Odd Shaped HT Room -- Need Advice

Discussion in 'Home Theater Projects' started by Roy Lumsden, Aug 24, 2004.

  1. Roy Lumsden

    Roy Lumsden Extra

    Joined:
    Aug 24, 2004
    Messages:
    17
    Likes Received:
    0
    Trophy Points:
    0
    First off, I'd like to say that I've been lurking on the forum for over a year. I've learned so much just reading, reading and reading.

    I've followed several HT build-outs and observed many more and, as a result, have decided to create my own HT. I WILL need YOUR help.

    Having said that, on to my first batch of (many) questions....

    The space that I'm considering for my HT is above my garage. I have room to build a 24' x 27' area but the shape is somewhat odd. At the peak the bottom of the trusses measures nine feet which slopes down to a three foot knee wall on both sides. If I decide to frame the walls so they are six foot high, the room width would be twelve feet. I would prefer to go a little wider but I am concerned about how a shorter wall will affect the accoustics. Opinions?

    One neat thing about the space is that I will have access to both side via a crawl space, the top through the roof trusses, and the bottom from the garage floor (no drywall on the garage ceiling). So all cabling can be done on a "as needed" basis rather than trying to install everything - current and future - before I close up the walls.

    I also like the idea of using a barrel style ceiling instead of a vaulted. Are there any benifits one over the other?

    Based of a room width of 12' to 15', is there an the optimum length that the room should be?

    Thanks in advance,
    Roy
     
  2. Tom D

    Tom D Stunt Coordinator

    Joined:
    Oct 29, 2000
    Messages:
    140
    Likes Received:
    0
    Trophy Points:
    0
    Hello, stereophile guide to home theatre, now ultimate a/v has a spread sheet available on their web site that will help you with optimum room dimensions and standing waves. good luck with your build. Tom
     
  3. Roy Lumsden

    Roy Lumsden Extra

    Joined:
    Aug 24, 2004
    Messages:
    17
    Likes Received:
    0
    Trophy Points:
    0
    Well... I downloaded the spreadsheet and played with it a little. Unfortunately, I'm not THAT much of an audiophile. Translation: I have no clue what I'm looking at.

    More than the size of the room, I'm concerned about the effects of the low side walls (5' to 6') and the vaulted ceiling. Any input is appreciated.

    Roy
     
  4. Wayne A. Pflughaupt

    Moderator

    Joined:
    Aug 5, 1999
    Messages:
    6,208
    Likes Received:
    56
    Trophy Points:
    9,110
    Location:
    Katy, TX
    Real Name:
    Wayne
    Roy,

    In my experience, and from what I’ve seen from others posting on this and other Forums, the last thing you want is a perfectly symmetrical room, that being where all surfaces are paralleled to each other (we’re talking shoebox here). What you tend to end up with is poor bass performance: The bass is “hot” along all the boundaries, and gets progressively weaker as you move towards the center of the room, culminating in a virtual dead zone in the center of the room.

    Therefore I think that your low sidewalls and vaulted ceiling should be a considerable improvement in this regard. You might still get some of the bass cancellation towards the center of the room, but I don’t expect it will be nearly as drastic as what I’ve seen in straight-up shoebox rooms. Just to increase the “asymmetricality” of the room, you might consider doing one side as the 3ft. knee wall and the other as the 6ft, but it’s understandable if you want to retain the extra space.

    Not sure what you mean by “barreled” ceiling, but if you mean rounded, I’m not sure what the effect of that would be from an acoustical standpoint. Perhaps someone else can comment.

    Regards,
    Wayne A. Pflughaupt
     
  5. Roy Lumsden

    Roy Lumsden Extra

    Joined:
    Aug 24, 2004
    Messages:
    17
    Likes Received:
    0
    Trophy Points:
    0
    Wayne,

    Thank-you for the input. Your comment about the bass cancellation makes sense. But,I'll probably keep the heights of both side walls the same. Your answer does however helps me to understand the advantages of using staggered wall panels which would creat unparallel surfaces.

    Yes. The barreled ceiling does mean rounded. But, in my case, I'm thinking about rounding only the peak (about two to three feet from the peak on each side). I may also round the side walls where they connect with the ceiling. While this may be better accoustically, I plan on doing some indirect lighting at the top of the side walls so the affect may be negated by molding. Not sure.

    Thaks again,
    Roy
     
  6. Tom D

    Tom D Stunt Coordinator

    Joined:
    Oct 29, 2000
    Messages:
    140
    Likes Received:
    0
    Trophy Points:
    0
    Hi Roy, I would have to disagree with Wayne slightly regarding his statement about paralell surfaces - bass cancelation occurs naturally in any environment - it is more pronounced when you are in a closed room. There are 3 modes that will cause this; front to back, side to side, and ceiling to floor. Think of sound waves as you would light waves and reflactions off walls, or as waves in the ocean. Some waves will cancel each other and some will reinforce each other, depending on how and when they intersect. The spread sheet that you now have, basically takes your room dimensions, and calculates the room modes for you. The basic idea behind having a shoe box is that you can now predict the sound characteristics of your room. Rooms that are odd shaped may or may not sound better - but that is like playing the lottery - you may get lucky and win. What is important to remember is to keep room dimensions from being perfect multiples of each other. These types of rooms tend to be worse for acoustics. You must remember that no room is perfect, you must work within the constraints of the space you have.
    When planning seating and equipment (speaker placement) another rule of thumb is to use 1/3, or 1/5 spacing front to back and side to side. I hope I have helped a little - Good Luck.

    Regards Tom
     
  7. Roy Lumsden

    Roy Lumsden Extra

    Joined:
    Aug 24, 2004
    Messages:
    17
    Likes Received:
    0
    Trophy Points:
    0
    Tom,

    I see your point. I'll play with the program a little more to see if I can gain some insight on what's it's trying to tell me. But, because my ceiling will not be flat, I'm not sure how much it will help.

    Thanks,
    Roy
     

Share This Page