I'm not really sure what it is, but it seems that grasping this topic of loudspeaker impedance or nominal impedance or resistance, even though resistance is not the right term for a loudspeaker load, it seems to stir up anytime I've made a video and there's been some recent videos about loudspeaker impedance and understanding why a lower impedance like 4 ohms is harder on a power amplifier or a receiver than an 8-ohm nominal loudspeaker. Now, through all of that and some of the comments and direct emails that I've had, there's one topic that maybe is also not clear, well, I know it's not clear, and that's the concept of running more than one pair of speakers at the same time because there are many, many receivers and amplifiers, particularly integrated amplifiers, that have a speaker switch on the front, speaker A and speaker B.
Now there's always an option with those systems that you can play pair of speakers A or pair B or A plus B, and that's where the confusion stems when it comes to load of the loudspeaker on the amplifier, what's safe, and what happens to the impedance. So the question I'm getting over and over again is, I have a pair of speakers that's 8 ohms and a pair of speakers that 4 ohms, and my amplifier receiver has an A and a B speaker switch. Can I run them both at the same time? So one thing that you have to be aware of that if your receiver or amplifier has a speaker A and speaker B selector switch, that doesn't mean that there's two pairs of amplifiers in there. There's only one amplifier, okay? So when you select pair A or pair B, those respective pairs are being driven by the same amplifier.
So now let's think for a second what happens if we select A plus B at the same time? Well, now we have two pairs of speakers being run off of the same amplifier channels, and what that means is that with more than one pair of speakers in play, the amplifier is going to see a lower impedance and a more difficult load. So for instance, we have two pairs of speakers or two speakers here, let's assume they were pairs. They're both 8-ohm nominal. If I play one or the other pair, it's going to be an 8-ohm load to the amplifier. If I select A plus B to play both pairs at the same time, that impedance now drops in half to 4 ohms and that's where the difficulty in the understanding is. So most manufacturers are good enough to tell you that if you use the A plus B feature, that the minimum impedance has to be this.
So for instance, if the amplifier is rated for 4 ohms for a single pair of speakers, in most cases, the manufacturer will say, if you use two pairs of 8-ohm speakers, that's okay and anything above that is okay, but don't go below 8 ohms. Heaven forbid, two pairs of 4-ohm speakers would present a 2-ohm load to that amplifier with A plus B running and that's going to be problematic for many, many amplifiers and receivers. So I hope that clears that up, that A and B speaker selectors on amps and receivers doesn't mean that there are separate amplifiers. They're sharing the same amp, so watch the impedance. Always the best thing to do is consult the original manufacturer's manual for information saying what the minimum loads are if you're running a single pair or an A plus B configuration. I hope that clears up that topic because I literally have got 20 people in the last month asking the same thing so I thought it was a good idea to do a video on it. Thanks a lot for watching.
