Subwoofer Cable and Wiring: What You Need and What You Don’t

Ryan Smith

Subwoofer wiring is simpler than most people think. The complication usually comes from either having the wrong cable type or dealing with a ground loop hum. Here’s everything you actually need to know.

The Standard Connection: RCA Cable

For almost every home theater setup: one RCA cable from your receiver’s “SUB OUT” or “LFE OUT” jack to the sub’s “LFE IN” or “LINE IN” jack. That’s it. One cable. Done.

Use a shielded RCA cable — unshielded cables pick up electrical interference that shows up as hum. You don’t need to spend $100 on a cable. A well-shielded cable in the $15-25 range is perfectly adequate. Anything beyond that is diminishing returns.

High-Level Connection (Speaker Wire)

Some subwoofers — particularly REL models — have high-level inputs that accept speaker wire directly from your amplifier’s speaker terminals. You run speaker wire from the amp’s left and right speaker outputs to the sub’s high-level input, in parallel with your main speakers.

This is REL’s preferred connection method and it has real advantages: the sub senses the exact same signal as your speakers, including the tonal character of the amplifier. For music-focused systems it can produce more natural integration. Use 16AWG speaker wire for runs under 20 feet, 14AWG for longer runs.

The Ground Loop Hum Problem

A constant 50 or 60Hz hum from your sub even with no audio playing is almost always a ground loop. Different pieces of audio equipment connected to different electrical outlets can have slightly different ground potentials. When they’re connected together via RCA cables, this difference creates a current loop that manifests as hum.

Fix in order of preference:

1. Plug all audio equipment into the same power strip or surge protector — this equalises the ground reference and eliminates most ground loops
2. Try a ground loop isolator on the RCA cable — available on Amazon on Amazon, works about 80% of the time
3. Try a different electrical outlet for one of the components
4. Use balanced XLR connection if your equipment supports it — balanced connections reject common-mode interference by design

How Long Can the RCA Cable Be?

Up to about 20 feet without any special precautions using a quality shielded cable. Beyond 20 feet, use a cable with double shielding. Beyond 50 feet, consider a balanced XLR connection if your equipment supports it — balanced cables reject interference over long runs that RCA can’t handle cleanly.

Wireless Option

If running a cable across the room isn’t practical, a wireless subwoofer kit transmits the audio signal from your receiver’s sub output to a receiver unit plugged into the sub. Quality matters here — budget kits introduce latency that can cause audio/video sync issues. The SVS SoundPath kit achieves under 5ms latency, which is effectively transparent. Budget kits vary and some add 30-50ms, which is noticeable in movies.

What You Don’t Need

Expensive “audiophile” subwoofer cables — the differences between a well-shielded cable and a $200 “premium” cable are not audible. The sub is handling bass frequencies that are far less sensitive to cable characteristics than high-frequency signals. Spend the cable budget on the sub instead.