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hey, well, another beginner question: what's impedance? how it affects everything when the components connected are not matched by this (e.g. amp with 4ohm output with loudspeakers of 8ohm, vice versa and other combinations)? Does anyone know for a web site with a [b]good[/b] (not native english speaker, so it wouldn't help if it's explained too complicated) explanation of all this (cos I think it's too much to explain it all here, isn't it?) Thanks for any help, Matej [ 10-29-2001: Message edited by: mte ]
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Impedance will be difficult to explain without some technical terms, but here's a small part of it. Impedance in amp/speaker combinations works something like this: A load (impedance) acts on the amp's ability to drive, or supply power. The higher the impedance, the lower the actual power output from the amp. If you drive too low an impedance with a given amp, it's similar to running down a steep hill. Eventually, the lack or back pressure forces you to move at a speed faster than your legs can move, and you wipe out. In electrical terms, lowering the impedance to dangerous levels will make the power supply overheat or burn out entirely. It can't keep up with the demand for power. At the other end, if you drive too low an impedance from a mic, into a high impedance input, the back pressure resists most of the signal, resulting in a weak signal at the input. Driving a high impedance from the mic into a low impedance input will clip the input into distortion. As you can see from these examples, it's very important to match impedances for clean, efficient performance from your sound system. Match high impedance outputs to high impedance inputs, low impedance outputs to low impedance inputs, or use impedance matching transformers (ie. a direct box) to correct descrepancies between gear. This barely scratches the surface on impedance. Someone else pick up the ball and run with it.. please.

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Bottom line - never use a lower impedance load than the amp is designed for. Say you have a amp that is rated for a 8 Ohm minimum load - connecting a 4 Ohm speaker cabinet to that amp is asking for trouble. Another amp may be rated at 200 Watts RMS at 8 Ohms and 350 Watts or so at 4 Ohms. In this case, you can (assuming speaker cabinets of equal efficiency - ie let's say effeciency ratings of 103 dB @ 1 Watt / 1 Meter for both cabinets) expect the 4 Ohm cabinet to be louder because the amp is seeing less impedance ("resistance to the flow of electricty") and is putting out more power. In this case, you can safely hook up a 4 Ohm speaker load to the amp because it is rated for it... and this will (normally) be the better option, although hooking up an 8 Ohm cabinet is also perfectly safe - just not as efficient or loud. Phil O'Keefe Sound Sanctuary Recording Riverside CA http://members.aol.com/ssanctuary/index.html pokeefe777@msn.com
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