BP 1803 "sag"?

Discussion in 'Home Theater Projects' started by JimPeitersen, Aug 6, 2004.

  1. JimPeitersen

    JimPeitersen Second Unit

    Joined:
    Dec 7, 2001
    Messages:
    470
    Likes Received:
    0
    I've got a question for all the guys with a BP 1803/1804, or experience with them (Kyle, Jack, Thomas, Craig, etc.) One of my 1803's have been in a sonotube (5 cu.ft. LT) for close to two years. I was looking closely at it the other day, and noticed that it may be sagging. Can anyone remember if these were rated for long-term horizontal applications? Thanks,
    Jim
     
  2. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Here's the formula

    http://www.adireaudio.com/Files/Tech...rientation.pdf

    BP-1803 T/S Parameters

    Fs= 25.0
    Re= 3.6/4 ohms
    dB/2.83V/m=95
    Xmax=51.9mm p-p
    Qts= 0.35
    Vas=279.4 literes
    Sd =1210 sq cm
    Bl=N.A.
    Fmax=300
    EBP=65.79
    RMS 1000+ watts
    Fs = 25.0 Hz
    Re = 3.6 Ohms
    Qms = 7.22
    Qes = 0.38
    Qts = 0.35
    Cms = 130.0 uM/N
    Mms = 300.0 grams
    Sd = 1217.0 cmsq
    Vas = 279.4 liters
    SPL = 92.1 dB
    X-max = 45mm p-p
    Power = 1000+ watts
     
  3. JimPeitersen

    JimPeitersen Second Unit

    Joined:
    Dec 7, 2001
    Messages:
    470
    Likes Received:
    0
    Thomas,
    Thanks for the link, I forgot about it.
    JP
     
  4. Janne Ahonen

    Janne Ahonen Extra

    Joined:
    May 4, 2002
    Messages:
    24
    Likes Received:
    0
    Location:
    Kuopio, Finland
    Real Name:
    Janne Ahonen
    Actually, sag can be calculated directly from fs (derivation skipped, this is result if you combine all the equations in Adire's paper):

    sag = ga/((2*pi*fs)^2)

    where ga is gravity acceleration (ca. 9.81 m/s^2), and fs in Hz. Sag unit is therefore, in meters.

    WinISD pro driver editor calculates sag percentage (see advanced parameters -> gloss).

    Regards,
    Janne.
     
  5. John E Janowitz

    John E Janowitz Second Unit

    Joined:
    Oct 30, 2000
    Messages:
    445
    Likes Received:
    0
    The formulas will tell you a pretty good estimation of the amount of sag you will have right away and give you an idea of whether you sould attempt a downfiring sub or not. There is no formula however that can tell you what will happen over time as the surround and spider become distorted from the continual effects of gravity. It all has to do with the elasticity of the foam or rubber used, the material and coatings on the spider, the amount of wear and tear on the spider and surround, humidity and other climate conditions, etc.

    John
     

Share This Page