REDCATT 21NPW
Best box: 84.9 L bass reflex tuned to 45.1 Hz · F3 44.3 Hz
Open and tweak this box live ↗
Will it fit your requirements?
Check the REDCATT 21NPW against your space and targets — instant, no sign-up.
Estimated retail 599.95 EUR · Check price & availability ↗
Free, no sign-up to simulate · a free account saves your design
Comparable 21.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the REDCATT 21NPW 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 (84.9 L at 41.0 Hz) would need a 51.7 cm port; the recommendation is retuned to 84.9 L at 45.1 Hz so the port can be built.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 84.9 Liters |
| Tuning Frequency (Fb) | 45.1 Hz |
| F3 (-3 dB Cutoff) | 44.3 Hz |
| F6 / F10 Extension | 39.6 Hz / 34.8 Hz |
| Port Inner Diameter | Ø 20.0 cm |
| Port Physical Length | 40.2 cm |
| First Pipe Resonance | 428.0 Hz |
| Estimated MOL @ F3 | 127.3 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 38.4 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 74.9 Hz |
| F3 (-3 dB Cutoff) | 79.3 Hz |
| F6 / F10 Extension | 59.2 Hz / 44.3 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 35.0 Hz |
| Total Q (Qts) | 0.32 |
| Electrical Q (Qes) | 0.329 |
| Mechanical Q (Qms) | 11.12 |
| Equivalent Volume (Vas) | 149.0 Liters |
| Diaphragm Area (Sd) | 1662.0 cm² |
| DC Resistance (Re) | 3.0 Ω |
| Efficiency Bandwidth Product (EBP) | 106.2 |
| Linear Excursion (Xmax) | 9.0 mm |
| Thermal Power (Pe) | 3600.0 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 REDCATT 21NPW?
Load Forge's calculated alignment puts REDCATT 21NPW in a 84.9 liter vented enclosure tuned to 45.1 Hz, reaching an F3 cutoff of approximately 44.3 Hz.
Can REDCATT 21NPW be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 38.4 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 79.3 Hz.
What port dimensions should be used for REDCATT 21NPW to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 20.0 cm with a length of 40.2 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 21NPW 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