That sounds too short.
The amp for my sub is on the narrow split of the back seat, the RCA routed the long way along drivers sill - to avoid the power routed in the passenger sill - mine were 15ft or 4.57m and had a just about the correct amount of spare for the seat to fold down & not much to hide.
If your stuck with the 12ft one you could route through the centre console under the carpet/ rear seat.
