OFC or CCA speaker cable: gauge and distance

Choosing speaker cable is not about buying the thickest or the most expensive one. You need to relate conductor material, cross-section, total length, speaker impedance, real power and type of installation. In a home system with short runs, several options can work correctly; in a large room, a shop or a fixed installation, a poorly thought-out decision can increase losses, complicate the installation or breach the cable's conditions of use.

The most common acronyms are OFC and CCA. OFC identifies high-purity copper with good conductivity. CCA uses copper-clad aluminium: it weighs less and is usually cheaper, but has higher resistance for the same nominal cross-section. This does not automatically make CCA “bad”; it means you should not treat two cables of the same cross-section as if they behaved exactly the same.

OFC and CCA: what really changes

Cable resistance causes voltage drop and power loss. The longer and thinner the run, the greater the effect. Copper conducts better than aluminium, so an OFC cable can keep a lower resistance than a CCA cable of the same cross-section and length. On long runs, low-impedance speakers or high-power systems, that difference becomes more important.

A 2 x 2.5 mm² OFC speaker cable is a useful reference for demanding runs where you want extra cross-section and a copper conductor. For moderate runs and tight budgets, a 2 x 1.5 mm² clear CCA cable can fit, as long as its spec sheet, length and approved use match the installation.

Do not rely on the outer diameter alone. A thick jacket can protect, but it does not increase the conducting cross-section. Look for the figure expressed as 2 x 0.75 mm², 2 x 1.5 mm² or 2 x 2.5 mm²: that is two conductors and the cross-section of each one.

Guide decision table

The table is a starting point, not a technical approval. 100 V line systems, evacuation installations, public venues or projects subject to regulations require calculations and specific cables.

How impedance matters

A 4-ohm speaker places more demand on the cable than an 8-ohm speaker over the same length, because the cable resistance represents a larger share of the load. If you connect several speakers in parallel, the total impedance can drop even further. Before sizing the cable, calculate the load the amplifier will see and confirm it is within its safe range.

As a practical rule, you want the resistance of the run to be small compared with the speaker impedance. Remember that current travels through two conductors: a physical run of ten metres means roughly twenty electrical metres of conductor. This detail is often forgotten and makes the calculation look more favourable than it is.

Cross-section and distance

In a living room, 2 x 1.5 mm² is usually a reasonable baseline for short or medium distances and typical speakers. As length, power or demand increase, 2 x 2.5 mm² gives more headroom. Larger cross-sections may be needed in specific cases, but they are also stiffer, take up more conduit space and may not fit well in the terminals.

Do not oversize without checking the termination. A thick cable that is poorly secured, has loose strands or is forced into a small connector can create more problems than a correctly sized, well-fitted cross-section. If you use banana plugs, spades or connectors, check the accepted cross-section and prepare the conductor without cutting strands.

How to measure before buying

Measure the real route, including rises, drops, bends, passes through furniture and service slack. Avoid calculating in a straight line. Add a sensible reserve so you can move the equipment and redo a termination; do not add dozens of unnecessary metres, because they also increase resistance, cost and clutter.

Keep similar lengths for the left and right channels when it is easy to do so, but do not coil large excess lengths just to match them. In a normal home system, a small difference in run length is usually less of a problem than an unnecessary coil hidden behind the cabinet.

Polarity and installation

The cable usually has a marking, colour or ridge to tell the conductors apart. Always use the same side as positive at both ends. Reversing one speaker does not usually damage it, but it can leave it out of phase with the other, reducing bass and creating a vague stereo image.

Strip only the length you need. No copper strand should touch the opposite terminal. Tighten firmly without crushing the terminal and check the connection after moving the equipment. In damp areas, outdoors or shared conduits, use a cable specifically suited to that environment.

Fixed installation and safety

A spec sheet stating that a cable is not approved for permanent installation must be taken literally. For wiring inside walls, suspended ceilings or buildings, check the CPR classification, jacket, smoke emission, reaction to fire and project requirements. Acoustic performance does not replace regulatory compliance.

In professional public address installations you must also distinguish low impedance from 70/100 V line. The way power, losses and speaker connection are calculated is different. If the system includes line transformers, do not simply apply the home 4 or 8 ohm rules.

Common mistakes

• Choosing by jacket thickness rather than by the conductor's mm².
• Assuming OFC and CCA of the same cross-section have the same resistance.
• Measuring only the outward run and forgetting that the circuit also returns.
• Buying domestic cable for a fixed installation without checking certification.
• Mixing up polarity between speakers.
• Splicing without protection or leaving loose strands.
• Using a cross-section that does not fit in the terminal.
• Confusing speaker cable with RCA or jack signal cable.

Practical example

For a stereo amplifier and two 8-ohm speakers placed six metres away, measure each route and check the power and the terminals. A 1.5 mm² cross-section can be suitable in many home setups. If the run grows, the impedance drops to 4 ohms or you want to reduce losses, consider 2.5 mm² and an OFC conductor. The final decision should be based on the published resistance and the manufacturer's instructions.

For a shop with speakers spread across several areas, do not improvise a parallel chain. Define whether the system is low impedance or 100 V, add up the power, set up zones and use certified cable for the run. It is better to settle the layout before buying the reel.

Frequently asked questions

Does an OFC cable always sound better?

Not necessarily in a noticeable way on short, correctly sized runs. Its measurable advantage is lower resistance than an equivalent CCA cable, which is especially useful as distance or demand increase.

Can I use 2 x 2.5 mm² for any speaker?

Electrically it offers headroom, but it must fit in the terminals and be manageable in the conduit. A larger cross-section does not fix an incorrect impedance or a faulty installation.

What does 2 x 1.5 mm² mean?

It means two conductors, each with a nominal cross-section of 1.5 mm². It does not describe the outer diameter of the complete cable.

Can I run speaker cable in the same conduit as mains power?

You should not assume so. Separation and routing depend on regulations, insulation and the project. Consult a qualified installer when it is a fixed installation.

Do the left and right cables have to be exactly the same length?

It is not essential in a normal home system, although it is best to avoid huge differences. Prioritise clean runs, secure connections and a suitable cross-section.

Note down impedance, power, metres per channel, type of installation and the cross-section the terminals accept. With those five figures you can choose with good judgement and avoid paying for an unsuitable solution.