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Connecting bass cabinets....impedance


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Anyone have advice on how to set-up/wire three bass cabinets so that the overall impedance is 4 ohms? Two of the cabinets are 4 ohm, and the other is 8 ohms. I know that there's a way to make a series cable setup to run the 4 ohms together to get an overall 8 ohms out of the two cabinets, but I forget how to wire this sort of cabling correctly. (I know/believe that if two 8 ohm speakers are operated in parallel that a 4 ohm impedance results....just need to be reminded how to wire up the specialized cable to run the two 4 ohm cabinets in series). Thanks.
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To wire the two 4 ohm cabs in series, which will give you an effective combined nominal impedence of 8 ohms for those two cabs, simply run a single conductor wire from the positive post of one cab to the negative post of the other. Then use the free positive terminal of one, and the free negative terminal of the other as your amp leads.


You can then treat those two cabs as one 8 ohm cab, which you can then wire in parallel with your third 8 ohm cab, to give you a total nominal impedence of 4 ohms for all three cabs used together as a system.


If your cabs do not have external binding posts, you can do the same thing by wiring the connectors inside the 1/4 inch jacks the same way.


Just make sure your cabs are all wired with the correct and same polarity phase, before you do anything.


I discovered that my SWR cab and my Eden cab actually had opposite polarity.


A simple way to check cab polarity is to hook up a 9v battery to a 1/4 inch speaker cable. Plug one end into the cab as normal. Touch the pos terminal of the battery to the tip of the connector on the other end of the cable, while holding the neg terminal of the battery against the sleeve. Watch the speaker cones while you make the contact. You should see it jump 'forward', if the polarity is wired correctly. Use the same cable to check your other cabs by the exact same method. If they all show their speaker cones jumping forward, then all are wired correctly, and share common polarity.


The 9v battery will not harm your drivers. Have no fear.



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