8 ohm - 4 ohm

Discussion in 'DIY Discussion' started by Danhoyland, Oct 8, 2009.

  1. Danhoyland

    Danhoyland

    Joined:
    Oct 2, 2009
    Messages:
    1
    Likes Received:
    0
    Hi guys. I wonder if you can help me. I have a pair of subs which are rated 650w RMS @ 8 ohms. I have an amp which is 450w @ 8ohm and 650w @ 4 ohm. Is there some way I can lower the resistance of the subs to get them to be a 4 ohm load? Is it just a case of wiring an 8 ohm resister in parallel with each sub? Help will be really appreciated. :)
     
    Danhoyland, Oct 8, 2009
    #1
    1. Advertisements

  2. Danhoyland

    themadhippy seen it done it smokin it

    Joined:
    Jun 19, 2003
    Messages:
    1,118
    Likes Received:
    1
    Location:
    by the cross
    yea just chuck in an 8 ohm resistor,make sure its rated for 450W as its going to get rather warm .Best give the amp an easy life and keep with 8 ohms,how much sub do you need any way?
     
    themadhippy, Oct 8, 2009
    #2
    1. Advertisements

  3. Danhoyland

    felix part-time Horta

    Joined:
    Dec 13, 2003
    Messages:
    757
    Likes Received:
    1
    Location:
    dead
    That'll gain you nothing - you'll be dropping about 320watts into the sub and 320watts as heat in the resistor - a complete waste.

    Just drive the sub as an 8-ohm load. The amp will do a better job, and apply the full 450w rating to the sub.
     
    felix, Oct 8, 2009
    #3
  4. Danhoyland

    granville

    Joined:
    Feb 11, 2006
    Messages:
    138
    Likes Received:
    0
    Location:
    The edge of reality
    Purchase another two subs, and connect each pair in parallel.
    sorted.
     
    granville, Oct 8, 2009
    #4
  5. Danhoyland

    robM

    Joined:
    Feb 6, 2004
    Messages:
    347
    Likes Received:
    0
    themadhippy
    Where on earth did you get this information from:confused:
     
    robM, Oct 10, 2009
    #5
  6. Danhoyland

    themadhippy seen it done it smokin it

    Joined:
    Jun 19, 2003
    Messages:
    1,118
    Likes Received:
    1
    Location:
    by the cross
    if you meen

    ohms law innit,2 8 ohm resitors in parralel gives 4 ohm,half the power to the driver,half the power to the resistor,cant be bothered with the maths but its going to get warm

    or do you meen
    more ohms law im affraid
    or
    If 2-3kw and a pair of twin 18" can produce bowel-loosening bass in a large venue then realisticly how much sub do you need in a domestic enviroment?
     
    themadhippy, Oct 11, 2009
    #6
  7. Danhoyland

    sq225917 Exposer of Foo

    Joined:
    Jan 11, 2007
    Messages:
    1,514
    Likes Received:
    0
    This is the best advice thread I've ever read...

    Add an 8ohm resistor- class.!
     
    sq225917, Oct 11, 2009
    #7
  8. Danhoyland

    robM

    Joined:
    Feb 6, 2004
    Messages:
    347
    Likes Received:
    0
    I think there should be a list of who can and who shouldn't give advise.

    themadhippy - the 8,6 or 4 ohm figure on the back of a loudspeaker is the mean impedance figure and not a pure resistance figure.
    Chucking a resistor somewhere on the rear terminal will do nothing but screw up the sound!
    Even so, please dismiss that last statement as that might temp you into designing a pair of loudspeakers:D
     
    robM, Oct 11, 2009
    #8
  9. Danhoyland

    Dev Moderator

    Joined:
    Jun 19, 2003
    Messages:
    5,764
    Likes Received:
    3
    Location:
    Ilford, Essex, UK
    I'd personally take this advice.
     
    Dev, Oct 11, 2009
    #9
  10. Danhoyland

    themadhippy seen it done it smokin it

    Joined:
    Jun 19, 2003
    Messages:
    1,118
    Likes Received:
    1
    Location:
    by the cross
    I have been toying with getting a pair of beymar 15" coaxials,but the 3 way 4 foot "coffins" i build several years back still sound pretty good,their even better when run semi active via the home brewed crossover and the valve amps,but i just aint got the space any more to set it all up, also a sever case of the travel bug keeps eating funds set aside for other things.
     
    themadhippy, Oct 12, 2009
    #10
  11. Danhoyland

    robM

    Joined:
    Feb 6, 2004
    Messages:
    347
    Likes Received:
    0
    I built a pair of 15" cabs years ago...it was great fun doing it and they sounded awful in 'hifi' terms but did the job...
     
    robM, Oct 12, 2009
    #11
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.