Help: Uneven bass response. Would 2nd sub help?

Discussion in 'Archived Threads 2001-2004' started by Paul Gere, Feb 17, 2002.

  1. Paul Gere

    Paul Gere Second Unit

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    My theater room is 32' long by 16' wide, 8' ceilings that are slightly sloped (attic). If it helps, see the room here:
    http://geretheater.homestead.com/main.html
    I've got an SVS CS-Ultra sub loaded in the front left corner of the room (not yet pictured on my web site) and get solid bass response. Problem is - bass response varies greatly between the front two seats in the room (about 14' back from front wall and 3-4 feet apart). Facing the screen, when the bass is right in the left chair, it's too much in the right chair. Conversely, when the bass is correct in the right chair, the left chair is weak. Yes, I've calibrated with my RS meter (placed between the two chairs!). Crossover is set @ 50hz.
    Any suggestions?
    Would a second sub in the right front corner fix this?
    Should I try moving my sub off the front wall? If I do, I'm afraid I'll localize the bass. For purposes of viewing distance, the front seating is not moveable.
    Thanks in advance for your thoughts.
    -Paul
     
  2. Steve Stogel

    Steve Stogel Supporting Actor

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    With your crossover set at 50Hz, I think you can pretty much put the sub wherever it gives you the best response. I don't think there's any chance of localization at that cutoff. Perhaps one of the rear corners? I've got my SVS in the right rear corner of my living room, and I can't localize it with my 80Hz cutoff. When I turn the sub off and on during music, it just feels like there's more sub "in the room" when it's on. I can't tell where it's coming from.

    Steve
     
  3. RichardH

    RichardH Supporting Actor

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    Adding a second sub and not putting it right with the first will likely cause more difficulties in the response. I would just split the difference between the seats and/or experiment with alternate placements.
     
  4. Michael Mohrmann

    Michael Mohrmann Screenwriter

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    14' from the back wall? Well, if the sub is in the front left corner, you must be at least 15' away in your 32' long room, is that about right? The suggestion by Steve to put it in a rear corner may not be a bad idea, as it would be a bit closer to the front seats.

    Are you using an equalizer? If not, that might also help in this situation. It would allow you to increase the low spots in the bass response while at the same time flattening those bass frequencies that have a peak.

    Michael
     
  5. Bill Lucas

    Bill Lucas Supporting Actor

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    You have a couple of things working against you. Your room dimensions are not good. You have three dimensions that are all divisible by 2, 4 and 8. I would not corner load a sub in your situation. Place the sub midway along the front wall for smoother response. Add a second sub midway along a side wall and you should get much smoother response. This method works very well in a room that is rectangular. If your room has any openings or alcoves results will not be as good. Localization of the sub will not be a problem. Regards and good luck.
     
  6. John*S

    John*S Agent

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    Bill,

    Can you explain or refer me to somewhere that I can learn about the 2, 4, 8 divisibility you mentioned? I understand the concept of bass's long waves and these cancellations and standing waves that can develop, but I need to understand more of the nuts and bolts.

    Thanks!
     
  7. Bill Lucas

    Bill Lucas Supporting Actor

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    John,
    It's not that the numbers are divisible by 2,4 or 8 but the fact that the room dimensions are all divisible by the same numbers. Russ Herschelmann has written some excellent articles in Stereophile Guide To Home Theater and he goes into the subject in a couple of his articles. I believe you can access the articles at http://www.guidetohometheater.com/. Regards.
     

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