Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm
Best box: 6.4 L bass reflex tuned to 119.7 Hz · F3 115.2 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm 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 (1.6 L at 133.0 Hz) would need a 17.2 cm port; the recommendation is retuned to 6.4 L at 119.7 Hz so the port can be built.
- Limited linear excursion (Xmax: 0.5 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) | 6.4 Liters |
| Tuning Frequency (Fb) | 119.7 Hz |
| F3 (-3 dB Cutoff) | 115.2 Hz |
| F6 / F10 Extension | 98.5 Hz / 90.2 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 2.8 cm |
| First Pipe Resonance | 6049.0 Hz |
| Estimated MOL @ F3 | 97.7 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 1.107 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.566; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 2.0 Liters |
| System Q (Qtc) | 1.566 (above Butterworth: Qtc cannot fall below Qts (1.11)) |
| System Resonance (Fc) | 221.3 Hz |
| F3 (-3 dB Cutoff) | 178.0 Hz |
| F6 / F10 Extension | 154.4 Hz / 129.0 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 156.5 Hz |
| Total Q (Qts) | 1.107 |
| Electrical Q (Qes) | 1.612 |
| Mechanical Q (Qms) | 3.53 |
| Equivalent Volume (Vas) | 2.0 Liters |
| Diaphragm Area (Sd) | 52.8 cm² |
| DC Resistance (Re) | 3.69 Ω |
| Efficiency Bandwidth Product (EBP) | 97.1 |
| Linear Excursion (Xmax) | 0.5 mm |
| Thermal Power (Pe) | 4.0 W |
| Nominal Diameter | 4.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm?
Load Forge's calculated alignment puts Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm in a 6.4 liter vented enclosure tuned to 119.7 Hz, reaching an F3 cutoff of approximately 115.2 Hz.
Can Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 2.0 liters with a Qtc of 1.566 (above Butterworth: Qtc cannot fall below Qts (1.11)), the system exhibits an F3 of 178.0 Hz.
What port dimensions should be used for Coast Buyouts CES SP-0039 4" Replacement Speaker 4 Ohm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 2.8 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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