Dual Fi Car Audio BTL‑3 12" 4th Order Bandpass Subwoofer Box Plans
Subwoofer Box Plans for (2) Fi Car Audio BTL‑3 12" – 4th Order Bandpass Enclosure
Build a violently powerful, deep‑hitting 4th order bandpass enclosure for two Fi Car Audio BTL‑3 12" subwoofers with these precision‑engineered subwoofer box plans. Designed for extreme output, massive low‑end authority, and wide‑bandwidth performance, this enclosure unleashes the full potential of the BTL‑3 — one of Fi’s hardest‑hitting, high‑motor‑force subwoofers.
Perfect for demo builds, high‑power daily setups, and anyone wanting chest‑crushing bass.
Save Money — Build It Yourself
Stop wasting materials and guessing on dimensions. These DIY subwoofer box plans make it simple to build a professional‑grade enclosure at home, giving you competition‑level performance without paying custom‑shop prices.
What’s Included
- Downloadable ZIP file
- Multiple 3D rendering images
- Detailed spec sheet with subwoofer & enclosure specs
- Professional optimized cut sheet with parts list
- Precision‑designed 4th order bandpass layout
Designed For
Dual Fi Car Audio BTL‑3 12" Subwoofers – 4th Order Bandpass Enclosure
- Woofer Type: (2) Fi Car Audio BTL‑3 12
- Woofer Size: 12"
- Outside Dimensions: 37.25"W × 14.5"H × 26"D
- Tuning: 4th order bandpass (sealed + ported chambers engineered to manufacturer specs)
- Performance Notes: Built for extreme output, deep low‑frequency punch, and wide‑bandwidth response with excellent cone control
May work for other 12" woofers — user discretion advised.
Why These Plans Perform
- Optimized specifically for the Fi BTL‑3 12"
- 4th order design delivers massive output and strong low‑end authority
- Wide bandwidth response for loud, clean, musical performance
- Engineered for high‑power daily setups and demo‑style builds
- Smooth, predictable response thanks to properly balanced sealed and ported chambers
- Eliminates trial‑and‑error and prevents wasted materials