EQ'ing help needed - ART-351/SV20-39CS+/Samson 1000

Discussion in 'Archived Threads 2001-2004' started by Jeremy Anderson, Apr 5, 2002.

  1. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Okay, so I've got the gear... SVS 20-39CS+ (one port plugged), Samson 1000, ART-351 EQ. I've got it all calibrated as-is (all EQ sliders at 0, subsonic filter at 10Hz, unity gain on EQ and amp, sub set 5dB hot from reference). Now I want to play around with EQ'ing. However, when I search on this topic, I don't find anything that clearly states just what in the hell I need to do.

    For instance, I see people using the Stryke disc to EQ... which uses sine waves at differing frequencies, right? Then I see these same people using the correction values to adjust for different frequencies on the SPL meter, even though I've also seen that the correction values only work properly for 1/3 octave white noise and not sine waves. Is there even a disc that has 1/3 octave noise?

    So what do I need to do here? I've got Avia, which has bass sweeps but not 1/3 octave white noise. I took a tone generator on my PC and burned a CD of sine waves matching the sliders on the ART-351. I tried using this CD to bring everything flat, and the result was a muddy nasty mess of sound. Could someone please give me an idiot-proof method for proper EQ'ing? I'm fairly proficient when it comes to this stuff, but this has me a bit befuddled.
     
  2. ColinM

    ColinM Cinematographer

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    Try the "House Curve" method - From 100 to 20, a gentle 8db rise.
     
  3. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    Can't you achieve basically the same effect by just not using the corrections for the Radio Shack meter? And do you just use sine waves for this or do you have to have 1/3 octave noise?

    I think I discovered part of my problem tonight... When I hooked up the SVS, I calibrated with Avia but I never bothered to check subwoofer phase. So tonight, I reversed the leads to the Samson and checked to see how it affected the bass levels using Avia's subwoofer tones. With phase reversed on the SVS, the bass was suddenly 5dB higher than before. I'm assuming this is because I was previously getting cancellation between my speakers and sub, and that reversing the phase made it reinforce frequencies across the crossover range. I backed off my Onkyo 595's sub level from 0 to -4 and that brought overall levels back down to my target (5dB hot). It's too late for me to test it out right now, but I'll throw some discs at it in the morning and see what I think.

    Anyone else got any EQ'ing suggestions?
     
  4. brucek

    brucek Second Unit

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    Jeremy,
    Generally, most people measure from 16Hz to 160Hz at 1/6 octaves, at about a level of 85dB to 90dB SPL taken with a Radio Shack SPL meter at your normal prime listening position using a source of a CD playing 3 to 5 second sine wave tones tones.. Take measurements using the sub only and your processor with normally used crossover frequency. The correction constants for the Radio Shack meter for 1/6 octaves are valid for sine waves and are:
    16Hz +11.5
    18Hz +8.0
    20Hz +7.5
    22Hz +6.5
    25Hz +5.0
    28Hz +4.0
    31.5Hz +3.0
    36Hz +2.5
    40Hz +2.5
    45Hz +2.0
    50Hz +1.5
    56Hz +1.5
    63Hz +1.5
    71Hz +1.5
    80Hz +1.5
    89Hz +1.5
    100Hz +2.0
    111Hz +1.0
    125Hz +0.5
    142.5Hz +0.5
    160Hz -0.5
    It's a good idea to use the information and Excel graphing tool on Sonnies site (listed below) which has the graphs all pre-done including compensation correction for the SPL meter: Read all the information on this site including the links.
    http://www.snapbug.ws/bfd.htm
    Download this FREE tone generator listed below and save the tones in three to five second files and burn them on a CDR.
    http://www.nch.com.au/action/index.html
    Scroll down to Freeware and click on TONE GENERATOR......
    It's only necessary to use sixth octave tones. One hertz increments might be useful around a peak to try and establish a better center frequency for a filter value, but your testing should be limited to sixth octaves.
    It's best to first do a frequency response without any filters and graph it, and then enter your equalizer filters and regraph a second line on top of the unfiltered graph to get a reference of the filters actual effects. The Excel tool on Sonnie's site is set up for this.
    If you are successful in creating a flat response using sixth octaves with an appropriate house curve (depending on your room), it will sound good.
    If you do a search on BFD in this forum, you will get hours of reading on how to equalize...
    brucek
     
  5. Matt Meyer

    Matt Meyer Stunt Coordinator

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    Can you explain "house curve"? You don't want a flat graph?

    I know I know but I'm very new at this.

    Matt
     
  6. brucek

    brucek Second Unit

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    Matt,
    Although debatable, a lot of people find that when they achieve a measured flat response from equalizing their sub, that it sounds, well, flat....
    The solution is to impart a slight to heavy rise from about 80Hz down to about 30Hz. It's up to you what sounds good. 8dB wouldn't be out of line as an increase over this range.
    Here's a thread to read...
    http://www.hometheaterforum.com/htfo...ouse+AND+curve
    brucek
     

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