Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

impedance

Discussion in 'Amps and Cabs [BG]' started by mclaud, Nov 8, 2001.


  1. mclaud

    mclaud Guest

    Oct 25, 2000
    portugal, lisbon
    hi!

    this may seem stupid, but here comes.

    what are the diferences between a 4 ohms cab and a 8 ohms cab with the same power.

    if i have a 4 ohms amp with 600 watts (mono), what would be the best choice, 2 cabs at 8 ohms or 2 cabs at 4 ohms and what would be the the impedance in both cases and why?

    one more thing, if you want to plat loud what would be best, a good power handling or a good sensitivity. for example, between a cab with 400 watts rms with 100 dB/1 W/1 m and a cad with 350 watts rms with 105 db/1 W/1 m what would play loud and why.


    tanks!
     
  2. downstairs

    downstairs

    May 13, 2001
    Pasadena, MD
    if you have 2 cabs of 8 ohms, it makes 4 ohms, if you have 2 4 ohm cabinets it makes 2 ohms, get the 2 8 ohm cabs just so you don't fry out your amp.
     
  3. ...a cab with 400 watts rms with 100 dB/1 W/1 m and a cad with 350 watts rms with 105 db/1 W/1

    The second cab is a better choice. The cab with 350 watts and 105db @ 1w has a five db advantage that the other cab can't match even with it's 50 extra watts of power handling capacity.
     
  4. Steven Green

    Steven Green

    Jul 25, 2001
    Pacific NW
    If I'm not mistaken, if you have a cab that have +5 dB more than the other, it will be nearly 4X as loud (I think+3 dB doubles volume).

    So, if you are giving specific examples that apply to you, go for the cab with the better sensitivity rating and only (1) 4-ohm, or (2) 8-ohm cabs giving you a total 4-ohm load, which would match the 4-ohm head in your example.
     
  5. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    No!

    +10dB is double volume

    To get a boost of +3dB you need twice the power, people confuse that often.
     
  6. One more nit to pick: +10 dB is perceived as double volume.

    In fact it's ten times the sound pressure and power, but we perceive it as approximately twice as loud. Damn human hearing ;)
     
  7. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Thanks master Joris ;)
     
  8. MikeyD

    MikeyD

    Sep 9, 2000
    Human hearing is actually pretty amazing. Probably this same phenomenon is why this particular "instrument" has a dynamic range of around 10^12 (one trillion) in pressure-squared (measured logarithmically with SPL, in decibels). That is a huge range - I can't think of many devices that have that kind of operating range.
    - Mike
     
  9. Yeah, the human hearing has yet to be equalled by equipment those humans build.
     
  10. MikeyD

    MikeyD

    Sep 9, 2000
    Puny humans! ;)
    - Mike
     
  11. Aren't we but dust?

    Oh well as long as I can play bass with my inferior equipment :eek:;)