why do speaker need resistance?

Question

just wondering

Answer 1

sciquest says " max power is delivered when the source amplifier and the load speaker are of the same resistance"

While true, that is of solely academic interest.

An audio amplifier's load resistance is never the same as the amplifier's source impedance.

An audio amplifier is a voltage source and its source impedance is very low indeed - tens or hundreds of milliohms.

Its lowest load impedance is dependent ultimately on power supply supply constraints.

Answer 2

I think what you meant is why some speakers are 4 ohms, some 8 ohms? It's a loose way to tell the sound tech how much that specific speaker will match to, and load down, an amplifier channel. The sound frequency band is low so those are more like a DC load where the max power is delivered when the source amplifier and the load speaker are of the same resistance. For higher frequencies, the wave energy cannot fully transferred from a source to a load unless the impedance of the source, all cables and switches, and the load are all matched.

Answer 3

The term used is impedance. This is due to the fact that a speaker has reactance from the voice coil, as well as resistance from the amount of wire used to wind the coil. The acoustic properties of the speaker and enclosure, and the frequncy being reproduced, as well as the reactive and resistive properties of the voice coil all combine to give the impedance (which you called resistance) of the speaker.
wikipedia.com may give you more detailed information under "loudspeakers". They are great for info and links.

Answer 4

Every thing in electronics is voltage ,current ,resistance . Speakers are considered impedance not resistance.

Answer 5

It is reactance not resistance. it has inductance component.