Thoughts on the initial plot of my sub

Discussion in 'Archived Threads 2001-2004' started by Ben Jordan, Oct 28, 2002.

  1. Ben Jordan

    Ben Jordan Stunt Coordinator

    Joined:
    Jul 4, 2002
    Messages:
    94
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    GSP
    Real Name:
    Ben
    Using an analog RS meter w/ corrected values, here is the plot (same numbers, but using 2 different spreadsheets I found browsing the forum):
    [​IMG]
    [​IMG]
    I was planning on getting a BFD. Do you guys think it would help me any?
    The sub is a SVS 22-31PCi, calibrated to approx. +2 to +3dB hot (with the receiver's dial at "0dB" calibrated to 85dB). I ran the test tones from Stryke's BassZone Test CD at "-29dB" on the receiver.
    Would appreciate any input you guys had!
    Thanks, Ben
     
  2. Mike Ford

    Mike Ford Extra

    Joined:
    Oct 24, 2002
    Messages:
    24
    Likes Received:
    0
    Trophy Points:
    0
    Just FYI if you used some kind of pure tones instead of bandwidth limited noise the results are pretty meaningless. Tones are just way too sensitive to source and microphone placement.
     
  3. Ben Jordan

    Ben Jordan Stunt Coordinator

    Joined:
    Jul 4, 2002
    Messages:
    94
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    GSP
    Real Name:
    Ben
    I used the Stryke BassZone Test CD which has many different 'sine' and 'warble' frequencies. Using the 'warble' ones, the graph goes like this:
    [​IMG]
     
  4. Brian Fellmeth

    Brian Fellmeth Supporting Actor

    Joined:
    Jul 30, 2000
    Messages:
    789
    Likes Received:
    0
    Trophy Points:
    0
    I am not one of the BFD heavyweights around here but will venture an opinion. It looks to me like you are very fortunate and don't need one. It took me hours to get a curve as good as your baseline.

    I do not agree at all with the above poster that pure tone curves are meaningless. In the anal quest for perfection, pure tones are essential. They will uncover narrow band anomolys of the room that can be corrected by the BFD and that would be obscured by warbles or noise bands.
     
  5. Greg_R

    Greg_R Screenwriter

    Joined:
    Apr 9, 2000
    Messages:
    1,996
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    Portland, OR
    Real Name:
    Greg
    If you are crossing over at 80Hz then I don't think you'll need a BFD. These measurements are at the seats, right? How is the response at other seats? I had to move my sub to flatten the response in other listening positions... this gave me 2 large spikes and a 3rd smaller spike which the BFD tamed. +/-3dB from 20Hz->80Hz is an excellent response.
     
  6. Ben Jordan

    Ben Jordan Stunt Coordinator

    Joined:
    Jul 4, 2002
    Messages:
    94
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    GSP
    Real Name:
    Ben
    I'll check out the other seats, and see how they are. Thanks for the responses so far! I might get a BFD anyways, cause it sounds like a fun toy! [​IMG]
     
  7. Mike Ford

    Mike Ford Extra

    Joined:
    Oct 24, 2002
    Messages:
    24
    Likes Received:
    0
    Trophy Points:
    0
    I would be curious to see just a plot of the sub, and just a plot of the mains (or two lines, one plot).
     
  8. Brian Fellmeth

    Brian Fellmeth Supporting Actor

    Joined:
    Jul 30, 2000
    Messages:
    789
    Likes Received:
    0
    Trophy Points:
    0
     
  9. Chris Tsutsui

    Chris Tsutsui Screenwriter

    Joined:
    Feb 1, 2002
    Messages:
    1,865
    Likes Received:
    0
    Trophy Points:
    0
    If I was you I would use the 3 trials in that excel sheet and show the overlapping graph of:
    The mains
    The sub
    Both
    At least the bass looks smooth below 32hz which probably means you don't have a large room with lengths 20+ feet.
    In case anyone was wondering here is a link to download the frequency response graph worksheet. The 3 trial comparison is a great tool for tuning a sub because you can put the sub in 3 locations and compare the response of the three. You can also see the overlapping graphs of 3 different seating locations.
    I still have work to do with my response and the info on that site, I'm gonna move both subs to one corner and take measurements and also try putting the subs behind the mains and towards the middle.
    Anyways, your response looks plenty acceptable but it still has room for improvement because even +/-3db can be noticeable. Another alternative to a BFD would be bass traps/helmholtz resonators but I still have yet to add them to my HT and run tests. (I'll add electronic equalization to the signal path as a last resort)
     
  10. Ben Jordan

    Ben Jordan Stunt Coordinator

    Joined:
    Jul 4, 2002
    Messages:
    94
    Likes Received:
    0
    Trophy Points:
    0
    Location:
    GSP
    Real Name:
    Ben
    Thanks Mike & Chris, good idea. I'll try to do those plots this weekend, and see how that turns out.

    Yes, it's not a huge room, but it is completely open to dining room, kitchen (over the bar), and a hall way.
     

Share This Page