How-To: Speaker Wiring, Setup and Troubleshooting

Wiring and polarity

Every speaker connection has a positive and a negative terminal, marked red and black. Wire one speaker the wrong way round and its cone moves out while the other moves in, which cancels bass and leaves the stereo image vague and hollow. This is the single most common fault I find in other people's systems.

Speaker cable is marked with a stripe, a ridge or a printed line on one conductor. Pick one convention and keep it at both ends of every run. If the bass sounds thin after an install, swap one speaker's connections and listen again before assuming anything is broken.

Series, parallel and impedance

Wiring two speakers in series adds their impedance together; wiring them in parallel halves it for an identical pair. Amplifiers state a minimum stable impedance, and going below it makes the amplifier work harder, run hot and eventually shut down or fail.

Two 8-ohm speakers in parallel present 4 ohms; in series they present 16 ohms. Two 4-ohm speakers in parallel present 2 ohms, which most home amplifiers will not tolerate. Work the maths out on paper before the soldering iron comes out.

Setting crossovers and levels

Set the subwoofer crossover roughly 10Hz above the point where your main speakers start to roll off — 80Hz is the standard starting point for bookshelf speakers, lower for large floorstanders. Overlapping the sub and the mains creates the boomy mid-bass hump most people mistake for good bass.

Level-match by ear with familiar music rather than films. Turn the sub up until you can hear it as a separate source, then back it off until it disappears into the mix but the bottom end stays full.

Diagnosing crackle, hum and drop-outs

Crackle is usually a mechanical connection problem: a dirty plug, an oxidised terminal or a stray strand of cable shorting across the binding posts. Work through the chain by swapping one cable at a time rather than replacing everything at once.

A constant hum at mains frequency generally indicates an earth loop, common when a television, a computer and an amplifier are all earthed through different sockets. Try running the audio equipment from one socket strip; a persistent hum with only one source connected points at that source's power supply.

Common symptoms and first checks

Buying checklist

• Keep positive to positive on every run, at both ends
• Calculate the final impedance before wiring multiple speakers
• Start the subwoofer crossover at 80Hz and adjust by ear
• Change one variable at a time when hunting a fault
• Power audio equipment from a single socket to avoid earth loops

Frequently asked questions

How do I know if my speakers are wired the right way round?

Play a familiar track with strong bass. If the low end sounds thin and the vocals will not settle in the centre, reverse the connections on one speaker and listen again — the bass should firm up noticeably.

What happens if I wire speakers below my amplifier's minimum impedance?

The amplifier draws more current than it was designed for, runs hot, and will either enter protection or fail. Always work out the combined impedance before connecting multiple speakers.

What crossover frequency should I use for a subwoofer?

80Hz is the standard starting point for bookshelf speakers. Use a lower figure with large floorstanders and a higher one with very small satellites, then fine-tune by ear.

Why do my speakers crackle?

Nearly always a connection fault — a dirty plug, a loose terminal or a stray cable strand shorting the posts. Isolate it by swapping one cable at a time rather than replacing the whole system.

How do I stop a hum from my audio system?

A steady hum usually means an earth loop. Run all connected equipment from the same socket strip and disconnect sources one at a time to identify which one introduces it.

Can I connect a soundbar and a separate subwoofer?

Only if the soundbar has a subwoofer output or supports pairing with the manufacturer's wireless sub. Most sealed bars do not, which is why choosing a 2.1 system up front matters.