2 broken 12" speakers in the same day with powerhead¡¡¡¡¡¡¡¡gggggggggggCAUTION

    This topic puzzles me...well, it is clear that a 600W@8Ohms can kill a speaker of lower wattage, but when does it?
    That is: is there a way to know the maximum volume you can bring your poweramp too, before your speakers are damaged?
    Or, even better is there an option in the Power Head/Rack to specify the cabinet wattage and thus limit the maximum volume that you can set on the kemper?
    I, for instance, own a Mesa Mini Recto 1x12, this one: http://www.mesaboogie.com/Prod…Recto1x12-SlantCab-LG.htm
    and I would gladly avoid damaging it, if possible :D

    the mesa boogie 1x12 is 60w......yes you can damage,i don´t know the limit,but i broke two speakers with the powerhead,now i have more caution.......


    however in 100 watt valve amps....where is the limit to drive a 60w speaker???? ?( ?(

    Quote from estocastico7

    the mesa boogie 1x12 is 60w......yes you can damage,i don´t know the limit,but i broke two speakers with the powerhead,now i have more caution.......


    however in 100 watt valve amps....where is the limit to drive a 60w speaker???? ?( ?(

    True, but is also true that, while it can't be done with a normal amp, a software based product like the Kemper could have a user-settable parameter specifying the wattage of the cabinet in use, and enforce a limit of volume based on that. At the moment I use it with a 20W tube poweramp, at home I never set it past 9 o'clock, and live I think I went as far as 1 o'clock (on a 2x12 cab), I really wouldn't see the need to push the volume much further

    Quote from Laimon

    This topic puzzles me...well, it is clear that a 600W@8Ohms can kill a speaker of lower wattage, but when does it?
    That is: is there a way to know the maximum volume you can bring your poweramp too, before your speakers are damaged?
    Or, even better is there an option in the Power Head/Rack to specify the cabinet wattage and thus limit the maximum volume that you can set on the kemper?
    I, for instance, own a Mesa Mini Recto 1x12, this one: http://www.mesaboogie.com/Prod…Recto1x12-SlantCab-LG.htm
    and I would gladly avoid damaging it, if possible :D

    The tricky part is that there are so large error margins that you have to be really conservative for an effective prevention.


    Loudspeakers have a maximum tolerated continuous power load, and a maximum tolerated impulsive power load. Manufacturers declare them in the technical sheets. But this is not enough to foresee their behaviour.


    Different power amps with the same nominal power output may have different impulsive powers. This is easily verified in the Hi-Fi realm. This means that if a very impulsive sound is reproduced, a "harder" power amp (as we say in Italy) will output a lower voltage than a "softer" one.


    To clarify, a hard power amp has a good nominal output voltage but its impulsive voltage is not much higher in comparison. A "softer" power amp, OTOH, could exhibit a lower nominal maximum voltage
    but is able to generate extremely higher impulsive voltages (that is, for a very short time).


    A loudspeaker's cone, given the finite speed of motion propagation through its surface and its "weak" material nature, is more prone to get damaged by an impulsive signal, which creates stronger pressure (and motion) differences in different parts of the cone.


    Add to the picture that, by international agreement, an amp's nominal power given a certain load impedance (say 8 ohm) is measured @ 1 kHz: actually, you don't know the real power at other frequencies. It might be lower or higher than the nominal power, depending on the amp design. So maybe two "100 W/8 ohm" amps can produce very different outputs at 100 or 3000 Hz, not to speak of their contingent different impulsive powers.


    Last but not least, volume has little to do with a loudspeaker's overload: it depends on the cone's efficiency, which is another parameter manufactures declare. The higher the efficiency, the louder the sound at the same amp signal and loudspeaker's impedance.


    Hope this clarifies things a bit, even tho I can't supply any concrete help.


    :)

    Edited once, last by viabcroce: Readability ().

    Thanks Gianfranco! You're superkind :D
    Well, I did learn something...not entirely sure what do with it though :P
    For instance: how do I know if the Kemper's poweramp is hard or soft?
    And even without considering the impulsive power (though it seems to be the most dangerous factor), how do I know how far I can push my poweramp's volume, based on the nominal power? Say, using the powered Kemper (600W@8Ohms) with my Mesa 1x12 (60W@8Ohms) should I keep the Kemper's volume at less than 10%? And would such a reasoning apply also to 4x12 cabinets?
    (sorry for the thousand questions :P )


    Great info, it's always an education here :)


    smfelton: thanks for your appreciation dude :thumbup:

    Quote from Laimon

    how do I know how far I can push my poweramp's volume, based on the nominal power? Say, using the powered Kemper (600W@8Ohms) with my Mesa 1x12 (60W@8Ohms)

    When blood starts oozing out of your ears, this means the poweramp is too loud, turn it down. :)


    Ingolf - please confirm this. :D

    IMHO there is a very easy rule:


    We should not put more into a speaker as the rating of the speaker allows.


    If the speaker is rated 60Watt and the amp 600Watt - and you turn it to max - your speaker will be killed.
    Some after a few seconds others may last longer - but they ALL will die.


    Since I don't know ANY guitar speaker being able to handle 600Watt - ALL will die after long loud playing @ max volume.

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    Great Profiles --> soundside.de

    Sorry but this rule is useless. I do not think that anybody play at max volume (power boost at +12, master at 10) with 1x12 cab.


    Question is what is the safe ratio at practical volumes.


    I would say at home with 1x12 cab is for sure OK.
    But at rehearsal with acoustic drummer is other thing.
    My experience is that a 60W speaker at 16 Ohm (Powerhead at 300W, power boost at +3, master at 5.5) works – still.
    My band mate use 2x12 box (120W) at 8 Ohm (Powerhead at 600W, power boost at +6, master <5).
    But I want to know if it safe and can I use it without the risk for the speaker.


    If the safe rule is: you must use 4x12 cab (300W) with the powerhead, fine.
    But in this case the advantage of Kemper Powerhead + Matrix Cabs (or any lighter and smaller cab) is diminished.

    Agreed - of course if you wanna stay on the safe side you have to do how Armin suggests, but poweramps do have a volume knob, it must be useful for something :D

    Quote from nightlight

    I think a "limiter of sorts" for the Power Amp output is a definite requirement for the Kemper. Great idea + 1.

    Exactly what I suggested some posts above: one setting in the system menu where to specify the wattage of your speaker, so that the kemper won't let you turn the volume beyond a computed safety threshold.

    Quote from Laimon


    ...
    Agreed - of course if you wanna stay on the safe side you have to do how Armin suggests, but poweramps do have a volume knob, it must be useful for something :D
    ...


    Yes, that knob may be useful - but NOT to limit the maximum power the amp can deliver - even when you turn the poweramp volume down (say to 50%) - in case you double the input from your preamp (think KPA) you get the same result. :D


    Whatever we do - a simple 600Watt power amp connected to a 60Watt speaker - is IMHO not a good idea.


    ... and if anybody uses something like this - then turn the volume WAY DOWN - and don't complain later :D

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    Great Profiles --> soundside.de

    Quote from Guitartone

    When blood starts oozing out of your ears, this means the poweramp is too loud, turn it down. :)


    Ingolf - please confirm this. :D


    I think you're quite right, Lance... ;(;)


    And I guess what you want to establish here should be some kind of common sense.
    Protect your hearing.
    Protect your gear.

    Sorry Ingolf, but your post is also useless.


    What we need is (I repeat myself) the orientation how to manage Powerhead + Guitar Speaker.
    Most of us used tube amp before and have experience with it.
    So I know that I can play 100W head at 1/4 volume to 1xV30 without danger for the speaker and when I need more I use 2x12 so I am on the safe side.


    Now I can hear that my 100W tube head, at about 1/4, is loud as Powerhead at 16 Ohm with Power Boost +3, Master at 5.4.
    But how to understand much more Watts of Class D vs tube head. Can I count on my experience/volume_hearing?


    Your post implicate that I need a full stack 2 x 4x12 (2x300 W) to play with the Kemper Powerhead at 8 Ohm.
    When I use less and something go wrong, I shall not complain. If this is true or must, fine, but then Kemper please communicate this.


    I think you misunderstood me. ;)
    1.) I'm all for a solution where the user gets a clear visual feedback of potentially overloading a connected cab, some kind of safety settings for different connected cab configurations.


    2.) OTOH it has not yet become clear (at least to me) if in the the case of the killed speakers there was a misconception about loudness per se. It goes with what sensible people like Armin propagate: Turn it down.


    I hope that makes more sense.

    Quote from Armin

    Yes, that knob may be useful - but NOT to limit the maximum power the amp can deliver - even when you turn the poweramp volume down (say to 50%) - in case you double the input from your preamp (think KPA) you get the same result.


    Well... Not always, and not necessarily :)

    Quote from Ingolf

    2.) OTOH it has not yet become clear (at least to me) if in the the case of the killed speakers there was a misconception about loudness per se. It goes with what sensible people like Armin propagate: Turn it down.

    ad 1) agree :)
    ad 2) It is easy to say "Turn it down", but playing with acoustic drums needs some volume, so "Turn it down" is not an option, it leads to: "Play your tube head instead of Kemper until it is clear how to deal with Powerhead, if you do not have 4x12 at your rehearsal place".

    Some good info on this:


    http://brain21.net/blues/blog/?p=432


    Quote

    for those with modeling rigs… if you run a modeler into a SS power amp (like say a Carvin or ART) and then into a cab, treat this whole setup as a solid state PA amp (because with very few exceptions, that is exactly what it is). So, if you have a 200watt cab, your old guitar head may have been a 100watt head, but you do NOT want to run a modeler into a 100watt SS power amp into that same cab! You’d have to crank that SS amp into distortion to get the volume you want with a band. For that same 200watt cab, you would run your modeler into a 400watt SS power amp and into that cab. If you run your modeler into a tube power amp, like a VHT or Mesa-Boogie tube power amp, then you treat it like a 100watt guitar cab.


    So, modeling rig into power amp into 200 watt speaker cab:


    With a SS power amp you want 400 watts
    With a tube power amp you want 100 watts


    Quote

    If the guitar amp is not powerful ENOUGH (in watts) for the speakers, you can get distortion, but it won’t damage the speakers. Damaging speakers with too little wattage is SORT OF a myth (particularly with a guitar amp). See next point for an explanation of “SORT OF”
    HOWEVER, a 200w **SS** amp puts out ~400w when it is clipping, so a 200w amp can burn up a 300w speaker cause when its clipping its putting out 400w. What’s really happening is an under-powered PA amp will tend to get cranked for more volume, and when it distorts, it’s suddenly sending TOO MUCH power to the speakers. The common thought in SS PA speakers, as you should know by now, is that you should have a 600w amp for a 300w speaker. Therefore if the amp is only 200w, it is WAY underpowered compared to the 600w amp. When it blows the speakers people think “an underpowered amp will blow the speakers” – however, at the point where the speakers were blown, the “underpowered amp” was delivering MORE than it’s rated 200w due to clipping. Higher power means less likelyhood of the amp clipping the speaker. You’ll get speaker distortion first, which you can turn down before anything gets damaged. This is why people tend to think that not enough power from the amp will blow up a speaker.