Bottoming out my shiva

Discussion in 'Archived Threads 2001-2004' started by AlexKunec, Apr 9, 2002.

  1. AlexKunec

    AlexKunec Stunt Coordinator

    Joined:
    Mar 9, 2002
    Messages:
    161
    Likes Received:
    0
    When I play my sub (looked to a PE 250w amp) at fairly high volumes it seems to bottom out or something. The volume on the amp is only about a 1/3 the way up. its in a 100l vented enclosure. It seems to make a rattling sound. Is that what it sounds like when its bottoming out?
     
  2. Ryan Schnacke

    Ryan Schnacke Supporting Actor

    Joined:
    Feb 5, 2001
    Messages:
    876
    Likes Received:
    0
    I've played my DVC 12 a few times in free air just to fool around with it until I finish the enclosure. Very quickly I noticed that the tinsel leads had a tendency to slap against the back side of the cone once it was moving past about 1/3 of its excursion limits. This was pretty easy to diagnose in free air since I could see both the front and back sides of the cone and it really didn't make much bass sound to compete with the lead slapping sound.

    From several of the descriptions of woofer bottoming it seems like you won't have to ask "is this what bottoming sounds like?" if its really bottoming. It'll be more like "that's GOT to be bottoming because if its not then I don't even WANT to know what it is!" I'd check for the tinsel lead slap or maybe some small defect (try shaking the woofer to see if something sounds loose inside).

    My solution was small bits of foam attached with double-sided mounting tape to the back of the cone where the leads hit. Now I think its completely gone. And even if it still makes a little noise at really high excursion, it won't be noticeable once its properly mounted in the enclosure.
     
  3. Patrick Sun

    Patrick Sun Moderator
    Moderator

    Joined:
    Jun 30, 1999
    Messages:
    38,674
    Likes Received:
    424
    Have you calibrated your sub to your HT setup?

    Conventional wisdom is to turn the amp's gain/volume all the way up, and then use your receiver's subwoofer output control to adjust/calibrate the sub to the rest of the speakers in the HT setup. This will give you some headroom to play with in determining the best sub setup.

    In my experience, when a Shiva driver bottoms, it makes a popping/farting sound. This is usually on extremely low/loud frequencies.
     
  4. Cam S

    Cam S Screenwriter

    Joined:
    Jan 11, 2002
    Messages:
    1,524
    Likes Received:
    0
    I'll be recieving my Shiva within the week, so what steps should I take to prevent the tinsel lead slapping the cone??
     
  5. AlexKunec

    AlexKunec Stunt Coordinator

    Joined:
    Mar 9, 2002
    Messages:
    161
    Likes Received:
    0
    Well, it is kind of like a slapping sound. It doesn't sound like a jackhammer though.
     
  6. Jim A. Banville

    Jim A. Banville Supporting Actor

    Joined:
    Jun 20, 1999
    Messages:
    630
    Likes Received:
    0
     
  7. Brian Bunge

    Brian Bunge Producer

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

    This doesn't work with my plate amps either. If I set the volume control to 1/2 way on the amp and set the sub out to minimum I can't calibrate anywhere near 75dB. It's way too loud. So I leave my plate amps at 1/4 and adjust the subwoofer level from there.

    Now on pro amps I can see turning the input gain all the way up and I actually did this with my K2. But I just don't see that working for the plate amps I've tried.

    I wish I had a scope so that I could set my subwoofer output to just below the point where the signal clipped. Then I would adjust the plate amp's control accordingly. But I don't have that luxury. Maybe I'll get one of those handheld jobs in the future.

    I know of some industry professionals on another board that suggest setting the plate amps on subs as low as possible and jack up the sub out's signal to calibrate. Their thinking is that the output signal from the amp to the driver will be much more distorted than the sub out's signal. They say this is the way to maximize your S/N ratio.

    Brian
     
  8. Ryan Schnacke

    Ryan Schnacke Supporting Actor

    Joined:
    Feb 5, 2001
    Messages:
    876
    Likes Received:
    0
     
  9. Dave Poehlman

    Dave Poehlman Producer

    Joined:
    Mar 8, 2000
    Messages:
    3,813
    Likes Received:
    0
     
  10. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Alex

     
  11. Cam S

    Cam S Screenwriter

    Joined:
    Jan 11, 2002
    Messages:
    1,524
    Likes Received:
    0
    Thanks for the help guys.
     
  12. Ryan Schnacke

    Ryan Schnacke Supporting Actor

    Joined:
    Feb 5, 2001
    Messages:
    876
    Likes Received:
    0
    Thomas, I never meant to imply that Shivas have tinsel lead slap problems. I was trying to help trouble-shoot the problem with my (limited) experience. But your comment has confused me. Is there some condition that makes drivers more suseptible to lead slap in open air vs. in an enclosure? I'm having a hard time imagining what that would be.

    The only thing I can come up with is that the enclosure would dampen the sound of the lead slap since it is occuring on the back side of the cone (not the front side). But the slapping would still occur and, in my case, would likely have been audible. What am I missing?
     
  13. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Ryan

    I'm just trying to control rumor mill. Anything potentially negative that gets posted about a driver, sends some people into a nervous fit of anxiety.

    High cone excursions occur more quickly/easily when the driver is just sitting in free air. As a result it easier to induce lead slap.

    One of the very early Shiva production runs (2yrs ago) had issue with lead slap. That problem was quickly fix. Since that time your's is the first post I've seen talking about it.

    If lead slap is occuring, it usually manifests itself as a very light buzzing, not a rattle. Rattles are usually an amp clipping, driver being overdriven (bottoming) or an air leak.
     
  14. Patrick Sun

    Patrick Sun Moderator
    Moderator

    Joined:
    Jun 30, 1999
    Messages:
    38,674
    Likes Received:
    424
    You lose headroom when you use the receiver sub preout "near max" levels and vary the sub's output volume with the amp volume knob, but however you achieve the sub output, the important thing is to make sure the sub is calibrated. We have no confirmation from Alex that he's calibrated his sub, so he could be running it too hot, which would cause some of the problems he listed.
     
  15. Ryan Schnacke

    Ryan Schnacke Supporting Actor

    Joined:
    Feb 5, 2001
    Messages:
    876
    Likes Received:
    0
    Thomas, I see. Thanks for the clarification. My sub with the lead slap "problem" is the parts express DVC 12, not the Shiva. So Adire owners need not worry. And I've heard that Dayton may have addressed the lead issue since I bought mine back in December. And really, its such a small issue - I'd have bought it even if I knew about this "problem" ahead of time.
     

Share This Page