Blown tweeter

Discussion in 'The Projects Forum' started by Jason87, Aug 26, 2012.

  1. Jason87

    Thread Starter Member

    Dec 10, 2009
    39
    0
    Hi,

    we are a company that rent speakers for small parties.

    Now a curious case happened to me last weekend.

    So basically we had a small system at a pool party and I was during all the party at all times watching the amplifier for not clipping and all night long it didn't clip at any time.

    At a point some plenty of water splashed on the mixer but since i was beside the speakers i couldn't notice if the tweeters where blown at that point in time, so i am not sure if that could have affected my tweeters and if it did how could a splash of water on the mixer blown my tweeters.

    Also one of the dj used a controller attached to my mixer, he kept all the knobs from his controller (include high, mid, low) blasted out and opened till the vary end. This is basically what happened during the party....i finished with the tweeters of the two speakers blown out (speakers where used in parallel on one channel of the amplifier)

    Can anyone help me out and tell me the possible reasons that blew out my tweeters?
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Water in the amplifier might have caused its output to produce DC which a fragile tweeter can not handle.

    Acid Rock and other severely distorted "music" has excessive high frequencies that can blow a fragile tweeter. Also the mid and high tone controls were set much too high.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    And perhaps the tweeters were simply not rated for the amount of power they received.
     
  4. Jason87

    Thread Starter Member

    Dec 10, 2009
    39
    0
    hi,

    audioguru water fall only on the mixer not the amplifier...could this have cause amplifier to produce DC voltage still? So you think the main reason was the tone knobs?

    So basically we had two wharafadale titan 15 speakers which handle 400watts rms,

    now we used an amplifier that gives 2200watts rms on 4ohm...(4ohm since they where on one channel, and the gain knob of the amplifier was set 2/3)

    Do you think that was ok?
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    It doesn't matter where the gain knob was set because if the input signal level was high then the output of the amplifier was also high.

    The speaker is rated at 400W continuously into its woofer at 8 ohms. Tweeters are never fed continuous high power.
    The tweeter is protected from overload by two light bulbs. When the light bulbs light up then it is because of the high current in the tweeter and in them and causes them to get very hot and raise their resistance forming an attenuator.
    Your amplifier produces 2200W into 4 ohms so each speaker received up to 1100W which is almost 3 times too high.

    EDIT: Maybe you just blew up the light bulbs.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    You must mean the Dynamic Thermal Filaments. ;)


    [​IMG]

    [​IMG]
     
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    My car has a "Dynamic Thermal Filament" that lights when the door is opened.

    When I worked for Philips 47 years ago they made an audio amplifier with a "Dynamic Thermal Filament" in series with the output to protect against a shorted output.
     
  8. dataman19

    Member

    Dec 26, 2009
    136
    29
    Actually - the poster answered his own question...
    The DJ had all the controls "maxed out". Has anyone here ever looked at an audio spectrum analyzer while being fed a "modern" production CD? It looks like a light bulb, max everything, max compression. The Harmonics themselves are also maxed everything.
    ..
    The speakers are not equipped to handle all that - no way. Even the (I quote) "Digital Rated Speakers" cannot possibly survive long. I mean "Digital Rated?" What's up with that. Who wants to hear a lot of dits and dahs - Music comes in Ditty Bop (Morse Code Now)?
    ...
    Given my experience with DJ's I would bet they were driving those poor 400W RMS rated speakers with 700W RMS Amps, being over driven by a factor of 1.5 to 3.5 times what they should have been driven at. This would put most harmonics in the range of say 1,100 to 2,600 watts peaks (since this includes high out of band harmonics - those little 150 watt tweets tweeted their last peeps.....
    ...
    Talk about hearing problems.
    Actually not too many Rockers understand the principal of "Sonic Headroom". Since many stereo purists drive speakers with amps rated at about 4/3 or even 5/3 of the speaker rating - it is no wonder that so many rockers who adopt this pure hi fidelity trick blow woofers and tweeters. The rationale is that to accurately reproduce dynamic sound and amp need enough power to faithfully reproduce the occasional high and low peaks without clipping. So an 8-watt amp would sound decent, but a 35 watt amp at the same volume level would sound a lot better.
    ..
    Enter the rockers (and most modern performance DJ's). Modern sound is highly compressed. This means there are not occaisional high and low peaks there are "constant high and lows". There is no dynamic range in modern sound - just heavy compression.
    ...
    I would also bet that the DJ was also using a gated compressor and dynamic equalizer to boost those sounds even more. So instead of having true audio exiting the amp, you essentially have slightly flickering DC.
    ...
    The speakers, the tweeters, and the woofers should have been protected with fuses. This was nothing more than a disaster in the making.
    ...
    Most professional sound techs do not get into a situation like this. That is why they are extremely protective about who plugs what into "their sound system". Trust me, some one will come out with an internet video where a rocker plugged a 12VDC power supply directly into his guitar cord and fed it directly into his amp. hen they will show on a scope where the signal levels (the white noise displayed all across the screen) were higher. then some one will come to a rock fest and attempt the same feat - excuse: "I just wanted to give my signal a boost"...
    ...
    We live in a crazy world, and every day I am led to believe that no one ever even reads a basic audio engineering reference any more - they are all just winging it.
    ...
    dave
    phoenix, AZ
     
    #12 and djsfantasi like this.
  9. dataman19

    Member

    Dec 26, 2009
    136
    29
    Incidentally - this is why most people think a class D amp is louder. It has all that extra intermod and max distortion. Trust me 10% and even 18% THD is not sound - it is noise. But you have to give credit where credit is due - a 60W Peak amp with 18%THD does sound louder that a 120W RMS Class AB amp. But it is definitely not clearer. Try listening to piano music and you will see the difference, real quick.
    Dave
    Phoenix, AZ
     
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