What does a sub 'bottoming-out" sound like?

Discussion in 'Archived Threads 2001-2004' started by Jack*Mains, Dec 24, 2002.

  1. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
    Before I ask anything, I would fist like to wish everyone happy holidays, and hope that the next year will be even better then passing one.
    As for my question, its just like the topic says, what would a bottoming out sub *Shiva Mach III specifically* sound like?
    I ask because I recently finished building an EBS Shiva, and at about 10mm excursion one way (I measured, maybe less) I hear this weird noise as if the membrane is hitting something. It doesn't sound like metal, but more as if you put your finger in front of it, and let the membrane hit it. There doesn't seem to be anything in the way that would cause this, so I am assuming that it's reaching the limits, even though the x max one would should be 15mm.
    If you can add to this, please do, I would greatly appreciate it. And I will post pics of this beauty as soon as I can get a digital camera [​IMG]
    EDIT: Also, how bad is this? Sometimes at rather high volumes, I cannot hear it unless I am standing very close to the sub, and sometimes just dont notice that it is happening.
    Happy Holidays everyone!
     
  2. Patrick Sun

    Patrick Sun Moderator
    Moderator

    Joined:
    Jun 30, 1999
    Messages:
    38,717
    Likes Received:
    463
    Sometimes the tinsel leads do a bit of slapping the woofer cone, and that causes a fluttering sound.

    Bottoming out sounds like a fart or popping sound.

    If your sub is trying to play clipped sound waves (the amp runs out of power/current to correctly drive the woofer), it'll sound distorted.
     
  3. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
     
  4. Brett DiMichele

    Brett DiMichele Producer

    Joined:
    Sep 30, 2001
    Messages:
    3,181
    Likes Received:
    0
    When you hear the loud popping sound that means you have
    exceeded the mechanical suspension limits of the motor
    structure. The voice coil former is striking the inside of
    the backing plate (yoke) and no this is not good at all.

    Prolonged bottoming can break or warp the voice coil former
    which in turn would mess up the voice coil that is wrapped
    around the former.

    As for Tinsel Lead Slap the only way to fix this is to see
    if there is enough slack so that you can glue the leads to
    the underside of the cone or spider or you could put soft
    pads on the cone where the leads will slap to deaden any
    slapping sounds.
     
  5. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
    Thanks a lot Brett, it does indeed sound like the sub is bottoming out. Just to be sure though, do you think its possible to bottom out the Shiva with a 250W AVA250 amp?
     
  6. Mark Fitzsimmons

    Mark Fitzsimmons Supporting Actor

    Joined:
    Aug 18, 2001
    Messages:
    539
    Likes Received:
    0
    Yes, below the tuning point there isn't very much resistance on the driver cone. Which allows it to move very far and can easily exceed the excursion limits of the driver.
     
  7. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
    What about above tuning point? What's bugging me is that I cant get it to bottom out by feeding it a 20Hz test tone, yet I get this farting sound fairly quickly when just listening to music.

    Could this actually be the problem with the box? Maybe the newly put veneer has something to do with it.

    I would just feel a lot better knowing that it IS bottoming and theres nothing I can do about it, rather then just ponder if I screwed up somewhere.
     
  8. Pete Mazz

    Pete Mazz Supporting Actor

    Joined:
    May 17, 2000
    Messages:
    761
    Likes Received:
    0
    At 20 Hz the sub is probably near tuning and that means excursion is near minimum. Excursion increases at higher freqs, so it's very possible, although most music doesn't have that much LF info usually. Is the sub calibrated properly?

    Pete
     
  9. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    Jack, I have a similar problem with my EBS Tempest. When turned up quite loud, I can hear a horrible noise near my sub, but only when I am right beside it or sticking my head behind it. I think it is my walls.

    Have you considered this? My walls are under tremendous pressure when I feel the need to turn it up (often).
    My AVA250 amp has a 18hz filter, and the sub is tuned to 16 hz, so bottoming should not be a problem for me. I am not 100% positive, but I think it is my drywall.

    Is your sub against a wall or in a corner?

    Also, another question for you all. Out of curiosity, what does an air leak sound like and what effects will it have??
     
  10. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
    Paul, I have considered this, but I've tried putting the sub in the middle of the room, and I still get the same notice. I can tell that it is coming from the sub.

    I think that this is simply due to the EBS design. It has a large volume, so the cone doesn't have as much resistance to keep it from bottoming. On the other hand, this gives it the low bass extension that goes down to 16hz.
    I really do think that the trade off is worth it for home theater, where I don't plan on cranking it too loud, and can enjoy every deep note recorded on the disk.
     
  11. PaulDF

    PaulDF Second Unit

    Joined:
    May 17, 2002
    Messages:
    354
    Likes Received:
    0
    So, in other words... An EBS design will bottom out when cranked listening to rock music?

    What about all the guys building infinite baffles? One would think they might have the same problem too then??
     
  12. Brett DiMichele

    Brett DiMichele Producer

    Joined:
    Sep 30, 2001
    Messages:
    3,181
    Likes Received:
    0
  13. Brian Bunge

    Brian Bunge Producer

    Joined:
    Sep 11, 2000
    Messages:
    3,716
    Likes Received:
    0
    Jack,

    From what you're saying it sounds like your amp is clipping. I remember my SV12's making the same sound when I would drive them hard with my PSA1 200W amps. But I'm running them each off of a channel of a K2 (that's 800W each) and have never heard that sound again. So there was no way I was bottoming them before since I'm driving them even harder now.
     
  14. Jack*Mains

    Jack*Mains Stunt Coordinator

    Joined:
    Sep 25, 2002
    Messages:
    156
    Likes Received:
    0
    Interesting, what If I hooked it up to a single voice coil resulting in 8Ohms. If I would still get this sound, would that mean that the sub is clipping because there is no way you can bottom out the sub with only 180W?
     
  15. Brian Bunge

    Brian Bunge Producer

    Joined:
    Sep 11, 2000
    Messages:
    3,716
    Likes Received:
    0
    Jack,

    It's the amp that clips, not the driver itself. If you still hear the noise then I would assume it's the amp clipping.
     
  16. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
     
  17. Bryan Michael

    Bryan Michael Supporting Actor

    Joined:
    Mar 2, 2002
    Messages:
    564
    Likes Received:
    0
    i have killed a car sub in a sealed 1 cube box it was rated at 250 and i threw 1000 wats on it and cranked it up it was sounded good till i went past its limit then it got stupid loud i actuley got the vc to melt to the backing plate i also had the sub rip the cone from the vc i had a 5 year warentee on it so i had some fun plus i wanted to show the sales person who said it can be done he was a idiot it takes alot to botom out a sub distorshon kills subs more than to much power
     

Share This Page