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Thread: Underpowering Speaker/sub Test (simple test)

  1. #1
    Maximum Bitrate Megalomaniac's Avatar
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    Underpowering Speaker/sub Test (simple test)

    Ok it made me too upset so i did a little test on my own today.

    SI Mag 12"
    SA70 Plate Amp 4 ohms: amp does 70 watts but i chose to give ~30ish watts to severely underpower it
    16awg speaker/conductor wire
    iPod video 60GB black
    ROE - 45HZ Track (looped)
    camera used was a JVC DV500 (for stationary video) & a Canon SD1000 for photos and 2nd clip
    1.5 sheet of Second Skin Damplifier (to stop rattling :P

    3hrs 6min 23sec and some
    speed up by 50k% to 22 seconds
    each frame is about 15seconds

    foam ball falls off for 30min, i didnt realize it, footage moves to fast to show it being placed back on, i can provide footage of my bro putting foam ball back on by request

    Foam ball just shows movement of sub







    captured in real time to hdd, real footage ended up being like 46gb, I should have cleared hdd some more to do longer testing


    just to monitor it that i am gettting video signa




    its on basket to stay elevated and not to block chamber vent for proper cooling




    This just shows proof that i did indeed try it
    Broadcast Your Audio System - CarAudioClips.com


    After: put back in my box at ~800 plays fine and dandy, no problems what so ever.
    Broadcast Your Audio System - CarAudioClips.com

    its fine


    Mythbusted!



    some might say that i put my sub at risk by underpowering , i was very confident, reason i did it.


    simple test i know, but that sums it up well
    screen name here use to be MegaloRESE15"

  2. #2
    Variable Bitrate
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    I just don't get what your test shows. Was the audio signal clipped?

    I ask because my understanding of under powering causing speaker harm occurs when one trys to use too small an amplifier and driving it into clipping to get the volume up to desired levels. Clipping changes the duty cycle of the speaker from that of a sine wave to something approaching a square wave (or from say 70% to near 100%). The damage caused is from overheating due to clipping, not absolute power levels.

  3. #3
    MySQL Error scott_fx's Avatar
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    it's not really under powering it that makes you put the sub at risk; rather it's not having enough power and trying to increase the spl by increasing the gain on your amp. that's what is commonly to referred to as risking damage by under powering a sub. :-)
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  4. #4
    Maximum Bitrate Megalomaniac's Avatar
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    Quote Originally Posted by lbridges View Post
    I just don't get what your test shows. Was the audio signal clipped?

    I ask because my understanding of under powering causing speaker harm occurs when one trys to use too small an amplifier and driving it into clipping to get the volume up to desired levels. Clipping changes the duty cycle of the speaker from that of a sine wave to something approaching a square wave (or from say 70% to near 100%). The damage caused is from overheating due to clipping, not absolute power levels.

    no the audio was not clipped. thats the point.

    underpowering a driver will not kill it. When you give a clipped signal thats when things start going "byebye"
    screen name here use to be MegaloRESE15"

  5. #5
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    I have been professionally designing speaker enclosures for more than 15 years and I am constantly annoyed by the confusion that surrounds this topic. The problems with busting the myths that surround this are that you can not rely on either the rated power out put of the amplifier or the thermal limitations of the sub. In the real world both of these specifications are at the mercy of a number of variables. You can measure the out put of the amplifier in order to eliminate that variable but you must understand that the speaker has been rated by approximation. You can play it at RMS power indefinitely but any thing over that for an extended period of time may lead to enough heat to cause thermal melt down. A common misconception is that this only happens at the speakers max rating. Not true. That’s a fact.
    The next but not least significant element is the speakers suspension. Even if the speaker is underpowered and never reaches its thermal limitations it can still easily be damaged due to over excursion. Excursion is not a direct result of input power and dose not necessarily result in more output. Also a fact.
    And not even close to least, most manufacturers build subs with obese inefficient motors and then under rate the thermal limitations. Think about it if you where a manufacturer with millions on the line what would you do?
    The problem here is not the manufacturers approach, it’s the testing approach. Lets say that you feed a 500 watt sub 800 watts in a .25 cubic foot sealed enclosure for 10 hours and nothing happens. You haven’t proved anything. That sub might be able to take 850 watts for 9.5 hours before melting down. The point is that you don’t know if the sub is under rated, or over rated, or if your amplifiers particular design causes unexpected levels of heat in the clipping stage. You cant prove anything in a test like this with out accounting for every variable. And the day that I see some one with the resources and the time to write a 20 page report on the definitive answer to this topic I will have to point out that they have one hundred thousand amplifier/sub combos left to test not to mention the sub/enclosure combinations and that they have effectively proved nothing.
    If you want to be safe stick to the numbers and power your speakers with the RMS rating. If you want to push the edge of performance you take the risk of exceeding the thermal limitations of your speakers. If you have an education in speaker design you can predict and push the limitations to new levels and only blow something up once in a while. Its life deal with it!

  6. #6
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    Question it has nothing to do with your testing

    But does this woofer always sound that way, I don't see the point in moving air and annoying noises, that does not complement the music to my ears, or was this also to make a point in your testing.

  7. #7
    Maximum Bitrate Megalomaniac's Avatar
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    Quote Originally Posted by ca55e5a View Post
    Question it has nothing to do with your testing

    But does this woofer always sound that way, I don't see the point in moving air and annoying noises, that does not complement the music to my ears, or was this also to make a point in your testing.
    noises you heard in 2nd clip were trunk rattles

    Quote Originally Posted by speakermakers View Post
    I have been professionally designing speaker enclosures for more than 15 years and I am constantly annoyed by the confusion that surrounds this topic. The problems with busting the myths that surround this are that you can not rely on either the rated power out put of the amplifier or the thermal limitations of the sub. In the real world both of these specifications are at the mercy of a number of variables. You can measure the out put of the amplifier in order to eliminate that variable but you must understand that the speaker has been rated by approximation. You can play it at RMS power indefinitely but any thing over that for an extended period of time may lead to enough heat to cause thermal melt down. A common misconception is that this only happens at the speakers max rating. Not true. That’s a fact.
    The next but not least significant element is the speakers suspension. Even if the speaker is underpowered and never reaches its thermal limitations it can still easily be damaged due to over excursion. Excursion is not a direct result of input power and dose not necessarily result in more output. Also a fact.
    And not even close to least, most manufacturers build subs with obese inefficient motors and then under rate the thermal limitations. Think about it if you where a manufacturer with millions on the line what would you do?
    The problem here is not the manufacturers approach, it’s the testing approach. Lets say that you feed a 500 watt sub 800 watts in a .25 cubic foot sealed enclosure for 10 hours and nothing happens. You haven’t proved anything. That sub might be able to take 850 watts for 9.5 hours before melting down. The point is that you don’t know if the sub is under rated, or over rated, or if your amplifiers particular design causes unexpected levels of heat in the clipping stage. You cant prove anything in a test like this with out accounting for every variable. And the day that I see some one with the resources and the time to write a 20 page report on the definitive answer to this topic I will have to point out that they have one hundred thousand amplifier/sub combos left to test not to mention the sub/enclosure combinations and that they have effectively proved nothing.
    If you want to be safe stick to the numbers and power your speakers with the RMS rating. If you want to push the edge of performance you take the risk of exceeding the thermal limitations of your speakers. If you have an education in speaker design you can predict and push the limitations to new levels and only blow something up once in a while. Its life deal with it!


    again in simpler words

    as long as the signal is clean and doesnt effect mechanical performance, like cooling, then it will not blow from underpowering.

    if the signal had been clipped it would drive the driver to its thermal limits a bit faster and then start to get "smelly"
    screen name here use to be MegaloRESE15"

  8. #8
    Car Audio Moderator durwood's Avatar
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    Not trying to be an *** here, but there is one even simpler way to think about it...

    Q: If a speaker could be killed with too little power, then everytime you turn your volume down then your speakers would run the risk of death?

    A: No.

    If you really want to discuss power delivery to a speaker I suggest doing some math and look at the difference between the power associated with a sine wave vs a square wave.

    The problem with too little power, is that a PERSON attempts to correct for this by getting more out of the amp in effect clipping the output. The difference in power of a sine wave (what manufacturers use to rate power) vs a square wave (clipped signal) is larger then you may think . It's all about duty cycle.

  9. #9
    Maximum Bitrate Megalomaniac's Avatar
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    Quote Originally Posted by durwood View Post
    Not trying to be an *** here, but there is one even simpler way to think about it...

    Q: If a speaker could be killed with too little power, then everytime you turn your volume down then your speakers would run the risk of death?

    A: No.

    If you really want to discuss power delivery to a speaker I suggest doing some math and look at the difference between the power associated with a sine wave vs a square wave.

    The problem with too little power, is that a PERSON attempts to correct for this by getting more out of the amp in effect clipping the output. The difference in power of a sine wave (what manufacturers use to rate power) vs a square wave (clipped signal) is larger then you may think . It's all about duty cycle.
    duwood you arent being rude at all
    i have thought about all those things. But on another forum i was criticized and name called "idiot" for even mentioning that. they all thought i was high and mighty. when i was just pointing out the "obvious". argument was that can Underpowering a sub cause damage, answer is no, clipping will cause damage

    so i took it to the next level. witht that Footage i did yesterday, I dont like to brag but it thought that video idea was brilliant. sorry enough with being all high and mighty now :

    if you seriously want to know why i was upset in did that test heres the thread with the argument, the admin is childish IMO i tried to speak respectfully and factually(if thats a word as possible) in that thread /rant

    http://www.stevemeadedesigns.com/boa...howtopic=11241
    screen name here use to be MegaloRESE15"

  10. #10
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    By the way I failed to mention that I think that your test here was a nice scientific, common sense type approach that you executed very well. And you are absolutely right.

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