FAW Speaker Logic Assembly: The 6 Key Components for Superior Cab Audio

Welcome to this in-depth technical breakdown of the FAW Speaker Logic Assembly. This is the complete, 4-speaker component audio system for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This assembly is the “voice” of the truck, responsible for translating electrical signals from the cab’s infotainment unit into clear, audible sound for the driver, covering everything from music and phone calls to critical system alerts.

The “Logic Assembly” designation is crucial. This is not a single part, but a multi-component system based on an advanced acoustic “logic.” The FAW Speaker Logic Assembly is a “component” system, meaning it separates audio frequencies across different, specialized speakers. This design is far superior to cheap “coaxial” speakers, as it uses two dedicated full-range speakers for high/mid frequencies and two dedicated low-frequency speakers (woofers) for bass.

This component-based logic ensures maximum audio clarity and reduced distortion. This guide is essential for audio technicians and parts specialists. We will deconstruct the entire FAW Speaker Logic Assembly into its 6 key component types, analyzing the two types of speakers and the specific fastening system that makes this assembly reliable in a high-vibration truck environment.

Core 1: The Clarity Drivers – Full-Range Speakers (MSUs 1 & 2)

This section, the “longer” module of our analysis, covers the most critical components for audio clarity in the FAW Speaker Logic Assembly. These are the ‘Left full-range speaker assy’ (7901015-A01) and the ‘Right full-range speaker assy’ (7901020-A01).

Acoustic Logic (Mids & Highs): A “full-range” speaker is designed to produce the middle and high frequencies (mid-range and treble). This is where the human voice, string instruments, and cymbals “live” in a piece of music. In the FAW Speaker Logic Assembly, their “logic” is to provide a clear, crisp sound stage for the driver.

Stereo Imaging and Placement: Having a separate ‘Left’ and ‘Right’ speaker is the foundation of stereo sound. These speakers are typically mounted high up in the cab, either in the A-pillars (the pillars beside the windshield) or in the upper corners of the dashboard, aimed at the driver. This “staging logic” is deliberate. By placing these directional speakers at ear-level, the FAW Speaker Logic Assembly creates a “sound stage” that appears to be directly in front of the driver, rather than at their feet. This is essential for understanding navigation prompts and phone calls.

Construction: These speakers are Minimum Serviceable Units (MSUs). Each assembly consists of several parts:

• The Cone: Usually made of a stiff, lightweight material like treated paper or polypropylene. This material must be durable enough to resist the extreme temperature swings and high humidity found inside a truck cab.
• The Surround: A flexible ring (often rubber or foam) that attaches the cone to the basket. It allows the cone to move back and forth, creating sound waves.
• The Voice Coil & Magnet: This is the “motor” of the speaker. The audio signal from the head unit flows into the voice coil, which becomes an electromagnet that moves within the permanent magnet’s field, pushing and pulling the cone.
• The Basket: A rigid frame (plastic or stamped metal) that holds all the parts together and provides the mounting points.

Serviceability (MSU): These are high-wear items. The most common failure is a “blown” voice coil, caused by overpowering the speaker (turning the volume up too high with distortion). This results in no sound or a “scratchy” sound. The surround can also tear or decay, causing a “buzzing” or “flapping” noise. As an MSU, a technician diagnoses the failed speaker and replaces the single unit (7901015-A01 or 7901020-A01), not the entire FAW Speaker Logic Assembly.

Core 2: The Bass Drivers – Low-Frequency Speakers (MSUs 3 & 4)

This is the second half of the acoustic “logic.” The ‘Left low-frequency speaker assy’ (7901025-A02) and ‘Right low-frequency speaker assy’ (7901030-A02) are the woofers.

Acoustic Logic (Lows): The “logic” of these speakers is to handle only the low-end frequencies (bass and mid-bass). Bass frequencies require moving large amounts of air, which is why these speakers (woofers) are physically larger, with more robust magnets and wider surrounds than their full-range counterparts.

Placement and Component Logic: These speakers are almost always mounted low in the truck doors. Bass is non-directional, so placement is less important for “staging.” The door panel itself acts as a large “enclosure” or “baffle,” which is necessary for the speaker to produce deep, rich bass tones.

This “component” separation is the most important feature of the FAW Speaker Logic Assembly. The head unit’s amplifier has a “crossover” that sends *only* bass signals (e.g., below 200 Hz) to these woofers and *only* high signals (above 200 Hz) to the full-range speakers. This “logic” prevents the small full-range speakers from trying to produce bass (which they can’t do well), resulting in dramatically cleaner, louder sound without distortion.

Serviceability (MSU): Like the full-range speakers, these are primary MSUs. They are even more prone to failure from distortion, as bass notes carry the most power. A “popping” sound at high volume is a sign of the voice coil hitting its limit. A “buzzing” sound is often a sign of a loose mounting screw or a separating surround.

Core 3: The Fastening System Logic (MSUs 5 & 6)

A speaker is a vibration-creating device. The mounting hardware for the FAW Speaker Logic Assembly is therefore not just an afterthought—it is a critical system designed to manage that vibration. The list calls for 16 screws and 16 washers.

1. ‘Cross recessed pan head self-tapping screw’ (CQ2714216): The parts list calls for sixteen (16) of these. The “self-tapping” logic means they are designed to cut their own threads into the plastic of the door panel or dashboard. The quantity (16) confirms a robust 4-point mounting pattern for each of the four speakers.

2. ‘Washer’ (Q40105): The list also calls for sixteen (16) washers. This is arguably the most important “logic” in the fastening system. A speaker’s frame is often made of plastic. A screw head creates a small, high-pressure point. The washer’s logic is twofold:

• Load Distribution: It spreads the screw’s clamping force over a wider area of the speaker’s plastic mounting flange, preventing it from cracking.
• Vibration Damping: It acts as a buffer between the metal screw and the speaker frame, and (if it’s a spring washer) provides constant tension. This prevents the screw from vibrating loose—the #1 cause of “rattling” speakers.

These tiny, low-cost components are critical MSUs. Using the wrong screw or forgetting the washer will result in a failed installation, poor bass response (due to an air leak), and eventual rattling.

FAW Speaker Logic Assembly Parts List

The following table provides the complete, detailed breakdown of all 6 component types identified in the FAW Speaker Logic Assembly diagram for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Speaker Logic Assembly are defined by its function as a multi-component audio output system. This assembly is designed to provide clear, full-range sound optimized for the cab’s acoustic environment.