ART 351 Question/sub calibration level

Discussion in 'Archived Threads 2001-2004' started by EarleD, Aug 11, 2002.

  1. EarleD

    EarleD Supporting Actor

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    Here is some background info. Room is around 20 X 14, but open to another room on the left. The only true corner without any openings in the right front. See my web site for some pictures of the room. Subs are SVS 20-39s with the upgraded drivers and a 25-31PCi. Reciever is a Denon 3802. All speakers are set to small and xover set to 80hz on the Denon. All subs are in the front right corner. All speakers are calibrated to 75db except the subs which are set to 78db.

    I have been trying to smooth my subs response and have run into a problem. I have the HP set for 20hz and have the level control at around 7-8.

    I have a peak at 40hz of around 10-12 db, and cant get rid of it. If I make a 12db cut at 40hz it does cut the peak alittle (3-4db) but not nearly enough. Any thoughts?

    I have the sub out on the receive split, where one side goes to a set of bass shakers and the other side goes to the ART input. The ARTS output is split with one side going to the PCi and the other going to the amp powering the 39's.

    Any thoughts?

    Earle
     
  2. Wayne A. Pflughaupt

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    Earle,

    How do you know the peak is at 40Hz?

    I’m guessing that either you have the EQ”s “Range” switch set to ±6dB instead of ±12dB, or the peak is actually at 45Hz or 38Hz – between two of your filters. Or possibly a combination of the two.

    Regards,
    Wayne A. Pflughaupt
     
  3. EarleD

    EarleD Supporting Actor

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    Wayne,

    Glad to see that you answered this thread.

    I ran 3rd octave tones and the results were:

    20hz 69db
    25hz 74db
    31.5hz 75db
    40hz 86db
    50hz 74db
    63hz 68db
    80hz 74db

    These are the uncorrected values

    I have the range switch set to 12db(the yellow light is lit).

    What is the bandwidth of each slider on the 351? Is it extremely narrow or fairly wide?

    TIA

    Earle
     
  4. Wayne A. Pflughaupt

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    Earle,
    Since you’re sure you’re in ±12dB range, it does seem a pretty strange.
    A few things to try:
    • Try cutting other bands to see if you get a measured result the same as the amount of cut applied. If other bands are behaving like the 40Hz band, the equalizer is defective.
    • It’s possible the two subs don’t have quite the same response. Try connecting only one at a time and see how the EQ works with each of them.
    • A 12dB differential from one frequency to another would send the SPL meter off-scale for the range it was set to. If you didn’t change the range setting when you played the 40Hz tone, it’s possible the 40Hz differential is actually much greater than 12dB. This would account for why a 12dB cut only “appears” to be 3-4dB.
    Good luck, and keep us posted.
    Regards,
    Wayne A. Pflughaupt
     
  5. Ned

    Ned Supporting Actor

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    Earle-

    On a side note, how did you set the HP to 20hz? If you turned the knob to what says "20" it's probably wrong.

    Play a 20hz sine wave at a low level (80db), put the HP knob far left. Then turn the HP knob slowly clockwise and watch your SPL meter. When the level drops you've hit 20hz. Turn it back counterclockwise until the SPL meter reads 80 again and it's set just around 19-20hz.

    On my ART351, the real 20hz position is about 12hz. If I use the 20hz marking, it's actually much closer to 28hz.
     
  6. Wayne A. Pflughaupt

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    Ned,

    With most filters (high or low pass) the designated number is typically the –3dB point. Thus for a true 20Hz high pass filter setting, the original 80dB reading should drop to 77dB. I really don’t know how accurate the 351’s knob calibrations are, but irrespective of that you’ve dialed in a filter lower than 20Hz.

    Regards,
    Wayne A. Pflughaupt
     
  7. Ned

    Ned Supporting Actor

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    And I don't want 20hz to be affected, what's the point of getting a sub that can do 20 and then snipping off 3db right off the bat? If it was a 25-35 then sure, start filtering at 24. The extreme increase in excursion begins below the tuning point, so that's what should be filtered.
     
  8. EarleD

    EarleD Supporting Actor

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    Wayne and Ned,

    I set the HP filter as described above, playing a 20hz tone and slowly turning down the HP knob until I saw a drop in SPL. It's setting is well below the marked 20hz mark.

    I'll try and do some more measurements this evening and post them here. I just noticed that the battery in the RS meter was near dead, so I'll see if that makes a difference tonight.

    TIA

    Earle
     

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