Eminence Sigma Pro-18A-2 18" Cast Frame Driver
Best box: 189.6 L bass reflex tuned to 35.8 Hz · F3 37.7 Hz
Open and tweak this box live ↗
Will it fit your requirements?
Check the Eminence Sigma Pro-18A-2 18" Cast Frame Driver against your space and targets — instant, no sign-up.
Estimated retail 249.99 USD · Check price & availability ↗
Free, no sign-up to simulate · a free account saves your design
Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Eminence Sigma Pro-18A-2 18" Cast Frame Driver 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
- Large enclosure volume (189.6 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 189.6 Liters |
| Tuning Frequency (Fb) | 35.8 Hz |
| F3 (-3 dB Cutoff) | 37.7 Hz |
| F6 / F10 Extension | 32.9 Hz / 28.5 Hz |
| Port Inner Diameter | Ø 12.5 cm |
| Port Physical Length | 6.2 cm |
| First Pipe Resonance | 2774.0 Hz |
| Estimated MOL @ F3 | 121.2 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 89.2 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 63.6 Hz |
| F3 (-3 dB Cutoff) | 66.6 Hz |
| F6 / F10 Extension | 49.9 Hz / 37.5 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 28.0 Hz |
| Total Q (Qts) | 0.29 |
| Electrical Q (Qes) | 0.301 |
| Mechanical Q (Qms) | 8.28 |
| Equivalent Volume (Vas) | 441.2 Liters |
| Diaphragm Area (Sd) | 1140.0 cm² |
| DC Resistance (Re) | 6.29 Ω |
| Efficiency Bandwidth Product (EBP) | 93.2 |
| Linear Excursion (Xmax) | 6.1 mm |
| Thermal Power (Pe) | 650.0 W |
| Nominal Diameter | 18.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Eminence Sigma Pro-18A-2 18" Cast Frame Driver?
Load Forge's calculated alignment puts Eminence Sigma Pro-18A-2 18" Cast Frame Driver in a 189.6 liter vented enclosure tuned to 35.8 Hz, reaching an F3 cutoff of approximately 37.7 Hz.
Can Eminence Sigma Pro-18A-2 18" Cast Frame Driver be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 89.2 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 66.6 Hz.
What port dimensions should be used for Eminence Sigma Pro-18A-2 18" Cast Frame Driver to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 12.5 cm with a length of 6.2 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
Embed this design card on DIYAudio, AVSForum, Reddit, or Facebook. It shows the calculated F3, MOL (when the power rating is published) and box parameters.
Not sure if Sigma Pro-18A-2 18" Cast Frame Driver fits your physical space?
Don't force a driver into the wrong box. Use Bass Match to calculate which of 8,000+ catalog drivers delivers the highest SPL, lowest F3, and cleanest port air velocity for your exact trunk or room dimensions.
Run Bass Match for Your Space