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Too much WATTS HELP!!!

Discussion in 'Amps and Cabs [BG]' started by Eelco, Nov 9, 2005.


  1. Eelco

    Eelco

    Nov 9, 2005
    Hello ereyone,

    i just ordererd an ashdown mag 600 head and added to that a 4x10 350 watt cabinet. Is there any danger connecting a 600 watt amp to a 350 cabinet. I havent got it yet so you could rescue me on time. TNX

    Eelco
    The Netherlands
     
  2. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    No. Just turn it down if you hear your speakers bottoming out.
     
  3. Two things.... first... you need to look at the cabinet impedence... is it 4 or 8ohms, and then the wattage that head puts out at 4 vs. 8 ohms. For example, I believe the MAG600 puts out 575 watts RMS into 4ohms. Iif you have an 8ohm cab, then my guess is the amp will put out around 300 watts..... which would actually be a little underpowered... but no problem.

    Second... (assuming a 4ohm cab) it's not really that bad to have more power going into a cab than the cab's rating. Of course, if you run the amp wide open, you'd be in trouble... but in general, higher watts usually means a cleaner (nunclipped) signal reaching the cab.... so it shouldn't be a problem unless you obviously hear speaker distortion.
     
  4. Exactly, its the DC component of the clipping signal that kills the speakers. The coils cant dissipate the heat from the DC, its like putting a 60v car battery across the terminals every 1/20 of a second, which over time is a straight DC current.
     
  5. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    The amp will probably reach TOF before the speaker cabinet. But in either case, when your rig reaches the "Threshold of Farting" just cut back the bass on your EQ or turn down your volume.
     
  6. Except this isn't the case. There's no DC in a clipped signal. There's more power in a clipped signal than in a clean one at the same voltage, but no DC. The DC thing is a common misconception.
     
  7. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    Ya'll and your confusing technical wisdoms.

    Here is an anectote that might make some sense.

    I used to own a Ampeg SVT-4 (1600 watts peak, 1200 realistically) through an 8-ohm Ampeg 4x10 cabinet (probably about 500 watts handling). 2 years later head is working fine, cabinet is sounding as good as new.

    Just use farting as your guide. :D
     

  8. Should be fine. It's not a big deal to use an amp rated for more power than the cab in most cases. Even when you're cranked pretty loud you're not using all of the amp's power all the time. If you're constantly clipping the amp to get loud enough you either need more speakers, a more powerful amp, or both! :D
     
  9. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    Just out of curiosity if you were running a cab with a head ratede twice the wattage of the cab.

    Would you keep the volume in or around 0dB to supply the cabinet with around its rated wattage of clean power?
     
  10. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    Wait that would probably only be true if there was no gain control. Which there is on the vast majority of amps. I never think things fully out:scowl:
     
  11. IMHO you have to match the watts to your venue. If you are constantly trying to push your rig to hear yourself, then you are clipping your signal, which as you know looks a lot like a square-wave but with a very high duty-cycle. "So what" you ask? This waveform has a lot of current flow behind it, which will heat up your voice-coil - poof!

    Musical waves (non-clipped) have a smaller average duty-cycle which allows the speaker to disipate the heat.

    SO... if your amp and cab can put out enough volume without clipping, and without hitting the physical limits of the speaker (extension and heat dissipation), then no worries :) If your speaker is bottoming out, you would hear it. If you're clipping, you would hear it. Moral of the story is: if it sounds normal, then it probably is.

    - Andrew
     
  12. Eelco

    Eelco

    Nov 9, 2005
    Thanks a lot for your responses I never expected this much expertise and replys in such a short period of time. I will certainly use this method again. Gretings from The Netherlands (somewhere in Europe)
     
  13. Its actually the DC power rails of the supply. The transitors can only be driven so far and the output swing is limited by the rails, max out the input and you reach the top of the supplies, hence a square wave, clipping, with a DC component.
     
  14. Not to Hijack your thread (although I am from South Africa - Hijack central!)

    Could someone explain to me how the distortion from clipping your amp causes damage to speakers, but the distortion from say a distortion pedal doesn't? what is the difference?
     
  15. What you're saying is correct about the mechanism of clipping, but there's no DC component. A square wave has no DC. I can prove that to you mathematically if you want. Draw a picture of one cycle of a square wave and add up the area under the curve. The area above the 0 axis will be exactly the same as the area below it, which gives exactly 0 DC component.

    The flat top of a square wave isn't DC. It may seem like that but it isn't. A 100Hz square wave will cause a speaker to move in and out the same number of times per second as a 100Hz sine wave. Now there's 2x as much energy in a square wave that a sine wave of the same amplitude, which is where people run into problems, but no DC.

    The pure square wave is a pretty extreme example, because no amp will ever really produce one, but it simplifies analysis a bit so it's a useful concept.
     

  16. There isn't really any difference. Distortion is distortion and the pedals produce their effect by clipping something. Like I alluded to earlier, it's not distortion that damages speakers it's too much power. The same caveats apply to distortion pedals. There's more energy in the distorted signal than in a clean one at the same level so you need to be mindful of it.
     
  17. Distorted signals at low levels won't do anything to a speaker. Its when you don't allow the speaker to cool off fast enough between peaks in the waveform. Speaker assemblies are designed to dissipate heat up to a given power level, its not until you exceed that power level for some amount of time that you're in trouble. A low-level distorted signal probably won't pass that power level.

    I also agree about the DC component not being present in the signal as such. If you look at ANY alternating signal, technically speaking, its ALL DC signal, its just that the DC's levels are changing over time. Eventually the DC signal reverses direction and goes negative. Its this crossing and changing direction that defines an AC signal. In a square wave, that direction change DOES take place, so its an AC signal, even though the shape of the peaks look straight. If you were to add a DC signal to a square wave, all it does is change the voltage levels of the tops and bottoms of the wave, and where the AC's "0 Volts" appears to be, ie: shifts the wave form by the DC voltage value. If you want to know if there's a DC component, look at the AC's cross-over point.

    - Andrew
     
  18. I stand humbly corrected. - rpm