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Under powered cabs...problem?

Discussion in 'Amps and Cabs [BG]' started by Jaruquin, Dec 5, 2012.

  1. Jaruquin


    Sep 8, 2012
    I was wondering if there is anything wrong with under powering cabs. So one had told me there is but I don't buy it. I'm think of buying a Aggie GS212 from a friend. It's 600w @ 4ohms, I'm only going to be able to push 400w to it. (only other 4ohm option is the full 900w to it).

    On a side note Aggie GS212 vs Avatar B210?
  2. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    Under powering is an urban myth you will find.:bassist:
    PS Cabs don't sound good or last long running at their thermal power ratings, you will probably only be able to put 400 watts into a 600 watt cab before it sound like a case of severe flatulence.
  3. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    If those are the only two options, the Aguilar.

    Can you get the cab in 8 Ohms?
  4. Jaruquin


    Sep 8, 2012
    The Aggie comes in 8ohms too but I'm getting it used from a friend. It will work because I want to replace the SWR sm-900 down the road. I've been looking at a lot of the 500w heads and the push that @ 4ohms.
  5. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    Its more of a "a 4 Ohm 212 is really limiting your volume options" type of question, not a "you need more power". IMHO unless the 212 in question is incredibly capable one would never be enough. You are not going to see a volume increase from 400 to 500 watts. In fact 400 or so watts is going to push that 212 pretty close to its potential. It wouldnt matter if you had 10,000 watts on hand, its not really going to get louder before destruction.

    Finding that cab in 8 Ohms on the other hand is going to give you the option of adding a second one down the line. Now you have not only doubled your power handling (~3 db increase), but you have increased the sensitivity of your rig (another ~3 db increase).
  6. Jaruquin


    Sep 8, 2012
    Do you think one 212 is loud enuff for bar gigs? And if I have PA help do you think it will do fine?
  7. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    Depends on what you really need as far as stage volume goes. If the PA is good and has subs and such, then it may meet your needs.
  8. 1958Bassman


    Oct 20, 2007
    Depends on the bar, the rest of the band's volume and whether you need the lowest notes to come out at high SPL. A 212 cabinet will not be as loud in the lowest range as an equally sensitive larger speaker, which means you'll need to change the tone settings. Whether you'll have an actual equalizer or just a bass control, it means that you'll either need to boost the bass or cut the mids/treble. In either case, you won't be able to play as loudly as if you already had the low end.

    Think of it this way- if your amp is capable of a certain power output, that's without using the tone controls/boost/EQ. If you boost the bass, the demands on the amp change and this means your power at the distortion spec decreases because the power isn't unlimited. If you boost the bass and the speaker can't even produce those frequencies, it's a complete waste of power and you'll blow the speakers. However, you may be able to use the 212 cabinet with good results as long as you don't need super low notes or the speakers and cabinet are setup to handle them. This last point is rare- small speakers may do deep bass but they're not usually efficient in that range. This means you'll need to send more power to them in order to hear it as well as you need.

    The first thing you need to do is determine the frequency range you need to use, then select the speakers based on this. Once this is done, you can select the amplifier- get the features and control you want and then buy the power. This is a good argument FOR using a separate preamp and power amp- you get the controls and features you want and if you really don't need a lot of power, you don't need to spend so much on that. Sure, it may take up a bit more space, but it gives you more control over what you get. For instance, if you need the controls and DI with XLR, like what a Gallien-Krueger 800RB has, the 400RB or 700RB won't quite do it. They'll work well, but power, bi-amping can't happen and control over the sound will be less.

    You need to hear yourself when you play. If you don't have enough speakers or power, you won't. I wouldn't expect the monitors to provide this, so you may find that your rig needs to. The PA is for the audience, not the band. If it's a large system and has side-fills or large monitors that can be mixed to let you hear yourself well enough, great, but don't expect this to be the norm- just the exception. Some bass players like it loud onstage, some don't. You'll need to determine where you fit.
  9. Jaruquin


    Sep 8, 2012
    I guess the the 4ohm 212 will work for now because it will be in stereo mode and if I need to I can hook up a second 4ohm cab to the other channel.

    How much volume increase do you think ill get going from my current 250w @ 8ohms 4x8 cab to the 400w @ 4ohms 2x12 setup? At practice I have my volume around 7 and I feel like I could use a little more.
  10. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
    Depends on the sensitivity of the cabs in question. Could be zero gain in volume, could be a slight increase but nothing earth shattering. In fact depending on the speakers it could be a decrease in SPL, not saying that it will be because I dont know the specs of the speakers you are using but it could be.
  11. will33


    May 22, 2006
    Not a problem.

    They are measured and tested using 1 watt. Can't get much more "under powered" than that.
  12. Depends on the bar. With PA, if it isn't enough you're all too loud on stage anyway.

    If the bar is 200 people big and has no PA for you then you will struggle a bit but so will the drums and vocals so you're stuffed anyway.

    For smaller bars and smaller crowds you're good so long as you aren't trying to blow the roof off the place and make your vocals inaudible.
  13. Tuned


    Dec 6, 2007
    You can blow a speaker by "underpowering" it, which is to say you drive a saturated level that exceeds 71% of the speaker's RMS level. With bass amps often there is a limiter on the output so with a 400W amp you can put out a saturated 400W signal that is virtually square wave. Square wave signals pass 41% more continuous power than an RMS signal (400W RMS only peaks at 400W). For example, if you slam the limiter of a 300W amp that is capable of fully saturated output (tube, older class AB solid state, all class D) you can blow a 400W RMS speaker.

    But slamming a limiter like that is either a deliberate tonal effect or careless abuse. If your amp use doesn't fall into those two categories, underpowering is totally safe. I drive my 700W cab with a 500W amp on purpose, because it has lights that comes on at half power and at full power (limiter/saturation), so I'm aware when I'm exceeding 1/3 and 2/3 of the cab's power handling. Having 40% more cab RMS power than amp power is best, because then even a total moron would have trouble blowing it, but it's still not impossible.
  14. ThisBass


    Aug 29, 2012
    Underpowering a 700 Watt RMS power handling cab by -40% translates to an amp power of:
    420 Watt
    Doubling the Wattage due to clipping calculates into:
    840 Watt

    Overpowering a 700 Watt RMS power handling cab by +40% translates to an amp power of:
    980 Watt

    840 Watt will fry the voice coils but 980 Watt results in good cooling voice coils. :bag:
  15. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    First, no prob running 400 watts into a 600-watt cab. I use my Bergantino AE212 at bar gigs and even outdoors. If you have PA support, all the better.
  16. Actually, UNDER powering is MORE likely to damage a speaker. The reason is that an amp slipping in to clip is VERY hard on a driver. You may not even notice that it's clipping by the sound once you figure the noise from the other insturments and the PA.

    Over powering can damage a speaker, BUT it's unlikely for two reasons.

    1) You'll hear the distortion sooner and turn down thus protecting the cab.

    2) Cabs are fused. If you OVER power and hit the cab to hard and ignore the obvious distortion coming from the speakers, the fuse will pop. You replace a 10 cent fuse and you're up running again.

    If you UNDER power the fuse will NOT pop because you never reached it blow rating. The drivers get to low power distorted signal and burn up.

    I used to run an 8ohm 800 rated SWR Goliath III with a Crown K1 bridged to 1100 watts and NEVER had a problem but I was very aware of the cabs sound. It really started to sing at around 1 o'clock on the amps volume. I turned it up full blast one time just to see what it sounded like. It was LOUD.

    SWR used to use a light bulb as a fuse. In the dark you could see it flashing. Pretty cool actually.
  17. CL400Peavey

    CL400Peavey Supporting Member

    Nov 7, 2011
    Grand Rapids Michigan
  18. Jaruquin


    Sep 8, 2012
    So I got a SWR sm-900, I'm thinking about buying a aggie GS212. The cab is 600w @ 4ohms. Should I hook it up in stereo mode and only push 400w or bridge it and send the full 900w and just watched the volume.
  19. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    All of that is backwards. Clipping an amp is the thing that lights up the bulb, and its to stop the tweeter being overpowered by a clipping amp, because tweeters handle 10w or something, and clipping puts lots of power into high frequencies where they don't belong.
  20. Under powering is a myth, read the sticky, or ask Bob from QSC the next time he is on here. It is a myth, an urban legend that won't die. Ask yourself this: if this underpowering idea was real, would getting a cabinet that supported fewer watts solve the problem? With the underpowering meme, it would. Simply ridiculous.