Quick Answer / Summary: Measure each run along the real path – up, across, down, around door frames – not the straight line. Add 30 to 50 cm of service loop at each end. Buy one continuous length per run; joints in speaker cable are weak points. Surface runs accept standard jackets; in-wall runs need CL2 or CL3. Order the longest run first and match the others to it in gauge.
The most common speaker-wire regret is length: a spool that ends half a metre short of the far corner. The fix is measurement discipline, not a bigger spool. This page covers measuring the actual route, allowing service loops, and choosing surface or in-wall cable before the order goes in.
Measuring the Route That Exists
Rooms are not rectangles at cable height: runs climb skirting, cross door frames, and detour around furniture that will never move again. Measure with a string along the intended path, then add the vertical drops at both ends. The number this produces is routinely 30 to 60 percent longer than the room’s diagonal, which is why diagonal-based orders come up short.
Service Loops and Future Moves
Half a metre of slack at each end covers re-termination, a shifted speaker stand, and the inevitable re-plug. Loop it neatly and secure it rather than leaving it coiled behind a shelf where it collects dust and kinks.
One Run, No Joints
A joint in speaker cable adds resistance and a corrosion site. Buy the length in one piece. Where a run genuinely must be extended, use a proper connector or terminal block rather than twisting and taping, and treat the joint as a serviceable point.
Surface, In-Wall, and the Rating Decision
Surface routes accept ordinary jackets and can be clipped, tucked under carpet edging, or run in trunking. Routes inside a wall or ceiling require the fire-rated jacket – CL2 or CL3 in North America, with plenum grades where air recirculates. The rating is printed on the jacket, and the decision must be made before the order because the same gauge in a rated jacket costs more and is not interchangeable at inspection.
Flat Cable and Carpet Routes
Flat speaker cable suits runs under carpet or along skirting where round cable would show. Its thin profile trades conductor spacing for concealment; keep runs short and gauge adequate, and avoid repeated foot traffic points that crush the conductors.
Ordering Discipline
Order per run, not per room: two 6-metre runs and two 14-metre runs is a different order from 40 metres of spool. Cut lengths from one spool preserve consistent gauge and copper, and the offcut becomes the spare for the next change.
The Spare That Pays for Itself
Keep two or three metres of the same gauge and copper from the original spool. The offcut re-terminates a damaged end, extends a moved speaker, and settles the next change without a second order. The spares coil is the cheapest insurance in home audio wiring.
Length and Route Planning
| Item | Rule | Why |
|---|---|---|
| Measure | String along real path | Diagonal undercounts by 30-60% |
| Service loop | 0.3-0.5 m each end | Re-termination and moves |
| Joints | None – one piece per run | Resistance and corrosion |
| In-wall | CL2/CL3 rated jacket | Inspection requirement |
| Order | Per run, cut from one spool | Consistent gauge and copper |
Practical Applications
Ordering cable for a new apartment, planning a renovation before plasterboard closes, hiding runs under carpet in a rental, and correcting a short-spool mistake without buying a second full roll.
Frequently Asked Questions
How much extra speaker wire should I buy?
Add 30 to 50 cm per end for service loops, and measure the real route with a string rather than estimating from the room’s size. The measured route is typically 30 to 60 percent longer than the diagonal.
Can I join two speaker cables?
It is possible with a proper connector or terminal block, but every joint adds resistance and a corrosion site. Buy one continuous length per run wherever possible.
Does in-wall speaker cable cost more?
Yes – the fire-rated jacket adds cost. It is also non-negotiable for routes inside walls or ceilings, and the rating must be printed on the jacket for inspection.