15W extension for an AC30??

Discussion in 'Amp Central Station' started by philthejuggler, Sep 11, 2019.

  1. philthejuggler

    philthejuggler TDPRI Member

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    Hi Guys

    I have an 15w 16ohm external vox speaker cab (alnico) and I reckon it should be OK to use it as an extension to run in parallel with my AC30C2x.

    Since the cab is in parallel the maximum load would be 15W (probably much less for the size of gigs I play) as it is split between internal speakers and the cab.

    Is this logic correct please?

    Thanks in anticipation!

    Phil
     
  2. Bartholomew3

    Bartholomew3 Friend of Leo's

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    Speaker rating should be double the advertised amp rating as the amp is not rated/advertised at peak power levels.

    So I would say you are 15 watts short on that speaker and will eventually blow it if you are a loud player.

    At low volumes it should work just fine.
     
  3. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    More info helps, assuming the amp has two 16 ohm speakers wired in parallel and is set for an 8 ohm load, adding a third 16 ohm speaker makes the speaker load about 6 ohms. Not too bad a mismatch but not the load the amp is set for.
    But if for example the amp has two 8 ohm speakers in series for a 16 ohm load, adding that third speaker makes an 8 ohm load so the amp should be set to 8 ohms rather than 16.
    The point here is to know your impedance specs, as much as you wattage.
     
    Tim S likes this.
  4. gusfinley

    gusfinley Tele-Holic

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    According to the manual:

    Extension SP: This speaker jack runs parallel with the internal speakers which are wired for 16 ohms. The Extension Cabinet must be 16 ohms.

    Be sure to set the impedance switch to 8 ohms. ( two 16 ohm cabinets in parallel = 8 ohms )

    I would verify that you have 2 8 ohm speakers (for 16 ohms total ) in your combo just to be safe.

    With the three speakers connected at the right impedance, each speaker will get 1/3 of the output power so around 10 watts instead of 15. This could help to protect both the external speaker and the speakers in the combo.
     
  5. philthejuggler

    philthejuggler TDPRI Member

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    Hi all - thanks for the responses. It is definitely a 15W 16ohm cab - in fact it is the cab from the HW series designed to go with the 50th Anniversary TV models. I've decided to be on the safe side to get hold of an AC15H1TV so I know the cab and amp are correctly matched. I think an AC15 will be plenty loud enough for pub gigs & the extension speaker will help with dispersion!
     
  6. philthejuggler

    philthejuggler TDPRI Member

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    So if I did want to run it off an AC30 it should be perfectly safe!
     
  7. Danjabellza

    Danjabellza Friend of Leo's

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    Thinking back to my ac30cc2, I think the extension speaker out muted the internal speakers... that said: isn’t the 30 watts at full output? So if you’re not running full output, you’re not running 30 watts... but I’m no expert, wait for verification from a more reliable source.
     
  8. Asmith

    Asmith Friend of Leo's

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    If its 2 8 ohm speakers in series, in parallel with a 16 ohm speaker then they dont get 1/3 each. The 16 ohm gets 1/2 and the 8 ohms get 1/4 each.

    It would be more useful if you could tell us what model the actual speakers are.
     
  9. POS Guitars

    POS Guitars TDPRI Member

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    It will work, but the single cab will get more beating.
     
  10. gusfinley

    gusfinley Tele-Holic

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    Doh! That's right. That's what I get for trying to quickly sneak in posts at work!
     
  11. gusfinley

    gusfinley Tele-Holic

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    The speaker types are indicated in the above text. The "x" in the model number indicates the vox/celestion blue alnico speakers, for the other speaker alnico was specified which should be the same type.
     
  12. Asmith

    Asmith Friend of Leo's

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    So all the speakers are Celestion alnico blues?

    If they are then I dont see a problem because vox puts these in 15 watt amps often. Its usualy an availiable feature on Ac15s and 2 in AC30s.
     
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