Limiting the bass????

Discussion in 'Home Theater Projects' started by EricDeB, Dec 8, 2005.

  1. EricDeB

    EricDeB Stunt Coordinator

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    Ok so I have a good 5.1 set up and I am very pleased, except that my subwoofer really shakes the entire house, even at low volumes. My parents complain a lot, and its fine if they're not home, because we live a good distance from any neighbors, but when they are home it can be a hastle. My question is, is there any way to prevent it from shaking the house, while still getting good sound out of it? Like, would some kind of stand or something work? I guess I don't really understand bass, because I'm wondering if you can limit the "shakiness" without losing the "sound" volume.

    Thanks
    Eric
     
  2. Jay Mitchosky

    Jay Mitchosky Producer

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    First question as you didn't cover it specifically - have you done a basic calibration of the system? Simple level matching of all channels, including sub, with a sound level meter? This is imperative.

    Secondly, how have you configured your bass management? Are your speakers set as small or large? If large can they truly handle the low frequencies? If not they'll sound bloated and fluffy which may worsen your issue. Does your rig allow you to run low frequencies to both the sub and speakers designated as large? If so try setting speakers only (again, just those that are designated large). Does your system allow you to adjust the crossover frequency? Speakers selected as small will receive frequencies only above this threshold with the rest going to the sub. If set too high the sub is getting too much mid bass which will be really prominent.

    Third, where are your subs located? They will have the most pronounced effect when in a corner. Each boundary adds 3dB of gain. You'll get less, but smoother, bass if your sub is along a side wall rather then a corner. You can also try the old trick of placing your sub in the sitting position (stick with me on this), playing some bass tones and walking around with a sound meter or by ear listening for the location with the smoothest, least boomy bass. That's your new sub location. Problem is that location may not always be practical but it's worth a shot.

    These are all things you can do with the only cost being $30 or so for the meter from Radio Shack. The next step would be to plot a frequency response curve for the room (play a test tone at frequency X, note sound level, play next tone, note sound level, etc - plot on a graph). This will show you the offending frequencies, ones that are clearly louder than others. Big spikes on your graph. When those frequencies come during a movie soundtrack you'll jump out of your chair as they are so pronounced. They also obliterate adjacent frequencies. Ideally the response should be flat but trending slightly upward.

    To correct there are a number of parametric equalizers on the market that allow you to isolate a specific frequency, determine how many adjacent frequencies will be included in your adjustment, and then cut those frequencies to a point that they are in line with the general curve. These EQs typically have a number of different memories so multiple frequencies can be adjusted. Note that you can cut peaks, but can't really boost valleys (where frequencies are sucked out and are too quiet). Boosting adds more noise then anything else. The result of a this type of tuning is a more uniform bass response across a wide range of frequencies, with none being too overpowering.

    Good luck.
     
  3. EricDeB

    EricDeB Stunt Coordinator

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    Thanks a ton. It's people like you that make me love this place!
     
  4. Jay Mitchosky

    Jay Mitchosky Producer

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    Hope it helps.
     
  5. joseph westcott

    joseph westcott Second Unit

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  6. Dick Knisely

    Dick Knisely Second Unit

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    Joe -- agree with you, that's an exceptional site for the audio side of things. May not be the best material on Bass Management available but it was the best I found -- and finally resulted in my understanding it!
     
  7. EricDeB

    EricDeB Stunt Coordinator

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    Alright well right now I have a lot of the stuff out of my room and I have my sub placed in the listening position. I have an SPL meter. As I've crawled around I noticed that in the corner (as everyone told me) the bass was a lot boomier. The problem with this test for me is that I have no idea what I'm looking for. If I have an SPL meter, do I want it to not spike as much, or spike a lot? Right now, I have only my subwoofer set up and none of my speakers. I guess I don't really trust my own ears to find the smoothest, clearest bass. Is there any way I can use the SPL meter to find the perfect subwoofer spot?

    Sorry about the cry for help here.
    Eric
     
  8. Jay Mitchosky

    Jay Mitchosky Producer

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    You don't want it too loud or too quiet. Look for some middle value. Let your ears be the judge too. Boomy will sound bloated and thick. Try listening to bass heavy music with a constant drum beat or bass line.
     

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