What Gauge Speaker Wire for In Wall Runs? The Math

Quick answer / TL;DR: What gauge speaker wire for in wall runs comes down to the run's loss: the 16/2 is the standard for the room's throw, the 14/2 the step at the longer distance, the 12/2 the very long run or the subwoofer's draw, and the 18/2 the short ceiling run the thin conductor holds. The rule is the round-trip resistance kept under about a tenth of the speaker's 8 ohm value, and the concealed path's permanence is the reason the gauge is measured before the drywall rather than after the system is built.

The gauge question for the in wall run is the same arithmetic the open run takes, and the concealed path adds one figure the open one does not: the run cannot be re-dressed once the drywall closes. The gauge is the conductor's size, the figure that sets the resistance the run pays and the loss the speaker's impedance reads against, and the in wall path's permanence is the reason the arithmetic is done before the wire goes into the cavity rather than after the system is built on the wrong line.

This is the gauge's view for the concealed run: the ladder the in wall stock carries, the loss math against the speaker's impedance, the run lengths each gauge serves, and the gauge the room's throw selects before the wall closes.

The Ladder the In Wall Stock Carries

The in wall stock carries the gauge ladder the concealed run selects from, and the ladder is the same one the open wire runs. The 18/2 is the thin stock – the ceiling's short run, the 16/2 the standard the room's throw serves, the 14/2 the step at the longer distance, and the 12/2 the very long run and the subwoofer's draw. The gauge is the conductor's size, the figure the resistance per foot reads from, and the run's loss is the round trip – the current out on one conductor and back on the other, the figure doubled for the path the circuit takes. The ladder is the stock's range, and the run's length is the figure that selects the rung.

The table is the ladder against the run's edge, and the reading is the rung each length selects. The 18/2's edge is the short ceiling run, the 16/2's the standard room's throw, and the 14/2's and the 12/2's the longer distances and the subwoofer's draw. The fractions are the loss against the 8 ohm speaker at each run's edge – the tenth the rule holds, and the margin the standard gauge carries at the throw it serves. The gauge is the rung the room's measurement selects, and the table is the arithmetic the selection runs on.

The round trip, and the concealed path's figure

The round trip is the figure the loss is measured on, and the in wall path's length is the one the measurement takes from the room rather than the drawing. The run's length is the throw from the amplifier's position to each speaker's wall, the path the cavity's route takes – the stud bay's up and over, the joist space's run, the turns the structure's framing forces. The measured path is the figure the gauge is selected against, and the concealed route's turns are the length the drawing's straight line understates. The round trip doubles it, and the gauge the arithmetic selects is the one the measured path's figure holds rather than the plan's.

The Rule, and the Fraction It Keeps

The rule is the fraction: the run's round-trip resistance kept under about a tenth of the speaker's impedance, so the amplifier drives the load it was matched to rather than the speaker plus the wire. The 8 ohm speaker's tenth is the 0.8 ohm the run's loss stays under, and the table's fractions are the figures each gauge's edge holds at the run's length. The 4 ohm speaker's tenth is the half – the 0.4 ohm – and the gauge the 4 ohm's run calls for is the one up: the 14 where the 16 served the 8, the 12 where the 14 served it. The rule is the fraction's figure, and the speaker's impedance is the value it is read against.

The subwoofer, and the draw the gauge takes

The subwoofer is the run the gauge's ladder steps for, and the figure is the draw the sub's amplifier makes at the 4 ohm load. The sub's line carries the current the amplifier's output drives into the 4 ohm voice coil, and the gauge the run takes is the one the fraction's figure holds at that load – the 12/2 at the long throw, the 14/2 at the standard distance the 8 ohm's 16/2 served. The in wall path's permanence is the reason the sub's gauge is the one the arithmetic selects before the wall closes rather than the stock the install had to hand. The sub's run is the ladder's heavy rung, and the draw and the distance are the two figures that put it there.

The Concealed Path, and the Gauge Before the Drywall

The concealed path's figure is the permanence, and the permanence is what the gauge's arithmetic is done for before the drywall closes. The open run's wrong gauge is the wire the install re-dresses: the roll replaced, the clips re-laid, the hour spent. The concealed run's wrong gauge is the wall opened, the drywall patched, the paint matched – the install's correction at the structure's cost. The gauge the room's throw selects is the figure the measurement states before the fish starts, and the in wall stock's ladder is the one the arithmetic reads at the spool. The concealed path is the run the gauge is right for the first time, and the fraction's figure is the check the measurement passes before the cavity closes.

In wall speaker wire is stocked in the 18/2, 16/2, 14/2 and 12/2 forms at the CMR rating, the two-conductor and the four-conductor runs, with the length per roll; the catalog lists the gauge, the conductor count, the rating and the length, and the run's measured path is the figure the selection runs on.

Real-World Applications

The home theater's four runs: the measured paths from the rack to each position, the 16/2 the three shorter throws select and the 14/2 the long one takes, the fraction each edge holds. The subwoofer at the room's corner: the 4 ohm draw and the long throw both calling the 12/2, the fraction the heavier rung holds at the distance. The ceiling's surround pair: the short cavity path the 18/2 serves, the thin conductor's loss the fifteen feet's figure, and the gauge the ceiling's throw selects before the panels close. In each the gauge is the room's arithmetic – the measured run, the round trip, the fraction against the speaker's impedance – and the concealed path's permanence is the reason the figure is read before the wall is the one it stays.

Related reading: The standard rung the room's throw takes: 16/2 in wall speaker wire — 16-2-in-wall-speaker-wire

Related reading: The four-conductor run the bi-wire takes: 16 4 in wall speaker wire — 16-4-in-wall-speaker-wire

Frequently Asked Questions

What gauge speaker wire should I use in the wall?

The run's length and the speaker's impedance select: the 16/2 for the standard room throw, the 14/2 for the longer run, the 12/2 for the very long run or the subwoofer's draw, and the 18/2 for the short ceiling run. The rule is the round-trip resistance kept under about a tenth of the speaker's impedance, and the concealed path's permanence is the reason the measurement is taken before the drywall rather than after.

Is 16/2 wire good enough for in wall speakers?

Yes, for the standard room's throw at the 8 ohm speaker – the 16/2's fraction holds under the rule's figure to about fifty feet, and the home's runs sit inside that distance. The longer run, the 4 ohm load and the subwoofer's draw are the figures the ladder steps for, and the 14/2 and the 12/2 are the rungs those runs select. The gauge is the run's arithmetic, and the 16/2 is the standard the room's measurement serves.

Does the wire gauge matter more in the wall than on the surface?

The arithmetic is the same, and the consequence differs – the surface run's wrong gauge is re-dressed, and the concealed run's is the wall opened. The gauge is the fraction's figure either way, and the in wall path's permanence is the reason the measurement is done before the cavity closes rather than after the system is built on the wrong line. The figure does not change with the path; the cost of missing it does.

What gauge for a long in wall run?

The 14/2 past the standard throw, the 12/2 at the very long distance or the subwoofer's draw. The figure is the run's round-trip resistance against the speaker's impedance, and the measured path – the cavity's turns and the stud bays' routes, not the plan's straight line – is the length the arithmetic reads. The long run's gauge is the ladder's heavier rung, and the measurement before the drywall is the step that selects it.

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