Question about blowing speakers

Discussion in 'Amps and Cabs [BG]' started by rayzak, Mar 2, 2006.

  1. rayzak


    Jan 13, 2001
    Louisville, KY
    I have my first real "big rig", a Mesa 400+ thru a Bergantino NV425. I love it!!!

    This past weekend myself, two drummers, and 2 gu@!ar playin' buddies of mine went out to one of the guys very secluded home and played all night and all day... all weekend... VERY LOUD!!! Over many beers and booze. We had a blast.

    It got me wondering if it would be possible for me to blow the speakers in my cab with the Mesa. I got quite a bit of distortion, but it sounded great to my ears, as well as the other guys. But is there some signs I really need to look out for?

  2. seamonkey


    Aug 6, 2004
    Does the head have a limiter?
    turn it on. Keeps the power amp from clipping. Preamp can still clip/distort.
  3. rayzak


    Jan 13, 2001
    Louisville, KY
    Nope. No Limiter.
    Would a compressor be a good idea?
  4. mphares


    Mar 1, 2006
    Yeah, a limiter is an excellent idea. I'd never play at high volumes without one. A compressor may give you some limiting but it will also change your sound and playability. You may or may not like that. One of my rules of thumb is, always run through an amplifier that's rated higher than your speakers, for bass, PAs, etc. Amplifier clipping will kill speakers faster than anything -- even a small-watt amp. If you turn any amp up beyond its maximum, it will continue to put out more power but it will all be distortion -- square-tooth waveforms. You can overdrive a 50-watt amp and tear up a speaker rated at 500 watts because anything over that 50 will be distortion. Conversely, if you want to drive that 500 watt speaker to its maximum, do it with a 600- or 800-watt amp. That way, all the 500 watts will be clean power. If you continue to turn up your 800-watt amp, you may still blow out your 500-watt speaker, but it will be from heat over time, not from speaker cone damage from distortion. And any decent 500-watt (RMS) speaker probably has a good peak rating that would save that speaker for quite a while before it dies, even at that high power output. So if your amp output and speaker ratings are fairly evenly matched, or if the amp doesn't quite equal the speaker ratings, be careful of overdriving. Just like computers, three things kill speakers: heat, dirt, and people, er, bass players. I'm not sure what your Mesa puts out, or what your speaker rating is, but you can figure it out from that.
  5. seamonkey


    Aug 6, 2004
    mpharas isn't right on the money.

    Compression can also give you a higher perceived loudness so you may be less tempted to turn up to a damaging levels.

    If you're at all handy with a soldering iron, for a very basic compressor, take a look at Rod Elliot's ESP site:

    For limiting, you really only want the thing to turn on at a certain threshold, so Elliot has a slightly more complicated circuit at:

    I've seen simple variations of the first circuit that put a rectifier and zener in series with the lamp to turn it into more of a limiter. (but I don't know where)

    Note that both these hook up to the speaker leads so you could calibrate them to your particular amp.

    Just an idea.
  6. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    No, clipping does not kill speakers in and of itself. Clipped waveforms are not automatically and inherently lethal to speakers. A clipping 50 W amp will hardly ever kill a 500 W cab, unless, conceivably, that cab has a low-rated tweeter. You won't get more than 100 W out of a clipping 50 W amp, and usually not even that, certainly not on a continuous basis. A search on clipping in this forum will be illuminating; it's been discussed a lot, and this myth has been repeatedly debunked.
  7. 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, that's almost impossible unless you're putting in a frequency that's way, way too low for it--and even then it's not likely.
  8. seamonkey


    Aug 6, 2004
    Looks right.
    but clipping can blow tweeters (if there's no protection). This cab has no tweeters.
  9. Petebass


    Dec 22, 2002
    QLD Australia
    Not exactly correct here either. Your emphasis is on blowing speakers via burning voice coils but there's another way to do it - You're not taking speaker excursion into account. Too many watts, too much low frequency boost, and feeding you cab frequencies which are significantly lower than the cab's tuning frequency can all cause a speaker to move further than it's designed to.

    Most pro audio speakers will have a generous amount of X-Mech (point of physical damage) relative to it's X-max (point at which suspension runs out of travel and starts to cause speaker distortion). In theory you should have plenty of warning that a speaker is about in danger of blowing this way. Audible distortion is a big warning sign, though at loud volumes, it can be difficult to detect.

    So the distortion rayzak could have come from one of two sources. Was it clipping, or was it speaker over-excursion? Unless you're there, it can be hard to say which was happening in this case.