Sub bottoming?

Discussion in 'Archived Threads 2001-2004' started by Adam O, Sep 11, 2002.

  1. Adam O

    Adam O Stunt Coordinator

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    Well I think my sub is bottoming out. It seems like the sub is hitting Xmax really easily and then just stopping, it sounds likes its popping.

    I have a Dyaton 15" DVC sub with a 220L enclosure powered by the PE 250w amp. I just got the amp less than a month ago and have just noticed the bottoming out on scenes in LOTR and StarWarsEP1.

    However, music is extremely well-defined, loud and very earth shaking, in some cases more so than DVDs.

    Is it possible that my design or the actuall [poor] building of the enclosure is to blame for the bottoming out?

    Anything I should know? I know lots of people have this exact sub/amp pair and have not heard of similar problems.

    BTW, would a ported/nonported design effect this?; mine is ported: tuned to 20Hz.

    Should I rebuild with a 16Hz tuning freq, Change the enclosure size? Thanks for the patience.

    Adam
     
  2. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    What you can do is maybe compare to others and find out what's the maximum volume you can achieve at specific test tones before the sub bottoms out.

    I don't have that sub but I can get 107.5db (adjusted) @ 20hz before my tempest bottoms out in my 11x12x8' room from listening position.

    Could that be clipping of the amp that you're experiencing? Because a bottoming out sub should sound more like a flutter and not a pop...

    I've never "noticed" distortion during those movies at reference and I have the same amp but with a tempest in adire alignment. What happens to my bass is at extreme levels, the bass sounds lumpier/muddier. (Maybe because of distortion)
     
  3. Patrick Sun

    Patrick Sun Moderator
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    LotR is also a sub-killer at even medium volume levels.
     
  4. Joe Tilley

    Joe Tilley Supporting Actor

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    Adam, how loud are you listing to it. I have the same sub & amp that I have had in three different enclosures without ever having it bottom out. Right know I am using a ported 270liter sono tuned to 17hz. Mine simply starts to distort at high vol, & its damn loud when I even get close to that.
    I have played LOTR, TPM, & Blade II at just ridiculous levels without mine even starting to flinch.
     
  5. Dan Wesnor

    Dan Wesnor Second Unit

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    LOTR ate my sealed 10" sub - separated the surround from the cone. It is dangerous, even at moderate volumes. I think the sound techs wanted to prove how much bass they could make. I can't image what it's doing to cheap store-bought subs.

    The sub had no problems with Episode I.

    A 12" sub w/ Xmax=16mm can only make about 100db @ 20Hz. Not very many movies have a lot of 20Hz in them. They used a LOT of 20Hz stuff in LOTR, much more than Episode I. If you're using a 12" sub (or any sub for that matter), I suggest you dial it back when a movie starts causing it to bottom.

    BTW, the 10" (SB-10) never bottomed. I just noticed the bass became very ragged. It never lost volume, because the low stuff was replaced by equally loud gushing air. In fact, by ear it sounded too loud, but it stopped shaking the couch.

    My Shiva will be back in the loop soon. If the Linkwitz box works out, I may have to go and do a 15" Linkwitz just to be safe.
     
  6. Adam O

    Adam O Stunt Coordinator

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    Actually in LOTR even at extremely low volumes, I have no numbers, but volumes you could not here in the room next to it without soundproofed room are making it pop. (If that makes sense[​IMG])
    Is this just because the base is just that low(
     
  7. Travis G

    Travis G Stunt Coordinator

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  8. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Ok, I might be getting this confused...

    When a sub bottoms out it's also called distortion right?

    Does the sound of a bottoming out sub sound different than the "fluttering" noise my tempest makes when I crank up a 15hz test tone?

    I've also noticed that when I physically push on one side of the tempest there's a scratching/rubbing noise. Could this be what I'm hearing due to the cone flex?

    Oh wait, I have heard a bottoming out sub, it sounds like a rapid fire popping noise like somebody is punching the driver. But, Adam said his sub:

    "It seems like the sub is hitting Xmax really easily and then just stopping"

    This is what lead me to believe that it was amplifier related.
     
  9. Patrick Sun

    Patrick Sun Moderator
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    Bottoming is popping/farting by the sub (you'll know it when you hear it at loud SPLs (running out of Xmax for the driver). The grinding/fluttering is more of distortion being sent to the sub (like when the amp runs out of juice and clips the waveform, which makes the sub driver try to play higher harmonics of the waveforms, which sound unnatural).
     
  10. Rory Buszka

    Rory Buszka Supporting Actor

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    That rubbing sound sounds like my first blown driver sounded. I took some old 3w speakers from an old boom box and hooked them up to an old 40w reciever and blew those suckers. They started rubbing and bottoming, and then they popped and smoked and quit. You're close to blowing your tempest, I'd imagine, depending on how much power you're driving it with.
     

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