How to increase rolloff of subwoofer?

Discussion in 'Speakers' started by MartyP, Apr 10, 2004.

  1. MartyP

    MartyP Stunt Coordinator

    Joined:
    Jun 5, 2003
    Messages:
    67
    Likes Received:
    0
    I'm trying to help a friend with his subwoofer problem. His sub has a rolloff of 6dB/octave and seems to let too much upper bass/midrange(?) through. The sub has no bypass switch. Is there any way to increase the rolloff slope of the sub at 80 Hz using the low level inputs?
     
  2. Edward J M

    Edward J M Cinematographer

    Joined:
    Sep 22, 2002
    Messages:
    2,031
    Likes Received:
    0
    Most speaker level connections on the subwoofer plate amp have a fixed 1st order high pass filter for the speakers, and a variable 2nd order (12 dB/octave) low pass filter for the subwoofer.

    I haven't ever seen a 1st order low pass filter on a subwoofer, but anything is possible, I guess.

    Regardless, if the subwoofer is playing too much mid range with a speaker level connection, then simply lower the frequency on the low pass filter.

    If you switch to a low level connection and set all the speakers to small and the sub to on/yes, most AVRs have a 2nd order high pass filter for the speakers, and a 4th order low pass filter for the subwoofer.

    If the sub is lacking a low pass filter bypass switch, then simply set the low pass filter control to its highest setting to avoid cascading the AVR and the subwoofer low pass filters.
     
  3. Paul_Wright

    Paul_Wright Auditioning

    Joined:
    Dec 6, 2003
    Messages:
    10
    Likes Received:
    0
    Behringer makes a small 2-way crossover (CX2310?...not sure about the model #) that also includes a variable frequency 24db/octave mono sub output. You can pick them up on the net for about $80 new. The only issue is that the inputs/outputs are pro-audio XLR connectors. If you don't want to make adaptor cables, Parts Express sells inexpensive RCA/Phone/XLR adaptors.
     
  4. Wayne A. Pflughaupt

    Joined:
    Aug 5, 1999
    Messages:
    6,098
    Likes Received:
    33
    Location:
    Katy, TX
    Real Name:
    Wayne
    Marty,

    What Paul is saying is that your best bet is to insert an external, line-level outboard crossover between the receiver and sub.

    Regards,
    Wayne A. Pflughaupt
     
  5. MartyP

    MartyP Stunt Coordinator

    Joined:
    Jun 5, 2003
    Messages:
    67
    Likes Received:
    0
    Wayne:

    So an external crossover can be used in addition to the built-in crossover? Should the built in crossover be set to it's highest setting? Are the crossover slopes additive (6dB + external crossover's slope)? Sorry about all the questions...

    Marty
     
  6. ScottCHI

    ScottCHI Screenwriter

    Joined:
    Feb 21, 2004
    Messages:
    1,292
    Likes Received:
    0
    does his pre/pro have bass management capabilities?
     
  7. John F. Palacio

    John F. Palacio Supporting Actor

    Joined:
    Jan 6, 2002
    Messages:
    575
    Likes Received:
    0
    I have used a Paradigm X-30 external crossover successfully for that same purpose. I have it in series with the sub output of a Sunfire Theater Grand processor and use it both as a level control, phase control as well as to "tighten up" the upslope of the sub. Other external crossovers will work just as well. The output of the X-30 then feeds the power amps that drive the subs.

    You can use this scheme with a receiver as well. It will also work with a sub with built-in amp. You just feed the output of the external crossover to the sub.
     

Share This Page