Building a New Trunk Floor and Adding a Subwoofer + Amp to the 1991 Honda Accord CB7

Product Reviewed / Installed

• Alpine S Series Type S 10-inch subwoofer (S10) Paired with an Alpine head unit and Alpine Type S speakers.

• Old-school Alpine V-Power subwoofer + amp setup Includes a single-channel amplifier with a low-pass filter.

• Amp installation kit / wiring kit Mentions SCAR kit for power/termination components.

• New trunk floor + OEM-matching trunk carpet (for a 1991 Honda Accord) Used to physically support the subwoofer/box.

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Key Features Mentioned

Subwoofer

• A 10-inch Alpine S Series Type S subwoofer planned to complement Alpine Type S components.
• Mounted in a slim subwoofer box to avoid filling the trunk.

Amplifier

• Single-channel amp with a low-pass filter
  • Frequency is settable, while slope/behavior isn’t configurable (as described).
• Coordination with head unit crossover
  • Amp set toward the highest/upper setting
  • Head unit crossover mentioned around 120–125 Hz

Wiring / Installation Approach

• Power wiring
  • Battery → trunk with an in-line fuse.
• Clean termination
  • Uses ferrules/terminals for modern-style connections.
  • Uses fork/Y connectors for the older amp’s wiring needs.
• Noise prevention
  • Power and signal/remote runs split and routed on opposite sides of the car to reduce interference (alternator noise concern).
• Routing
  • Uses grommets and factory pathways when possible.
  • Includes firewall pass-through using a grommet and a drilled hole.
  • Uses under-carpet routing with cable protection (e.g., crinkle wrap for a factory-like blend).
• Safety
  • Disconnect battery during wiring, reconnect at the end.

Trunk Floor / Carpet

• New fiberboard trunk floor created via CAD/cardboard templating, then carpeted.
• OEM-matching burgundy carpet sourced (notably from eBay).
• Notes the earlier trunk lacked carpet and the proper wood floor.
• Test-fit described as “tight,” then finalized with proper retention/clip points.

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Pros (As Described)

• Good integration/compatibility
  • Alpine S subwoofer planned to “go great” with Alpine head unit and Type S speakers.
• Clean, professional-like installation
  • Careful cable routing using grommets, avoiding heat/moving parts, and hiding cables under carpet.
• Tunable audio setup
  • Head unit crossover (~120–125 Hz) coordinated with amp low-pass strategy.
• OEM look
  • Matching burgundy carpet and saved clips to preserve correct trunk appearance.
• Space-conscious
  • Slim sub box chosen for daily-driver usability without overfilling the trunk.

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Cons / Limitations Mentioned

• Carpet availability delays
  • No carpet at first forced a choice (fabric vs OEM replacement); ultimately OEM carpet used.
• Older amp terminals
  • Required Y/fork connectors instead of a modern ferrule-only approach.
• Preference for separation
  • Strong preference to keep power/signal on opposite sides; implied shielding might make it unnecessary, but method wasn’t changed.
• Wire color confusion
  • Blue/dark-blue conductors were difficult to distinguish, especially on camera.

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User Experience / Build Flow (Project Walkthrough)

1. Build a new trunk floor
   • Template, then cut fiberboard to fit using the described method.
2. Source and install OEM-style burgundy carpet
   • Purchased on eBay; arrived in “good shape” (no “murder stains” mentioned).
3. Install the subwoofer in a slim box.
4. Run power wiring using an amp kit
   • Cut cable, add fuse holder, route to trunk via firewall pass-through with grommet.
5. Run signal/remote away from power to reduce noise.
6. Mount amp near/behind the seat area using carpeted board work.
7. Terminate wires cleanly and connect to battery at end.
8. Test listening confirms: “It works.”

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Comparisons Made

• Amp mounting style
  • Some opinions suggest mounting the amp on the sub box, but this build mounts it on the back of the seat instead.
• Routing philosophy
  • Some argue shielded cables reduce the need for separation; builder keeps power and signal on opposite sides anyway.
• Reference build
  • Uses the builder’s other car (Prelude) as reference for similar under-carpet amp wire routing/board approach.

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Unique Points Mentioned

1. Car: 1991 Honda Accord CB7 trunk needed repair (missing correct carpet and wood floor).
2. Build goals: lowering, exhaust, period-correct stereo/speakers; subwoofer was missing.
3. Subwoofer target: Alpine S Series Type S 10-inch for compatibility with Alpine head unit + Type S speakers.
4. Trunk floor solution using cardboard-aided templating.
5. Planned trunk floor shape described as conceptually built from rectangles (with corners cut).
6. Trunk cavity depth roughly 13–14 in (with 13 in referenced).
7. Material: composite fiberboard (8x4 ft sheet referenced at about $16 at Home Depot).
8. Cut/final fit required minor adjustments; integrated with trunk clip/retainer.
9. Carpet sourcing: initially no carpet, forced selection between fabric vs OEM replacement.
10. OEM carpet purchased on eBay in burgundy matching original color.
11. Replacing carpet: the previous one-piece trunk carpet was cut; clips saved with the right tool.
12. Subwoofer installation: Alpine Type S in slim box for daily-driver use.
13. Additional component: “old-school” Alpine V-Power used with the speaker.
14. RCA cables already run from earlier head unit work; only power needed to the trunk.
15. SCAR kit details: includes ring terminal; in-line fuse used (left disconnected until final hookup).
16. Routing rules: avoid hot/exhaust and moving parts; follow existing factory paths.
17. Firewall routing: removed a plate, drilled for a grommet for pass-through.
18. Emphasis on supplies/grommets beforehand to avoid mistakes.
19. Signal routed away from power to avoid alternator noise.
20. Tools: plastic pry tools from Amazon praised for routing/hiding under upholstery cracks.
21. Amp characteristics: single-channel with low-pass filter; slope not configurable.
22. Crossover suggestion: head unit around ~120–125 Hz, amp low-pass set high.
23. Amp wiring connectors: kit connectors included; prefers rubber grommet for pass-through; older amp uses Y/fork connectors.
24. Remote wire: kit lacked one, so a custom approach was used.
25. Amp grounding limits: cannot ground too far (>18 in warning) and must ground to bare metal.
26. Ground preparation: remove nut/bolt and use Dremel/sandpaper to reach bare metal.
27. Amp mounting method: does not mount to box; mounts behind seat on a carpeted board.
28. Carpet holes cut for wire passage; amp wires routed under carpet for easy folding.
29. Speaker wire choice: kit wire too thin; used 16-gauge instead.
30. Speaker connection: ferrules preferred for “correct” termination.
31. Wire color issue: blue/dark blue hard to distinguish on camera.
32. Safety: disconnect battery during wiring; reconnect at end.
33. Final result: test listening confirms it works.
34. Overall objective: “fix the trunk, wire an amplifier, terminate everything just right.”

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Speakers / Perspectives (Who Contributed What)

• Main builder (primary voice)
  • Handles most of the build: templating/floor, carpet sourcing, wiring/crossover strategy, routing philosophy, and termination methods.
• Diego (secondary speaker)
  • Helps with quick confirmations during test fits and placement (e.g., amp placement).
• Ad-hoc dialogue
  • Brief contextual exchanges (mostly not technical).
• Teaching-style aside
  • Mentions possibly making a future video about crossovers if needed.

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Concise Verdict / Recommendation

This isn’t just a subwoofer review—it demonstrates a clean, compatibility-focused Alpine sub + amp installation in a CB7 Accord, emphasizing:

• OEM look (new trunk floor + matching carpet)
• Proper wiring practice (grommets, fused power, separated power/signal routing, correct grounding)

Based on the build steps and final “It works” listening test, the recommendation is yes: this Alpine S Type S 10-inch approach is a solid fit for a period-correct daily-driver build, especially when installed carefully and tuned with coordinated crossover settings (with ~120–125 Hz mentioned as the head unit target).