Acura CL (1G): Adding Amplified Subwoofers to the Factory Bose System

Map the full path each cable will take before cutting anything: the power lead from the battery through the firewall and along the body to the trunk, the remote turn-on lead from the head unit, and the RCA signal leads. Cut every run longer than you think you need. Extra length at both the engine-bay end and the trunk end gives you room to route around obstacles and to reposition the amplifier later, and it is far easier to trim excess than to splice a run that came up short.

Locate an existing rubber firewall grommet between the engine bay and the cabin. Pierce the rubber with an ice pick to make a small hole sized to the cable. Tape the cable end to a long rigid rod such as a long drill bit so it stays straight, coat it with silicone oil, and push it through from one side. Piercing a snug hole lets the rubber seal tightly around the cable, keeping water out of the cabin and preventing the sheath from chafing on metal. Do not enlarge the grommet into an open gap: one follow-up install forced a 4 gauge cable through a torn opening because the cable would not fit the original cover, which leaves the pass-through unsealed and exposed to water intrusion and abrasion.

The amplifier needs a switched remote lead so it powers up with the stereo. Remove the factory head unit (follow a separate stereo-removal procedure for this car) to access its harness. On the Bose head unit, the remote turn-on lead is the yellow/white wire. Tap into it and route the remote wire back toward the trunk alongside the other cabling.

Lift the door sill trim on the side you are running wires. Pull back the carpet edge to expose the factory wiring channel and tuck the new power and remote leads in alongside the existing harness. Keeping the new cables under the same path as the factory bundle protects them and keeps them hidden when the trim goes back on.

Lift the door seal at the rear to reach the access point behind the rear seat trim, then release two retainer clips. From inside the trunk, pull the carpet down near the left rear strut tower until you can see the cables that continue from the door sill. Feed a coat hanger through from the trunk side and probe carefully until you catch the leads, then draw them into the trunk. Move slowly here so the hanger does not snag a wire or the interior trim.

Pull the power and remote leads through to the amplifier location in the trunk. Find a solid, bare-metal chassis point for the amplifier ground and secure a short, heavy ground wire there. A clean metal-to-metal connection is essential; a poor ground is a common cause of noise and weak output.

A line out converter (about $15) lets you drive the amplifier from the factory Bose system without swapping the head unit. Splice into the rear speaker wires and run those taps to the LOC inputs; mounting the converter up out of the way, such as strapped to the trunk ceiling, keeps it secure. Connect RCA cables from the LOC outputs to the amplifier inputs, following the wiring guidance supplied with your amp and converter.

Before applying power, check the install with an ohm meter. Confirm continuity through each connection, paying special attention to any solderless splice connectors: these can look seated yet fail to bite through the insulation, leaving an open circuit. Catching a bad connection now saves you from tearing the trunk apart after the system is buttoned up.

Only after the entire install is complete, connect the power cable to the battery positive terminal (fuse the cable close to the battery). Then set up the system: bring the amplifier gain and the LOC output up from a low starting point, listening as you go, and stop before the bass distorts. Starting low and working up protects the subwoofers and lets you dial in a clean level.