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Underpowered Ampeg 610HLF

Discussion in 'Amps and Cabs [BG]' started by Tames, Aug 28, 2005.

  1. Tames


    Dec 31, 2002
    Decatur, IL, USA
    One of my very good friends is a bass player in another band who recently got set up with a new rig... an Ampeg SVT 450H head, and an Ampeg 610HLF cabinet.

    Now using common sense, we BOTH would imagine that these would be an "optimum" configuration as they are very similar in power, yet using the 450H head on the cabinet, it sounds like the head is just forcing the speakers beyond belief. Although not a cab pairing problem... it seems like the preamp clip is ALWAYS on and no matter what gain.

    I actually played a show using my friend's cabinet and MY head, which is an SWR Workingman's 4004 400 watt, playing my "normal" stage volume, and normal EQ and gain settings, and everything sounded fine.

    I've always understood that there is much greater of a problem when you underpower a cabinet than if you are over powering. IE, using a 150 watt head with an 8x10 cabinet that can handle 1600 watts is worse than running a 1600 watt SVT4 Pro through a 200 watt cabinet at a very low volume.

    Is this head/cabinet the right configuration? What are we doing wrong?

    The head is 450 watts @ 4 ohms and 250 watts @ 8 ohms. The cabinet is 4 ohms, and shows program handling at 1200 watts. Why would this be wrong?
  2. You understood wrong, I'm afraid, if by "worse" you mean more likely to damage the cab. 150 W into a 1200 W cab is not a problem unless it's not loud enough. It's very unlikely to damage the cab no matter how far you turn up, despite the common myth. (See the sticky thread up top, and look for the ones on clipping and clean power.)

    There is absolutely nothing wrong with the setup you mention in the last paragraph, if it's enough to get you the volume and tone you need. There isn't some magical bad thing that happens when cab power handling exceeds the size of the amp. If you're not getting the volume and tone you need, then you need to change some aspect of your gear.

    Ask yourself if you would be better off if you had the same 450 W/4 ohm amp, but your 4 ohm cab only had a power handling capacity of 200 W (but was equivalent in other respects). The answer is no, you wouldn't. If you use such a rig in the same settings, you would not have more headroom, and you would actually be less safe from speaker damage, not more.

    That said, having more amp power than you need is never a bad thing for bassists, unless you're one of those who prefer the sound of a bass amp starting to break up. So getting a bigger amp wouldn't be a bad thing either, as long as you use it wisely.
  3. 8mmOD


    Mar 20, 2005
    I endorse & use Tech 21 pedals, Eminence loaded cabs, EMG pickups, Jim Dunlop picks & Ernie Ball Strings, BC Rich Basses.
    you already tried your head with a different cab... how does the 610 cab sound with a different head?
  4. Lync

    Lync Supporting Member

    Apr 13, 2004
    I have the SVT610HLF and I can say that it likes power...I mainly use a Thunderfunk TF-420 with it and the cab sounds best with the the amp at about 11:30 and gain adjusted accordingly.

    I've also used it with my B2R and it sounded fine (although the B2R did hit its limit).
  5. Sounds like your just clipping the amp, pre or otherwise, turn the pre-gain down, and use the padded input

    the 610 is just putting out what its being fed, most cabs will do that when your clipping an SS amp like that

    If its clipping the pre no matter what you do, it might be a faulty head?
  6. There's your problem, doesn't matter whether its the preamp clipping, the power amp clipping or the speakers bottoming out, if any part of the signal path is overloaded, it sounds strained and distorted. Back off the input gain, use the input pad until the clip light isn't lighting up much. Once in a while on hard hit notes is ok. If you can't get the clip light to quiet down even then, there's something wrong with the input stages of the amp.

    So the cab isn't the problem.

    A 150 W amp will drive a 1600W cab just fine PROVIDED you're playing quiet enough so that wattage gives you the volume you need. You probably can't blow a 1600 watt cab with a 150 watt head, under normal circumstances no matter how hard you try. A 1600 W amp will not blow a 200W speaker PROVIDED you play quiet enough that the amp only averages less than 200 watts.

    A Ferrarri won't go over 20 mph unless you hit the gas. A yugo won't smoke Goodyear eagles.

    A 200W amp can put out more than 200W when its clipping, maybe 300-400w. So you can blow a 250W speaker by "underpowering" it with a 200 W amp if you run it into clipping all the time so the 200W amp feeds the 250W speaker 400W.

    Or take a cab with a tweeter. The tweeter can maybe handle 40W, the cab 250W. That's fine because the power is spread out over the freq range you're reproducing. Bass has very little high freqs, so they're assuming your avg 250W of bass guitar signal has about 210W of power below the crossover freq, and about 40 above it. Now take your 200W amp and clip it. Its now putting out 300-400 watts. However, a clipped waveform has a totally different mix of frequencies than the same clean signal. That's why guitars sound different with distortion. Clipped waveforms have massively more high freqs than the same clean signal. So suddenly your 250W of DISTORTED signal may only contain 125W below the crossover freq, and 125w above the crossover freq. What do you think happens when you feed 125W of power into your 40W tweeter? It blows.

    That's what "underpowering" is. Its really a misleading term. The speakers are blown by overexcursion or too much power going to them.

    Its just that cabs that are crossed over have made assumptions regarding "normal" signals and power handling of the tweeter that are violated when the amp driving them is clipped, amps can put out more than their rated power when they're clipped.

    So "underpowering" is a bit of a misleading term. You're not blowing speakers cause you have too little power. You're still blowing speakers by feeding them more power than they can handle. Just that it's possible to do that by overdriving a "smaller" wattage amp than you would think.

  7. Great explanation IMHO.
  8. KJung

    KJung Supporting Member

  9. Ding ding ding!!!

    I've been ranting about this for years...:D
  10. Tames


    Dec 31, 2002
    Decatur, IL, USA
    Thank you guys for all the information. I told him to do the basic gain test... turn the master down and turn your gain up and play as hard as you would during a show and keep backing off the gain until the clip light barely shows. Eh? Simple enough?

    Also, I warned him about not clipping the EQ by ramping all the frequencies well above the zero detent position.

    HOPEFULLY this helps! If not, I think we may have run into a problem with a bad cabinet. Mainly the gain shouldn't be a huge problem because he's playing a mexican p-bass (passive) through it. Hmm, we'll see how it works... once again thanks everyone, and we'll keep you updated!