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 Post subject: Impedance Mismatch
PostPosted: Thu Jan 13, 2011 8:20 pm 
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Mark II

Joined: Fri Sep 14, 2007 7:48 pm
Posts: 64
I know the amp can tolerate certain mismatches, but I have two 8 ohm cabs and no parallel box. Can I safely plug one into the 8 ohm output and the other into the 4 ohm output?

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 Post subject: Re: Impedance Mismatch
PostPosted: Fri Jan 14, 2011 12:07 pm 
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Mark II
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 Post subject: Re: Impedance Mismatch
PostPosted: Fri Jan 14, 2011 12:14 pm 
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Mark II

Joined: Fri Sep 14, 2007 7:48 pm
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Well, I tried it anyway and actually preferred the sound of the Thiele only so that's what I'm going to go with. ;-) I still may need the answer for other speaker cabs.

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 Post subject: Re: Impedance Mismatch
PostPosted: Sun Jan 16, 2011 2:37 pm 
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Mark I

Joined: Sun Oct 19, 2008 4:48 pm
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 Post subject: Re: Impedance Mismatch
PostPosted: Mon Jan 31, 2011 1:23 pm 
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Mark I

Joined: Wed Oct 27, 2010 11:42 am
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Location: Tampa, Florida
can't you just chain the cabs together and run them out of the 4 ohm output? (most cabs, in my experience, allow you to do this)

(1/R equivalent) = (1/R1) + (1/R2)

So you would have 1/8 + 1/8, which is 2/8, which is the same as 1/4. So your total resistance would end up being 4 ohms.

http://www.1728.com/resistrs.htm

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 Post subject: Re: Impedance Mismatch
PostPosted: Mon Jan 31, 2011 2:06 pm 
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Mark II

Joined: Fri Sep 14, 2007 7:48 pm
Posts: 64
Sacausey wrote:
can't you just chain the cabs together and run them out of the 4 ohm output? (most cabs, in my experience, allow you to do this)

(1/R equivalent) = (1/R1) + (1/R2)

So you would have 1/8 + 1/8, which is 2/8, which is the same as 1/4. So your total resistance would end up being 4 ohms.

http://www.1728.com/resistrs.htm


That works if one of the cabs has two jacks. In this case, both have only one. But it turns out I liked the sound of the Thiele by itself better than both together so the issue became moot.

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 Post subject: Re: Impedance Mismatch
PostPosted: Sat Mar 05, 2011 5:55 pm 
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Bottle Rocket

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 Post subject: Re: Impedance Mismatch
PostPosted: Mon May 02, 2011 5:18 am 
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Mark I

Joined: Sun Oct 19, 2008 4:48 pm
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Location: England

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 Post subject: Re: Impedance Mismatch
PostPosted: Mon May 02, 2011 10:37 pm 
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Bottle Rocket

Joined: Mon Feb 28, 2011 12:37 pm
Posts: 19
For anyone with doubts on this topic I put an Excel sheet on another forum that will help you calculate the total impedace, even using the different outputs of the amp.
http://www.marshallforum.com/attachment ... hookup.zip

Always check what you are doing and read the manual :) The sheet is just a calculation tool and does not replace checking the connection and feasibility.


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 Post subject: Re: Impedance Mismatch
PostPosted: Tue May 03, 2011 5:48 pm 
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Bottle Rocket

Joined: Mon Feb 28, 2011 12:37 pm
Posts: 19
By the way: One 8 Ohm cab into each output is not OK. It's like plugging in an 5,33 Ohm cab into the 8 Ohm output.
Good you didn't like it.


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