How to Connect Two Speakers to One Output

By Robert Jones · 2021-07-23

Apparently, the idea of connecting two speakers to one output sounds impossible.

Right, let's get straight to it. People often ask me, "Can I hook up two speakers to a single output on my amp?" The short answer is yes, you usually can. But and it’s a big "but", you’ve got to know what you're doing. If you get it wrong, you’ll end up with fried equipment, and nobody wants that. I’ve seen enough blown amps in my workshop to know a thing or two about pushing limits too far.

It’s not rocket science, mind. It all boils down to something called impedance – measured in ohms (Ω). Think of impedance like resistance in a pipe. The lower the resistance, the more water (or electricity, in our case) can flow. Your amplifier is designed to work within a specific range of impedance. Most hi-fi amps are happy with 8-ohm speakers, and many can handle 4 ohms. Some even go down to 2 ohms, but those are usually pretty hefty beasts designed for it.

Every speaker has an impedance rating. An 8-ohm speaker wants to see a certain amount of power at 8 ohms. When you start wiring speakers together, you change that total impedance. If the total impedance drops too low, your amplifier has to work much harder. It starts pulling more current than it’s designed for, gets hot, and eventually, poof – no more music. Or worse, no more amp. I had a mate years ago, bless his cotton socks, who tried to run four cheap car speakers off a little stereo amp in his garage. Smelled like burning electronics all afternoon. Lesson learned, eventually.

This is where most people get into trouble, but it’s also the most common way to wire multiple speakers. When you connect speakers in parallel, you connect all the positive (+) terminals together and all the negative (-) terminals together, then run a single pair of wires from those connections to your amplifier output.

What happens to the impedance? It halves. So, if you’ve got two 8-ohm speakers wired in parallel, the amplifier sees a 4-ohm load. That’s usually fine for most modern amplifiers. If you connect two 4-ohm speakers in parallel, the amplifier sees a 2-ohm load. Now, that’s where you start getting into dicey territory for many standard home amplifiers. You’d need an amp specifically rated for 2 ohms, and even then, I’d keep an eye on it.

I’ve done this plenty of times, especially in workshops or bigger spaces where I want more spread of sound. For instance, I’ve got a pair of old Tannoy 609s (8-ohm) and some smaller satellite speakers (also 8-ohm) I sometimes use for background music in my testing room. Wiring them in parallel gives me a 4-ohm load, which my old Rotel amp handles without breaking a sweat. Sounds a treat, too.