Weber Mass 50 in parallel

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by slipperyfingers, Oct 22, 2005.


  1. slipperyfingers

    slipperyfingers Member

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    Hi, I was wondering if someone can tell me how to safely connect my Weber Mass (old style) in parallel with my speakers. I have an eight ohm cab with two inputs. I have a Z ghia head with a four and eight ohm out. (can I use the 50 watt attenuater with an eighteen watt head?)

    Thanks in advance,
    Bill
     
  2. 908SSP

    908SSP Member

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    The two jacks on your cab should already be wired in parallel. Plug your Weber Mass into one of the speaker jacks. Run the speaker cable from the input of the Mass to the speakers jack. Set the Weber for 8 ohms and maximum attenuation. Run a speaker cable from your amps 4 ohm output to the other jack in the speaker cab. Now you have two 8 ohm loads run in parallel for a total of 4 ohms. You will not do any harm running a 50 watt attenuator with your amp the wattage rating of an attenuator tells the maximum heat dissipation.
     
  3. slipperyfingers

    slipperyfingers Member

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    Thanks so much...I just wanna be sure of something. When you say max attenuation..should the weber mass be on ten or one...I'm thinking one. I'm going to try this as soon as I hear back from you

    -Bill
     
  4. 908SSP

    908SSP Member

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    I sold my Mass a while ago, It would be one on my Weber Load Dump.
     
  5. slipperyfingers

    slipperyfingers Member

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    Thanks 908SSP,

    I tried it last night, it works very well. It knocks the volume down some...anybody know how many decibles it knocks off this way?

    Bill
     
  6. John Phillips

    John Phillips Member

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    3dB - the same as halving the power of the amp, because it's divided equally between the cab and the dummy load if they are the same impedance.

    You can also achieve slightly more attenuation by deliberately mismatching, if you know what you're doing.

    A 4-ohm load in parallel with an 8-ohm speaker will give about 5dB attenuation (2/3 of the power is going to the load), and a 4-ohm load with a 16-ohm speaker will give about 7dB (4/5 of the power goes to the load) - both are safe with the amp set to 4 ohms.
     
  7. slipperyfingers

    slipperyfingers Member

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    John,
    As always thanks. Sounds like if I set the MASS to 4 ohm, and my speaker cab is 8 ohm, I would use the 4 ohm output from the head to achieve a 5db attenuation...this is a question not a statement?

    Bill
     
  8. John Phillips

    John Phillips Member

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    Yes, that's right. The total impedance will then actually be 2.66 ohms not 4, so you've got a mismatch and will wear the power tubes a bit faster. It's within the normal safe range though so it shouldn't cause any other trouble.
     
  9. slipperyfingers

    slipperyfingers Member

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    Thanks John, I'm going to give it a go!
     

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