What would you consider a "reasonable" spl level for HT @ 20hz

Discussion in 'Archived Threads 2001-2004' started by Anthony_Gomez, Jan 25, 2002.

  1. I want to build a small sealed/EQed sub with lots of power, but I am not sure what a realistic spl to shoot for.

    Using UNIBOX (ie anochaic freespace), I am getting a max of [email protected] While this is pretty good for a 16.5"cube, I wasn't sure if it will cut it for HT duty. I don't need my teeth to rattle out of my head, but I do like to feel the bass..like with TPM THX intro=)
     
  2. ...anybody?[​IMG]
     
  3. Jack Gilvey

    Jack Gilvey Producer

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    Well, it's no fun to shoot for "reasonable" goals. [​IMG]
    DD reference level would require about [email protected] if all bass is going to the sub...how's that sound? I listen/watch at 10db below that, so I'm happy with 110db or so.
     
  4. Steve Hanna

    Steve Hanna Agent

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    Since LF won't harm ears nearly as much as midrange on up, I'd shoot for as much over 120dB as you can afford to build or tolorate. Explosions seem more realistic that way and music can actualy move you and your house.
    [​IMG]
     
  5. Mark Seaton

    Mark Seaton Supporting Actor

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    Anthony,

    It is important to understand the numbers your software is generating and how they relate to application in your room. Typically the numbers generated are half-space values, ie outdoors, on the ground, one meter. Each boundary which is within about 1/4 wavelength of the radiator will add 3dB to the effective SPL. So, a rear wall adds 3dB, and placement will dictate at what frequency other boundaries will become "close." You then also need to calculate losses based on distance from the sub. This is calculated at -20 log (distance(m)).

    Then I would start by shooting for about 115dB at the seats and see what it will take to get to 120-125dB peak.

    Mark Seaton

    Sound Physics Labs, Inc.

    ServoDrive, Inc.
     
  6. Mark Seaton

    Mark Seaton Supporting Actor

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    I should really qualify that suggestion of 115dB better. I would make sure you can reach that level in the passband of the subwoofer. IF you are limited to not going any larger, more drivers, and/or more power, make sure you can hit this level at say 25-30Hz, and then accordingly roll-off the bass below this to keep excursion in check. Going for an additional 3-6dB gets expensive or large very quickly. You will also want to do some guestimating as to the room gain, which you can roughly figure off of the longest dimension of your room, typically the diagonal from floor to cieling. The equivalent 1/2 wavelength is about where the room will start to boost the bass response, in the exact same manner as a car does. The more "sealed up" your room is, the closer to the ideal 12dB/oct. in gain you will get, but with many windows, stairways, walkways, etc., you can end up closer to 3-6dB/octave.

    Mark Seaton

    Sound Physics Labs, Inc.

    ServoDrive, Inc.
     

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