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Watts vs Ohms in Ampeg b2

Discussion in 'Amps and Cabs [BG]' started by a00nick, Dec 29, 2005.

  1. a00nick


    Dec 28, 2005
    Chapel Hill, NC
    So for chirstmas I got an Ampeg b2 used for $300 at my local music store. I'm now thinking of what cabinet to get but im a little confused about how much power I need in my speaker. The B2 is rated at 350 watts at 4 ohms and 200 watts at 8 ohms. Now from what I know about electronics, I figure ohms are resistance, so 350 watts at 4 ohms could go a lot louder than an 8 ohm speaker with 200 watts. That doesnt really make sence though because then why wouldnt everyone get 4 ohm speakers. Sorry if this doesnt make much sence, im having trouble wording it. Basicly, do I want to get a 4 ohm speaker cabinet or an 8 ohm speaker to get the loudest volume possible. Thanks

  2. fatsobasso


    Dec 24, 2005
    Ormond florida
    Most people like to mix and match bass cabs,so if there head is
    lowest 4ohms and 2 speaker outs,then they usually get 2 8 ohm cabs,4-10 1-15 ect.. 8+8=4ohms in parallel.
  3. ras1983


    Dec 28, 2004
    Sydney, Australia
    if you see yourself as a single cab guy(or gal) then you would run a single 4 ohm cab to get maximum power.

    if you like to have two different (or two of the same) cabs for tonal or speaker coverage reasons then you would use two 8 ohm cabs.
  4. a00nick


    Dec 28, 2005
    Chapel Hill, NC
    Ok, i was planning on getting 2 cabinets so I should get 2 8 ohm ones to maximize power outage. I was also wondering, how do you find the total power when using 2 speakers. If I was putting out 350 watts, and i had 2 200 watt speakers, would it just split the power between the 2 evenly? Thanks

  5. Thor

    Thor Moderator Staff Member Gold Supporting Member

    Nick, that is correct.

    If you have them hooked up together in parallel or
    'daisy chained together' like this

    [amp] -> [cab] -> [cab] and each cab is rated as an 8
    ohm impedance load, the cabs each get 50% of the output.

    The 2 cabs linked together present a 4 ohm total load to the amp.

    Also read the ohm thread in FAQ for more info. That is a
    helpful thread.
  6. Herman


    Dec 25, 2005
    Lynchburg, VA
    How loud your speaker cab(s) will be depend more on their sensitivity then on their resistance (4 ohms or 8 ohms). A speaker cab's sensitivity tells you how loud (in dB SPL) it will be given a 1 watt input - SPL=Sound Pressure Level. For every 3dB of sensitivity (up or down), you'd need 1/2 or 2X the power (watts) into the speaker to get the same loudness level. That means that if you had one cab that was 4 ohms and only 100dBSPL sens and another that was 8 ohms and 103dBSPL, you'd need twice the power into the first one to get the same loudness. With your amp, you'd get about the same loudness out of each since you'd be able to put almost twice the power into the 4 ohm cab. But, if there were greater difference between the two cabs (say 6dB), the 8 ohm cab would be louder at its max power than the 4 ohm cab. So whether you're looking at a 4 or 8 ohm cab, make sure you check its sensitivity.