mixing an 8ohm and 16 ohm in one cab?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by buddyboysteve, Dec 25, 2009.

  1. buddyboysteve

    buddyboysteve Member

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    Merry Christmas everybody. Got a question. What would happen if you put an 8ohm and 16 ohm speaker in the same cab? Transformer was set for 8 ohm as if both speakers were 16's and it was wired in parallel. I didn't set it up this way. It came this way when I bought it. Just discovered this when I was swapping speakers. BTW, it's a Vox AC30TB and the speakers were Weber Blues. Curious how it would effect the sound and wondering if it would damage the transformer or any other parts in the amp. Thanks for the info.
     
  2. IBTom

    IBTom Member

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    I also am interested in seeing what replies you receive on this one.

    Based on the research that I've done, with this combination as you've described, it should put a 12 ohm load on the secondary of the OT. And based on how I understand it, this secondary load can be used to drive up the primary load in an effort to better place the OT into it's designed operating range. A bit of math is necessary here....

    That said, I've also recently been informed by a non musician electronic tech that to the contrary, when pairing up a mis-match impedance load such as the 8 and 16 ohm speakers, that the ot will only see the resistance load of the smaller of the two speakers.

    So...I'm curious as to which, if either of these are correct.

    tom
     
  3. VacuumVoodoo

    VacuumVoodoo Member

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    Your OT will see a combined load impedance of 5.33 Ohm
    Basically you can have the impedance selector set to 8 or 4 ohms without any problems. Some amps in the past had just a 6 ohm output so you could use any speaker between 4 and 8 ohms.
    The 8 ohm speaker will take 2/3 of power and the 16 ohm speaker 1/3.
    If you have different speakers with roughly same efficiency the 8 ohm one will dominate in the resultant combined tone.
     
  4. buddyboysteve

    buddyboysteve Member

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    Thanks. That is not what I expected! I have never heard of putting different ohm speakers together. They are both alnico blue Weber's and even though they were the "same" speaker, just different ohm's, they did sound different. If I understand you correctly then, I can run these together without a problem. My transformer is tap for 16 ohm right now though. Is that too much? Should I run it in the 8ohm tap? Thanks for the help.
     
  5. VacuumVoodoo

    VacuumVoodoo Member

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    Yes, run it on 8 or 4 ohm tap. Let your ears decide which sounds better.
     
  6. VanR

    VanR Senior Member

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    Send one of those back to Weber to be reconed the same as the other. I think they charge $25 to recone their own speakers.

    edit: here's the Weber recone page
    http://tedweber.com/recone/index.htm
     
    Last edited: Dec 26, 2009
  7. rockon1

    rockon1 Member

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    As the others have stated run it at 8 or 4 ohms. Its important to note(as VacuumVoodoo did) that the 8 ohm speaker will recieve 2/3's the amps power. Bob
     
  8. buddyboysteve

    buddyboysteve Member

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    Man, big help everybody. I appreciate the info and will consider having that Weber reconed as well. Thanks again.
     
  9. solitaire

    solitaire Senior Member

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    I would not run the speakers in this config as it would most certainly detract from the tone. According to the rule of least resistance the 8 Ohm one will recieve more power than the 16 Ohm one and therefore play louder. Now, had one been twice the sensitivity rating and you had separate outputs they would be about as loud but with a slight strain on the 16 ohm channel + it would go middier than expected.
     

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