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deeper impedence question

Discussion in 'Amps and Cabs [BG]' started by Snarf, Mar 20, 2005.


  1. Snarf

    Snarf

    Jan 23, 2005
    New York, NY
    Hypothetical setup:

    1 head of your choice, 4 ohms
    1 210 cab, 8 ohms
    1 212 cab, 8 ohms

    So there you have the amp delivering its full power into 4 ohms. However, most heads don't go to 2.6 or lower, so adding another cab isn't practically possible. So, you couldn't add, say, a 410 and 115.

    How would you accomplish running a 3-4 cabinet setup? My initial hypothesis is get a separate preamp, and for 3 8-ohm cabs have a 2 ohm power amp. But what about 4 cabs? Are we talking 2 power amps? How would you connect these?

    And no, I don't have the funds/transportation/strength for such a rig. This is just for my curiosity/pipe dreams.
     
  2. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    There are a lot of ways to accomplish this, but if you wanted similar tone coming from everything, you could do a preamp/poweramp setup. Most separate power amps can handle loads like you are thinking of.
     
  3. You could use a SpeakerMate to do this. It's basically a handy little box that is pre-wired for series/parallel speaker configurations. For example, my full stack is two Aguilar GS112s and a modded Yorkville 1x15. All 8 ohm cabs. The SpeakerMate allows me to run the Aggies in series with each other, parallel with the 1x15. The total load works out to about 5.3 ohms. Granted, the slight drop in wattage due to the impedence increase is more than worth it for the increased speaker area. Plus, the SpeakerMate only weighs about 1lbs. I use the Model Six, which only went for about $100 canadian.
     
  4. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    One of those speaker mates can be made with 3 speaker jacks (whatever they may be) and a box to mount them in, then just a bit of soldering. Not worth 100 bucks IF you know how to solder, but if not, they are a good idea in this case.
     
  5. Definately something that you can custom wire on your own. I used to have a custom wiring setup, but I opted for the SpeakerMate because it's SUPER rugged. Plus, with the switching jacks, I can mix and max up to 6 cabs on the fly.
     
  6. Trevorus

    Trevorus

    Oct 18, 2002
    Urbana, IL
    Well that's cool. That's a nice idea.
     
  7. Man that thing is cool!..... I have a 215XL that is 4 ohms and was wondering how I was going to add a 410XL (8 ohms) down the road. would the Model four work for me? I just want to add the one cab. What would the total load be in that situation? I'm no electrician so $89.00 would be a cool investment if it would work in my situation........Thanx
     
  8. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    take the price of the switch thing and then add the speaker cable costs....

    I needed to run 2 4ohm cabs in series to make an 8ohm load.... for a custom cable to fit my exact needs with 2 speakon and 1 1/4" jacks made from 12 guage wire cost me under $50 shipped. I also got a 1/4" to speakon adaptor to use my pre/power setup instead of my tube head.
     
  9. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    I run the woofer(s) in parallel with a set of smaller speaker(s).

    However, there's a trick. Let's say, for instance, I have a single 15, and two 12's, all at 8 ohms.

    What I do is, run the two 12" speakers in series, to get an aggregate impedance of 16 ohms for the high end. To run the two 12" speakers in series, I have a special cable made specifically for that purpose. With BagEnd's or other cabs that have banana jacks, that's trivially easy, but with speakers that only have 1/4" jacks or speakons, you need to wire up a special "series" cable, observing the proper phasing.

    Then, I take that whole high-end series setup, and simply plug it in parallel with the 15. What that means is, I get an uneven power distribution, my 15 ends up seeing most of the juice, and the two 12's end up getting less. But, that works perfectly well, 'cause most of the time the high end only needs a "slight" emphasis, and the smaller speakers don't like lots of bass anyway.

    The aggregate impedance in this setup ends up being around 5.3 ohms, which is fine for most amps. What ends up happening in this case is, that when you're beating on the bottom end, the 15 ends up delivering most of the juice, with the 12's "supplementing" it. When you're up high though, the 12's take over, 'cause they usually have better high end response. It's not quite like a bi-amp, but it has some similar effects.

    If you have two 15's and one 12, this method probably won't work as well, because putting the 15's in series means that your 12 will probably be getting most of the juice, which probably isn't the desired result. In that case, if it were me, I'd nix the 12 and just go with the 15's, or buy another 12 so I'd have two of each, and then I'd be back to the balanced setup. Actually that's the way I run most of the time, with "mini-stacks", consisting of a 15 and a 12 in parallel, for an aggregate impedance of 4 ohms for each stack. Then I can either run the stacks in series or in parallel, depending on how many of 'em I'm using. I regularly run my WW Ultra with four mini-stacks, wired with each pair in series (for an aggregate impedance of 8 ohms for the four speakers), and then the two pairs of stacks in parallel (for a total impedance of four ohms).
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    This is much easier than you think. Get hold of a 2 ohm capable amp, then get 4 cabs of 8 ohms each.

    1 head of your choice, 2 ohms
    1 210 cab, 8 ohms
    1 212 cab, 8 ohms
    1 410 cab, 8 ohms
    1 15" cab, 8 ohms