Ciare NDH18-4S (4Ω)
Best box: 67.4 L bass reflex tuned to 49.8 Hz · F3 51.3 Hz
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Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Ciare NDH18-4S (4Ω) 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 (67.4 L at 45.3 Hz) would need a 53.8 cm port; the recommendation is retuned to 67.4 L at 49.8 Hz so the port can be built.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 67.4 Liters |
| Tuning Frequency (Fb) | 49.8 Hz |
| F3 (-3 dB Cutoff) | 51.3 Hz |
| F6 / F10 Extension | 45.4 Hz / 39.6 Hz |
| Port Inner Diameter | Ø 20.0 cm |
| Port Physical Length | 42.0 cm |
| First Pipe Resonance | 409.0 Hz |
| Estimated MOL @ F3 | 122.6 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 34.3 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 83.8 Hz |
| F3 (-3 dB Cutoff) | 84.5 Hz |
| F6 / F10 Extension | 63.4 Hz / 47.6 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 31.0 Hz |
| Total Q (Qts) | 0.25 |
| Electrical Q (Qes) | 0.257 |
| Mechanical Q (Qms) | 9.8 |
| Equivalent Volume (Vas) | 240.0 Liters |
| Diaphragm Area (Sd) | 1164.0 cm² |
| DC Resistance (Re) | 3.0 Ω |
| Efficiency Bandwidth Product (EBP) | 120.8 |
| Linear Excursion (Xmax) | 11.5 mm |
| Thermal Power (Pe) | 1000.0 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 Ciare NDH18-4S (4Ω)?
Load Forge's calculated alignment puts Ciare NDH18-4S (4Ω) in a 67.4 liter vented enclosure tuned to 49.8 Hz, reaching an F3 cutoff of approximately 51.3 Hz.
Can Ciare NDH18-4S (4Ω) be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 34.3 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 84.5 Hz.
What port dimensions should be used for Ciare NDH18-4S (4Ω) to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 20.0 cm with a length of 42.0 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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