PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm
Best box: 110.6 L bass reflex tuned to 46.8 Hz · F3 46.9 Hz
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Comparable 21.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm 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 (110.6 L at 40.7 Hz) would need a 53.6 cm port; the recommendation is retuned to 110.6 L at 46.8 Hz so the port can be built.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 110.6 Liters |
| Tuning Frequency (Fb) | 46.8 Hz |
| F3 (-3 dB Cutoff) | 46.9 Hz |
| F6 / F10 Extension | 41.9 Hz / 36.8 Hz |
| Port Inner Diameter | Ø 25.1 cm |
| Port Physical Length | 43.3 cm |
| First Pipe Resonance | 397.0 Hz |
| Estimated MOL @ F3 | 126.6 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 52.9 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 74.5 Hz |
| F3 (-3 dB Cutoff) | 76.4 Hz |
| F6 / F10 Extension | 57.4 Hz / 43.2 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 30.8 Hz |
| Total Q (Qts) | 0.28 |
| Electrical Q (Qes) | 0.287 |
| Mechanical Q (Qms) | 12.33 |
| Equivalent Volume (Vas) | 284.6 Liters |
| Diaphragm Area (Sd) | 1924.0 cm² |
| DC Resistance (Re) | 1.8 Ω |
| Efficiency Bandwidth Product (EBP) | 107.5 |
| Linear Excursion (Xmax) | 15.0 mm |
| Thermal Power (Pe) | 2000.0 W |
| Nominal Diameter | 21.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm?
Load Forge's calculated alignment puts PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm in a 110.6 liter vented enclosure tuned to 46.8 Hz, reaching an F3 cutoff of approximately 46.9 Hz.
Can PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 52.9 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 76.4 Hz.
What port dimensions should be used for PRV Audio 21SW4000-NDY-2 21" Professional Subwoofer 2 Ohm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 25.1 cm with a length of 43.3 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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