School me on 1x12s vs 4x12s and wiring

Discussion in 'Amps and Cabs' started by eicca, Mar 24, 2015.

  1. eicca

    eicca Member

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    So I have a 100W amp driving one 12-inch speaker at 100 watts peak.

    If I have a 100W Marshall head driving a 4x12 cab, does that mean each speaker is being driven at 25W each?

    Can I take my amp and plug it into a 4x12 cabinet and still wind up with the same volume? Better yet, since my amp is capable of driving both 100W outputs at once, could I use it to drive two 4x12 cabs?

    If I were to build the cabs, would I have to wire the speakers in series? Or in two pairs in series and both pairs in parallel?
     
  2. Phletch

    Phletch Member

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    Yes. The wattage is split evenly regardless of how the speakers are wired.
    Theoretically,yes, You'll have more "perceived volume" because of more speaker surface area. If you like speaker "break-up", you'll have less of it because each speaker won't be pushed as hard. On the other hand, that can result in more perceived headroom from the speakers since they won't be pushed as hard.
    Which amp do you have? When you say "both 100W outputs" are they different impedances (ie, one is for an 8 ohm load and the other is for a 4 or 16 ohm load)?

    Regardless, the best way is to run 2x cabinets daisy-chained in parallel to the amp output that matches the total impedance. For example, if you have 2x 16 ohm cabs in parallel, that totals 8 ohm. You would then plug the daisy-chained cabs into the 8 ohm output on the amp.
    You could, but you wouldn't have to. Most times it's not done that way.
    That's the common way to do it. It's known as "series-parallel".
     
  3. eicca

    eicca Member

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    Thanks for the info! I've got a TubeWorks RT-2100. It says in the manual that all speakers should never be less than 4 ohms combined. I would imagine that each output should be loaded equally.

    I am making an educated assumption that each output will push 100 watts based on the input wattage (300) and some user reviews. Plus there's this line in the manual that says "Mos-Valve can easily produce 100 watts per channel under typical overdrive conditions." which sure makes it sound like two output channels functioning while the overdrive channel is selected.
     
  4. Phletch

    Phletch Member

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    OK, I looked at the owners manual. It's a 100W hybrid amp; tube pre, SS main. As for the speaker outputs, it's not a dual-channel "stereo" configuration; it's just two switchable channels. It appears that the amp has 2x 8 ohm outputs wired in parallel; one main output for the on-board 8 ohm combo speaker, and the other output for an 8 ohm extension cabinet. When just using the combo speaker, the amp is configured for an 8 ohm load. Plugging in an extension cabinet into the second jack switches the amp to operate with a 4 ohm load.

    Basically, you can substitute the combo speaker with a cab or cabs with a total combined load of 8 ohms, and just use the one jack that the combo speaker is plugged into. Or you can use the combo speaker AND plug another 8 ohm cab into the other jack. That will give you a 4 ohm total load in parallel.
     
  5. eicca

    eicca Member

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    So I guess my dreams of two 4x cabs at 100W each on either side of this little guy are unrealistic.

    But it sounds like it'd handle a single 4x cab with dual inputs ok!
     
  6. Phletch

    Phletch Member

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    Not at all. You don't have to use both outputs. You can use anything you want as long as:

    - the total load is 8 ohm if solely using the primary output. As I said in my first reply, you can daisy chain or "piggy-back" two 4x12 16 ohm cabs in parallel, plugging the first cab into the 8 ohm output on the amp. Most cabs have jack plates wired in parallel for just this purpose.

    OR

    - use both outputs with a total combined load of 4 ohms, ie, two 8 ohm cabs, one in each output (and forget about the combo speaker).

    It seems like you're hung-up on the "100W each on either side". There is no "either side". You've got 2 channels - one clean, one dirt (or something like that). They don't run simultaneously like a home stereo "right" and "left". Whichever channel you're on, that is what the amp is sending to the speaker output(s). It's not one output dedicated to one channel or the other.

    Also, you realize that the amp isn't always putting out 100W, right? If you're running the amp at or near the max volume setting, sure, you're probably at or getting close to the amp producing 100W. Are you playing at that level most or all of the time? Regardless, as long as the total rated power handling capability of all speakers combined exceeds the max wattage of the amp, you're fine, ie, 2x 4x12 cabs (8 speakers) rated at 25W each.
     
    Last edited: Mar 25, 2015
  7. eicca

    eicca Member

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    Lol my bad by "either side" I literally envisioned my amp flanked by two monstrous cabs. I know it's not stereo and not always running at full power but I always think in full power to make sure my equipment will handle it.

    Thanks again for your help :)
     
  8. Phletch

    Phletch Member

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    No worries. Hope it all works out for you. :)
     

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