Will a sub eventually bottom out?

Discussion in 'Archived Threads 2001-2004' started by Mitch Stevens, Mar 9, 2003.

  1. Mitch Stevens

    Mitch Stevens Supporting Actor

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    Hi Everyone,

    I was watching LOTR - FOTR last night (the 2 disc version) and of course it sounded amazing. It had incredible bass. The SVS has absolutely no trouble at all playing those extremely deep notes.

    Anyway, my question was, if a person were to play something with this much bass or even more bass (like those bass CDs that people play in their cars) will a sub eventually bottom out and not work anymore? I'm talking about playing stuff like this ALL the time. Right now, it has no trouble at all, but I'm just wondering about the future.
     
  2. keir

    keir Stunt Coordinator

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    if it bottoms out a lot it might be damaged. why worry about it.
     
  3. terence

    terence Supporting Actor

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    If the sub is calibrated right and most important capable, then you need not worry. I have a 20-39PC+, the only problem i have is my house tends to bottoms out not my sub.[​IMG] My house is 3,100sq feet and it shakes the hell out of it when i'm running my HT at high volumes. This includes 2ch & muti-ch music as well, but i do tend to get carried away at times.

    Why not my system can handle it, but it sure is nice knowing that if you want to take there you can with no worries.
     
  4. JamesFarina

    JamesFarina Agent

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    There are two things that can damage a speaker other than putting a hole through it.
    Thermal damage - too much current through the voice coil. DO NOT TRY THIS but if you hooked your speaker terminals to an AC outlet it will play at 60hz but eventually the voice coil will melt causing permanent damage because of the excess current. This also can happen if you play sine wave test tone through your speaker for extended periods of time (sometimes 3 seconds depending on the speaker and amp power). Normal listening, like LOTR will not cause the speaker to fail, thermally speaking, as long as proper calibration procedures were used.
    Mechanical damage - this is what people call "bottoming out." When a driver is forced to play past its mechanical excursion limits (Xmax) and the voice coil hits the back plate of the speaker causing it to become damaged. Now if you hear a speaker "clank" it doesn't mean it is permanently damaged. Its kind of like if you dropped a bottle on the ground and it doesn't break, but if you continue to drop the bottle it will eventually break. The same goes for a speaker, if it bottoms out occasionally then you probably won't have a problem, but if it bottoms out every time you watch a movie then you may need to make some adjustments like lowering the calibration for the sub.
    If your calibration levels are reasonably set then I wouldn't worry about anything. Nothing lasts forever but you shouldn't have any problems for a very long time.
     
  5. Mike Up

    Mike Up Second Unit

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    I have a modest Velodyne CT-100 subwoofer with a 10" woofer and a 100 watt RMS/250 watt Dynamic power output internal amp.

    Driving the subwoofer volume 10db louder than it's calibrated level with loudspeakers, plus driving the HT receiver's volume 50% in a 2000 cubic foot room never gave any problems. Never a sign of strain, compressing or bottoming out in the sound. I think most high performance subs shouldn't have any problem. BTW, that was with RAP to test the sub's capabilities in the room.[​IMG]
     
  6. Michael R Price

    Michael R Price Screenwriter

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    I like this one: "but if you hooked your speaker terminals to an AC outlet it will play at 60hz but eventually the voice coil will melt..." Eventually? It might last a few milliseconds unless it's a monster subwoofer! Wall voltage is 115-120V and it would be happy to supply something like 1,600 watts into a normal speaker load.

    Seriously, playing something within it's limits won't hurt the subwoofer unless there's something wrong with it already. Bottoming out one *might* cause damage, but if it happens by accident for a moment during a movie and you never play it that loud again, you're fine. At least in my limited experience, that is.
     
  7. JeremyFr

    JeremyFr Supporting Actor

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  8. David_Stein

    David_Stein Second Unit

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    would the wall plug give the speaker trouble because its AC?
    would it just be like switching a 0-180 phase switch 60 times a second?

    also, by my calculations 15amps*120Volts=1800W, whcih is the best equation i know for power (P=IV), the same would work out if you did an 8ohm speaker and used P=V^2/R. with a 4ohm subwoofer driver you would get 3600W, but it would be limited by the 15amps...
     
  9. Mike Up

    Mike Up Second Unit

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    1600 was about right. 15 amps X 120 volts = 1800 watts. Ohms law = I^2 X R = P or Current squared multiplied by the Resistance = Wattage.

    A speaker with a 4 ohm impedance will draw 30 amps when 120 Volts are applied to the speaker. I * R = E(volts) . 30 amps * 120 Volts = 3600 watts. The speaker with a 4 ohm impedance would draw 3600 watts. Drawing 30 amps would trip the circuit but most likely would fry the speaker in that limited time. An 8 ohm speaker would draw 1800 watts, 15 amps tripping the breaking again.

    Actually, after the voice coil was fried, it would create a short and trip the breaker also(at least hoping before a fire would develop[​IMG] ).

    Take it easy.
     
  10. Mike Up

    Mike Up Second Unit

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    Man, is there an echo in here?[​IMG]
     
  11. Mike Up

    Mike Up Second Unit

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  12. David_Stein

    David_Stein Second Unit

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    why did i not realize that before? man, i feel sheepish...
     
  13. JeremyFr

    JeremyFr Supporting Actor

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    see what I get for getting confused and remembering something wrong its 60 watts=.5 amps oh well I'm not always right hehe
     

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