1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

CAB QUESTION 4 or 8 Ohms? Why? Thanx!

Discussion in 'Amps and Cabs [BG]' started by old grouch, Jan 15, 2006.

  1. old grouch

    old grouch "Old Fool? Ya don't get old, bein' no fool!"

    Ampeg or Mesa or Ashdown? 4 OHMS, OR 8 OHMS? Why-what is the end product difference?

    In 4 OHM selections...
    This is the ampeg I'm peepin'! NOTE-The Ashdown is more power, and 12 pounds lighter?!
    Ampeg BSE-410HLF 4x10" Bass Cabinet Features:

    * 4 - 10" woofers
    * High-frequency horn
    * 400W RMS, 800W program power handling
    * Front-shelf port for thunderous low-end response

    Ampeg BSE-410HLF 4x10" Bass Cabinet Specifications:

    * Impedance: 4 ohms
    * Crossover frequency: 4kHz
    * Frequency response: 50Hz-18kHz
    * 400W RMS, 800W program power handling
    * Sensitivity: 99dB
    * 22-3/4"W x 25-3/4"H x 17-1/2"D
    * 91 lbs.


    Ashdown ABM 414T 4X10" Bass Speaker Cabinet with Tweeter Features:

    * 600W continuous, 900W program power handling
    * 4 - 10" BlueLine speakers
    * High-frequency tweeter
    * High-grade birch plywood construction
    * Buffalo leather cloth covering
    * Chromed metal corners
    * Metal handles

    Ashdown ABM 414T 4X10" Bass Speaker Cabinet with Tweeter Specifications:

    * Power handling: 600W continuous, 900W program
    * 4-ohm impedance
    * Frequency Response: 70Hz-20kHz
    * SPL: 103dB 1W@1m
    * 24"W x 26"H x 16-1/2"D
    * 79 lbs.
  2. Alvaro Martín Gómez A.

    Alvaro Martín Gómez A. TalkBass' resident Bongo + cowbell player

    The Ohm is the measurement unit for impedance. Basically, the less the impedance, the more the power your amp will deliver.

    Amps' power rating depends on the total impedance of the speakers connected to it. You must know the minimal impedance that your amp can handle. In your amp's manual you'll see something like "power @ xxOhms: xxWatts. Power @ yyOhms: yyWatts". The higher the impedance, the less the power you'll get from your amp.

    So the question may be: If 4 Ohms give me more power, why should I consider buying an 8 Ohm cab? Because perhaps you'd like to add another cabinet to your head. Normally, amps have two speaker outputs, so you can connect two cabinets. When you do that, both cabinets are conected in parallel mode (as opposed to series). In such conditions, and assuming that both cabinets have the same impedance (say 8 ohm each), the total impedance equals half the impedance of each cabinet. So it means that if you connect two 8 Ohm cabinets to your head (I mean, the amp), total impedance will be 4 Ohms. Most amps go as low as that. If you connect two 4 Ohm cabinets, total impedance will be 2 Ohms, which will be dangerous for your amp if it doesn't support that minimal impedance (Mine does).

    (Just in case: If you ever want to connect an 8 Ohm cab and a 4 Ohm cab to an amp, total impedance will be 2.67 Ohms.)

    A common misconception (at least among many people I know where I live) is that the "Watts" specs of a cabinet determine the power you'll have. What brings the power is the amp, not the cab. For cabs, the "Watts" specs mean how much power they can tolerate, so before buying a cab, you must perfectly know your amp's power ratings.

    Hope this helps.
  3. chaosMK


    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    I've gone through all kinds of 8-ohm cabs. I prefer 8-ohm cabs because I like to use two cabs on stage for a more impressive looking setup. About 80% of the venues in this town don't have PA support for bass so it works out well for me volumewise.

    4-ohm cabs are harder to pair up unless you have a head capable of a 2-ohm load. These are usually the higher end and more expensive amps.

    Also, I would be careful about the wattage ratings of different cabs. I find that perceived volume is loosely linked to the power handling rating. I would pick a cab that has the right push to it for the style of music you are playing. For example, the SWR Goliath III 4x10 I used for a while just had the wrong tonal character for cutting through in a rock/metal band. I ended up replacing it with an Avatar 2x10. Actually, you might want to check out Avatar speakers. They are top quality for the price.