Monacor SPX-30M
Best box: 1.5 L bass reflex tuned to 93.5 Hz · F3 119.6 Hz
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Comparable 3.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Monacor SPX-30M 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 (1.5 L at 85.0 Hz) would need a 50.7 cm port; the recommendation is retuned to 1.5 L at 93.5 Hz so the port can be built.
- Limited linear excursion (Xmax: 1.1 mm); set a high-pass subsonic filter at 25–30 Hz when driven with high power.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 1.5 Liters |
| Tuning Frequency (Fb) | 93.5 Hz |
| F3 (-3 dB Cutoff) | 119.6 Hz |
| F6 / F10 Extension | 99.9 Hz / 78.8 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 41.3 cm |
| First Pipe Resonance | 416.0 Hz |
| Estimated MOL @ F3 | 93.3 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.71 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.004; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 1.8 Liters |
| System Q (Qtc) | 1.004 (above Butterworth: Qtc cannot fall below Qts (0.71)) |
| System Resonance (Fc) | 141.4 Hz |
| F3 (-3 dB Cutoff) | 116.8 Hz |
| F6 / F10 Extension | 96.0 Hz / 76.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 100.0 Hz |
| Total Q (Qts) | 0.71 |
| Electrical Q (Qes) | 0.894 |
| Mechanical Q (Qms) | 3.45 |
| Equivalent Volume (Vas) | 1.8 Liters |
| Diaphragm Area (Sd) | 32.0 cm² |
| DC Resistance (Re) | 6.4 Ω |
| Efficiency Bandwidth Product (EBP) | 111.9 |
| Linear Excursion (Xmax) | 1.1 mm |
| Thermal Power (Pe) | 20.0 W |
| Nominal Diameter | 3.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Monacor SPX-30M?
Load Forge's calculated alignment puts Monacor SPX-30M in a 1.5 liter vented enclosure tuned to 93.5 Hz, reaching an F3 cutoff of approximately 119.6 Hz.
Can Monacor SPX-30M be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 1.8 liters with a Qtc of 1.004 (above Butterworth: Qtc cannot fall below Qts (0.71)), the system exhibits an F3 of 116.8 Hz.
What port dimensions should be used for Monacor SPX-30M to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 41.3 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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