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Project Overview

1. Complete Bill of Materials (BOM)

1.1 Main Carrier

1.2 5.1 Channel Audio Drivers (Harman Style: Clear Vocals & Solid Bass)

Professional Tip for Harman Style Matching: Choose neodymium magnet drivers with sensitivity ≥ 85dB. These units deliver prominent midrange and decent low-frequency extension, avoiding harsh treble caused by metal enclosure reflection.

1.3 Circuit System (Mini Integrated Design for Compact Space)

1.4 Acoustic & Structural Accessories (Critical for Metal Enclosure Sound Quality)

1.5 Hand Tools

2. Step-by-Step Illustrated Tutorial

Note: [Image X] refers to key frame screenshots captured from the original video; all procedures follow the standard workflow for speaker making: Planning → Drilling → Wiring → Final Assembly.

Step 1: Disassemble the Model & Measure Internal Space

1. Operation Steps
   
   
   1. Carefully detach removable parts including cab top, cargo box rails and chassis cover. Do not use brute force to avoid deforming the aluminum shell or scratching the paint.
   2. Remove all factory-installed plastic accessories and foam fillers to ensure a clean hollow cavity.
   3. Measure the length, width and height of available space on the front face, grille, cargo box sides and chassis with a tape measure, and mark pre-defined mounting positions for all drivers.
   
   
2. Professional Craft Notes
   
   
   • The irregular cavity of a truck model requires reasonable layout: place the large subwoofer in the chassis (the largest cavity, which is essential for low-frequency performance); install small surround drivers on both sides of the cargo box.
   • Centralize all circuit modules and batteries inside the cab, keeping them away from audio drivers to eliminate current noise and interference.
   • Plan wire routes in advance and avoid movable parts of the model.
   
   

Step 2: Mark Positions & Drill Precise Holes

1. Operation Steps
   
   
   1. Draw circular holes according to the outer diameter of each driver. Keep the left/right main drivers and rear surround drivers strictly symmetrical to ensure balanced sound field.
   2. Install matched micro hole cutters on the drill, set the drill to low speed, and drill vertically. Aluminum alloy is hard; high-speed drilling will cause slipping and chipped edges.
   3. Polish hole edges with a metal file after drilling to remove sharp burrs.
   
   
2. Key Tips & Common Mistakes
   
   
   • Clean up all metal debris inside the cavity after drilling. Metal scraps may cause short circuits and abnormal noise.
   • Do not drill oversized holes. Reserve 1~2mm clearance for rubber gaskets to guarantee airtightness.
   
   

Step 3: Install & Seal Audio Drivers

1. Operation Steps
   
   
   1. Attach a full-circle ultra-thin butyl rubber gasket to the mounting face of each driver with no gaps.
   2. Insert the driver from the inside out and press firmly to make full contact between the driver panel and aluminum shell.
   3. Apply a small amount of low-temperature hot melt glue around the driver base for extra fixation. Do not touch the driver cone and surround with glue.
   
   
2. Acoustic Principles
   
   
   • Airtightness is the top priority for speaker enclosures. Any air leakage from driver holes or model gaps will severely weaken bass response.
   • Never use cyanoacrylate (super glue) to fix drivers. Hard glue transmits metal resonance and causes unwanted noise. The combination of soft hot melt glue + rubber gasket is the optimal solution.
   
   

Step 4: Internal Acoustic Treatment for Metal Enclosure

1. Operation Steps
   
   
   1. Cut sound-absorbing cotton into suitable sizes and paste evenly on all inner walls of the cab, cargo box and chassis.
   2. Add extra cotton at right-angle corners and narrow gaps to suppress standing waves (a typical acoustic defect of rigid metal enclosures).
   3. Lay cotton loosely behind the subwoofer instead of compacting it, to reserve sufficient air volume for low-frequency extension.
   
   
2. Senior DIY Experience

   
   

   Aluminum alloy is a rigid material. Compared with wooden enclosures, it is more prone to resonance and harsh treble reflection. Sound-absorbing cotton is a must-have material to soften tone and achieve warm vocals matching Harman Kardon sound style.
   
   

Step 5: Layout & Fix Circuit Modules with Vibration Isolation

1. Operation Steps
   
   
   1. Lay silicone shock pads on the vacant area inside the cab, then place the 5.1 channel amplifier board, Bluetooth module and battery pack in position.
   2. Apply hot melt glue only on four corners of each module. Do not cover heat dissipation holes — amplifier boards generate heat during operation.
   3. Drill small holes on the truck side for charging port and power switch, then install and seal the accessories.
   
   
2. Safety Notes
   
   
   • Keep the battery pack away from heat-generating amplifier board to prevent accelerated battery aging.
   • Centralize all electronic components to minimize long-distance wiring across separate cavities.
   
   

Step 6: Soldering & Cable Routing (Anti-Interference & Short-Circuit Prevention)

1. Operation Steps
   
   
   1. Follow standard color rules: Red wire for positive (+), Black wire for negative (-). Wire each driver (Left/Right Main, Center, Surround Left/Right, Subwoofer) to the corresponding port on the amplifier board.
   2. Use a soldering iron at low temperature. Ensure full solder joints with no cold solder joints or solder bridges. Wrap all exposed solder points with insulation tape to avoid short circuits on conductive aluminum shell.
   3. Route all cables along inner walls and fix them section by section. Leave slight slack on wires and do not pull tight.
   
   
2. Circuit Standards
   
   
   • Group cables by channels separately. Do not twist different channel wires together to reduce audio crosstalk.
   • All exposed metal solder points must be fully insulated, as the aluminum shell is conductive and will burn out the amplifier board once contacted.
   
   

Step 7: Reassemble the Model & Final Sealing

1. Operation Steps
   1. Double-check all wires to ensure no extrusion or tension, then reinstall cab roof, cargo box rails and chassis cover in order.
   2. Fill small assembly gaps of the model with flexible metal sealant to further improve enclosure airtightness.
   3. Test all movable parts to guarantee the model’s original functions are not affected after modification.
   
   

Step 8: Power On Test & Sound Tuning

1. Operation Steps
   
   
   1. Toggle the power switch; the indicator light will turn on. Enable Bluetooth on your phone and pair with the speaker.
   2. Test channel by channel: check if each driver works normally, no static noise or distortion.
   3. Play vocal music, pop tracks and low-frequency test tones for fine sound tuning.
   
   
2. Harman Style Tuning Reference
   
   
   • Bright vocals: Slightly boost midrange gain on the amplifier board to enhance center channel performance.
   • Weak bass: Recheck sealing of the subwoofer and add a small amount of sound-absorbing cotton at the bottom.
   • Harsh treble: Add extra sound-absorbing cotton behind main drivers to soften high-frequency reflection from metal shell.
   
   

3. 5.1 Channel Standard Wiring Diagram & Definition

Amplifier Board Port Matching Rules (International Standard)

1. L / R → Left / Right Main Channel Drivers (Front Stereo)
2. CEN → Center Channel Driver (Core for human voice)
3. SL / SR → Surround Left / Surround Right Drivers (Spatial sound field)
4. SW → Subwoofer Driver (Low-frequency dynamics)
5. POWER+ / POWER- → Battery Positive / Negative
6. CHARGE → External Type-C Charging Module

Critical Soldering Rule: Never reverse positive and negative polarity of any channel. Reversed polarity causes sound field cancellation and degraded bass. Reversed power polarity will directly burn out the amplifier board.

4. Dedicated Acoustic Optimization for Metal Enclosures

1. Resonance Suppression: If the truck body vibrates abnormally with bass output, add extra thin silicone gaskets between drivers and the shell to cut off resonance transmission.
2. Standing Wave Elimination: Narrow cargo box cavities easily generate standing waves. Add thickened sound-absorbing cotton at diagonal corners and avoid large bare hard wall areas.
3. Long-Term Airtightness Maintenance: If bass becomes weak after long use, re-seal loose gaskets and gaps.
4. Harman Style Enhancement: This speaker is optimized for vocal and pop music. Moderately boost midrange and low frequency, and attenuate excessive treble.

5. Common Troubleshooting & Pitfall Guide

1. Single driver no sound: Check for cold solder joints or broken wires on the corresponding channel.
2. Constant background hum: Cables are tangled and cause crosstalk → re-group wires; modules touch metal shell → add extra insulation pads.
3. Weak & hollow bass: 90% caused by air leakage. Re-seal driver holes and model gaps completely.
4. Overheated amplifier board: Check for short circuits or mismatched driver impedance.
5. Scratched model paint: Always use low-temperature glue and low-speed drilling. Avoid corrosive adhesives on aluminum surface.

6. Advanced Upgrade Solutions for Enthusiasts

1. Add Passive Crossover: Install mini 2-way crossovers for main drivers and subwoofer to separate high and low frequency for better resolution.
2. LED Ambient Light: Embed micro LED lights inside the cab for music rhythm lighting effect.
3. Higher-Capacity Battery: Replace with 3000mAh 18650 batteries for longer playback time.
4. Wired AUX Input: Expand AUX port for wired connection with computers and professional audio players.

Supplementary Notes for Independent Site Use

1. All professional audio terms adopt international mainstream DIY audio vocabulary, consistent with European & American speaker maker communities;
2. The full text retains the original hierarchical structure and table format, which is compatible with most independent site editors (WordPress, Shopify, etc.);
3. You can directly replace [Image X] with your actual screenshot links to complete the graphic layout.

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