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Foam vs Rubber vs Accordian Cloth Surrounds

Discussion in 'Amps and Cabs [BG]' started by ESP-LTD, Nov 11, 2001.

  1. Nov 11, 2001 #1
    ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    I have read in prior threads that some folks have made cabinets with car audio drivers and home audio speakers. I have seen in the smaller drivers that folks are occasionally using rubber surrounds.

    I was curious what the lifespan of foam and rubber surround drivers was like. I know typically the big players typically use cloth accordian surrounds for bass, I imagine because the dynamic range of the bass guitar is rough on suspension.

    Is the trick using a low mass cone? Are some surrounds "ok" and others not appropriate at all?
     
  2. Nov 11, 2001 #2
    bgavin

    bgavin

    May 3, 2001
    Orangevale, CA 95662
    Foam is more prone to deterioration from atmospheric pollution. It is also reputed to have better sonic capabilities than Santoprene (rubber) surrounds. Both have significantly higher excursion limits than accordion fold surrounds.

    I have many JBLs in my garage and all have foam surrounds eaten away by smog. Orange County Speaker Repair, and others, does a very tasty refoam job for 1/5th the price of a JBL recone.

    I am one of those using Rockford subwoofers and they all have Santoprene long-excursion surrounds. The amount of cone excursion increases 4x for every octave lower, to maintain the same loudness, i.e. a cone moving 0.125" at 80 Hz has to move 0.500" at 40 Hz. The Xmax on mine are 0.5300" compared to 0.1 or less for the Eminence Legend bass drivers. Low frequencies at high volumes are what is rough on the suspension.

    Low mass cones are usually more effiecient, therefore louder with less input power, but they don't get down as low.
     
  3. Nov 11, 2001 #3
    leper

    leper

    Jun 21, 2001
    quick question...

    Is it the higher mass that directly improves low end response or is it that the added mass means added stiffness (in theory), and its that stiffness in the cone which helps it get down lower?
     
  4. Nov 11, 2001 #4
    bgavin

    bgavin

    May 3, 2001
    Orangevale, CA 95662
    The mass lowers the resonant frequency of the driver. This is one of the primary controlling parameters of low bass response. As the resonant frequency goes lower, so does the efficiency nearly all the time.

    Stiffness is to prevent cone flexure and the subsequent breaking-up of the reproduction. It's difficult to get a really stiff cone combined with very light weight.
     
  5. Nov 11, 2001 #5
    leper

    leper

    Jun 21, 2001
    thanks, hadnt thought of the whole resonant frequency thing

    now off to glue bricks to all my speakers ;)