Conference cookie::notes$archive:cd_v1

1450.0. "The best acoustics for Surround Sound." by SNOC01::KINGSTON () Wed Dec 28 1988 18:26

    Acoustics and Surround Sound
    
    I am after advice as to the optimum acoustics and dimensions for
    a Hi Tech "Dolby Surround Sound Home Movie Theatre" that I wish
    to build.
    
    I believe that the bigger the room the better, that the walls should
    be of solid concrete, that the floor should be thickly carpeted,
    and that the area around the front speakers should be reflective,
    (as in sound), while the area at the rear of the room should be
    NON-reflective, (also known as "dead, (wide open windows would have
    this effect)). A suspended, sound absorbent ceiling would be mandatory.
    
                        ---------------------
    
    However, the successful design would appear to be more of an art
    than a science. I am also getting a range of contradictory opinions.
                              
    Some say that the room should be square, or even cubic, (to reduce
    the number of "resonance points"). Since a room as high as it is
    wide is a little impractical, a sloping ceiling has been suggested
    to eliminate the ceiling's "resonance point".
     Would this be true?
    
    Another viewpoint that I have received is that one wall should be
    curved, (such as the wall behind the main speakers). Another viewpoint
    suggests that the walls should not be exactly parallel.
    
    Would a "totally dead" anechoic chamber be an acceptable comprimise?
    
    What is the difference between an echo and a standing wave?
    
    WHat design features would be advantageous? What should I avoid?
    
    Best regards,
    Brent J. Kingston
    

    You'll probably find out a lot more information by asking this question
    in DSSDEV::AUDIO.
    
    Your idea about a live end/dead end might be good depending upon
    the speaker you are using as your mains.  With most box speakers,
    however, it is usually recommended that the dead end be behind the
    speakers and the live end behind the listener.
    
    I have never seen a recommendation that all of the room dimensions
    be equal.  In fact, everything I have ever read has recommended
    against that very thing.  It seems that the ideal ratios are something
    like .68:1:1.68.  I'm not positive on those numbers, but I do remember
    reading that ideally none of the three dimensions should be a multiple
    of any of the others.
    
    It seems to me that with a four or six speaker set up, an anechoic
    chamber might be a good way to go.  It will require more amplifier
    power and probably will be less attractive than other options. 
    It will probably be quite expensive as well.