Can you bottom out an SVS with 150W?

Discussion in 'Archived Threads 2001-2004' started by Steve Stogel, Jan 28, 2002.

  1. Steve Stogel

    Steve Stogel Supporting Actor

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    I just bought a used 25-31CS (22.5Hz tune). I'm pushing it with a pretty inexpensive dbx amp that I got from J&R years ago. It's rated at 150W into a four ohm load. So can 150W bottom out an SVS? I ask because I fully expected to hit the limits of this thing in my living room, which is open to the breakfast "nook" and the kitchen. Add to that the 10-foot ceilings, and I've got probably 6000+ cubic feet. Well, I've watched all of U-571 and bits of the Matrix at probably -5dB of reference. I may have even gone to reference on some scenes. This thing will not bottom out! I'm not saying I want it to, but I bought this sub as a stop-gap until the PC+ series is launched, hoping to buy one of those. At this point (and I haven't played with it a whole lot yet), I just have trouble figuring out why I'd make that jump. Seems the 31 is doing just fine.

    So is my amp just petering out before the sub gets a chance to bottom out? What scenes of what movies should I listen to to see if this little beauty is indeed all I need in my house? And during those scenes, what kind of levels should I get on the SPL meter? I'm just very surprised at the seemingly effortless way this thing churns out the bass. I expected the port to blow like a hair dryer, and it seems that it just purrs along while pumping out huge amounts of bass. Sorry for rambling, but I just get a little chatty when I talk about this thing (I think I should name it, by the way). Thanks.

    Steve
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    It would be unlikely that you could bottom that model at or above tuning with 150 watts, or experience much port noise from the 4" flared. Even though you're getting very high output, there's probably lots of headroom left in the sub itself, if not in the amp. The only thing that might do it would be material that had significant content down below 20Hz or so (unless there's some sort of filter in the dbx). The THX intro from the Star Wars DVD comes to mind as particularly cruel in this regard. [​IMG]
    I think people would be amazed to find that they might actually prefer the higher-tuned subs for the vast majority of program material, HT or otherwise. Having just completed my first such sub (23Hz or so), I know I was.
     
  3. Steve Zimmerman

    Steve Zimmerman Second Unit

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    I have the CS Ultra with the Samson S1000 amp and a similarly sized room. The clip light on my amp flickers on the Phantom Menace THX intro at somewhere around 7-8 dB below reference.

    What that tells me is that even though you're not bottoming out the subwoofer, you are almost certainly reaching the clipping point of the amplifier if you're playing the particular scene louder than that.

    --Steve
     
  4. Steve Stogel

    Steve Stogel Supporting Actor

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    Thanks, Steve.
    That's what I figured was that the amp was giving out way before the sub. Now, if my amp is clipping (no indicator on amp itself), could this damage the sub in any way? I listened to the Matrix this morning (very end when he stretches his back after dismissing the bad dude). When the guy blows up, my SPL meter hits 100dB. Then, when Neo stretches, the meter goes up to 106dB. That is calibrated to reference with VE and then playing that scene. Main seat is about six feet from sub.
    Now, I figured that the meter should have hit 105 during some of the high-frequency peaks, but I only got 100 for some reason (?). The part where he stretches, like I said, hit 106. I don't know how that really equates taking into account the roll-off of the SPL meter and the distance (2 meters away). My best guess from things I've read is that you add 3dB for the SPL meter (maybe a 22Hz signal) and 3dB for the 2 meters. So, if my math is correct (big IF), then the SVS is putting out something like 112dB in a very open living area with a very cheap 150W amp. YIKES!!!!!! Does all that sound right? $250, what a joke (good joke, not bad joke [​IMG] ).
    Back to the main question, will the amp clipping hurt the SVS? It doesn't sound like it's doing anything to it, but I'm no expert.
    Steve
    P.S. The wall in the hall (about 35-40 feet away from the sub) is the same wall that my bathroom mirror is on on the other side. That thing makes a very uncomfortingly loud rattle when playing stuff loud. Gonna have to try to do something about that [​IMG]. Thanks, SVS.
     
  5. KevinHunt

    KevinHunt Stunt Coordinator

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    Steve, although I tried to sell you one of my 46's, I think you see now how potent even the little guy is. [​IMG] Imagine if you had two of those puppies in there. It's just a fact, the little guys have more output and punch than the 46s with everything except the low, low stuff, of which there is not much material anyway. Glad you like it. [​IMG]
     
  6. ColinM

    ColinM Cinematographer

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    I don't think subs are as likely to be damaged by clipped amps. I don't have any facts before me, but I read somewhere that if an amp clips on a sub, the thing just 'takes it', where as a tweeter would fry...
     

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