# impedence questions.

Discussion in 'Amps and Cabs [BG]' started by bassist286, Apr 11, 2002.

1. ### bassist286

Nov 22, 2001
rhode island
hello, i own an swr jr. which is 8 ohms, and i own a S.O.B. witch is also 8 ohms, but now i found a great trade in deal on a big bertha. The only problem is that the swr jr. is 8 ohms and the bertha is 4 ohms. the mimimun load on a swr 350 is 2 ohms, could i make this work or would i have to trade my 8 ohm jr. for a 4 ohm one. to make 2 ohms? thanks a bunch
-chris

2. ### JMXVorsprung durch Technik

Sep 4, 2000
Cologne, Germany
The load of a 8 Ohm and a 4 Ohm cab in parallel is 2.67 Ohm, so you'll be ok.

Cabs are usually connected in parallel.
You calculate their impedance like this:

1/Rtotal = 1/Rcab1 + 1/Rcab2

In this case:

1/Rtotal = 1/4 + 1/8 = 3/8

=> Rtotal = 8/3 Ohm = 2 2/3 Ohm = 2.67 Ohm

As long as it's over 2 Ohm you're ok. Fractions don't matter, and Impedance numbers are not that accurate anyway.

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