Subwoofer RCA Cables: One Socket or Two
Subwoofer connections cause more confusion than most audio wiring, largely because there are two entirely different ways to feed one and the sockets look similar.
Quick Answer
| Subwoofer input | Signal level | Cable | Typical source |
|---|---|---|---|
| LFE, single RCA | Line level | Single RCA coaxial | Receiver LFE output |
| Line level, RCA pair | Line level | Two RCA or a stereo pair | Preamplifier output |
| High level, speaker terminals | Speaker level | Speaker wire | Amplifier speaker output |
| Combined LFE and line stereo | Line level | Single cable with a Y splitter into both | Receiver with one output |
For a single LFE output, one RCA cable is enough. If the subwoofer has two line inputs and the receiver has one output, a Y splitter feeds both, which also raises the level slightly.
Cable Characteristics
Coaxial construction
A 75 ohm coaxial cable with a solid centre conductor and good shielding is the right choice. Video coaxial cable works well.
Shielding
Low frequency content is not delicate, but hum and interference are. A double shielded cable helps in a rack.
Length
Line level signals tolerate length, but long runs near mains wiring invite interference. Keep runs reasonable and route away from power.
Connector quality
RCA plugs vary. Tight fitting, gold plated plugs reduce contact noise in a system that is rarely touched.
Chasing Hum
Hum with the cable connected only
Suggests a shielding or cable fault. Try another cable before anything else.
Hum when another component is also connected
A ground loop. Try a ground loop isolator or a different mains outlet.
Hum that changes with the volume
Usually an earthing or gain structure issue rather than the cable.
Clicking or popping
Often the subwoofer auto power circuit waking, not the cable.
Real-World Applications
- Adding a powered subwoofer to a receiver.
- Connecting a soundbar subwoofer output.
- Two channel systems with a stereo preamplifier.
- Studio monitoring with a sub.
Related Guides
For the other direction, read RCA to 3.5mm. For speaker level wiring, see RCA to speaker wire. For connector types, start with RG6 coaxial cable.
FAQ
Do I need one RCA cable or two?
One for a single LFE output. Two if the receiver has stereo preamp outputs and the sub offers both.
Will a Y splitter damage anything?
No. It feeds both inputs from one output and slightly increases the level.
Can I use a normal audio RCA cable?
Yes, though a coaxial cable with better shielding is preferable in a rack with other equipment.
Why does the subwoofer hum?
Most often a ground loop. Test with other components disconnected to find the source.