Room modes causing a 20 dB dip???

Discussion in 'Archived Threads 2001-2004' started by Scott S, Apr 5, 2001.

  1. Scott S

    Scott S Auditioning

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    Okay now I'm confused. I got my Bass test tone CD the other day and started doing some in-room measurements. I found that my "Normal" location for my sub has a nasty (20dB down) dip around 55-60 hz. I experimented with corner loading the flattened out fairly nicely, although I lost a good bit of extension (~30 hz versus 20 hz.) My room is about 14'x18' and is fairly open to the kitchen on one side (~14'x14'). Can anyone provide any thoughts on better placement. FYI I'm using a modified RS meter (replaced several caps) and a Stryke Bass test CD as the source. As a check, I measured the response in my van, using the same sub and CD and I didn't measure any noticable dips, so I dont think it's the meter or the CD. Any help you can provide would be appreciated.
    Thanks, Scott
     
  2. Timmy

    Timmy Stunt Coordinator

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    Scott; probably the best way to pick sub location (an old but proven trick) is to physically locate the sub at your primary seating location. Then take your SPL meter to the possible "real" sub locations and see what wall/corner gives you the best response. Then move your sub to that location.
     
  3. Deane Johnson

    Deane Johnson Supporting Actor

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    This kind of a dip is pretty hard to get rid of. I think the "big guys" use bass traps and other room modification devices well beyond what most home theater people are going to do.
    Most of us have those dips and most of us have spikes. The dips, for the most part, just have to be ignored. A bigger problem, and one that can be dealt with is a room spike. I had a 16 db at 42 hz spike. Messed up my sub performance pretty well. Got rid of it with a Behringer digial equalizer in the sub feed circuit.
    If you have any interest in reading other threads about these problems do a search for "BFD" in this section. There has been a lot written.
    Deane
     
  4. Phil A

    Phil A Producer

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    I measured my room and have multiple tube traps and a treatment from Acoustics First (www.acousticsfirst.com). If you have flexibility where to place it that is great. I have 2 subs in the main system (stereo for music and distributed ".1" for HT) and pretty much have to live with them in certain locations. I then needed to determine the problem and treat it. If I had more flexibility with available placementment (I too have an odd room that is 2 stories high and open to other spaces), I could have tried different things. You may wish to look for FAQ and subwoofer resources at www.rel.net too and see if that provides any useful data.
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  5. Kyle Richardson

    Kyle Richardson Screenwriter

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    Locating the perfect spot for a sub is about the hardest thing to do in home theater. Subs are usually pretty big and thus, cannot be placed in the ultimate spot most of the time.
    Corner loading is usually the best solution. Obviously this will not work in your situation so I would then try the method that Timmy described. Another sub can be used to help flatten out the response, but there are a couple of drawbacks with this as well. 1. Double the money. 2. Sometimes you will fix the initial problem but introduce others at the same time.
    ------------------Instant Messenger Name: kyler70
     
  6. Timmy

    Timmy Stunt Coordinator

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    The BFD is great for taming peaks, but won't help for dips if they are caused by cancellation waves.
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