Celestion NTR21-5010JD
Best box: 149.2 L bass reflex tuned to 35.0 Hz · F3 34.2 Hz
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Comparable 21.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Celestion NTR21-5010JD 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 (149.2 L at 33.3 Hz) would need a 46.7 cm port; the recommendation is retuned to 149.2 L at 35.0 Hz so the port can be built.
- Large enclosure volume (149.2 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 149.2 Liters |
| Tuning Frequency (Fb) | 35.0 Hz |
| F3 (-3 dB Cutoff) | 34.2 Hz |
| F6 / F10 Extension | 30.5 Hz / 26.8 Hz |
| Port Inner Diameter | Ø 21.4 cm |
| Port Physical Length | 43.7 cm |
| First Pipe Resonance | 394.0 Hz |
| Estimated MOL @ F3 | 122.4 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 66.2 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 60.4 Hz |
| F3 (-3 dB Cutoff) | 62.1 Hz |
| F6 / F10 Extension | 46.7 Hz / 35.2 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 30.0 Hz |
| Total Q (Qts) | 0.34 |
| Electrical Q (Qes) | 0.383 |
| Mechanical Q (Qms) | 3.0 |
| Equivalent Volume (Vas) | 220.0 Liters |
| Diaphragm Area (Sd) | 1870.0 cm² |
| DC Resistance (Re) | 6.0 Ω |
| Efficiency Bandwidth Product (EBP) | 78.2 |
| Linear Excursion (Xmax) | 15.0 mm |
| Thermal Power (Pe) | 1600.0 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 Celestion NTR21-5010JD?
Load Forge's calculated alignment puts Celestion NTR21-5010JD in a 149.2 liter vented enclosure tuned to 35.0 Hz, reaching an F3 cutoff of approximately 34.2 Hz.
Can Celestion NTR21-5010JD be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 66.2 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 62.1 Hz.
What port dimensions should be used for Celestion NTR21-5010JD to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 21.4 cm with a length of 43.7 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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