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Help me with this ohm calculation please

prater

prater

Aug 4, 2011
211
24
#1
I'm running a GK 400 rb iv rated for a minimum of 4ohms.

I don't want to do anything that would damage my head.

I have been running a 210 cabinet with two 16 ohm speakers in it wired in series.

I want to add a 4ohm cabinet to the mix.

If I'm running the two cabinets out of the parallel outputs of my head what will my impedance be?

I know this is kind of a mess, but I can't afford to buy new cabinets so I use whatever I have on hand and this is all I have right now.
 
#2
I suspect there is a misunderstanding here. If you have a 210 with two 16 ohm speakers running in series, you just add up and get 32 ohm total, which is imo very unusual. More likely they run in parallelle, which would get you 8 ohm.

If you run a 4 ohm cab in parallelle with 8 ohm, you get a total 2,67 ohm load. A 4 ohm cab parallelle wired with a 32 ohm cab, would get you a total 3,55 ohm.

I wouldn't recommend any of the above, 2,67 ohm will harm most amps. 3,55 ohm is also also a serious risk of harm for most amps.
 
#4
Total series resistance = R1 + R2 + R3...
1/(total parallel resistance) = (1/R1) + (1/R2) + (1/R3)...

http://www.bcae1.com/spkrmlti.htm

http://www.speakerimpedance.co.uk/

2_series.png
srprllgd.gif
spk4sp4.gif
 
#5
By chance would the 4 ohm cabinet also be two 8 ohm speakers in series?

If so, then my recommendation would be to wire those in series to get 16 ohms. Then take the other cabinet and wire in parallel to get 8 ohms. Then those could go in parallel to give 5.3 ohms which is above your 4 ohm rated amp.

The compromise there would be unequal power distribution between the speakers. The 8 ohm series speakers would each take 1/6th of the power while each of the 16 ohm speakers take 1/3rd of the power. As long as the speakers are rated for this or you keep the levels down to what they can handle it will technically work.

If your 4 ohm cabinet is not two 8 ohm speakers in parallel then you are probably not going to be able to use them together.

Good luck!
 

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