"I gots ta know." (Amp Wattage)

Discussion in 'Amps and Cabs [BG]' started by D-Man VanKrill, Dec 13, 2007.

  1. D-Man VanKrill

    D-Man VanKrill Guest

    Dec 4, 2007
    This may be an amp ? so sorry but, Im thinking of getting a rather big bass amp setup sometime between now and later (who isn't) but before i do so, I would like to know how much a cabinet ,or cabinets', watt handleing capabilities should exceed that of the head.
    Example, say one has a 300watt head, would he be alright if he had a 300watt cab, 400watt, 600watt etc. I don't know.
    Also I believe I heard somwhere that certain amps can only function long term at certain ohm levles, meaning might 8ohms or more be a bit to much for certain cabs. Your answers will be greatly appreciated :)
  2. Panda Licker

    Panda Licker Guest

    Jan 5, 2005
    Coaldale PA
    You can underpower a cab, but should never overpower one. So if you run a 600W cab off of a 300W head, you'll be fine, but if you run a 300W cab on a 600W head, it will be very easy to blow said cabinet out

    As for ohms? Most amps will run between 4 and 8 ohms, with some going down as low as 2 (Check the manual to see if yours can or can't). If you don't know for your particular head, your best bet is to run no less than 4 ohms on it. And as far as running a cabinet at too many ohms? Unless you're building it, you would never have to worry about changing the resistance of your cabinet. Its the cabinet itself thats going to decide the resistance of your rig. Cabinets come from the factory rated at a certain resistance. You can't really change that, unless you rewire it.

    if you don't know how to figure out ohms, btw

    if you're running them series, add the resistance together. So two 8ohm cabinets run in series will give you 16 ohms of resistance

    if you're running them parallel, you figure it out by adding the inverses of the ohms, then taking the inverse of your answer

    as in.. for two 8 ohm cabinets..

    1/8ohm + 1/8ohm = 1/4. Take the inverse of that and you see that two 8 ohms run parallel is 4 ohms.
  3. bongomania

    bongomania Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    OP, you'll want to do the following things:
    1) Check out the amps forum. Yep, we got a whole forum dedicated to amps.
    2) Read the FAQs and Stickies in that forum. Then re-read them. :D
    3) Use the search function and search on the words "underpowering" and "overpowering". There is a lot to read and learn on those subjects, taking particular note of the fact that people disagree about them pretty strongly.
  4. D-Man VanKrill

    D-Man VanKrill Guest

    Dec 4, 2007
    Thankyou to both u yuz.
  5. embellisher

    embellisher Holy Ghost filled Bass Player Supporting Member

    Umm, we do have an Amps forum.:rollno:

  6. Tim1


    Sep 9, 2005
    New Zealand
    "You can underpower a cab, but should never overpower one. So if you run a 600W cab off of a 300W head, you'll be fine, but if you run a 300W cab on a 600W head, it will be very easy to blow said cabinet out."

    This is not quite the way I have understood it to be - while it makes sense I was always told that if you underpower a cab and crank the amp you are MORE likely to blow it as when driven hard a transistor amp will deliver AC/sharp sine waves(?? something like this) into the cabinet. I always thought that overpowering is safer so long as you use your ears sensibly. This probably applies less to tube amps. Happy to be corrected if I am wrong here.....
  7. Briefly, not quite. No offense, but this has been discussed a lot here, and if you take the advice given above in post #3 and search, looking particularly for posts by folks such as Bob Lee, billfitzmaurice, and Mark Reccord, you will find good and full explanations of this stuff.
  8. SERPENT865


    Jan 1, 2007
    Wichita , KS
    +1 with Richard.
  9. Chazinroch

    Chazinroch Guest

    Feb 2, 2003
    Ontario N.Y.
    FWIW I've been under the assumption that if you are under powering a speaker cabinet and clipping the amp you are likely to damage the speakers as well. I believe I read this in the "Sound Reinforcement Handbook" that Yamaha puts out. I also have in my little hands "The Basics of Sound and Sound Systems (Hal Leonard) and right on page 58, and this confirms the effect that clipping has on underpowered speakers. So my guess it would be alright to use an underpowered amp, but don't run it full out to the point of distortion/clipping. Best to match as close as possible power output of the amp to power handling of the speaker with the venues and volume your band will be playing at.
  10. joegeezer

    joegeezer Guest

    Mar 9, 2005
    Northern Wisconsin
    Avatar Club#12 Eden Club Lucky# 13--USA Peavey Club#37 Carvin Club#5
    Get an amp that puts out twice as much power as you think you might need, then double that, and get one. In the end you will be about right. I run a Carvin DCM2500. 850 watts per channel into two 4 ohm cabs, when I need the big power. If I need less, it has knobs for that.