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Ohms Question

Discussion in 'Amps [BG]' started by Delehanty1996, Dec 6, 2013.


  1. Delehanty1996

    Delehanty1996

    Aug 8, 2013
    I'm thinking about buy a new head/cab figuration and the ohms are seriously pissing me off. I see a 500 watts head at 4 ohms and a 400 watt cab at 8 ohms... will these two work together? What is the suggested wattage for a head that loud?
     
  2. B-string

    B-string Gold Supporting Member

    It will work fine at reduced power. The lower the number in ohms the less it impedes current flow (harder load for an amp to drive). Add a second like cab latter if you need more volume. The added speakers as well as the "slight" bump in amp power output will be attained by twice the speakers and 4 ohm operation on the amp head.
    Amps OUTPUT watts, cabs are rated for "safe" INPUT from an amp.
     
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  4. Troph

    Troph Supporting Member

    Apr 14, 2011
    Kirkland, WA
    Double negatives for the win. :)
     
  5. Delehanty1996

    Delehanty1996

    Aug 8, 2013
    How would I reduce power?
     
  6. oboylebass

    oboylebass

    Oct 31, 2006
    AMERICA
    No, you should not use an 8 ohm cabinet combined with a 4 ohm cabinet. Your best bet is to use two 8 ohm cabinets, which will yield a nominal impedance of 4 ohms. You have to be careful about mismatching the impedance...this can cause damage to the head (amp).
     
  7. BassCliff

    BassCliff

    May 17, 2012
    So. Cal.
    Hi,

    At the top of this section FYI:
    Sticky: AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

    The 500 watt figure is into a 4 ohm load. The amp will also work with an 8 ohm load but have a little less total output power. If you take two 8 ohm cabinets and daisy chain them together you will end up with a 4 ohm load total which will take advantage of the full power of the 500 watt amplifier.

    The higher load on the amps reduce the power output and lets the amp run cooler, and vice-versa.


    Thank you for your indulgence,

    BassCliffa
     
  8. It is a 4 ohm minimum head combined with an 8 ohm cab - no problem.

    Matching impedance is important with tube amps (or any other amp with an output tranny).

    Solid State heads only require you to stay above the minimum rating.
     
  9. B-string

    B-string Gold Supporting Member

    An 8 ohm load (cab) does not load the amp as heavy so not as much power is produced by the amp. It's automatic with 99% of the SS output amps. Nothing for you to do, it is just how it works.
     
  10. BassCliff

    BassCliff

    May 17, 2012
    So. Cal.
    Hi,

    As I read the post, the question was not about mixing different impedance cabs. It was about using an amp (500w output into 4 ohms) with a single cab (8 ohm, 400w). In a word, yes, this will work just fine but it's possible to fry your speakers if you turn it up way too loud. But I guess 500w into 4 ohms would be about 400 watts into 8 ohms. So you're cool.

    Forgive me. I was told there would be no math today. ;)


    Thank you for your indulgence,

    BassCliff
     
  11. orangejulius3

    orangejulius3 Supporting Member

    May 6, 2013
    La Habra CA
    Delehanty1996

    What are the 2 items in question?
    We can probably help you.

    Also, are you looking for a certain volume or a certain tone?
     
  12. Delehanty1996

    Delehanty1996

    Aug 8, 2013
    The 2 items were:
    Hartke LH500 (Head)
    Hartke 410XL (Cab)
     
  13. Kmonk

    Kmonk

    Oct 18, 2012
    South Shore, Massachusetts
    Disclosures:
    Endorsing Artist: Fender, Spector, Ampeg, Curt Mangan Strings
    "You" do not reduce power. The power will be reduced due to the higher impedance (ohms rating) of the cab. If you run an 8 ohm cab, your head will most likely run somewhere around 250 watts. If you run a 4 ohm cab, your head will operate at 500 watts.
     
  14. Have you read the sticky, linked for you by Cliff up there ^^^^ ?
     



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