Speaker Impedance Switch? - Jemsite
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post #1 of 4 (permalink) Old 07-26-2009, 11:12 AM Thread Starter
 
Join Date: May 2008
Location: Philippines
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Lightbulb Speaker Impedance Switch?

Hello guys, I am very optimistic that I will be able to build my own 2x12 speaker cabinet in the near future. I plan to use two Jensen MOD 12-110 or 12-70 speakers for this project and I was wondering if I could put an impedance switch on it that would be able to switch the ohms rating from 4 ohms to 8 ohms? I found that 8 ohms is the standard speaker impedance for guitar amplifiers, but I also plan to use this on my crappy (but useable) Marshall MG100DFX combo with a 4 ohms rating for the speakers.

I one website, it shows how a 2x12 speaker configuration can be wired such that a switch would be able to go from parallel wiring (8 ohm speaker + another 8 ohm speaker in parallel = 4 ohms impedance) to series wiring (this time 8 + 8 = 16) but I would like to be able to switch to 8 ohms instead so that it would match most amps' ohms rating. I was thinking maybe there is a resistor of some sort that could be used to achieve the desired rating?

An advanced thank you for the replies.
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post #2 of 4 (permalink) Old 07-26-2009, 04:05 PM
 
Join Date: Dec 2000
Location: wolverhampton
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Re: Speaker Impedance Switch?

Hi there

It's definitely not a resistor that you need to sort the impedance of a speaker cab out but you can achieve what you need by using a DPDT switch. Marshall use this type of selector on their cabs and a more detailed description of what you need can be found my putting this into google:

speaker cab impedance dpdt switch

and choosing the first result. I can't post the link direct as I haven't made enough posts myself - will try to pm it to you.

Hope this helps

Simon
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post #3 of 4 (permalink) Old 07-26-2009, 04:08 PM
 
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Location: wolverhampton
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Re: Speaker Impedance Switch?

Ooops...

Just re-read what you wanted to do - if your speakers are both 8ohm you won't be able to switch between 8ohm and 4ohm, you will only be able to choose 4ohm or 16ohm when running mono or 8ohm in stereo - which i guess you know already. The way Ohms law works as I understand it means you won't be able to do what you want.

Sorry

Si
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post #4 of 4 (permalink) Old 07-27-2009, 02:50 AM Thread Starter
 
Join Date: May 2008
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Lightbulb Re: Speaker Impedance Switch?

Simon:
I was actually thinking that maybe some device can be used as a "dummy load" for the 16 ohms rating (when the speakers are in series) to go down to 8 ohms?

---8 ohm speaker 1-+-8 ohm speaker 2--
| |
| |
----------16 ohm "dummy load"----------
| |
| |
---------- ----------
| |
Total: 8 ohms

Maybe this would work? Or maybe not?
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2x12 cabinet , impedance , ohms , switch

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