Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil
Best box: 372.5 L bass reflex tuned to 21.3 Hz · F3 19.3 Hz
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Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil 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 (372.5 L at 16.4 Hz) would need a 79.7 cm port; the recommendation is retuned to 372.5 L at 21.3 Hz so the port can be built.
- Large enclosure volume (372.5 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 372.5 Liters |
| Tuning Frequency (Fb) | 21.3 Hz |
| F3 (-3 dB Cutoff) | 19.3 Hz |
| F6 / F10 Extension | 17.5 Hz / 15.6 Hz |
| Port Inner Diameter | Ø 20.0 cm |
| Port Physical Length | 41.4 cm |
| First Pipe Resonance | 415.0 Hz |
| Estimated MOL @ F3 | 116.9 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 318.6 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 28.6 Hz |
| F3 (-3 dB Cutoff) | 29.6 Hz |
| F6 / F10 Extension | 22.2 Hz / 16.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 22.0 Hz |
| Total Q (Qts) | 0.53 |
| Electrical Q (Qes) | 0.67 |
| Mechanical Q (Qms) | 2.53 |
| Equivalent Volume (Vas) | 248.3 Liters |
| Diaphragm Area (Sd) | 1184.0 cm² |
| DC Resistance (Re) | 4.2 Ω |
| Efficiency Bandwidth Product (EBP) | 32.8 |
| Linear Excursion (Xmax) | 28.0 mm |
| Thermal Power (Pe) | 1200.0 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 Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil?
Load Forge's calculated alignment puts Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil in a 372.5 liter vented enclosure tuned to 21.3 Hz, reaching an F3 cutoff of approximately 19.3 Hz.
Can Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 318.6 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 29.6 Hz.
What port dimensions should be used for Dayton Audio UMII18-22 Ultimax II 18" DVC Subwoofer 2 Ohm Per Coil to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 20.0 cm with a length of 41.4 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
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