Monacor SP-4/60PRO
Best box: 4.5 L bass reflex tuned to 64.4 Hz · F3 85.8 Hz
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Comparable 4.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Monacor SP-4/60PRO 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
- Limited linear excursion (Xmax: 2.3 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) | 4.5 Liters |
| Tuning Frequency (Fb) | 64.4 Hz |
| F3 (-3 dB Cutoff) | 85.8 Hz |
| F6 / F10 Extension | 61.3 Hz / 49.4 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 28.0 cm |
| First Pipe Resonance | 615.0 Hz |
| Estimated MOL @ F3 | 99.6 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 7.7 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 106.0 Hz |
| F3 (-3 dB Cutoff) | 102.6 Hz |
| F6 / F10 Extension | 79.6 Hz / 61.1 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 92.0 Hz |
| Total Q (Qts) | 0.6 |
| Electrical Q (Qes) | 0.676 |
| Mechanical Q (Qms) | 5.35 |
| Equivalent Volume (Vas) | 3.0 Liters |
| Diaphragm Area (Sd) | 68.0 cm² |
| DC Resistance (Re) | 6.76 Ω |
| Efficiency Bandwidth Product (EBP) | 136.1 |
| Linear Excursion (Xmax) | 2.3 mm |
| Thermal Power (Pe) | 30.0 W |
| Nominal Diameter | 4.5" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Monacor SP-4/60PRO?
Load Forge's calculated alignment puts Monacor SP-4/60PRO in a 4.5 liter vented enclosure tuned to 64.4 Hz, reaching an F3 cutoff of approximately 85.8 Hz.
Can Monacor SP-4/60PRO be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 7.7 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 102.6 Hz.
What port dimensions should be used for Monacor SP-4/60PRO to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 28.0 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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.
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