Calling all Amp experts !

Discussion in 'Amp Central Station' started by AxRookie, Aug 10, 2019.

  1. AxRookie

    AxRookie Tele-Meister

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    I have a speaker wiring question, I have a 4x12 cab and 2 each Fender "special design speaker" 16 ohm speakers and 2 each Celestion G12L-35 8 ohm speakers that will be driven by a little Marshall MG15MSIIthat has 2 "16ohm loudspeaker outputs" and it states "do not use with a load of less than 8 ohms".
    What would be the best way to wire up the speakers and should I use all 4 or just wire up two of the speakers and leave the other two disconnected, Or something else???
    Also, this I what I have and I want to make it work so please no advice on buying something else...

    Here is what I have...

    [​IMG]
    [​IMG]
    [​IMG]
     
  2. tubelectron

    tubelectron Tele-Meister

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    Hi @AxRookie :

    Go for a serial/parallel combination. You would be able to achieve 12 ohms terminal impedance : that's more than 8 ohms so you will be right... ;)

    Look at the schematic below, and consider the upper speakers being your 16 ohm ones :
    [​IMG]

    16+8 in series = 24 ohms.
    24 ohms and 24 ohms in // = 12 ohms, which will be your terminal impedance to your amp.

    I advise you to put the 16 ohms speaker in the high position of your 4x12 cab (moreover if it is a slanted one) : due to their 16R, they will be less sensitive than the 8R (theorically 2x), so less loud, so suitably placed in high position.

    Hope this helps,

    -tbln
     
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  3. radiocaster

    radiocaster Poster Extraordinaire

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    If the cab has two outputs, wire the two 8 ohms in series for 16, and the two 16 ohm speakers in parallel for 8 ohms, each to a different jack. You won't be able to use all 4 at the same time.

    Wire the pairs diagonally diagonally to get a better spread. Or stereo if you want to use two amps, but the spread is not very good.

    Alternatively, you could use 3 speakers and wire the 2 8 ohm speakers in series with a 16 ohm in parallel for 8 ohms total.

    Chances are you have no idea what I'm taking about, so you might consider going to a professional.
     
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  4. AxRookie

    AxRookie Tele-Meister

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    I understand what you're "talking" about and the cab does have two inputs I could use...
     
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  5. AxRookie

    AxRookie Tele-Meister

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    I'll prob try everything anyone suggests to see what sounds best, It's really not that much work to change it around...
     
  6. Wally

    Wally Telefied Ad Free Member

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    Be advised that the lower impedance speakers will be working harder than the 16 ohm speakers if you do mix them together. I do not mix and match impedance or efficiency ratings.
     
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  7. AxRookie

    AxRookie Tele-Meister

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    What I'm going to try first is run one 16 ohm speaker to one input jack and run the two 8 ohm speakers in series to the other input jack on the cab and see how those two setups sound...
     
  8. driprail

    driprail TDPRI Member

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    First off, know that the jacks on the back of your amp are wired in parallel. If you plug two 16 ohm speakers into them, the load will be 8 ohms.

    Second, I disagree with others about connecting an 8 ohm speaker and 16 ohm speaker in series. They will both see the same current flow and you will wind up with one loud speaker and one soft (1/2 the sound) speaker. Probably not what you want.

    Third, you can recone the pair of 16 ohm speakers with 8 ohm voice coils. Now connect the like speakers in parallel to form 4 ohms. Connect the 4 ohm pairs of speakers in series to make 8 ohms. They should have the similar volume and loudness.

    Fourth, you can take the 16 ohm Fenders and trade them for 8 ohm Celestions at a used equipment store.

    Best!


     
  9. PCollen

    PCollen Friend of Leo's

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    You have a 15 watt solid state amp that you want to drive 4 speakers with. None of the speakers are ever going to get enough juice to really start working. It was designed for 2 1x12 16 ohm cabs, for a total of 8 ohms (parallel ) load. If you want to use all four speakers in your 4x12 cab, post #2 is the way to go, electrically. But no guarantee how the speakers will blend with each other and sound together.
     
    Last edited: Aug 10, 2019
  10. AxRookie

    AxRookie Tele-Meister

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    No, I'm not looking to use all 4 speakers at the same time, I don't know where you got that idea???

    I'm going to have two speaker setups in one 4x12 cab with each speaker setup running to one of two jacks on the 4x12 cab, Both jacks will have close to a 16-ohm load with one jack having the two Celestion speakers running in series and the other jack having only one of the Fender 16 ohm speakers connected and the other will just be a disconnected dummy.

    I will only be plugging into one jack or the other but not both at the same time and both will have close to a 16-ohm load EACH, AND as I just said I will only be plugging into one jack or the other at a time...

    like I can plug the amp into this...

    [​IMG]

    or this...

    [​IMG]

    either one will be a 16-ohm load...
     
    Last edited: Aug 11, 2019
  11. Wally

    Wally Telefied Ad Free Member

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  12. AxRookie

    AxRookie Tele-Meister

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    First post...

    "should I use all 4 or just wire up two of the speakers and leave the other two disconnected, Or something else???"

    Nowhere did I say anything about wanting anything, I was wide open to any and all suggestions...

    And I still am open to any suggestions, My post before this one is just the first thing I'm going to try...
     
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  13. Wally

    Wally Telefied Ad Free Member

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    I’ll give you that you were open to all suggestions. You can have twp 16 ohm jacks with the method you are going to try first or one 16 ohm jack and one 8 ohm jack. Have fun.
     
  14. AxRookie

    AxRookie Tele-Meister

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    I know the amp states it can use an 8 Ohm load but what effect will using an 8 Ohm load have on this type of amp?
     
  15. Wally

    Wally Telefied Ad Free Member

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    Solid state amp isn’t it? With a solid state amp, the speaker load impedance has a direct and considerable effect on output power.
    The amp will make roughly twice the power with an 8 ohm load compared to what it will produce with a 16 ohm load. If one makes the mistake of using less than an 8 ohm load, the amp’s output will soon be cancelled....the output transistors will not last long.
     
  16. AxRookie

    AxRookie Tele-Meister

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    On closer look of the manual, it turns out it's a 8 ohm amp that can use a 16 ohm load so I'm going to wire the 16 ohm speaker pair in parallel on on jack for a 8 ohm load and on the other jack I'm going to use only one of the 8 ohm speakers for a 8 ohm load and maybe wire in a switch to put the other 8 ohm speaker in series for a 16 ohm load with the switch flipped...

    [​IMG]
     
  17. Wally

    Wally Telefied Ad Free Member

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    And when you run a 16 ohm load the amp’s output will be cut in half.
     
  18. AxRookie

    AxRookie Tele-Meister

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    Cool, That will be handy...

    I've got the switch mounted in the jack plate and I've got the wiring fig out to switch between one 8 ohm speaker OR two 8 ohm speakers ran in series for 16 ohms...

    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Aug 15, 2019
  19. AxRookie

    AxRookie Tele-Meister

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    I was thinking today about what I could do with the unused side of switch I added to the jack plate...

    [​IMG]

    and it hit me, I'll use it to disable the other jack if the switch is flipped for a 16 Ohm load that way even if both jacks were plugged into an amp the amp will only ever see a 16 Ohm load.

    In that way the cab can only ever be a 16 Ohm load max OR an 8 Ohm load min no matter what is plugged into it...
     
  20. AxRookie

    AxRookie Tele-Meister

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    I have all the jack plate wiring done, I used much heavier gauge wire...

    [​IMG]
    [​IMG]

    And my kit of new wire connectors for connecting up the wires to the speakers came today, Good quality connectors with nice soft silicone jackets!

    [​IMG]

    Now to add all the speaker wire connector to the wires and reassemble the cab...
     
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