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Frequently Asked Questions (FAQ)

1. What is this subwoofer enclosure designed for?

Our custom 3D printed enclosure is designed to replace the weak factory subwoofer in the BMW Z3 Roadster. It fits into the original factory location with no cutting or major modifications required, and delivers significantly improved bass performance tailored to the acoustics of the Z3 cabin.

2. What is the enclosure volume?

The Stealth Box has a volume of 5.3 litres and is optimized for 6.5-inch subwoofers designed to produce tight, controlled bass.

The Big Box has a volume of 11.05 litres and is optimized for 6.5-inch subwoofers intended for maximum low-frequency output.

3. What subwoofers can I choose from?

We offer three professionally installed and tuned 6.5-inch subwoofers:

• SWS Earthquake 6.5X (100W RMS, 4 ohm)

• Helix IKW6 DVC 2 ohm (150W RMS, dual 2 ohm)

• JL Audio 6W (150W RMS, 4 ohm, not compatible with the Stealth Box)

4. Is the subwoofer installation included?

Yes. Each subwoofer is installed with an airtight seal, matching black hardware, enclosure tuning, and full installation instructions.

5. What is the lead time?

All enclosures are handmade and built to order. The typical production time is approximately 4-5 weeks.

Enclosure Upgrade Options

Every enclosure includes standard acoustic fill and one sheet of sound deadening on the rear wall. The following upgrades are available for improved performance:

Premium Full Sound Deadening

This option applies higher-density vibration-absorbing material to all exterior sides of the enclosure. It reduces cabinet resonance and unwanted vibrations and helps produce cleaner, tighter bass, especially at higher volumes or with the top down.

Premium Acoustic Fill

A denser internal fill material that increases the effective acoustic volume of the enclosure. This allows the subwoofer to reach lower frequencies and improves the overall smoothness and depth of the bass. This is the same material used in my personal Big Box system.

XL Upgrade

Available for both the Stealth Box and Big Box. This upgrade includes an enlarged internal chamber section, added internal bracing, and modified internal geometry for higher output capability and improved structural integrity. It is designed for audiophiles who want maximum performance and plan to run their systems at elevated output levels.

Dual Input Terminals

A plug and play option that allows the amplifier to fully utilize a dual 2 ohm subwoofer. This upgrade is recommended for Z3 models originally equipped with the non Harman Kardon system, which used two 5.25 inch speakers in the factory sub enclosure. If you are unsure which configuration your car has, you may send a photo or arrange a brief video call to confirm.

Enclosure Vibration Isolation Pad

Already stable by design, the enclosure can be paired with an optional TPU vibration-dampening pad for even greater control when you really turn things up.

Seat Belt Retainer Guide Clips

Reinforced clips that help prevent the factory seat belt guides from cracking or breaking.

Sun, Rain and Sound (SRS) Upgrade

The Sun, Rain and Sound upgrade uses a high-heat-resistant filament and moisture resistant treatment for improved durability in harsh or unpredictable climates. It is recommended for hot or humid regions such as Florida, Texas, Ontario, and South Carolina. It also improves low-frequency clarity by approximately 10 percent.

The SRS upgrade protects the enclosure from heat, humidity, and unexpected rain, and maintains consistent acoustic performance even when exposed to weather with the top down.

Cosmetic Upgrades (Big Box Only)

• Standard Black Leather Wrap

• OEM+ Marine Soft Touch Leather Wrap in Beige

• OEM+ Marine Soft Touch Leather Wrap in Black

These materials are UV-resistant and weather-resistant and provide a refined appearance that blends with the interior.

7. Can I buy the enclosure only?

Yes. You may purchase the enclosure alone, although optimum performance is achieved when paired with a professionally installed and tuned subwoofer.

8. Do you provide amplifier recommendations?

Yes. When placing an order, you may request a list of recommended amplifiers matched to your selected enclosure and subwoofer.

9. What are the shipping options?

North America: 49 to 79 USD

Europe: 60 to 90 EUR

Australia: 59-99 AUD

10. How do I place an order?

Select the Order Now button on the product page or complete the order form at www.z3subwoofer.com.

For questions or custom requests, contact BMWZ3Enclosure@gmail.com.