How to set B&K notch filter

Discussion in 'Archived Threads 2001-2004' started by DavidHos, Mar 21, 2002.

  1. DavidHos

    DavidHos Auditioning

    Joined:
    Mar 10, 2002
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    How is one supposed to adjust the notch filter of the B&K 307? The manual is vague and my monkeying with it does not seem to change anything. I started by running the B&K test tone from the room equaliztion setting page (at -30db) and logging the results. I have a huge dip at 40hz. But, setting the notch at 40 hz does not seem to change the reading at all. this is also with running through the different width settings.

    I have a room that is horrible for bass to begin with and i would like to dial in as best as possible. Any pointers at all?

    Thanks

    Dave
     
  2. Robert George

    Robert George Screenwriter

    Joined:
    Jul 3, 1997
    Messages:
    1,097
    Likes Received:
    74
    Trophy Points:
    1,610
    I may be a little fuzzy on the exact details and I no longer have the manual to fall back on, but I recall there being two separate settings for the notch filter. First is setting the width of the notch then setting the level of cut or boost.

    After determining what the frequency range is you want to affress, set the width of the notch in the menu. In the same menu should be the setting for the amount of cut or boost. Fairly straightforward, if my memory is accurate.
     
  3. DavidHos

    DavidHos Auditioning

    Joined:
    Mar 10, 2002
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    Ah, it sounds like the steps would be to set the freq you want to adjust, the width of the adjustment, and then there are two other settings - bass & treble. Does one then reduce or boost the bass to take the range (40hz in my case) up to the level of the other freq readings?

    Does this make sense?

    Thanks

    Dave
     
  4. Robert George

    Robert George Screenwriter

    Joined:
    Jul 3, 1997
    Messages:
    1,097
    Likes Received:
    74
    Trophy Points:
    1,610
    Hmmm...that may be it. Again, I'm going strictly off memory and I haven't performed this adjustment myself in several months. My B&K was sold several weeks ago so I can't go through the steps myself.

    You should be checking how much of a dip there is at 40Hz using a SPL meter. Stepping through the tones beginning at 20Hz and going well past 40Hz should show how much you are dropping around 40Hz. Depending on where exactly the lowest level is, I'd set the notch range somewhere from the high 30's to the low to mid 40s. Then boost the level by however many dBs you measured low. After setting, step through the tones again to see if you were able to flatten the response.
     
  5. Duke

    Duke Stunt Coordinator

    Joined:
    Aug 8, 1998
    Messages:
    65
    Likes Received:
    0
    Trophy Points:
    0
    The notch filter is a used to decrease it does not increase

    the notch depth will decrease the level 0 thru -18

    The bass frequecy and bass gain will boost to +6

    try the EQ setting of Loudness
     
  6. Pete Mazz

    Pete Mazz Supporting Actor

    Joined:
    May 17, 2000
    Messages:
    761
    Likes Received:
    0
    Trophy Points:
    0
    As stated, the notch filter is only a cut. Be aware that the bass and treble sliders will affect any freqs above the treble setting and below the bass setting. For instance, if you set the bass to 60 Hz and +6 dB, everything below 60 Hz will be boosted. Also note these settings are only active when you have the Variable EQ set to ON for a particular input or preset. The notch filter is a global setting that is always active.

    Pete
     
  7. DavidHos

    DavidHos Auditioning

    Joined:
    Mar 10, 2002
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    Thanks for all of the replys. Its funny, the first time I took my measurements, I tried to hold the SPL meter around head level like I do when setting speaker level. This gave me the huge drop at 40hz. Took the measurements again, except set the meter on the ottoman, and the 40hz reading was not near so bad. Adjusted the bass slider a bit and got 2db more at around 44 and below. Recalibrated the sub. Don't really know if I changed much but am going to try some of the usual suspects and see if there is any diff. Thanks again

    Dave
     
  8. Pete Mazz

    Pete Mazz Supporting Actor

    Joined:
    May 17, 2000
    Messages:
    761
    Likes Received:
    0
    Trophy Points:
    0
    That's the thing with EQing. If it's not for a specific location (and I mean specific), it's usually not worth taming all but the most generic problem freqs. Get a FR perfect, move the mic a few feet (sometimes less), and you'll wonder why you bothered.

    Pete
     
  9. Harold Leroy

    Harold Leroy Stunt Coordinator

    Joined:
    Dec 29, 2001
    Messages:
    51
    Likes Received:
    0
    Trophy Points:
    0
    Pete,

    You're sure right about moving the mic a few feet and the changes. I decided I could do the best for position "A", my spot, and that's all I could reasonably do.

    David,

    I use my B&K 307 notch filter for one bad peek/hump 56HZ-70HZ. I finally decided to try a BFD parametric EQ to get everthing as flat (with a 10db house curve). I'm pleased with the result--no nulls or peaks. Before I started I had some real bad spots and it sure could be heard. I first noticed it on a Moby track--one of the synthesized base notes wasn't there--it was in a null. There was another note that was real boomy, now all of that is gone!!
     

Share This Page