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!  

Cabs that switch impedance?

Discussion in 'Amps and Cabs [BG]' started by RumbleMan3, Dec 20, 2019.


  1. RumbleMan3

    RumbleMan3

    Apr 14, 2018
    Australia
    Talking about cabs that are able to swap between 8 ohm and 4 ohm, via a button or switch or something. Does such a thing exist? If so can someone give me some names cos I’d love to take advantage of this technology.

    Imagine, u have 1 head, and 1 cab, that u can use for both practice, jamming and gigging situations. Set up in your bedroom? Switch it to 8 ohms to get the lower power.
    Got a gig? Have no fear, swap it to 4 ohms for the extra power.

    Seriously I want this.
     
    dbsfgyd1 likes this.
  2. flojob

    flojob Gold Supporting Member

    Oct 15, 2011
    I think some audiokenesis cabs do this. I think a one of the hartkey cabs does also
     
  3. RumbleMan3

    RumbleMan3

    Apr 14, 2018
    Australia
    Do u remember model names?
     
  4. ahc

    ahc

    Jul 31, 2009
    No. Virginia
    The Barefaced Two10s and a Hartke 112 (HX or HD or maybe both, don't remember) can switch impedance.
     
    Helix, monsterthompson and RumbleMan3 like this.
  5. brocket

    brocket

    Sep 12, 2017
    Coastal NC
    Clutchcargo, BOOG, stigbeve and 2 others like this.
  6. Jim Bergantino

    Jim Bergantino Commercial User

    Feb 27, 2003
    Bergantino Audio Systems
    No free lunches here and could even be a net negative if it involves using dual voice coil woofers, which is usually does.
     
    Last edited: Dec 20, 2019
  7. Not as good as it sounds.
    Sucking all the watts by switching to 4 ohms does not give enough to make it worth the compromises made to achieve this ability, or fried driver.

    Just get a good cab and use the volume knob to create what is appropriate for the setting.
     
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Absolutely (like most things in life, right?)!!!

    The only exception to this rule (that I am aware of) are the dual motor differential drive speakers by JBL, but they are stacked axially within a tight gap clearance.
     
  9. Jim Bergantino

    Jim Bergantino Commercial User

    Feb 27, 2003
    Bergantino Audio Systems
    Not familiar with those but a standard DVC woofer was never meant for impedance switching, but for summing two channels in subwoofers. What happens with impedance switching is the designer has to decide what to do with the unused coil when switching impedances. If it is left open if changes the q of the speaker because there is now less damping due to weakening the motor. Plus you have the added mass of an unused coil which reduces the sensitivity of the speaker. If you short it, you maintain the q/damping of the system but now you have a motor (active coil driven by amp) driving a generator (shorted coil). Us old dogs remember what this is when we had to adjust the idle of our cars with the lights on before the days of computer systems in cars. This also reduces the sensitivity of the speaker. I wish this industry would just move on from this and realize any designer utilizing this approach would be laughed out of the PA industry!

    Summing up, the only free lunches I ever got were at mom’s House. Oh yeah those Stuff pepper sandwiches, eggplant parm sandwiches, and of course meatball sandwiches! I don’t know why all this tech talk is making me so hungry!;-)
     
    Last edited: Dec 20, 2019
  10. Zbysek

    Zbysek

    Mar 23, 2017
    Czech Republic
    Epifani D.I.S.T. line has this feature...
     
    db59, DMoney4, baxter_x and 1 other person like this.
  11. seamonkey

    seamonkey

    Aug 6, 2004
    Here's hoping powered cabs catch on like they have in the PA, FOH side of music.
    More pre-amps please.
     
    agedhorse likes this.
  12. 707GK

    707GK

    Jun 13, 2013
    Northern California
    Would an attenuator achieve the same desired outcome?
     
  13. fjbass78

    fjbass78

    Jun 21, 2007
    Indiana
    My Accugroove El Whappo Jr has that ability to switch from 4 to 8 ohms, but i have never used it. I think I remember a discussion here on TalkBass specifically about the Accugroove cabinets that "claim" to be able to switch ohms. Most people thought it was a gimmick and that their claim was really not true/accurate. I use it as a stand alone cab anyway.
     
  14. CyberSnyder

    CyberSnyder Gold Supporting Member

    Jun 19, 2003
    Maryland
    I Endorse Alien Audio Basses
    Yeah, that ended badly when revealed that it was effectively smoke and mirrors.
     
    packhowitzer and fjbass78 like this.
  15. CyberSnyder

    CyberSnyder Gold Supporting Member

    Jun 19, 2003
    Maryland
    I Endorse Alien Audio Basses
    I think this is eventual - if we even need cabs. Clean stages may take over more than a powered cab. Your powered cab may just be for home use and when there isn't a PA.
     
    seamonkey likes this.
  16. mmbongo

    mmbongo Five Time World Champion Supporting Member

    Aug 5, 2009
    Carolinas
    It would, and his amp should have one built in as a knob labeled ‘volume’.
     
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Here's a drawing of JBL's differential drive (common magnet, dual motor) technology:

    JBL_7series_03-S7zpSDuWC9lzf_Pyc8D1BFDgNeGPbgEX.jpg
     
  18. Eddie LeBlanc

    Eddie LeBlanc

    Oct 26, 2014
    Beaumont, Texas
    None
    Thanks for the great info Jim.......
    Yeah I remember tune ups with lights on. And damn, you got me hungry now, too. Merry Christmas.
     
    Jim Bergantino likes this.
  19. As already stated, it does work the way you think it will.
     
  20. Jim Bergantino

    Jim Bergantino Commercial User

    Feb 27, 2003
    Bergantino Audio Systems
    I vaguely remember that. Were they trying to offset non linearities or just make sure these non linearities were symmetrical throughout the coil’s travel.or just increase motor strength with the extra coil.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.