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I need help with ohms and watts

Discussion in 'Amps and Cabs [BG]' started by xax712, Mar 10, 2002.


  1. xax712

    xax712

    Dec 25, 2001
    Northwest Arkansas
    OK I'm looking at putting two cabs together that are both 400watts@8 ohms. How many watts is that at 4 ohms...it does go to 4 ohms right?
    OK and my next wuestion is what heads would be good for such a situation? I'm trying to go fairly cheap, but just want to know what kind of head to look for mainly and what type of output to look for to power this.
    Thanks,
    Brad
     
  2. If you wire the cabs in parallel, you will halve the impedance to 4 ohms, but double the power handling capability. So, your two 400 watt, 8 ohm cabs will become 800 watts at 4 ohms. Makle sure your head can source the extra power at 4 ohms. If she's only rated for 8 ohms, don't do it.

    If you wire your cabs in series, you will end up with 400 watts rating still, at 16 ohms. If you have a tube head, good chance you'll have an internal (or external) jumper to go 16 ohms.

    :)
     
  3. xax712

    xax712

    Dec 25, 2001
    Northwest Arkansas
    How do you wire in parallel??? And give me some name of good heads to use for this. What about the GK 800rb or the SWR bass 750???? Help!!!!!!!!! I'm not very knowledgeable in this area.
     
  4. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    The 800RB's a great head, but the problem is that GK's quality control is about the same as a lemon factory... "Yes, it's a lemon, we'll let it through!"

    GK's been known to put out plenty of lemons...
    I'm fond of the 800RB tone-wise, but it's main problem is the fail rate. :(

    I would've bought one if they wouldn't have such a damned high fail rate.
     
  5. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Oh, yeah... "Wiring in Parallel" would be plugging your cabs into the "parallel out" jack on your head. :)
     
  6. Hategear

    Hategear Workin' hard at hardly workin'.

    Apr 6, 2001
    Appleton, Swissconsin
    Am I crazy, or is there a thread like this every week?
     
  7. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania

    You're crazy. ;) :D


    Actually, no... If the rhythm's still going, it's the same thread each week just being droned.

    It's alright though... Someone needs to inform.
    If it weren't for threads like these a lot of people would be playing using instrument cables on their cab/heads. :D
     
  8. xax712

    xax712

    Dec 25, 2001
    Northwest Arkansas
    What's the difference between using instrument cable and speaker cable other than sheiding and why not use them on your cab/head? Sorry I'm so retarded about this it's my first venture outside of combos. And what's a good list of heads that can push 800 watts @ 4 ohms???
     
  9. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    You don't 'need' an 800W head. You can use any head you like, you just won't be able to drive the cabs to their full potential if the head has less power.

    but attention: if you use a head which is rated less than 800W you still have to be careful with the master volume! when you drive your head into clipping this can blow the speakers. We had many threads on this topic please do a search if you need more details.

    you can also use a head rated higher than 800W as long as you are careful with the master volume.

    IMHO it 'makes sense' to look at heads rated between 400W and 1000W, personally I would go for 800W to 1000W.

    Most brands offer heads in that range, it's really a question of what you like and what you can afford.

    Using a preamp and a (PA) power amp would be another possibility.

    Matthias
     
  10. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    As far as I know the shielding of an instrument cable has the effect of a capacitor, this can cause problems at higher power levels, you could even blow the amp.
    But I used an instrument cable to connect a speaker to a 50W amp for years without problems (I didn't know any better then)

    Matthias
     
  11. bben

    bben

    Feb 28, 2002
    Santa Fe, NM
    Hookup cable and speaker cable are two different things.

    Hookup cable has the live wire in the middle and the ground wire woven as a shield surrounding the live wire. This keeps it from picking up hum and other interference. It is not designed to conduct heavy loads.

    Speaker wire has two stout conductors in it, designed to carry heavy loads. The conductors are side by side, not arranged "coaxially" like signal cable.