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RMS

Discussion in 'Amps and Cabs [BG]' started by BassRocker8713, Sep 6, 2005.


  1. BassRocker8713

    BassRocker8713

    Jul 15, 2003
    Ok, so I've done searches and read through different threads, but I still can't seem to find my answer. What I've gathered from other threads is that it is pretty much safe to put 2x the RMS watts into a cab, as long as I don't run "on 10". Is this true? For example, if my cab is rated at 500 watts RMS, is it safe to use a 1000 watt head, as long as I don't max out? I'm sorry if I'm being unclear, but I'm very confused on the subject. Thanks!
     
  2. The simple answer is yes! :bassist:
     
  3. BassRocker8713

    BassRocker8713

    Jul 15, 2003
    Thanks a lot!
     
  4. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    I had a speaker that was buzzing in one of my cabs, There was some delamination under the gasket at the edge of the cone.
     
  5. I take you mean an SS amp then, with the turning up = clipping
     
  6. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Clipping happens with every amp if you turn it up. Tube amps tend to sound better to most musicians' ears when you do this, but it's still clipping.
     
  7. A tube amp experiences soft clipping whereas a SS amp experiences hard clipping, the soft clipping is not the same as hard clipping and as a result wont damage speakers as hard clipping does IIRC
     
  8. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    No, not entirely true, as has been explained many times in this forum. If you search on "clipping" in posts by Mark Reccord or Bob Lee, you will get the right dope.
     
  9. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA

    you can run a 5K watt head with a 10 watt speaker without damaging it, but you have to be careful.

    If you are going to run a cabinet rated at 500 RMS with a head that makes a true 1K watts, keep your ears open. If you begin to experience distortion or other noises out of the cabinet, it probably because you are pushing it too hard. It only takes a few times of bottoming out a driver before starts sounding like it has been abused.
     
  10. bassix

    bassix

    May 1, 2000
    Denver, Colorado
    Essentially, clipping the output of the amplifier is what damages speakers not excessive power. Of course there are limits, but that's a general rule. One other thing; I've found that using big, clean power can have very good results on your sound. Unless you're going for the 'grunt' that pushing a smaller amplifier produces, I think that having all that headroom really just simply sounds better.
     
  11. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    No, this is not quite right either, not as you've stated it. Again, it's been discussed repeatedly here.

    For instance,

    http://www.talkbass.com/forum/showthread.php?t=182626
     
  12. bassix

    bassix

    May 1, 2000
    Denver, Colorado
    I didn't see anything on your link that challenges what I've said here. As I stated, speakers are damaged by clipping (amplifier distortion, square waves). As long as you're sending your speakers nice, clean sine waves they like that. When they're asked to produce square waves, they don't like that. I've had the cones SR speakers physically tear away from the voice coils when this happened.
     

  13. See post #6 in this thread by steveksux. It's pretty concise and hits the nail on the head.

    http://www.talkbass.com/forum/showthread.php?t=199149

    Basically, speakers don't really care about waveform. If distortion/square waves were so destructive to speakers you couldn't use distortion effects, etc....

    I don't have time to go further in depth right now.
     
  14. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    It is absolutely possible for a "nice, clean sine wave" to easily destroy the motor in speaker from over-excursion or to melt a voice coil underrated for for the output power that is being provided by the amp.
     
  15. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Read to the end. You discover that no, it's not the waveform itself that causes speaker damage, it's either (1) the speaker getting more power than it can handle (which may, but doesn't necessarily, happen with clipping) or (2) overexcursion. Speakers don't care about square waves as long as you're not giving them too much power to handle or trying to make them perform mechanically beyond their limits. You can clip a 50 W amp into a 600 W sub all day and be very unlikely to hurt it at all. Why do you think guitar speakers don't immediately fry when you crank a Marshall?

    And steveksux's explanation in that thread Mark cited is good.
     
  16. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    True, except for the "run on 10" bit.
     
  17. Well, I wouldn't exactly call it concise.... :D

    Clipped amp puts out more than the rated RMS power, so a 200w amp clipped can put out 400W of filthy power and burn out your unsuspecting 200W speaker.

    Clipped signals have higher ratio of power in the high end. So tweeters are at more risk from clipped waveform than clean given the same power.

    So given a 200W RMS speaker with an appropriately rated tweeter, it will likely survive short peaks of 400W from a 400W amp, where as the 400w clipped watts of a 200W amp will be more likely to fry the tweeter. 400w clean might split 350 w to woofer, 50 to tweeter, and 400w clipped might be more like 300w to woofer, 100w to tweeter. That's why tweeters are more vulnerable to distortion. That applies if you clip your input, ala "crunchy" sound on purpose. Guitar players with 200w speakers and 50W amps can distort all they want, the waveform isn't the issue, its avg power in the voice coil. Amp can't put out enough to burn out the speakers in that case.

    The extra power generated when clipping a 200w amp can blow your 200w speaker given enough time if you don't hear the distortion and turn down. Same for a 400w amp driving your 200w speaker though. Distortion is generally a warning sign, ignore at your own risk.

    Randy
     
  18. Compared to what could be written about it, it's pretty concise, and it's understandable to non-technical people. :D
     
  19. Monomer

    Monomer

    Jul 22, 2005

    on that note:


    when will a bass ever produce a true sine wave?
     
  20. bassix

    bassix

    May 1, 2000
    Denver, Colorado
    ooooooooooooo,,kay. I started to write a long reply here, but I doubt if it would do any good. But I'll ask this,,,,if your concepts are correct, why have power demands in live sound systems increased so dramatically in recent years? I'm sure Bob Lee will attest to the fact that companies like QSC are designing more and more powerful amps all the time. Why do live sound sytem engineers routinely power their subs with 2000+ of RMS power per cab? Why do sound system processors like the dbx Driverack, BSS Omnidrive, Lake Contour utilize limters on the outputs of each band of their onboard crossovers? If power amp output distortion (square waves) didn't matter, why would they go to such lengths to eliminate it? And lastly, why do power amplifiers routinely have clipping eliminators (a design specific limiter) built into their output stages? Again, if clipping didn't matter,,,,,,why would they bother?