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Amp/clipping/general question.

Discussion in 'Amps and Cabs [BG]' started by Grahams Groove, Jun 28, 2001.

  1. Grahams Groove

    Grahams Groove Can we please just groove for a while? Supporting Member

    Apr 13, 2001
    Boulder, CO
    Say i have a 8 ohm 4x10 cab that can handle 300 watts RMS, and the amp i am powering it with is like 240 watts @ 8 ohms. So the cab capable of handling 300 watts is only getting 240 topps or in normal playing condition only like 200 (cuz i wouldnt crank volume all the way...) would this be bad for the amp or the cab? Is it bad to only give a 300 watt cab 200 watts?? Or would it be cool?? (Also, i would consider adding an 8 ohm 1x15 later in which case the amp would be dishing out 350 watts, and then the 1x15 is capable of handling i think 150 or 200 watts rms) But the first thing is will this be ok with the 4x10??

    Oh, and the amp would be tube/ss (Its a hartke 3500...)
  2. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    Thats a normal match.
    No problem there, I believe.
  3. The only thing that matters is that the power amp doesn't clip. This will blow your speaker pronto.

    Otherwise, your spec.'s are ok.
  4. jrich


    Jul 10, 2001
    Chicago, IL
    I am not totally positive on this but here is what I have been told.

    It is not good to push a cab with less power because of some type of modulation or something it causes the amp to compensate for not being that powerful, thus causing clipping. This is not good for both the amp and speaker, and I believe it can cause something on the speaker to melt. I'm don't understand the technical stuff, but I've been told more than once that the amp should push more than the speaker is rated for. Speakers blow from being underpowered more than from being overpowered.

    What I have also heard is that if the cab is 8ohms and the head is 4ohms, it basically halves the amount that its receiving or is getting put out (not sure). So a 300 watt 4 ohm amp into an 8 ohm speaker, the speaker should be rated at 150 watts or less. If what I was told is completely wrong someone please tell me!

    hope this helps and that i'm not wrong!

  5. Grahams Groove

    Grahams Groove Can we please just groove for a while? Supporting Member

    Apr 13, 2001
    Boulder, CO
    I dont think that's correct...because if i recall correctly, eden makes some cabs that can handle like 700-800 watts. And im posiytive that not all of these cabs are recieving the full amount of power. And if you are correct, it's gonna be damn hard to find an amp that can push 600 watts @ 8 ohms in my pricerange....somethign just seems wrong about that theory.
  6. No, that's not right AFAIK. Underpowering, *in and of itself,* doesn't hurt a speaker at all. If I use a 400 W amp into a cab rated to handle 800, that won't hurt the cab at all, nor will it hurt the amp one teeny bit. There is no modulation of the sort you describe; that is, merely having an amp that puts out less power than the cab can handle does NOT cause clipping.

    What WILL hurt a speaker in the scenario I just described is when, for whatever reason (not enough amp watts, inefficient speakers, whatever), your rig isn't giving you enough volume, and you (not the amp) compensate by cranking tone controls and volumes and basically forcing the amp to clip. Be clear on that: the cab will never "force" the amp to clip; only you, the user, can do that.

    Gernerally, unless you like your speakers to break up, I think it's preferable to have speakers rated *higher* than what your amp can dish out. The real key IMO, however, lies less with cab ratings than with MAKING SURE THAT YOU HAVE ENOUGH AMP FOR THE JOB. If you have a 300 watt amp that isn't powerful enough for your needs, going from a 400 watt-capable cab to a 100 watt cab, in and of itself, is NOT going to help that--all it's gonna do is increase the risk of blowing the speakers without giving you any more usable volume. On the other hand, going to a cab rated to handle 1000 W will not save you if your amp isn't up the job and you persistently force it into clipping.

    Now this doesn't mean that you can never use an amp of a given power rating into a cab with lesser power handling. I've done it: I've put 600 watts into a cab rated for 350. That particular combo sounded great, though that doesn't mean all such combos would. But there's a subtle distinction here. In that setting, I didn't deliberately look for a cab that handled less than my amp's power. That, in itself, would be of no benefit. Rather, I figured out roughly how many watts of amp i thought I'd need--then I got *more amp* than the minimum I needed, so I wouldn't have to work the amp so hard. See the difference?
  7. Grahams Groove

    Grahams Groove Can we please just groove for a while? Supporting Member

    Apr 13, 2001
    Boulder, CO
    Ok, here's a question for you...i have a Nemesis 2x10 combo rated at 200 or 225 watts, and i have a mesa 4x10 hooked up to the combo as an ext. cab. I have the master cranked to the max, but i adjust the gain so that there is very little/no pre-amp clipping...am i doing anythign wrong? although the master volume is up all the way, the speakers do not seem to be distorting, and i cannot hear any clipping.

  8. Who was it said, if it sounds good, it is good?

    Doesn't sound as if you have a problem. But make very sure to check the impedances of the speakers you plug in, and confirm that they don't present too low a load for the amp. For instance, if the amp is rated to handle a minimum load of 4 ohms, and you're giving it 2.67, you might want to worry. I'd guess the Mesa cab is an 8 ohm cab (don't take this as gospel, check it out). Your manual and/or the printing on the back of the cab should tell you what kind of load you can plug into the external speaker jack. Something like, ext. speaker min. load 8 ohms. Call or e-mail Eden (the maker of Nemesis) if you're not sure. This is important.

    I don't know the controls of that amp, so I don't know if your gain control is for input sensitivity or preamp volume. If it's the former, i.e., to set optimum level for the bass as it comes in, it should be set reasonably high, nearly as high as you can do it, provided that you don't clip the input when you play as hard as you ever would. If, however, it sets the overall preamp level to the power amp, then you can keep it lower. Again, I'd say to contact Eden--they know this amp far better than I.

    But so far it sounds as if you're fine.
  9. jrich


    Jul 10, 2001
    Chicago, IL
    Thanks Richard

    What you said makes sense. I knew there was something I was leaving out of my explanation but I wasn't sure what it was. The whole watt/ohm thing confuses the hell outta me. Soryy for the mistake.

  10. MikeyD


    Sep 9, 2000
    Several comments:
    _ 1. Grahams Groove: please try not to post the same question in more than one thread. Thanks. We'll get to it a lot faster that way. :)

    _ 2. Richard Lindsey: I concur with your very good explanation. You are 100% correct that an amp whose output is less than a speaker's handling is perfectly safe as long as you don't drive it into clipping.

    _ 3. Donne Demarest: Clipping will *not* blow a speaker "pronto" unless you are clipping something like a 100-watt amp into a 10-watt speaker. Clipping is a phenomenon that changes the waveform of the output and can *at most* double the RMS sine output rating of the amplifier. I have an amp (80 watts) that I could drive into heavy clipping for 24 hours straight and its associated cabinet (200+ watts handling, with no tweeters) will just sneeze at it. Now, a 240-watt (sine) amp can damage a 300-watt speaker if it is driven into clipping for too long. But a momentary clip is unlikely to be a problem with that situation.

    You are right that people should avoid clipping, but that is not the whole story. You can certainly blow a speaker without clipping. Try a 1000-watt head at full volume into a 100-watt speaker (hey how's that for *not* underpowering?), without clipping. Try a 200-watt head into a 300-watt speaker, but push a 10 Hz. waveform at full output into it. Try a 100-watt head into a 100-watt speaker, but feed it a signal with heavy distortion effects. These are other ways to destroy speakers.

    The best advice is: avoid frequent or prolonged clipping of the amp. If you find you have that situation (i.e., more than just occasional light clipping), you need either a bigger amp or more (or more efficient) speakers, or both.

    - Mike

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