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would this hurt the speakers

Discussion in 'Amps and Cabs [BG]' started by sidhk817, Jan 6, 2005.


  1. i remembered that somebody here in TB said that using a low wattage amp to drive a highly rated cab would easily damage the speakers,eg. use a 100W amp with a 1000W rated cab,
    is this true?
     
  2. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    +1

    Exactly.

    :)

    Joe.
     
  3. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    +1, except that you'd be very unlikely to hurt a 1000 W cab even if you overdrove a 100 W amp mercilessly. Unless maybe it had a tweeter with a relatively modest power rating. It's not clipping/distortion *in and of itself* that damages speakers.
     
  4. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    I don't think so. Would you mind explaining what you mean? Power amp distortion KILLS speakers, undeniably positively. Done it m'self. Preamp distortion is just an effect.

    :)

    Joe.
     
  5. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Power amp distortion does not have any inherent ability to kill speakers. First, amp distortion, fundamentally, is not *qualitatively* different from preamp distortion. Distortion is distortion. Either a device passes a signal accurately, or it does not.

    Second, think of a guitarist playing a Marshall stack turned up high. That guy is putting out a lot of power amp distortion (in addition to preamp distortion). Hell, think of a bassist who's turned his SVT up to where it starts getting "that" sound--again, substantial power amp distortion. By your logic, everybody playing a cranked Marshall or SVT should be immediately frying their speakers. Yet that doesn't happen on a wholesale basis. And it's not because they're tubes versus SS. I've personally brutalized SS amps into distortion without harming the speakers ... well, more times than i really enjoy remembering, though not lately. I certainly don't recommend that, but in my situation it was relatively safe because I was abusing a fairly small amp into a speaker with high power handling.

    Speakers die mostly because they're being fed more energy than they can dissipate or because they're being forced into overexcursion. If you killed your speakers, odds are it was for one of those two reasons. Not distortion in and of itself.

    This has been discussed a lot around here. A search on "clipping" will yield you some good info, supplied by people a lot more knowledgeable than I.
     
  6. 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
    The effects of excessive power--heat or overexcursion--are what kills loudspeaker drivers, not distortion.

    Power amp distortion is dangerous in that an amp that is severely clipping is putting out more power than its rating (which is measured just at the onset of clipping) would indicate. With really severe clipping, where the output waveform becomes a square wave, the power put out would be close to double the amp's clean rated power.

    Could you damage a 1000-watt loudspeaker with a 100-watt amp that is clipping badly? It's not likely, but it would sure sound like crap.
     
  7. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Dude you are so wrong...


     
  8. 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
    No, he's right.
     
  9. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Hey Bob,

    What you are telling me is different from a conversation I had with some folks at Bag End.

    According to them because of the near dc voltage of a clipped power amp you turn your voice coil into a heater since it isn't moving in and out (excursion) properly (venting). Thus Frying your speaker.

    Now maybe I'm standing here with egg on my face or maybe I'm not but what they said makes logical sense to me.

    Now don't get me wrong...I love my QSC PLX 2402 and my RMX 850...but could you explain a little more in depth what you mean?

    :)

    Joe.
     
  10. 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
    Who were you talking to at Bag End? Somebody technical or somebody not? Someone who is technically astute would not make such claims.

    As I said, excessive power damages loudspeakers.
     
  11. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    You didn't really answer my question. All you did was ridicule.

    Please reread my post then respond.

    Thanks!

    :)

    Joe.
     
  12. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Well, in fairness, Joe, he did answer. He said it was excessive power that was the culprit. In other words, not distortion per se. Meaning that if the Bag End rep told you differently, the rep was wrong.

    And not meaning to be a PITA about it (really, I'm not), but if you do a search on clipping and look particularly for the contributions by Bob Lee and Mark Reccord, you will see this explained quite well.
     
  13. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Originally Posted by Second, think of a guitarist playing a Marshall stack turned up high. That guy is putting out a lot of power amp distortion (in addition to preamp distortion). Hell, think of a bassist who's turned his SVT up to where it starts getting "that" sound--again, substantial power amp distortion. By your logic, everybody playing a cranked Marshall or SVT should be immediately frying their speakers.[/QUOTE

    You are not factoring the difference in frequency ranges between bass and 6 string. THEREIN LIES THE DIFFERENCE.


    The difference in frequency range is utterly irrelevant. Either distortion kills or it doesn't. Or are you saying only distortion in a certain frequency range kills? If so, exactly where does the "danger range" start? Presumably you know that the frequency range of the bass and that of the guitar are not separate but actually overlap substantially?

    And what about the bassist with the SVT? That's bass range too. Why doesn't every speaker in a pushed SVT blow immediately? Those 6550s are certainly distorting.
     
  14. 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
    I read your post and answered. I did not ridicule. I could repeat what I posted if you want.
     
  15. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Michigan
    Eight more headroom, to be exact. :ninja:
     
  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
    It depends largely on the amp. An amp that clips very softly will squash the peaks before it hard clips, and that may cause the phenomenon you describe if it does a lot of squashing before the flat-topping occurs.

    Usually, though, it takes a certain amount of clipping to occur before the distortion components start becoming audible. With a sine wave the peaks will flatten a bit before you can hear the new harmonics created by the distortion (it will depend a lot on the fundamental frequency and how loud it is). With complex waveforms, like music and regular audio stuff, it usually takes somewhat more clipping to make the distortion audible because the distortion components are both intermittent and often masked by other sounds.
     
  17. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Here is the problem. Myths are easily propogated and are heard repeatedly over the Internet so many times that people begin to believe them as fact. The myth of underpowering is just that. There is no scientific basis for the argument. If you are exceeding the amp's output rating then you may also get to the point where you exceed the speaker's output rating. Like Bob said, overdriving a 100W amp isn't going to blow a 1000W speaker cabinet.
     
  18. This kind of expounds on this matter a little further. Bob, if you could answer this, it would be great. I have a BBE BMax pre going into my QSC RMX850 which is pushing my Ampeg 410HLF. I have my gain on my pre at about 4, my master on about 4-5 and on the 850 I have it in bridged mode and about halfway up. When I really start dig in the amp starts to clip and has actually shut off on me a couple of times. I don't understand why it would be doing this. My cab is rated at 500/1000 watts and runs at 4 ohms.

    Why is this?? What do I need to do to resolve this issue??

    Here is a pic of my rig to give you a better idea
     

    Attached Files:

  19. 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
    Shut off in what way? For how long?