Why do my speakers blow?

Speakers blowing is a problem that we have all encountered at one point or another and one which anyone with a P.A. system should really know about.

There are a few reasons why a speaker would ‘blow’, the most common of which are described in the following text.  Although active speakers are less likely to blow, due to the amplification matching stage, they still can if you don’t use them correctly. In any of the following situations, your local PA dealer (if he knows what he’s talking about) should be able to confirm the problem by looking at the voice coil.

Signal Burn is the first process that we’re going to look at. This is caused by the amplifier in use working fine, but the user attempting to use more power than the speakers are capable of dealing with. A knowledgable PA dealer will be able to match the power of an amplifier to your speakers (or vice versa) to stop this happening.

DC Burn (Direct Current Burn) is where the user is misusing either the amplifier stage or the mixing desk output stage. In most cases, this fault is caused by the amplifier ‘clipping’ the input signal due to the user trying to get more out of the amplifier than it will give. This causes an increase in input level, therefore a larger sine wave. If this sine wave is pushed too hard, the amplifier will ‘clip’ (A red light is normally an indicator of this) the top and bottom of the wave and produce a square wave output which your speakers don’t like. At the peak of a sine wave, the voice coil of the speaker is pushed out and therefore, if a square wave is produced (by clipping the amplifier) the voice coil is spending more time out of the gap than it would like. This leads to a poor heat distribution through the magnet which overheats the voice coil and burns it. In the case of DC Burn, you could, as long as your speakers will handle the power, move to a larger output amplifier in which you have more headroom, and less chance of ‘clipping’ the signal. As a loose rule of thumb, in the case of professional speakers, your amplifier should give an RMS output rated higher than the RMS rating of your speakers. In some cases you should double the power to give plenty headroom. If you are unsure, your PA Dealer should be able to confirm this. If budget is a concern, then there are options available that you could use to lessen the chance of your amplifier clipping. These are called limiters, and are available from manufacturers including, Alesis, Behringer  and Samson , among others. It  must be stressed that these units only work if they are set up correctly and the user doesn’t attempt to get that “little bit more”!

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6 Responses to Why do my speakers blow?

  1. Josh says:

    hi i have a sound master VF200 and wen i meseuer the out put voltage i’m getting nothing on DC volts but on AC i will get around 50-60 volts flat out. but i put an LED across the speaker out put and it came on. does this mean my power transistors are shot. or is my amplifier no good ?

    any help i would be grateful for cheers
    Josh

  2. Gerard says:

    Hi, I have 2 x ‘Wharfedale EVPX15’ (2-Way 300W RMS 8 Ohm) Speakers and a Hybrid 1600w Amp…

    Sometimes I run 4 speakers, and sometimes 2 (all 15” mids)….

    I tend to keep blowing the coil…

    I’ve been told to run the amp on full, and I’ve run it on half at times (cos I was scared)……but in both instances I’ve blown speakers, and its costing me an arm and a leg to repair them each time…

    I have no bass bins, and I’ve thought those would take up the power that is killing my poor mid-subs…

    Ultimately, should I just get a less powerful amp?

    Thanks in advance for your advice 🙂

    • soundslive says:

      Hi… without knowing the model of your amplifier it is difficult to say exactly why you are blowing your speakers, although it does seem from the information that you have given, that you are blowing your speakers as you have your amp turned town. By doing this, you are reducing the amplifier’s headroom and causing clipping (you have most probably seen the red lights on the amp). It is important to remember that the volume controls on your amp are input gain and NOT output volume. So by reducing them to half way, you have tried to put a higher signal into a smaller gain, therefore clipping.

      To solve the issue of blowing your speakers, turn your amplifier up to full and control your volume from the mixer. If you still blow your speakers, then a more powerful amplifier could be required.

  3. Alex says:

    Hi i also have speaker problems, with regards to them blowing…

    Is it possible that speakers blow from recieving super low frequencies. for example if the desk im using is sending sub lows under 80hz to bog standard pa speakers, could this be killing them even at non-ridiculous volumes. Apparently the cone damage looks like a sudden pop… could this be to do with just a sudden pop of sub lows that the speakers can’t take??

  4. Pingback: Would it hurt to do this to my speakers? - Page 5 - DIYMA.com - Scientific Car Audio - Truth in Sound Quality

  5. tbird10030 says:

    Hi, I just picked up both a McIntosh Mac1900 & Mac1700. 1) The Mac1900 works fine except for the phono volume output, the sound comes out low with one channel having no bass at all. The sound & volume from the tuner and tape comes out just fine. 2) Regarding the Mac1700 I am afraid to hook it up to any of my speakers and test it out! I was told that it starts out working fine but soon after it blows out the woofers? Are these easy fixes? I don’t have the money to pay a repair man but if it is possible I may be able to fix it myself if the repair is simple or not to difficult. I am very handy sometimes in being able to repair these old unit if I can fine what’s wrong and if the part/parts or components causing the problems can be easily repaired or replaced. Can you tell me what are problems in both units and give some details on how to fix them? Thanks You Very Much, Anthony

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