Ugh..having trouble figuring out what OHM my subs are in: 2 single 4ohm subs.

Discussion in 'OT Technology' started by StealthMode, Jan 21, 2005.

  1. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    I have two single 4ohm subs running off the bridged rear channel of a Rockford 800a4.
    Each sub is wired to the bridged channel. (basically the positives are twisted together and plugged in, same with the negatives, on the amp end)

    Kind of hard to explain, but I think you get what I mean.. What OHM load are my subs wired into by chance? This was how they were wired when I bought them from my buddy, and they still work fine, so ... any ideas?
     
  2. Afterimage

    Afterimage Guest

    if the positives and negatives are wired together then that's what's called parallel. 2 drivers of 4 ohms each wired in parallel = 2 ohms.
     
  3. chewymang

    chewymang New Member

    Joined:
    May 2, 2004
    Messages:
    174
    Likes Received:
    0
    Location:
    cali
    briged to the amp at 2 ohms, but the amp is seeing 1 ohm
     
  4. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    ...So, I'm running my subs at 1ohm? :eek3: I think I am a little confused..

    I was reading the manual online from Rockford, and it seems she's onyl stable down to a bridged 4ohm load... It doesn't say how much power she puts out at 2ohms bridged.. But she's been running real strong with no problems since I got it, and my buddy ran it for a couple years without any problems. :noes:
     
  5. veonake

    veonake OnT poster, OT lurker

    Joined:
    Apr 11, 2004
    Messages:
    4,235
    Likes Received:
    0
    Location:
    NYC
    Why is the amp seeing 1 ohm?
     
  6. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    Thats what I am running....I always thought the amp pushed what the subs dictated.
     
  7. Afterimage

    Afterimage Guest

    Because when you bridge a pair of amp channels to make a mono channel each half is seeing it as half of the load. Example: you have a 2 channel amp that can drive each channel at a 2 ohm load. That means you should be able to drive a 2 ohm woofer off of each channel. Now if you took that same amp and bridged both channels to make a monoblock one channel becomes the positive side and the other channels becomes the negative. In this mode you'd only be able to drive a 4 ohm load because each half of the amp is seeing a 2 ohm load.

    I'm sure somebody can describe it better. I know why it works, just not any good at describing it. :o
     
  8. DaddyThirdLeg

    DaddyThirdLeg SMASH puny humans

    Joined:
    Oct 9, 2001
    Messages:
    3,258
    Likes Received:
    0
    Location:
    Canada
    2 ohms mono = 1 ohm stereo
    The older rockford amps are much better then the newer ones, just make sure it doesn't heat up too much and you should be alright.
     
  9. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    Alright. She's been runnin strong, but I'll keep an eye on it. I have it running in a mono load right now. If I can find my digi cam back I will post a pic of it.. Thanks. :)
     
  10. 04

    04 Guest

    Running an amplifier in bridged mode does not decrease the impedence of the speakers. The voltage rails are 2 times as high (since one channel drives the negative portion of the waveform, and the other channel drives the positive). You will reach the current limitations of the amplifier much sooner in bridged mode than in stereo because of this, when you have the same impedence for both configurations.

    StealthMode, I wouldnt reccomend running your amplifier in that configuration. I'm pretty sure that Rockford's amplifiers are only rated for 4ohm mono operation, and the way you have it now is 2 ohm mono operation. I would suggest wiring the woofers in series for an 8 ohm load. If you don't run the amplifier hard though, it probably wont be an issue, however.
     
  11. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    Ok, thats what I thought.. The online manuals don't have anything on running the amp in a bridged 2ohm load, just 4.

    Whats the worst that could happen? Won't it just go into protect mode or something before it blows/fries?
     
  12. DaddyThirdLeg

    DaddyThirdLeg SMASH puny humans

    Joined:
    Oct 9, 2001
    Messages:
    3,258
    Likes Received:
    0
    Location:
    Canada
    it should go into protection mode before it fries but that doesn't mean it will, do a search on some audio forums you'll see you aren't the only one running the older RF stuff at below their rated impendace, but you'll also find stories of people whose amps suddenly stop working after 3 months or a year, it's up to you how you wanna do it, and at 8 ohms mono your subs will be getting around 150 watts each.
     
  13. twistid

    twistid Banged By Super Models Moderator

    Joined:
    Jul 15, 2001
    Messages:
    40,727
    Likes Received:
    81
    Location:
    The Kansass/Oklahomo Border
    though rockford's are pretty bullet proof only the 04/05 power series amps are 2ohm mono/1ohm stereo... but not the older amps. not that it's under warranty or anything, but rockford would consider it as abuse if it went in for service. i just sent in a 351m(the first one to come back out of the couple hundred we sold.) that a kid did basically the same thing with, but did not take the hint when it kept shutting down on him... until it finally stopped playing altogether. luckly it was still under warranty, and rockford is pretty mellow with the warrantied stuff.
     
  14. StealthMode

    StealthMode Active Member

    Joined:
    Mar 12, 2003
    Messages:
    3,763
    Likes Received:
    0
    Location:
    MN
    Yea...thats what I was afraid of... 150watts...might as well buy a different amp :p
     

Share This Page