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How safe is using more watts than the cabinet is rated?

Discussion in 'Amps and Cabs [BG]' started by Mastermold, Mar 18, 2009.

  1. For example, take a 4 ohm cabinet rated at 500 watts. Is it okay to run a 600 watt Genz Benz Shuttle 6.0 through it? How far is it safe to push before you risk actual damage?

    I'm sure some of the answer is that each cabinet varies, but I'm just wondering if there is a general rule.
  2. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    Yes, that's why they give you a volume control, so you can set it less than full blast.

    There's a sticky thread with plenty of information.

    If the speakers fart out, turn down. Most cabs fart out LONG before they hit their rated power limit anyway.
  3. Zero issue, especially with that particular head (since it doesn't inherently put out a lot of super deep low end, which can get you into a bit of trouble sometimes). The relationship between published power specs of a head (often a fantasy), and maximum power rating of a cab (my guess is, even more of a fantasy) is relatively meaningless and uninteresting in general.

    Per the above post, regardless of the power ratings, if you hear the cab starting to compress, or hear farting, just turn down a bit and you will be cool!
  4. Double Agent

    Double Agent

    Mar 10, 2006
    Lakeland, FL
    Agreed with the above statements. Use your ears to determine whether or not you are sending the speaker more than it can handle and you should be fine.

    You might actually find the speaker sounds better since it will be driven harder before the amp starts to distort. In other words, you will get the speaker moving with less stress on the amp, you'll have more headroom and a cleaner sound. Just don't go crazy with the volume or overboosting the EQ and you shouldn't have any problems.
  5. Ryan L.

    Ryan L. Moderator Staff Member Supporting Member

    Aug 7, 2000
    West Fargo, ND
    I agree with KJung.

    I used to use an SVT4Pro mono-bridged (supposedly 1200 watts) into an SVT410HLF (supposedly handles 500 or 600 watts, can't remember anymore). Never blew a speaker. The cabinet let me know when I was approaching "too much". I was careful not to over do it with the EQ, too.

    I ran that setup for quite a few years and never had a problem.
  6. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    He refers to power compression, a point where the cabinet simply doesn't get louder with more power. You pump in more power and it doesn't get louder...it simply heats the speakers.

    All cabs can reach power compression, but it depends on the design of the speakers and especially the cabinet.

    Pushing hard into power compression is what burns up speakers, because all you're doing is heating them up.
  7. allexcosta


    Apr 7, 2004
    Using amps with 2x the power rating of the cabs is the standard of the audio enforcement industry.
  8. Let's be honest, just because your amplifier is capable of giving 1200W doesn't mean it's doing so. If your amp did produce its full capacity you would not be able to be in the same room as it. MY preference is to give a cabinet what it is rated for. My Acme B2s are rated at 350W each and I give them that availablility via a Carvin DCM1000 (350W/CH @ 4Ω). I have never used all that power. Probably 300W maximum between them.

    If you listen to your speakers and turn down at the first sign of distress you should be fine. However be aware that the amp does have the ability to destroy your speakers if you are not careful. If your clumsy guitar player knocks your bass over that pulse of noise could mean the end of your drivers.

  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The single biggest cause of failure of bass guitar speakers is exceeding the mechanical limits of the driver.

    Myth #1: The power rating of a speaker is one, fixed number.
    Truth #1: The power rating of a speaker is a complex set of equations that manufacturers have attempted to simplify into a single, simplistic (sometimes marketing based) number. In fact, the mechanical power handling of a speaker DECREASES with frequency, so a speaker with a "rated" power of 350 watts RMS may have a real world power rating of 200 watts at say 35-40Hz. It may also have a thermal rating of 600 watts but that becomes unimportant since the weal kink in the chain is almost always mechanical for the higher quality speakers.

    Myth #2: You should always use an amp w/ 2x the "rated power" with your speaker.
    Truth #2: In fact, you should understand how your speaker is really rated as spec. creep due to marketing issues have resulted in an otherwise identical speaker system increasing in "rated" power handling over it's product lifecycle even though the drivers remain unchanged. Also, using heavy compression or limiting will increase the thermal power to the point that the average thermal power can increase by a factor of 2 or 3. Therefore it would be prudent to de-rate the driver under these conditions as well.

    Myth #3: It's safe to power a speaker at up to the peak rating of the driver.
    Truth #3: The peak rating of the driver is (typically) based on peak voltage. This means that an amplifier capable of delivering say 1000 watts RMS is also delivering 2000 watts peak (there's a 1.414**2 factor involved) so it's purely a math conversion. This is a common misconception.

    There's more myths but I'll hold off on anything more technical.
  10. Hey thanks, agedhorse, it's especially nice having a Genz Benz engineer weigh in! Much appreciate the explanations. And likewise thanks to everyone else for posting!
  11. hasbeen

    hasbeen Commercial User

    Sep 23, 2004
    Vice President, KMC Music. Warwick U.S. distribution, Ampeg distribution
    well, I'm not an engineer like Andy but, from a bassist's experience, if it sounds bad "at" your speaker cab, turn down.

    When I say turn down, that can also mean turn down you lows on the amp. If you have those cranked, our eq section is VERY powerful.

    Of practical note: I play a GBE1200 through a Neox-212T all the time....without problems. BUT, if my speaker sounds like it is straining, I turn down.
  12. Not to highjack the thread or anything, but would the same rules apply with a power amp going into bass cabs? I hear they are less bloated in their power ratings, but would a 1400w amp in bridged mono damage a 1200w 4x12's bass cab?

    For reference sake, the amp is a Behringer EP1500 and the cab is a GK Neo 4x12's cab
  13. SanDiegoHarry

    SanDiegoHarry Banned Supporting Member

    Aug 11, 2008
    San Diego, CA
    oh lord... I can see this thread creeping toward the dreaded "too little amp / too much speaker blowing up my amp" discussion...
  14. tidnab


    Jan 21, 2009
    Simi Valley, CA
    I know people that use a pre and a QSC amp.. one guy I know uses an RMX4050... that's 1400 watts (I guarantee his mesa cab isn't rated @ 1400w) bridged mono it'll put out ~4000.. I think you get the idea... a little common sense goes a long way.... underpowering cabs are more likely to cause damage (unless you do the back to the future trick)
  15. Uh oh...the "U word" :bag:
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Depending on how the speaker is rated, I would say it's a possibility. With common sense you would, probably be ok.

    I wouldn't say that any amp type is more or less bloated, but there are different ways of rating an amp that would be more application specific in that two amps rated one way may result in an identical set of numbers but the real world experience may be different. This is because there are many different variables and parameters that define an amp's performance into a real world load. So one amp may sound considerably louder than another. This is generally across intended markets of amps... so for example a car amp might have rating of 1000 watts but looking deeper into the details may show one channel driven, maybe peak power (1.414**2 factor) while a pro audio amp may be both channels driven, with a dynamic hedroom of 2 or 3dB, into a 45 degree lagging load, capable of short term currrent delivery into sub-nominal impedances. Here the pro amp would stomp the car amp into the ground in real world tests because they are not anywhere near equivelant product types.

    For a few specific examples of how the real pro audio guys rate their amps (especially the bigger ones), they look at adequate current capability into reactive loads, sub-nominal loads, thermal capacity, dynamic headroom (energy storage) with an appropriate duty cycle for the dominant frequency range, attention to details of amplifier dynamic limiting including excellent recovery from clipping, etc. These are all things that I spend a lot of time with on the amplifiers that I design. They are what make the difference between a bunch of numbers and a loud, good feeling, playable amp.

    And I will say again that speakers are damaged ONLY by overpowering. It's important to understand that overpowering can be accomplished with an amp that is too small for the job and when it clips it will generate harmonics that increase the power greatly at frequencies above the fundamental as well as deliver more thermal energy (as much as 2x the rated power) at heavy clipping.

    Also, an amp that is driven heavily into limit will result in an increased thermal energy as the peak to average ratio of the bass signal can be greatly altered.

    Also, an amp driven into clip may lose control of the speaker because as the amp clips the amp's internal feedback is no longer valid and the output impedance of the amp increaes maybe 40-100x which means the damping factor may decrese to around 10 or so and the cone is free to flop back the other way.

    Not so simple eh?
  17. Seems that way to me too. Thanks for the info, it's greatly appreciated! I doubt I would ever need to crank my amp to the level that it WOULD blow out my cab at...I would more than likely go deaf before then. :crying:

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