Obi's Tower of Power!! **Updated (new pics)**

Discussion in 'Archived Threads 2001-2004' started by Robert George, Sep 23, 2001.

  1. Robert George

    Robert George Screenwriter

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    They say that necessity is the mother of invention. Well, I just invented one mother of a subwoofer...
    [​IMG]
    In this case, the necessity was to get one of my SVS 25-31CS subs out of a corner and still be able to place both subs on the same side of the room. You see, the corner loading with two subs side by side was introducing some nasty room modes and some serious humps in the lower frequencies. In moving the subs around, I discovered, with the expertise and encouragement of Mike Knapp and another chum with just as accute hearing, Ken Gunlock, that my low bass was overpowering my mid-bass and midrange frequencies and totally muddying up my soundstage. This was much less of a problem with movies than with music, however, with the recent upgrade to some beautiful sounding B&W Nautilus 804 main speakers, my music reproduction has become far more critical.
    I've been kicking around the idea of stacking two SVS subs for some time, though not for this reason. My original idea was to use TWO two-sub stacks in a larger theater room so one could get four subs in a room without some of the placement problems that goes with such a configuration. I decided to make a practical application out of my idea with my two subs to see if it would solve the placement problem I had in my room. This is what turned out...
    [​IMG]
    Here's a closer look at the joining of the two subs...
    [​IMG]
    The resulting sound, I am very pleased to report, solved my problem. My bass cleaned up nicely and I didn't lose any impact on movie soundtracks. Music sounds way better. I don't know if I can recommend this application to everyone, but for the record, my wife prefers the "tower of power" over putting one sub on either side of the mains.
     
  2. rodneyH

    rodneyH Supporting Actor

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    I noticed you have the 804s, I am consirering purchasing a SVS, but haven't decided one a 20-39 or a 25-31, If you were to only have 1 sub, would you still opt for the 25-31, or a 20-39???
    btw, I am running cdm7nt (similar characteristics to 804)
     
  3. Trevor Schell

    Trevor Schell Supporting Actor

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    I love it! [​IMG]
    Looks like you just took off the top grille and added three extra spindles.
    Shouldn't be too hard to do.
    ------------------
    Trevor..[​IMG]
    My HomeTheater S.E. Sonically Enhanced
    *Outdated new pictures
    due to recent upgrades!
    **Equipment list current
     
  4. Will

    Will Guest

    Obi --- you still live in northern California?
    I was going to ask if you were worried about an
    earthquake knocking down your tall stack, but then
    remembering that the stack consists of subwoofers
    thought better of asking that question.
     
  5. John Morris

    John Morris Guest

    OBI: Cool! It has been suggested but it took YOU to actually do it nicely! It looks like you also left the 4 inches recommended to avoid port compression too!
    Are you powering them as independent subs or in parallel or in serial connection? Are they 20-39cs units, or the smaller subs?
    ------------------
    Take Care,
    merc
    ----------------
    [​IMG]
    God Bless America!!!
     
  6. Robert George

    Robert George Screenwriter

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    John:
    My subs are rather unusual. They started out as 25-31s, but Tom made me a custom port to lower the tune to around 22Hz. Then, the drivers have been upgraded to the same driver used in the new Ultra. The two subs are still being powered independently (Samson S1000).
    Rodney:
    I personally would recommend the 25-31 for its higher output in the 27-35Hz range, however, the 20-39 would probably do a fine job as well in most rooms. Also, you should consider what type of music you listen to most often. The 20-39 will go a bit lower than the 25-31, but at the expense of a few dB in what I consider a critical frequency range. Maybe ask SVS if they can provide you with custom porting for the 25-31. That would lower the tune and you would still lose a little around 27-30Hz, but not quite as much as the 20-39.
    Trevor:
     
  7. Bruce Hedtke

    Bruce Hedtke Cinematographer

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    Obi,
    Very cool and professional looking. I am green with envy.
    Bruce
    ------------------
    [​IMG]
    Welcome aboard the Satellite of Love
     
  8. Mike Knapp

    Mike Knapp Supporting Actor

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    Mike
    I notice that the mains are away from the rug again....dont make me come back up there! [​IMG]
    Mike
     
  9. rodneyH

    rodneyH Supporting Actor

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    tom, you have mail
     
  10. DonnyD

    DonnyD Screenwriter

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    SVS is great at everything .....
    This is proof that they will go to great lenghts and considerations to keep their users happy. Thanks TomV and Ron for being who you are and for having a product that pleases most of us regardless of price.
    ------------------
    "I am part of all that I have met, yet all experience is an arch wherethru gleams that untraveled world whose margin fades forever and forever...."
     
  11. Robert George

    Robert George Screenwriter

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    Thread edited to return it to original topic.
     
  12. Robert George

    Robert George Screenwriter

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    I've been talking to Tom V. and he has made some suggestions and I've had another idea myself. I'll be posting some pics of the "Tower of Power" Ver. 2.0 in a couple of days. Same basic design, but with a couple of design changes to improve asthetics and, as it turns out, improve (measurable) performance.
     
  13. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    push pull is cool, but while it is generally known to lower even orders(due to motor non-linearity)...it's hard to predetermine exactly what the reductions are going to be.I don't think you could assume a 50% reduction across the board though...maybe on paper. And since it's the ODD harmonics that are the bad guys anyway...
    reactive cancellation is something else...not related except incidentally. What you're talking about here is...when the driver moves one way, the baffle(enclosure)it's mounted to will try to move the other way. If you have one large enclosure with 2 drivers moving in OPPOSITE directions...the reactive forces will tend to cancel. This holds true for PRs too. In this case, the more resistant the subwoofer design is to these reactive forces...the less you'll gain by implementing it as a modification. I agree, the TN series will benefit. I don't think the SVs would benefit nearly as much though.(I know you know all this JG---just trying to clarify for any lurkers).
    TV
     
  14. Chris White

    Chris White Second Unit

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    Robert, you should make up a list of possible answers to the inevitable question, "What the heck is that!" [​IMG]
    For example,
    1) It's an air purifier.
    2) It's an antenna.
    3) It's a security device. That's all I can say.
    ------------------
    http://www.bus.ucf.edu/cwhite/theater/theater.htm
     
  15. John-D

    John-D Stunt Coordinator

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    .. reminds me of Shrek
    "Do you think he's trying to compensate for something...??"
    .... just a joke Robert.... just a joke.. [​IMG]
    ------------------
    The things we own end up owning us
     
  16. Robert George

    Robert George Screenwriter

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    Chris:
    It is a security device. That's all I can say.
    [​IMG]
    [Edited last by Robert George on September 25, 2001 at 09:33 AM]
     
  17. BryanZ

    BryanZ Screenwriter

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