Quick answer: Speaker cable conduit is chosen before any cable is bought. Size the tube so the cable pulls without strain, keep the bends wide enough that the jacket is not dragged around a tight corner, and leave a draw line plus space for one more run. A conduit that is full on the day it is installed is a wall that opens again later.
The first run goes in easily because the tube is empty and the walls are open. Two years later a second pair is needed for a zone that was not planned, and the same tube is packed, has two tight bends and no draw line. Almost every conduit regret is decided at the sizing stage, when a larger tube costs very little and nobody is thinking about the next owner of the room.
Fill: how much cable belongs in a tube
A conduit is not a storage space. Cable needs room to slide, and a bundle that fills the tube will jam on the first bend no matter how hard it is pulled.
Counting the cables, not the pairs
Work out the outside diameter of each jacket, not the conductor count. Two thin two conductor cables often occupy less space than one thick four conductor cable, and a bundle of round jackets leaves gaps that a flat profile does not.
The draw line counts as a cable
A pull cord takes space too, and it has to move freely after the install. If the tube is filled to the point where the cord cannot slide, the next cable has to be pulled with the old ones as a guide, which is exactly when jackets get scuffed.
Bend radius and pull tension
Every bend adds friction, and friction is what turns a gentle pull into a stretched conductor. Two long sweeps cost less effort than one tight elbow.
Wide bends at both ends
The ends matter most, because that is where the cable is being fed and where hands are pulling. A wide sweep at the entry lets the cable enter straight, and the same at the exit stops the jacket from being dragged over a sharp lip while the last few feet come through.
Pulling by hand, not by force
Pull steadily and stop when resistance rises, rather than adding force. A cable that has been stretched has thinner copper at the stretched point, and the fault appears as an intermittent channel long after the wall is closed.
Sizing for a spare draw
The right size is the size that still has room after the first pull. The table gives a working guide for typical two conductor speaker cable, with the spare capacity stated in whole runs rather than percentages.
| Conduit size | Cables that pull easily | Spare runs to plan | Main watch point |
|---|
| 1/2 in | One thin jacket | None | Jams on the first bend |
| 3/4 in | Two thin jackets | One short run | Cord left too tight |
| 1 in | Three or four jackets | Two runs | Sharp exit lip |
| 1 1/4 in | A full zone bundle | Three runs | Sag between clips |
Pulling without damage
Feed from the spool, keep the cable straight as it enters, and have one person at each end so the pull stops the moment something catches. Tape the leading end into a smooth nose rather than leaving a stub of jacket to catch on joints, and never pull on a connector that has already been fitted.
Fishing into a finished wall
Where a tube has to reach an existing wall, cut small access openings at each end rather than one long chase. Fish the tube through, fix it, then patch the two openings. A short length of surface channel can bridge the last few inches to a plate, which is far easier to make good than a chased slot.
Practical scenarios
- New build: Fit the largest tube the stud bay allows, because the wall is open once and the extra capacity is free at that moment.
- Retrofit along a ceiling: A short surface run of conduit can bridge a joist line that cannot be drilled, and it keeps the cable out of the ceiling void.
- Multi zone rack: One tube per zone rather than one tube for the whole house keeps a fault isolated and makes each pull short.
- Outdoor run: A tube keeps sunlight off the jacket, which matters more than the extra protection from rain.
FAQ
Can speaker cable share a conduit with mains cable?
It should not. Mixing the two puts a low level signal beside a power conductor for the whole length of the run and creates a fault path between systems that are supposed to stay separate.
Do I need conduit if the cable is rated for in wall use?
Not always. A rated jacket can sit inside a finished wall, while conduit adds protection from nails, rodents and later work. In a wall that may be opened again, the tube is worth the effort.
What should the draw line be made of?
A stiff poly line that will not rot and can be tied off at both ends. Leave it long enough to wrap around a clip, and leave it in place after the pull so the next cable has a path.
Next step
Match the jacket to the route with the four conductor CL2 cable notes, compare ratings in CL2 and CL3 compared, and check the two conductor CL2 cable sizes before the tube goes into the wall.
See the matching cables and adapters
