how much does it take to blow out speakers?

Discussion in 'Speakers' started by KyleCT, Sep 21, 2003.

  1. KyleCT

    KyleCT Stunt Coordinator

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    I just bought some Polk R30 floor standing speakers. They are rated at 100 watts. My audio reciever is rated at 300 watts. Does this mean that if i turn up the reciever to 1/3 of its potential my speakers will not be able to handle it? Thanks
     
  2. Mark All

    Mark All Second Unit

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    Kyle,
    I'm not aware of any receiver that puts out 300 watts per channel. Are you sure of the specs? What receiver are you using?

    Even if you have a 300 watt per channel Adcom amp or something similar and crank the volume way up, you're unlikely to blow up your speakers before your ears start to bleed. Speaker damage is usually caused to by too little amplifier power, not too much. The great majority of receivers on the market put out 100 watts or less continuous rated power.
     
  3. Kenneth Harden

    Kenneth Harden Screenwriter

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    My dad has a old Kenwood that REALLY puts out 300 watts X 2. It was $600 back in the day (early 80's) and is very nice.

    However, it takes very little bad power to blow up a speaker, and it takes a LOT of good power to blow up a speaker. Because of that, until I get my Harman Kardon, I treat my system like it was borrowed from a friend (I don't push it at all)

    I delbt with a PA system, and it has some semi-expensive JBL cabs on it (2 15" woofers and a massive horn tweeter.) The guy used a stage monitor amp (small and cheap, like 150 watts/channel) by accident when we were setting it up and it sounded bad at higher levels, but he switched the Speakon cables and POW!!! POWER!!! THUNDER!!! It was night and day. I think the amp he was using was 1500-2000 watts per channel and had a LOT more 'drive.'
     
  4. GregGreenman

    GregGreenman Auditioning

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    Kyle,

    The volume control controls gain - not power. Therefore, you can't assume that 1/3 volume on a 300 watt amp is 100 watts.
    It depends on what the strength of the input is.

    Additionally, volume controls are not linear - more often they are logarithmic. If you find a volume control that is has
    markings in "dB" - then it is logarithmic. A 3 dB change means a factor of 2 in power. Therefore, if full volume was 300 watts,
    then 150 watts would be just 3 clicks down - not 1/2 volume.

    In general, you can't set volume "by the numbers" - you don't know what the signal strength is, or how the volume control is
    "contoured", and may not be familiar with logarithms.

    Set your volume control by ear - and turn it down if the speakers exhibit the least little bit of distortion or stress.

    Also - too little power in the amp is usually more dangerous. If you overdrive a small amp into and
    cause it too "clip" the resulting distortion will fry the speakers. Again watch that volume.

    Otherwise, you are risking blowing the speakers.
     
  5. John Garcia

    John Garcia Executive Producer

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    If your receiver is rated at 300w TOTAL, then it is likely not capable of putting out it's full rated power into a single channel. What is the rating for a single channel on this receiver?
     
  6. Brett DiMichele

    Brett DiMichele Producer

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    The killer of any driver is heat. Voice Coils can only take
    so much heat before the varnish burns off of the coil and
    it shorts out.

    Now with that in mind, the easiest drivers to damage (this
    is a generalization and holds true most of the time) is the
    tweeter. The tweeters always have the most delicate Voice
    Coils wound from very fine high guage wire. Next in the
    list would be Midranges then followed by Woofers and Sub
    Woofers.

    Now what causes too much heat in the Voice Coil in the
    first place? More times then not, it is the phenomina
    called "Clipping". See too few watts are always more deadly
    to a speaker than too many.

    As has been eluded to by others in this post, too many watts
    and your ears will give out before your speakers do and you
    will decrease the volume. But with too little power you are
    constantly raising the volume more and more. And all the
    while you are driving the speakers with a Clipped signal.

    What does Clipping mean?

    Speakers reproduce Sine Waves. A sine wave looks like a
    gentle ripple with a rounded dip and peak. The peak and
    valleys are gentle and rounded and the speaker can reproduce
    these sine waves with no problem. But when you drive an
    amplifier past it's linear amplification range (all amplifiers
    can only amplify a signal so much) the nice smooth sine
    wave that we spoke of gets the dip and peaks chopped off.

    The result is a square wave and speakers do not reproduce
    square waves. Where the gentle curveature of the dip and
    the peak have been replaced with a flat top and bottom this
    causes an abrupt and distoted movement of the speaker and
    builds heat in the voice coil. The longer the clipped signal
    is fed to the speaker the hotter the voice coil will get
    and it will fail.


    In conclusion:

    Too Much Power = GOOD!

    Too Little Power = BAD!

    Any questions?
     
  7. Phil Iturralde

    Phil Iturralde Screenwriter

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    FYI: For a more in-depth discussion, see JBL PRO on-line article "Danger: Low Power": (PDF file 204kB) : Information on one of the most common causes of speaker failure -- (under powering).

    Phil
     
  8. Michael R Price

    Michael R Price Screenwriter

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    In response to the original question:

    A lot. I don't know of any reasonably sized speaker that would not go pretty damn loud before blowing. Whether it sounds good at high power may be another story.
     
  9. KyleCT

    KyleCT Stunt Coordinator

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    Thanks guys. I jsut wanted to know if i had the power to blow out my speakers and it doesn't sound like it.
     
  10. KyleCT

    KyleCT Stunt Coordinator

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    ok my speakers ate sh*t last night. we had fairly loud for a while and now the woofers in both speakers dont work.

    I have a Yamaha RX-V870 receiver which has the following specs[​IMG]ower: 80w x2 stereo, 80w center, 25w x2 rear

    The speakers (Polk R30) have the following specs:20-100 Watts / 6 1/2" Woofer / 3/4" Dome Tweeter

    So doesn't this mean that even with the volume all the way up the speakers still wont come close to blowing out? I know for a fact they weren't even turned up half that loud.

    Is it possible that the leads on the woofers just disconnected? It seems unreasonable that both speakers disconnected at the exact same time.

    Any ideas? I just bought them a week ago at circuit city. This would be covered under warranty, correct?

    Thanks
     
  11. Steve Lucas

    Steve Lucas Stunt Coordinator

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    Kyle,
    Go back and read this thread. It's obvious that your speakers are underpowered . This is the death of speakers that are played loud. Your amp is rated at 80w/channel on the fronts, but that is probably optimistic, most receivers are. You actually have less clean power than that available. When your amp begins to distort, regardless of how much power it's putting out your speakers are in danger. I'll bet dollars to donuts that you turned it up loud enough to distort the signal from the amp, especially if you had the bass turned up (bass takes more power to reproduce than other frequencies) and fried the voice coils in your woofers.
    As for warranty, I guess it depends on how nice you are and what mood they are in. With both woofers blown, it will be obvious to them that it wasn't a manufacturers defect, but they may be in a good mood and still cover them. Keep your fingers crossed and learn to recognize distortion when you hear it. Your speakers will last much longer that way, and sound much better as well.


    Steve
     
  12. KyleCT

    KyleCT Stunt Coordinator

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    from the user guide for the speakers, the recomended amplification is 20-100 watts. why would they recomend to use such little power if the speakers blow out with that power. Also, if more power is better for the speakers, then why wouldn't they recomend to use over 100 watts?
     
  13. KyleCT

    KyleCT Stunt Coordinator

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    my guess is that the volume was at about -16 db. I was keepin an eye on it all night and i dont think it got much above that. doesn't that seem a little low to make speaker take a dump?
     
  14. Steve Lucas

    Steve Lucas Stunt Coordinator

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    Because the speakers are rated to handle that much continuous, clean power. Audible distortion, regardless of the power level will damage speakers. You have to use your ears and turn down the volume when you hear distortion. I can blow a 100w speaker with a 6w amp if I push it to distort horribly. Not to be mean or anything, but if you truly can't hear distortion that is bad enough to blow speakers, especially woofers, then you paid too much for your speakers anyway. You should have bought the cheapest audiovox or soundesign you could find. Not only would they sound just as good to you, but they would be much cheaper to replace when you burn them up.
     
  15. KyleCT

    KyleCT Stunt Coordinator

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    i actually wasn't here when they blew out. i was next door. there were a lot of people in the room so unfortunately nobody had the idea to turn them down.
     
  16. Anthony_I

    Anthony_I Stunt Coordinator

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    I got a question.
    If heat (well basically heat) is the cause of damage to speakers, then wouldnt having a plate amp with its transformer INSIDE the box, create a shitload of heat and contribute to the overloading of the voice coils?

    Those transformers get mad hot, and in the long run would heat the entire inside of a box correct? the air gets hot and heats up the voice coil through the vent.
     
  17. Michael R Price

    Michael R Price Screenwriter

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    Don't plate amps have heat sinks outside the enclosure to dissipate their heat?

    Kyle,

    Ouch... I think the best idea is to stay around and make sure nothing goes wrong. [​IMG] It may have been that you set the volume for a somewhat quieter CD and then when a louder one came on, everyone else didn't notice the distortion enough to turn it down for you?

    Are you sure the receiver is alright? Potentially, it could have overheated and if the protection circuits didn't work correctly, that could have damaged your speakers. It's sort of weird that the speakers would work fine for awhile and then just die.
     
  18. James~P

    James~P Stunt Coordinator

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    for example:




    my B&W 602 S3s are rated at "120 WATTS continous, unclipped programme"


    ie: they can take 120 watts of clean power.


    if i dimed an 80 watt amp infront of them, they'd fry.



    if you want very loud playback, you should just get some horn loaded PA speakers
     
  19. Tim Streagle

    Tim Streagle Stunt Coordinator

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    When I was young, I spent three years working as a sound engineer for a large touring ensemble up and down the east coast. I was very interested in finding out the facts about the relationships between amplifier power, speaker ratings, excursion limits, etc. I once bought a pair of super cheap car speakers (Automatic Radio 5-inch full range) and connected each to a bridged Peavey CS-800 amp. We actually used this configuration for an hour or so in the band house for background music! When we finally increased the volume to the point where the amp's clipping indicators began to light, one speaker's voice coil became lodged in the gap and burned out. The other driver actually tore the surround but kept the integrity of the voice coil wiring.

    Over the years in various groups and bands I have seen very few drivers (in particular low frequency drivers) damaged by too much undistorted, clean power. Most low frequency damage occurred as a result of amplifiers misbehaving and throwing DC current when under high stress or peak demand. Other low frequency damage often happened when synthesizer players would send extreme low frequencies through the system before the limiters and compressors could react quickly enough. Dropped microphones were a killer too.

    Over the years advances in amplifier design and outboard processors have made this type of speaker damage less prevalent. I have formed my own opinions about the relationships of wattage, speaker design, and other audio criteria that has carried over into my dabbling with home theater. At the risk of being criticized, I offer you one of my percieved "truths"- Manufacturers suggested power ranges for speakers are an indication of a model's efficiency, and are not to be taken literally. All circumstances are different. For your own set-up, I recommend consulting a well known dealer or reputable professional for advice before testing your eqt. to it's limits.

    Sorry this was so long.

    P.S. Lightly press the woofer cone in and see if there's any resistance or dragging- this is a bad sign. Test the driver for continuity across the terminals (requires access to the back of the driver itself). Don't open up anything before the warranty process is exhausted.
     
  20. John-Miles

    John-Miles Screenwriter

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    Kyle, I Dont have the same model Amp as you, but I also own a Yamaha, and personally with my 80 watt bookshelf speakers i cannot physically listen to volues as low as -16 dB the yamaha's only go to 0 whereas some amps go from -75 to plus 25. either way its usually a 100 dB range and on the Yamaha -16 is pretty close to the end.

    So likely your amp was clipping the 80 watts it was sending to the speakers cause people wanted the music louder at the party.
     

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