Coaxial Cable for Subwoofer: Picking a Line Level Cable That Stays Quiet
A powered subwoofer takes a line level signal through a single RCA connector, and the cable carrying it runs across a room full of mains wiring, HDMI cables and wireless access points. Shielding, not exotic conductor material, is what keeps that signal clean.
Quick Answer
Use a 75 ohm coaxial cable with a heavy braided shield and RCA plugs on both ends, connected to the LFE or sub out socket. RG-6 with a copper centre conductor and double or quad shielding is the safest choice for runs over 3 m. A standard stereo audio RCA patch cable works electrically over short distances, but its light shield often picks up hum in a home theater cabinet.
Cable Types Compared
| Cable type | Impedance | Shielding | Suitable run |
|---|---|---|---|
| Audio RCA patch cable | Not specified | Light spiral shield | Up to 1 m |
| RG-59 coaxial | 75 ohm | Foil plus braid | Up to 5 m |
| RG-6 coaxial | 75 ohm | Foil plus braid, copper core | Up to 15 m |
| RG-6 quad shield | 75 ohm | Four layers | Long runs near mains and dimmers |
| Dedicated subwoofer coaxial | 75 ohm | Double braid, directional design | Any domestic length |
Why Shielding Decides Everything
Hum pickup
The subwoofer band sits below 120 Hz, where mains frequency and its harmonics live. An inadequate shield turns a subwoofer cable into an antenna for 50 Hz and 60 Hz hum.
Return path and loop area
A coaxial construction keeps the return conductor concentric with the centre conductor, which minimises the loop area that picks up interference. That geometry is the reason coaxial cable beats twisted audio cable for long line level runs.
Connector quality
A crimped or screw on RCA plug that fits loosely breaks the shield connection intermittently, producing crackle and hum that comes and goes as the cable moves.
Length and Splitting
Line level coaxial runs are comfortable to 15 m in a domestic setting. Many powered subwoofers offer two RCA inputs, left and right, which are internally summed. In that case use a single RCA to dual RCA Y splitter, or feed only the LFE input if the receiver provides one and the subwoofer label marks it.
Real-World Applications
- Home theater with the subwoofer across the room from the receiver: 10 m RG-6 coaxial with quad shield.
- Studio monitoring with a powered sub: short 1 m coaxial cable from the monitor controller.
- AV cabinet dense with mains cables: double shielded coaxial run to avoid hum.
- Restaurant background audio: long coaxial run from the rack to a wall mounted powered sub.
Installing and Troubleshooting
- Connect to the LFE or subwoofer pre out, not a full range output.
- Keep the cable away from mains leads and amplifier power supplies.
- Set the subwoofer crossover to maximum and control the crossover at the receiver.
- If hum appears, unplug sources one at a time to find the ground loop.
- Never disconnect the earth pin on mains equipment to cure hum.
Related Guides
For passive subwoofers driven at speaker level, read Subwoofer speaker wire. For balanced professional connections, see XLR audio cable. For the HDMI audio path into the receiver, start with HDMI eARC cable.
FAQ
Can I use a normal RCA audio cable for a subwoofer?
For a very short run, yes. Over longer distances the light shielding makes hum and interference much more likely, so a 75 ohm coaxial cable is the better choice.
Does a subwoofer cable need to be 75 ohm?
The LFE signal is low frequency analogue, so impedance is not critical, but 75 ohm coaxial construction provides the shielding geometry that keeps the signal clean.
Why does my subwoofer hum and how do I stop it?
Most hum is a ground loop between the receiver and the subwoofer, or a poorly shielded cable. Test with a shorter double shielded cable first, then isolate sources.
Is RG-6 better than RG-59 for a subwoofer?
RG-6 has lower loss and better shielding, so it is preferable for any run over about 5 m. Both are 75 ohm and both work electrically.