When planning a sound system upgrade for your Audi A4 B5 (1994–2001), one of the most common questions is: should you start with a subwoofer or an amplifier? While both upgrades can significantly improve your sound experience, the better first step depends on your current setup, listening preferences, and budget. This guide will help you decide where to begin for the best value and results.
Understanding the Factory Audio Limitations
The stock audio system in the Audi A4 B5 isn’t exactly high-end. It typically includes basic speakers in the front and rear doors, and sometimes rear shelf speakers in the sedan model. These setups can sound flat, especially at higher volumes, and often lack depth in the lower frequencies.
Why Start with a Subwoofer?
Adding a subwoofer – especially a compact, active underseat unit – instantly fills in the missing low-end and adds impact to your music. Here’s why it often makes sense to begin here:
Quick improvement: The difference in bass performance is noticeable right away.
Doesn’t require changing speakers: You can keep your existing components.
Great for OEM integration: Many underseat subwoofers come with high-level inputs and are easy to install.
No trunk space loss: Models like the Caliber BC121US fit under the front seats.
If you want to add punch to your music without tearing out your whole system, the subwoofer is a smart first move.
Explore subwoofer options for your model at Audi A4 B5 Lautsprecher.
When to Prioritize an Amplifier
However, there’s a strong case to be made for upgrading the amplifier first — especially if your stock or aftermarket speakers are capable of more than the factory head unit can deliver.
More power = better clarity: Most OEM radios offer around 15–20 watts RMS per channel. Even basic amps like the Hertz DPower 4.300 offer 4x105W RMS at 2 ohms — a huge jump.
Better control over sound: External amps often include filters, gain control, and sound tuning features.
Future-proofing: A proper amp supports upgrades like component speakers or additional subs.
Find more on external amp integration at Auto-Lautsprecher.
But What About the Factory Radio?
Here’s the catch: the Audi A4 B5’s factory radios usually don’t offer RCA pre-outs, which are typically needed to connect amplifiers and subs.
So how do you make this work?
High-level inputs: Choose amplifiers like the Hertz DPower 4.300 that accept speaker-level signal directly from the factory head unit.
T-harness adapter: Install this between the radio and car wiring. It splits the signal cleanly to feed your amplifier or sub without cutting factory wires.
This way, you retain all OEM functions like fader/balance and steering controls.
Want to learn more about integration? Check out Autoboxen.
Ideal Upgrade Path for Audi A4 B5
If you’re unsure where to start, here’s a practical and affordable sequence:
Add an underseat subwoofer (e.g. Caliber BC121US)
Instant bass, clean install, works with OEM radio
Install a 4-channel amplifier (e.g. Hertz DPower 4.300)
Run front and rear speakers for more clarity and control
Upgrade front component speakers (e.g. Hertz DSK 130.3)
Better mids, highs, and soundstage
Add rear coaxials (e.g. Hertz DCX 165.3)
Complete the system with balanced rear fill
Final Thoughts
Whether you start with a subwoofer or an amp depends on your priorities. If you want quick, easy bass enhancement, go for the underseat sub. If you value clarity and power — or plan to upgrade all speakers — a 4-channel amp might be the better first step.
In either case, you can build a great-sounding system in your Audi A4 B5 without changing the factory radio. Just be sure to use high-level inputs and proper harnesses for clean, reversible installation.
Ready to transform your sound? Start smart, and enjoy the ride.