Quick answer: Both CL2 and CL3 are Class 2 and Class 3 cable ratings under the National Electrical Code, and both are accepted inside a wall for speaker wiring. CL3 carries a higher voltage rating and can be used where Class 3 circuits are involved. For a normal 8 ohm speaker run either works, and the plenum version CL3P is required only in air-handling spaces.
The letters on the jacket decide whether an inspector passes the job, and they have nothing to do with audio quality. Understanding what the rating covers prevents both overbuying and a failed inspection.
What the CL rating actually covers
Article 725 of the NEC divides low voltage wiring into Class 2 and Class 3 circuits, based on voltage and power. The CL2 and CL3 marks on a cable show that the jacket and insulation have been tested for those circuits, including flame spread and smoke characteristics for the listing.
Class 2 against Class 3
Class 2 covers circuits up to 150 V and limited power, which includes every passive speaker line in a home. Class 3 covers higher energy circuits, such as some 70 V distributed systems. A CL3 cable may be used in a Class 2 circuit; the reverse is not automatically allowed.
What the letters do not cover
They say nothing about conductor material, gauge or sound. A CL2 jacket can be wrapped around 22 AWG copper clad aluminium, and it will still pass inspection while sounding worse than a bare 14 AWG oxygen free copper cable.
Where the class limit comes from
The limit exists to stop a low voltage cable from overheating if it is accidentally connected to a power circuit. A speaker cable normally carries a few volts, but a fault inside an amplifier can put the full supply rail on the line. The jacketed insulation system is what buys time before that fault becomes a fire, and it is the only reason the marking matters at all.
CL2, CL3 and the plenum variants
CL2 and CL3
Riser and general in-wall use. The jacket is flame retardant and the cable is listed for concealment in walls and ceilings. CL3 has a thicker insulation system because of the higher voltage rating.
CL2P and CL3P
The P suffix means plenum rated, for spaces used as air return. These cables have low smoke and low toxicity jackets and cost noticeably more. If the ceiling void is a return air path, the code requires the P rating even for a speaker run.
CL2R and CL3R
The R suffix marks riser cable, for vertical runs between floors in a shaft. A riser run in a non-plenum building usually uses this.
Rating and application
| Marking | Class | Where allowed | Typical use | Cost |
|---|
| CL2 | 2 | In wall, in ceiling | Home speaker runs | Low |
| CL3 | 3 | In wall, higher voltage | 70 V distribution | Medium |
| CL2R | 2 | Vertical shafts | Multi floor homes | Medium |
| CL3P | 3 | Plenum air spaces | Office ceilings | High |
| Unmarked | None | Exposed only | Bench and shelf | Lowest |
What an inspector looks for
Three things: the marking printed on the jacket, the cable secured at intervals, and no power cable sharing the same hole without a separation. The marking has to be legible along the run, which is why cheap cable with faint print fails. Keep a one foot tail of jacket inside the wall box so the marking remains visible, and staple every 1.2 m on horizontal runs.
Practical scenarios
- Living room surround install: CL2 14 AWG in the walls, CL2P only in the ceiling void if it doubles as an air return.
- Restaurant with 70 V ceiling speakers: CL3, because the distributed line runs at a higher voltage than a home system.
- Three storey house: CL2R for the vertical chase to the second floor, CL2 horizontally.
- Rental apartment: surface trunking with unmarked cable, because cutting the wall is not permitted and the run stays exposed.
FAQ
Is CL3 better for sound than CL2?
No. The rating describes fire and voltage performance. Sound depends on gauge, conductor material and run length, all of which are separate from the class marking.
Can I use CL2 cable in a plenum ceiling?
No. A plenum space requires the P suffix. Using CL2 there is a code violation even if the cable never carries high voltage.
Does the marking have to be visible after installation?
It has to be legible on the cable, which is why inspectors look inside the box. Leave a tail and do not cover the print with tape or paint.
Next step
Match the marking to the space, then buy the gauge the run actually needs, because the jacket does not carry current. The CL2 speaker wire page covers the common in-wall format, the speaker cable guide explains gauge and length, and the OFC speaker cable page covers conductor material.
