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Crossover- Total Cab Ohm question

Discussion in 'Amps and Cabs [BG]' started by Cúl-Báire, May 28, 2005.


  1. Howdy Howdy...

    Well I missed out n my GK RB 800- although I will be keeping my eyes peeled for another one if it should come up someday. Or Buy an Ashdown AMB 500 :bassist: ...

    Anyways I have a question regarding a hamemade cabinet OHm's- This project is in the works- and I'm not quiet sure weather I will go a full range or just lowend yet.


    So I was building a 1x12" cabinet, using an 8ohm Delta 12LF- I have also concidered purchasing another one and building a 2x12" instead but I have a few questions regarding the Ohmage of the cabs.

    Now I have a feeling the 2x12" wont quiet have enough treble to it so I would like to install a 6" or 8" midrange speaker however this is what confuses me.

    So We have one 12" already rated at 8ohms.
    One Propsed 12" rated at 8 Ohms.
    This would make a 4 ohm cabinet, pure and simple, now the bit that confuses me...

    The Mid range speaker is also rated at 8ohm's - so far this gives us like 2.6ohm or there there abouts... And according to Emenance it's crosovers are also rated at 8ohms.


    Question of the day: Does the Crossover and the Midrange speaker which will be run through the crossover add to total impedance? And If so- how can I wire it up so the impedance will be either 4ohm, or 8ohm? (my Amp has a 4ohm minimum, and future amps probably will too)

    Thanx
    -Cul
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The crossover's listed impedance refers to the impedance of the drivers it must be used with. If you use different impedance drivers the crossover frequency will be shifted.

    For electric bass a Delta 12LF should be loaded into about a 3 to 4 cu ft cabinet. Two require 6 to 8 cubic feet for best results. Jammimg two woofers into a box only large enough for one won't allow either to work properly, so be quite sure of what you're really trying to do before you do it.

    The crossover maintains the correct impedance load with multiple drivers.

    If you decide on a 2x12 (4ohm load) along with an 8 ohm midrange driver chances are you'll have to scratch build your own crossover to get the component values correct.

    Before embarking on DIY it's a good idea to read at least one book on the subject. Vance Dickason and David Weems both have excellent books, and every serious musician should have one of them, if only to understand how the tools that you make your living with work. Then if you decide DIY makes sense for you you've got a good reference to guide you along the way.
     
  3. 44me

    44me

    Jun 17, 2002
    Bedford, NH USA
    Good advice from Bill – One other thing you can do if the mid driver has higher sensitivity than the 12’s (3dB ideally), is just put an 8 ohm resistor in parallel with it. Then a crossover for 4 ohm drivers will work as designed.

    - John
     

  4. Hi Bill,

    Thanx for your help- I am still debating the 1x12" or 2x12" question... However the internal cabinet volume for the 2x12" will be around 185l (6.5ft cubed), seems to give a pretty good responce curve on winSID.

    I have read many online articals about building bass cabs- books and stuff on the subject are generally pretty hard to find in Australia- But the online articals have given me a good idea of what to expect and how to go about it.

    Thanx
    -Aaron
     
  5. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Jaycar Electronics always have the Vance Dickason book in stock.
     
  6. Cool... I shall have to go buy a copy then :)