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What is meant by 28Hz at -6db

Discussion in 'Sound Science' started by Nails, Aug 30, 2019.
  1. Nails
    I hope this is the right place to post this question, I tried some searches but couldn’t find an answer. Must be a silly question, but I would like to understand why the negative 6? This (28Hz at -6db in room) is listed in the specs for my new subwoofer under lower frequency response. I would’ve thought it would be +6, and why ‘in room’?
    Thanks
     
  2. bigshot
    -6dB is a significant drop in the level. -3dB is enough to clearly notice. -6dB is quite a bit. What that means is that 28Hz is significantly quieter than the rest of the frequency spectrum. Your speaker probably gets closer to balanced around 35 or 40Hz.

    In room is BS. They don't know what your room is going to do. They are guessing.
     
    Last edited: Aug 30, 2019
  3. old tech
    Basically it means that the sub will go down to 28hz but you wouldn't hear it!
     
    bigshot likes this.
  4. Nails
    Thanks, that makes sense now
     
  5. what?
    You're right ! A subwoofer *in a room / car, can experience volume gain (and sometimes loss) at certain frequencies,
    that is why designers typically design the subwoofer to 'roll off' -6DB @ @28hz because 27 26 and 25 hz can do all kinds of strange things to eardrums, china ware and the drivers themselves.

    I like this explanation

    http://www.teamrocs.com/technical/pages/aiming.htm
     
    Last edited: Aug 31, 2019
    Nails likes this.
  6. 71 dB
    Due to the laws of physics reproduction of low frequencies is hard. You'd need driver of the size comparable to the wavelength of the sound. At 28 Hz the wavelength is about 12 meters ( ~ 40 feet ) and the driver of your subwoofer is only 1 feet or so. So, it has HARD TIME producing 28 Hz! Maybe your subwoofer has a reflex port to help a bit. That's why -6 dB.

    In room is assuming an "average" room. In YOUR room it is what it is and where in your room you put the sub affects the sound dramatically.
     
    Last edited: Sep 7, 2019

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