Hearing Speaker Distortion -- please help me learn!

Discussion in 'Speakers' started by Sam Pat, Aug 31, 2004.

  1. Sam Pat

    Sam Pat Stunt Coordinator

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    I'm an audio noob and I'm slowly and steadily learning more and more about speakers. Today I upgraded my HT Speakers to ones costing considerably more and I want to make sure I take good care of them.

    Basically, I want to make myself more sensitive to any signs of speaker distress.

    I've heard and recognized very obvious distortion, like when playing a very loud movie scene on my small satellite speakers, I've heard the tweeters make a buzzing noise when they're playing a high-pitched sound. Obviously, I was overdriving them and I backed off immediately.

    However, I've been reading that alot of times, distortion isn't so obvious and alot of non-audiophiles don't even recognize it. I read a primer on amp clipping and it said something like most "normal" folk don't recognize light to moderate clipping and can end up damaging their speakers.

    Most manuals and people will tell you that when you hear a distorted, harsh or grating sound from your speakers, you should back off or else you will hurt them. But that description is pretty vague. People say that when the sound is "distant" or "thin", distortion is happening. Those are vaguer still.

    Can you give me some pointers and guidelines on what to look out for?

    If it is indeed so hard to describe in words, perhaps my best bet is to go down to my dealer and ask them to show me what a distorting speaker sounds like.
     
  2. Tom D

    Tom D Stunt Coordinator

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    Hi, this may or may not help, but here is my 2 cents worth. On older volume controls rule of tthumbwas not to crank the volume control past its half way point. On new digital rcvr's you really shouldn't go past the 00 mark on your volume display. It is also recommended that treble and bass controls should be left at 0 or neutral positions. Your speaker settings should normally be set to small and let a sub handle the lower frequencies.

    Most speaker damage is caused by overdriving the amplifier, all amplifiers have a window of linear operation, when pushed past this window the amplifier starts to clip, when clipping occurs, distortion follows. In essence the clipping is distortion. If you increase the treble and/or bass controls you are boosting certain frequencies (check your amp manufacturers literature for details) but this in effect lowers the level at which the amp will start to distort (distortion will set in earlier).

    Speakers require a clean a/c ( alternating current) signal. As the signal varies from positive the speaker cone will move forward, as the signal moves to negative the speaker cone also moves back wards. This pulsing, speaker moving back and forth is the sound we hear. This movement of air also acts to cool the voice coils within the speaker. When clipping or distortion occurs the speaker actually stops moving, when this occurs for a long period of time we hear its affects. Unfortunately by the time we actually hear the negative effects of distortion damage may have already occured. This damage may be heard right away as unnatural sound, buzzing, rattle... or it may have only slightly damaged the voice coil and its effects wont be heard until a later date.

    Most often it is the tweeter that is damaged. This is because the wire wrapped around the voice coil is thinner and more fragile than the woofers voice coil. That is not to say that woofers are not susceptible to damage.

    This is the reason why more powerfull amps are normally suggested, because they have a higher threshold before clipping. Its like having a 300hp car as opposed to 100hp, both cars will get you from point a to point b, both cars will only use 15hp to travel at a steady speed, however, when you want to pass, the 300 hp car will be safer and faster for overtaking on the highway. Especially when its a 2 lane highway, those on coming cars can be fatal.

    I hope I was a little helpful. I guess the best way to recgize distortion is to play it safe and not even push your equipment into that territory. If you are not satisfied with your particular sound, then you need to start evaluating your equipment and plan for upgrades.


    [​IMG] Regards Tom
     
  3. John Garcia

    John Garcia Executive Producer

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    Some amount of distortion is always present. As you said, you noticed it when it was very obvious - this is bad. This akin to what is known as the TLV, or threshold limit value, meaning by the time you realize it, you are already in trouble.

    "Thin" would be an example of the amp bumping up against it's limit - the music no longer sounds full and rich, highs are not as crisp and bass is sloppy; you can just detect that it the sound is not quite right. This can still damage a speaker.


    The wire IS the coil.
     
  4. Tom D

    Tom D Stunt Coordinator

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    :b Yes John you are right the wire is the voice coil. :b

    Regards, Tom
     
  5. Sam Pat

    Sam Pat Stunt Coordinator

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    Thanks for the pointers, fellas! Those were helpful.

    My mains are Paradigm Esprits and Paradigm CC270. Surrounds are small Energy Take satellites.

    My amp is a Sony STR-DET595, which claims 100 W/ Channel.

    I'm thinking that since it is an entry level amp and I play at modest volumes (my receiver doesn't give values at -X db, etc. instead going from a scale of 1-65 or so), I think my first signs of distortion will be from the amp and unlikely to be from the speakers getting too much power.

    Can I make this assumption? In that case, the onset of distortion will be from the amp and the symptoms will be a thin sound, right?
     
  6. John Garcia

    John Garcia Executive Producer

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    This receiver will not be able to deliver enough current to OVERdrive these speakers. It says 90x6 all channels driven, but I doubt that seriously.

    Do you have a sub also? If not, the Esprits are where your problem will lie, as they are going to draw plenty of current during bass heavy passages. Adding even a basic sub should go a long way to alleviating this and reducing the stress on the reciever.

    It's those loud burst moments or sustained loud action scenes where you have to watch out. When the receiver can't deliver enough power, the speakers are trying to reproduce a "damaged" signal; this causes them to heat up, and if it happens for too long or at too high of a level, the voice coil can melt or fracture, much like a light bulb filament.
     
  7. Sam Pat

    Sam Pat Stunt Coordinator

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    I have a sub, yes. A Paradigm PS1200 which I adore. I have always set my speakers to "Small" and I don't add anything for Bass and Treble.

    Right. Although it's hard with loud action sequences to try and hear distortion cause the explosions, flying debris, gunshots, etc. are rough, coarse sounds to begin with, unlike with music where it's easier.
     
  8. Sam Pat

    Sam Pat Stunt Coordinator

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    Also, will having my amp plugged into a Surge bar, as opposed to the wall, have any effect on its power?
     

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