MTX Audio FPR12-04
Best box: 70.6 L bass reflex tuned to 17.8 Hz · F3 29.9 Hz
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Comparable 12.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the MTX Audio FPR12-04 does not fit your target box volume or tuning. Each entry links to its full enclosure design and Thiele/Small parameters.
⚠️ Engineering Notice for Builders
- The textbook alignment (35.3 L at 25.5 Hz) would need a 95.4 cm port; the recommendation is retuned to 70.6 L at 17.8 Hz so the port can be built.
- Port length (98.1 cm) exceeds a straight internal run; use an elbow bend, slotted vent or 3D folded duct to fit the enclosure.
Recommended Bass Reflex (Vented)
PORT NEEDS ELBOW / 3D| Net Box Volume (Vb) | 70.6 Liters |
| Tuning Frequency (Fb) | 17.8 Hz |
| F3 (-3 dB Cutoff) | 29.9 Hz |
| F6 / F10 Extension | 23.4 Hz / 14.2 Hz |
| Port Inner Diameter | Ø 10.0 cm |
| Port Physical Length | 98.1 cm |
| First Pipe Resonance | 175.0 Hz |
| Estimated MOL @ F3 | 111.1 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.8 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.131; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 44.1 Liters |
| System Q (Qtc) | 1.131 (above Butterworth: Qtc cannot fall below Qts (0.80)) |
| System Resonance (Fc) | 42.4 Hz |
| F3 (-3 dB Cutoff) | 35.4 Hz |
| F6 / F10 Extension | 29.7 Hz / 24.1 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 30.0 Hz |
| Total Q (Qts) | 0.8 |
| Electrical Q (Qes) | 0.936 |
| Mechanical Q (Qms) | 5.52 |
| Equivalent Volume (Vas) | 44.1 Liters |
| Diaphragm Area (Sd) | 543.3 cm² |
| DC Resistance (Re) | 3.36 Ω |
| Efficiency Bandwidth Product (EBP) | 32.1 |
| Linear Excursion (Xmax) | 13.0 mm |
| Thermal Power (Pe) | N/A W |
| Nominal Diameter | 12.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for MTX Audio FPR12-04?
Load Forge's calculated alignment puts MTX Audio FPR12-04 in a 70.6 liter vented enclosure tuned to 17.8 Hz, reaching an F3 cutoff of approximately 29.9 Hz.
Can MTX Audio FPR12-04 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 44.1 liters with a Qtc of 1.131 (above Butterworth: Qtc cannot fall below Qts (0.80)), the system exhibits an F3 of 35.4 Hz.
What port dimensions should be used for MTX Audio FPR12-04 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 10.0 cm with a length of 98.1 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
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