Is this real?

Discussion in 'Archived Threads 2001-2004' started by MichelF, May 19, 2001.

  1. MichelF

    MichelF Extra

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    Hi,
    I am trying to equalize my subwoofers with a Behringer DSP1100. As a measurement tool I am using Smaartlive (4.5) with the Furman AIS-10E microphone preamp and the Behringer measurement microphone.
    I managed to have a flat response except at one frequency, at around 50 hz I have a 6 dB peak. I tried to cut it with a filter but when I apply the filter things are getting worse... the peak increase!
    I found that to kill this peak I had to boost (and not cut) this frequency by 16 dB!!! I really don't understand, is this really a peak in the response or some artifact (note that I am here in Europe and the power supply is preciselly 50hz here)?
    Thanks in advance,
    Michel
     
  2. Cees Alons

    Cees Alons Moderator
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    Cees Alons
    Michael,
    Although theoretically it could have anything to do with a 50Hz filter (to suppress 50Hz hum), I doubt it. It's not very likely in a quality sub like yours.
    More likely is a phase effect. Do you measure your sub alone, or are there other speakers working while you measure? Where (exactly) is the filter located you tried to use?
    Exactly how do you perform your calibration?
    Cees
     
  3. StephenL

    StephenL Second Unit

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    Check for harmonics: 25 Hz and 100 Hz, for example. When I set up my Behringer Feedback Destroyer using a Radio Shack SPL meter and Avia low frequency sweep I found a large peak at 81 Hz. When I used Spectra Plus Real-Time Spectrum Analyzer software and a low frequency sweep the graph had a dip at 81 Hz and a peak at 162 Hz. 8 dB of attenuation at 81 Hz eliminated the dip at 81 Hz and the peak at 162 Hz.
     
  4. MichelF

    MichelF Extra

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    I found the problem in the settings of the measurement system, my Windows mixer settings were totally wrong... I corrected them and I validated my new measurements with an SPL meter (I measured the response at the listing position between 20 and 200 Hz with a 1 Hz step using a sine wave signal).
    Thanks for your help anyway.
    Michel
     

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