Measure the route, not the distance
The cable does not go in a straight line. It goes down the wall, along the skirting, behind the furniture and up again. Measure that path with a piece of string before ordering, then add a little.
Then buy the shortest cable that reaches
Length is the single biggest cause of HDMI trouble at 4K and high refresh rates. A two-metre certified cable is more reliable than a five-metre one and costs less.
Leave slack at both ends
Enough to pull the equipment forward and reach behind it. A run pulled taut is a run you will cut when something changes.
Separate mains from signal
Cross them at a right angle rather than running alongside them. It costs nothing and removes more hum from a long subwoofer run than any upgrade on that shelf.
Label the ends
Two minutes with tape and a pen, once. Every subsequent change to the system becomes a five-minute job instead of a crawl behind the furniture with a torch.
Where this page stops
Anything inside a wall or a ceiling void is governed by building rules and by the cable’s own rating, and those vary by country. This page covers the run in the room.
Questions people actually ask
How long can an HDMI cable be?
A passive copper cable carries the full 48 Gbit/s reliably to about three metres. Beyond that the honest options are an active cable, which is directional and marked accordingly, or an optical one. Buying a long passive cable and hoping is the most common cause of a picture that drops out at high refresh rates.
Can I run speaker cable inside a wall?
Only cable with the appropriate fire rating: ordinary PVC-sheathed cable is not permitted in a cavity under most European building rules. That is a regulatory question rather than an audio one, and it is answered by the cable's own specification.
Last reviewed 4 September 2026
