Bessel vs Linkwitz

Discussion in 'Archived Threads 2001-2004' started by Dan Pawlowski, Aug 21, 2002.

  1. Dan Pawlowski

    Dan Pawlowski Stunt Coordinator

    Joined:
    Aug 12, 2002
    Messages:
    100
    Likes Received:
    0
    Trophy Points:
    0
    I am thinking about replacing the xovers for my sub and mains with active 4th order Bessel filters(Q=0.31 xover at 55Hz) I am currently operating with 4th order active Linkwitz-Riley filters xovered at 55Hz. Has any one done this?? If so, I would like to hear your comments as to what you experienced with the improvement or deterioration of sound quality.

    Dan
     
  2. Dennis XYZ

    Dennis XYZ Stunt Coordinator

    Joined:
    Jun 1, 2002
    Messages:
    115
    Likes Received:
    0
    Trophy Points:
    0
    I haven't tried them myself but I believe the Q values are as follows:
    Butterworth .707
    Bessel .577
    LR .50
    The main advantage of Bessels is maximally flat group delay. The down side is the summed amplitude response is not perfectly flat and the lobing is not symmetrical. Everything's a trade-off.
    Bessel white paper
    Passive crossover design formulas
     
  3. Dan Pawlowski

    Dan Pawlowski Stunt Coordinator

    Joined:
    Aug 12, 2002
    Messages:
    100
    Likes Received:
    0
    Trophy Points:
    0
    Thanx Dennis

    I dont know where the .31 came from maybe the couple of beers i had earlier.

    about the lobing: can it not be discounted since my sub woofer is not located on the same baffle as my mains?; which would create a lobing problem by physical placement not to mention 55Hz a is fairly low frequency.

    The improved group delay is the whole reason i would like to change the xovers. LSPCad shows 2nd order LR at 5.6ms @ 10Hz and 2nd order Bessel at 5.0 ms @ 10Hz. Would i hear (feel) the .6ms difference? Also, there is a bump in level of 1.25dB at 55Hz. Placement of the sub will create greater changes in levels.

    Any thoughts??
     
  4. Dennis XYZ

    Dennis XYZ Stunt Coordinator

    Joined:
    Jun 1, 2002
    Messages:
    115
    Likes Received:
    0
    Trophy Points:
    0
    Sounds like more trouble than it's worth for a sub. Room interactions totally muck up the theoretical phase stuff anyway. If you're using EQ on the sub that changes it too.
     

Share This Page