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How to match head watts and cab watts?

Discussion in 'Amps and Cabs [BG]' started by jpowell, Sep 29, 2008.

  1. jpowell


    Sep 15, 2008
    The more I have read in this forum the more confused I have become. I need accurate info on the above. I am a singer songwriter/acoustic guitarist that is also taking up bass. I have narrowed my choices to the following:

    GK Backline 300W Amp - GK Goldline GLX 2x10 and 1x15 300W

    GK 700RB11 480W Amp - Same as above

    GK " " " GK RBX 2x10 400W and SBX 1x15 400W

    I suppose I could pick up a used 1001RB11 if it would make any difference. Please respond if you feel you have ACCURATE info. Thanks!!
  2. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    Don't worry about it. A 2:1 ratio in either direction could help narrow your choices but it really isn't very important at all. Your cab will tell you when you're putting too much power into it by getting more and more distorted.

  3. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Right- the "accurate info" is that you need to listen to the speakers, and if they start flapping, buzzing, farting, etc. then you need you turn down the amp (and/or engage a limiter), dropping your peaks below the level that caused the speakers to fart/distort.

    As long as you've got that in check, over/under doesn't matter. Also remember that the published specs are usually more of a "general guideline" than a "fact".
  4. jtc_hunter


    Feb 16, 2007
    I have the same amp and if I were doing it all over again, I would get 2 Avatar 112's 8 ohm ea. in LineX. You would save money, have a lighter pack, and just as good , if not better sound, and more durable cabs.
  5. jpowell


    Sep 15, 2008
    I have not purchased yet and do not want to test for distortion AFTER I have done the deal. This seems like a fairly straight forward question even though I can't confidently answer it yet. Thanks.
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Try before you buy. If the amp causes the speakers to fart out it's got plenty of power for them. OTOH if the amp when fully cranked won't cause the speakers to fart out chances are you need a larger amp.
    BTW, a speaker's wattage rating does not tell you how much power it will take without farting out. The average figure is 20 to 40%.
  7. Well, it's not, or at least not in the manner you seem to think it is. The "matching" you're talking about is really kind of a red herring--as many, many threads in this forum have explained in some detail.

    The short answer is that the amp power:cab power handling ratio (whether 1:1, >1:1, or <1:1) is of no real importance as long as you (a) have enough amp power to do the gigs you do comfortably (without straining the amp) and (b) have enough cab power handling to handle the level of power you are actually using (as opposed to the amp's max rated power, which you should not be approaching on any regular basis). Re (b), remember that an amp's stated rating is usually its MAX output in a specified setting, and if you have enough amp for your gig, you will only be using some fraction of that maximum on a regular basis.

    Practically speaking, you'd probably want to avoid extreme amp:cab ratios in either direction. But at the ratios you're talking about, it generally doesn't matter much.

    The advice you've been given to try the rig out is sound. If possible, you should take it. See if the rig can get up to the volumes you think you'll need. How does it sound? Is the amp peaking or running out of gas? Are the speakers complaining? Is the tone what you want? Etc.
  8. CapnSev


    Aug 19, 2006
    Coeur d'Alene
    You will be fine with either of those setups. I would go the 700RB for the quality/extra features if you have the money. It won't blow either of those cabs, let alone the two of them together.
  9. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    The farting-out situation is based on the cabinet design. Even cabs of the same style from different companies can behave differently: don't assume that everyone builds them identically.

    If it farts out, turn down volume or bottom end, otherwise you risk damaging the speakers.

    As Bill said, try the setup. If you can make the cones fart, you have all the power you need.
  10. jpowell


    Sep 15, 2008
    Thanks so far. I am leaning strongly towards the GK 700 head. Could I get some input on the speakers I mentioned in my first post? That would be great. Thanks again.
  11. georgestrings

    georgestrings Banned

    Nov 5, 2005

    Agree on all of the above, and would just add:

    Speakers that are driven hard on a frequent basis do not last as long as speakers that are "moderately" driven - in my experience, if a rig or PA isn't loud enough, or marginally so - adding speakers is typically a better solution and throwing watts at the problem...

    - georgestrings

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