REDCATT 81NPM
Best box: 6.4 L bass reflex tuned to 82.0 Hz · F3 77.8 Hz
Open and tweak this box live ↗
Will it fit your requirements?
Check the REDCATT 81NPM against your space and targets — instant, no sign-up.
Free, no sign-up to simulate · a free account saves your design
Comparable 8.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the REDCATT 81NPM does not fit your target box volume or tuning. Each entry links to its full enclosure design and Thiele/Small parameters.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 6.4 Liters |
| Tuning Frequency (Fb) | 82.0 Hz |
| F3 (-3 dB Cutoff) | 77.8 Hz |
| F6 / F10 Extension | 70.2 Hz / 62.3 Hz |
| Port Inner Diameter | Ø 7.5 cm |
| Port Physical Length | 25.4 cm |
| First Pipe Resonance | 677.0 Hz |
| Estimated MOL @ F3 | 113.8 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 2.9 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 151.2 Hz |
| F3 (-3 dB Cutoff) | 144.2 Hz |
| F6 / F10 Extension | 107.0 Hz / 79.4 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 72.0 Hz |
| Total Q (Qts) | 0.33 |
| Electrical Q (Qes) | 0.344 |
| Mechanical Q (Qms) | 7.97 |
| Equivalent Volume (Vas) | 10.3 Liters |
| Diaphragm Area (Sd) | 219.0 cm² |
| DC Resistance (Re) | 5.2 Ω |
| Efficiency Bandwidth Product (EBP) | 209.1 |
| Linear Excursion (Xmax) | 6.0 mm |
| Thermal Power (Pe) | 400.0 W |
| Nominal Diameter | 8.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for REDCATT 81NPM?
Load Forge's calculated alignment puts REDCATT 81NPM in a 6.4 liter vented enclosure tuned to 82.0 Hz, reaching an F3 cutoff of approximately 77.8 Hz.
Can REDCATT 81NPM be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 2.9 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 144.2 Hz.
What port dimensions should be used for REDCATT 81NPM to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 7.5 cm with a length of 25.4 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 81NPM 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