Please I need help with bass management.

Discussion in 'Archived Threads 2001-2004' started by Edil Cajigas, Dec 26, 2001.

  1. Edil Cajigas

    Edil Cajigas Extra

    Feb 16, 2001
    Likes Received:

    While running the Avia LFE frequency sweep I'm noticing this:

    100 Hz - volume start to increase until it reaches 76 Hz.

    76.47 Hz - reach a peak and then start to go down until it reaches 51 Hz.

    51.83 Hz - at this point volume is barely noticeable and starts to go up again until it reach 48 Hz.

    48 Hz - another peak but here volume goes off the chart and start to go down again.

    41.26 Hz - at this point the volume has gone down but I can still hear it and stays in level until it reaches 30 Hz.

    30 Hz - I can not hear anything from here on, the sub goes totally silent. I carefully touch the speaker with one finger and the woofer is still vibrating even when the sweep is at 20 Hz.

    As you can see what I'm getting is like a wobbling sound that goes up and down I will like a more continuous sound. Also the sub is supposed to go down to 25 Hz but at 30 it goes silent. How can I accomplish this? and how can I make the sub to extend down to 25hz.

    The Avia DVD doesn't stop at each frequency, so measuring the exact SPL at a given frequency is difficult. Is there a DVD or CD that plays a LFE frequency sweep but allows you to control the steps in frequency so you can measure the SPLs?

    My subwoofer is an SVS 25-31PC and my receiver is a Yamaha RX-V3000. My room is very small (14 wide, 11.5 long). The sub is placed on the right front corner. Before running the sweep test I calibrate the SPL level and phase using Avia, both things seems to be ok.

    Thanks for your help!!!
  2. Geno

    Geno Supporting Actor

    Oct 1, 2001
    Likes Received:
    To be able to control the frequencies you are putting thru your stereo, I think you need an oscilator. Although not sheap, you can use it to fine tune everything.
  3. BruceD

    BruceD Screenwriter

    Apr 12, 1999
    Likes Received:
    Stryke offers a bass test CD with individual frequencies. The website for their CD is:
    test CD
    You should also find the radio shack SPL meter correction chart (search here, the FAQ, or the archive) to apply to the numbers you record at each frequency.
    Then come back here to ask more questions with your frequency chart results.
    Basically what you are observing with the up and down frequency response is what we call room mode peaks and valleys. This is caused by room dimensions and speaker and sub placement.
    One method of testing - since the AVIA DVD doesn't have a separate sub channel output test - would be to run the test with only the sub producing sound into the room.
    The VE DVD (Video Essentials) does provide a separate sub channel (LFE) test signal (another reason to own both test DVDs).

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