External Speaker Jack Usage

[V-Mike]

How do multiple cabinets work as far as impedance is concerned? To run two 16 ohm cabs, would you use two 8 ohm inputs, or two 16 ohm inputs??? It is very confusing... I know I run one 8 ohm cab in one 8 ohm input, simple enough, but if I want to run two 8 ohm cabs, would I simply plug them both in 8 ohm output jacks??? Help me please...

[jh45gun]

Simple rule of thumb is if you run two cabs say at 8 ohms in parallel you drop the impedence by half so it would be 4 ohms. Unless the amp is wired different any amp I ever used plugging in two cabs of indentical ohmage would decrease it by half. So two 16 ohm cabs would be an 8 ohm load. If you parallel you drop in half if you run in series you double the ohmage. The way most cabs are wired two together would be parallel. I suppose their could be a way to series cabs if in doubt use a meter to check the ohms of the two cabs together. Most amps that have an external speaker jack the jacks are wired in parallel. Then their are some that are multi tap but they are marked either 2,4,8,16. If a cab has two jacks in the back chances are they are in parallel and you could run a cord from the extra jack of one to the other and run then a cord to the amp for a parallel load. If you run a oddball cab like a 16 and a 8 or a 8 and a 4 you then get a ohms reading that is inbetween the two which does not work well as the lower ohm cab will take most of the power.

[V-Mike]

OK I have an Epi Blues Custom 30 and it has 1-16ohm, 2-8ohm, and 2-4ohm speaker outputs. If I were to run two 16 ohm 1x12" cabs I would plug them into the two 8ohm inputs?

[jh45gun]

Well first thing I would do is ask Epiphone or look at a schematic to make sure those two 8 or two 4 are parallel outputs. Or do you have a manual for it if not you could get it on line and it should tell you how to hook up speakers to this amp. I would guess they are parallel but since I am not familular with that amp guesses do not count I would check to make sure. If they are parallel then yes you could plug a 16 ohm cab in each one for a 8 ohm load. For some odd reason if they are not then you would have to plug both speaker cabs into one of the 8 ohm jacks. I would look it up then go on from there.