ebs shiva bottoming out?

Discussion in 'Home Theater Projects' started by john bourne, Mar 18, 2004.

  1. john bourne

    john bourne Extra

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    First I would like to take a second to thank everyone here for a wonderful education that you have provided me in the area of home theater. This is simply the best resource available and over the past several months has provided a wealth of free insight.

    Now my question - I currently have a shiva built to the Adire EBS specs powered via a PE 250 plate amp with gain set to 12 o'clock position. The voice coils are also wired in a 4 ohm config. I have calibrated to mains (-3dB)through my receiver via a RS SPL meter.

    My problem is it recently began bottoming out to several demanding bass sections on DVD. This is occurring on far from reference levels with my HK 525 volume set to -30 in a huge room (27' x 33' basement HT). I haven't noticed a problem other than the when the driver is really being called on(i.e. music playback is fine). Also, when I press the driver in manually I can reproduce the "metallic clanking" noise that I am referring to as bottoming out. Anyone with any ideas? I thank you in advance for any opinions as to how I can bring my baby back to health.
     
  2. ThomasW

    ThomasW Cinematographer

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    Yeap sounds like bottoming. Only option is to turn it down.......

    Might want to consider using a more appropriately size setup for that large a space... a couple of 15"s might be just the ticket...
     
  3. john bourne

    john bourne Extra

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    ThomasW, yeah that's what I was thinking too... I just wanted another opinion. Those last few BPD 1503 drivers are looking pretty tempting. Anyone know of any available plans out there? Thanks for the rapid reply, this place is great.
     
  4. ThomasW

    ThomasW Cinematographer

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    1503's are great drivers and a steal at the price.

    I've got a 1503 ported tube design on the AudioWorx website.

    There's a seal tube design using 2-1503's too. It takes CUBIC horsepower to drive it given the small box/tube. But it can literally shake my entire 2500 sq ft brick house. [​IMG]

    Also we retrofitted a Stryke cube (PR design) with a 1503. It sounded very good.
     
  5. Robert_J

    Robert_J Lead Actor

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    Besides the ones at ThomasW's sites, Dan Marx has one. There's a pic at the bottom where someone uses a 1503 in his cabinet. I also modeled a PL15D4 in Dan's cabinet and the response is very close to the 1503. This driver gets very good reviews at the car audio sites. $2.95 shipping on your entire order and search the web for coupons. You can probably get another $10 off.

    -Robert
     
  6. ThomasW

    ThomasW Cinematographer

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    Robert,

    Where are the T/S parameters for that woofer?
     
  7. Jerry Parker

    Jerry Parker Stunt Coordinator

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    Thomas, this site appears to have them: http://www.dbdrive.net/tech/speakerspecs.html

    Around 20mm throw according to that website. I HOPE they are talking about one way linear xmax though...

    I can't tell if its a underhung or overhung design either by the pictures [​IMG]
     
  8. ThomasW

    ThomasW Cinematographer

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  9. Jerry Parker

    Jerry Parker Stunt Coordinator

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    It's got a rather high inductance though, would it be able to play up to 100hz with relative ease?
     
  10. Justin Ward

    Justin Ward Supporting Actor

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    Maybe you could activate the subsonic filter? Perhaps it is bottoming out on bass below tuning.
     
  11. GrahamT

    GrahamT Supporting Actor

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    Maybe there are air leaks
     
  12. perry web

    perry web Stunt Coordinator

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    maybe your speaker is bad. How far can you move it before you hear the "bottoming" out noise? I had a bad shiva. it would move in fine w/o any noise but sounded bad when it hit anything above a footstep. i pulled it from the box and pushed from the back and it would only move about 3mm before it made bad noises. the replaced it under warrenty since it was brand new.



    http://www.hometheaterforum.com/htfo...hreadid=184772
     
  13. john bourne

    john bourne Extra

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    Thanks for the ideas guys,

    I have already checked for air leaks and everything checks out fine.

    Justin, the subsonic filter sounds like an idea. Please forgive the stupid question but I know I can change resistors to add boost, can I mod the amp to cut off low frequencies? I did a search and saw some filters that go in line between the amp and receiver is that what you are referring to?

    Perry, I'll pull the driver again and take a closer look at how much movement it has but I think it is a combination of the room being too big, the driver too small and me asking too much. -I just realized I described my sex life.

    I am thinking seriously about just building a bigger sub using a Stryke, Blueprint, or Tempest. Funny 9 months ago I thought that I would be happy with the shiva for years, a dedicated room later and I'm back to the drawing board. I guess the upgrade path never ends.
     
  14. Justin Ward

    Justin Ward Supporting Actor

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    I'm not sure about the specifics on modifying the plate amp. I've been told that those in line filters would work just fine though. Check your receiver as well, it may have a sub-sonic filter.
     
  15. Geoff L

    Geoff L Screenwriter

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    If the driver re-checks out ok, (dose not sound right that you can easly bottom it by hand), you might grab a Harrsion Labs filter from PE (24-db), for an in line fix.. Belive thats the product you might have been refering to.

    By the way, what tuning are you using?

    Definitely re-check the "possible premature" bottoming, from both a front and then (a rear push as Perry mentioned). Not unheard of to see a bad driver, or maybe you hurt it a bit. Hope not!

    As you've mentioned already, along with others, more/bigger/badder maybe!
    Those 15's looking more tempting by the minute don't they...[​IMG]

    Regards
     
  16. Kyle Richardson

    Kyle Richardson Screenwriter

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    Before you try a new driver you may want to put the Shiva in a smaller enclosure of around 85-95 liters. It will be harder to bottom out with the 250 watt amplifier you have.

    Of course, that is an awefully large room for a single 12" driver being asked to play at the SPL levels I think you are asking it.
     

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