Dual Shiva, Saturday construction progress!

Discussion in 'Archived Threads 2001-2004' started by Brian Steeves, Aug 4, 2001.

  1. Brian Steeves

    Brian Steeves Second Unit

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    Here is the link to my makeshift webpage of today's progress. Be patient if you don't have a high speed connection because I didn't compress the photos this time. They look much better uncompressed!
    http://home.tampabay.rr.com/bpsdesigns/August4th.html
    Tell me what you think Guys..
    [Edited last by Brian Steeves on August 04, 2001 at 11:01 PM]
     
  2. Wayne A. Pflughaupt

    Moderator

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    Very nice woodwork, Brian! Good luck with the project.
    Regards,
    Wayne A. Pflughaupt
    ------------------
    My System
     
  3. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Looks like a killer! twin shivas in this is really going to knock out some very serious bass...painting it purple by any chance?
    TV
     
  4. Brian Steeves

    Brian Steeves Second Unit

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  5. Patrick Sun

    Patrick Sun Studio Mogul

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    Brian, the only thing I would have done differently, especially with the tools at your disposal, is to create a 1/4" thick plywood ring and glue it around the driver hole on the inside of the endcap. And then drilled the screw holes through the MDF/plywood layers, and then installed the t-nuts with the teeth biting into the plywood because MDF strips a lot easily than plywood or real wood. And with MDF starts stripping, you'll start cursing!
    It's a darn shame all that nifty work for the t-nut platform can't be seen by admirers later on, since it'll be on the inside of the sub.
    I do the plywood layer with all of my baffles that will be accepting drivers/t-nuts/screws for my speakers, and so far I'm happy I did. I've seen what happens when the t-nut strips the MDF near the driver hole. (I have a subwoofer box where that's happened, and I'm not sure how I will fix it so that I can still have a t-nut to accept a screw - I'm toying with the idea of just filling the hole and not putting a screw there at all, relying on 7 screws to hold in the driver).
     
  6. Patrick Sun

    Patrick Sun Studio Mogul

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    Oh yeah, the only way to make sure the Dual-Shiva sub doesn't fart on the super-low-material at high SPLs is to tune it for around 16Hz. I learned this by starting at around 20Hz and than extending the port until I was down to 16Hz before I was able to relieve 99.99% of any farting on the tough DVDs with the super-low LFE content.
    ------------------
    PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; LDs
     
  7. Brian Steeves

    Brian Steeves Second Unit

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    Parick,
    What do you mean about stripping the MDF? I don't understand unless you mean the MDF breaks loose and the t-nut spins. But that's why I used the liquid nails.
    And about the 16hz tune to relieve any "farting"? What kind of porting did you use when you tuned to 20hz and had the problems? I am using a 8" port just like Mike Knapps "waterheater". I don't ever remember hearing any problems on his when we did the comparison between the "waterheater" and my single Tempest "Silo".
     
  8. Julian Data

    Julian Data Second Unit

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    Brian,
    Since yesterday was my BDay is that my present? [​IMG]
    Great work!
    I can't wait for you to your towers!
    ------------------
     
  9. Patrick Sun

    Patrick Sun Studio Mogul

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    Brian, re: stripping, yes, if you torque the screws too much, there exists a small possibility of stripping the MDF regardless of the adhesive, it has more to do with MDF than any sort of glue used to keep the t-nut in place. So just be careful not to over-tighten the screws.
    Re: farting, ask Mike about the TPM pod race scene played at fairly loud levels and the waterheater popping every now and then. On my Sunosub I webpage, towards the very bottom, I outlined what I did to extend the porting (8" wide Quikrete tube) to drop the box tuning frequency from 19/20Hz to around 16Hz and it gave the drivers some more low end protection. Toy Story 2's opening (around 54 seconds IIRC into the film) made it pop, and so did some of the scenes from the dts Haunting DVD. But these represent an extremely small segment of the DVD releases that'll make most subs without limiters or low box tunes pop/fart when the LFE are played at a loud volume.
     
  10. Jack Gilvey

    Jack Gilvey Producer

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    Brian,
    Pat's referring to the fact that ported subs "unload" the driver below the tuning point, meaning it's possible, at moderate levels, to "bottom" the driver when fed such low signals as Pat mentioned. Lowering the tuning obviously decreases the chances that the sub will see a signal low enough in frequency to cause this. The tradeoff is you might give up some output up higher.
    Another way to help avoid this is with a subsonic "rumble" filter, like the 18Hz one in the Adire AVA250.
     
  11. Brian Steeves

    Brian Steeves Second Unit

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    Yeah I know what you are talking about guys I just didn't remember hearing any problems with Mike's. But then again I think he has a peak limiter on his Marantz pre/pro.
    I had a low tune of about 16-17hz on my last sub "The Silo," but it lacked a little in the midbass area. That's why I decided to tune a little bit higher this time. I know it's not a huge difference but that's what's fun about this hobby if I don't like it I can make another one!
    Also I have a spare Shiva laying aroung that I plan to make a sealed sub with for s**t's and giggles.
     

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