energy in it. Both receivers and speakers have this rating (whether vendors choose to disclose it or not).
    Generally, this value is not the be-all and end-all of describing audio gear. Receivers have this rating to indicate how much power they can drive to a speaker. Speakers have this rating to indicate how much power they can handle before blowing up [​IMG] . It is important to note that RMS power has nothing to do with sound quality. Tube amps, for instance, have very low RMS power ratings, and many people praise them for their sound.
    This may not be common knowledge, but the vast majority of audio information is down in the 1-watt range. Only on very strong peaks (e.g. loud passages) do more watts help you.
    I hope this helps clear things up. [​IMG]
     
  6. Bob McElfresh

    Bob McElfresh Producer

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    Brad: In most systems today, the DVD player does not do the decoding. It sends the data to the receiver which does the decoding.
    In the early days, some receivers were called "Dolby Digital Ready" and had 6 RCA input plugs. If you had one of these, you needed to buy a DVD player with a built-in decoder and run 6 analog cables between the two.
    Avoid This if possible.
    Speakers: You can typically ignore the "100 watt speaker" label. You should also NOT try and match a receiver and speaker based on power numbers. This is a bad criteria.
    Suggestion: Buy a speaker because it sounds good to you.
    Tastes in speakers is like tastes in ice cream. If I layed out 5 bowls of different ice cream and we each rated them "best" to "worst", your order would be different from mine.
    Using the "xxx watt speaker" numbers to pick a speaker is like picking ice cream by reading the ingredents labels. It really does not tell you how the product would taste.
    Hint #1: If you are shopping for speakers, bring along a favorite CD and a favorite DVD movie to stores. High-end audio stores will expect this, and even chain stores will appreciate you bringing your own.
    Hint #2: Do not buy after only 1 audition. Take notes of which speakers sounded good/bad. Then go back next week. You may be suprised at how your impression changes.
    Hint #3: Let us guide you to some speakers that have a good reputation so you dont waste your time. Tell us:
    - How much music vs movies do you intend to listen to
    - What is your budget
    - How much equipment you need for that budget
    And we will try and recommend things for you to go audition.
     
  7. Brad Craig

    Brad Craig Stunt Coordinator

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    Thanks for the answers guys... [​IMG]
     

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