Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm
Best box: 2.7 L bass reflex tuned to 77.3 Hz · F3 109.1 Hz
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Comparable 4.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 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
- Limited linear excursion (Xmax: 1.75 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) | 2.7 Liters |
| Tuning Frequency (Fb) | 77.3 Hz |
| F3 (-3 dB Cutoff) | 109.1 Hz |
| F6 / F10 Extension | 89.3 Hz / 68.3 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 32.9 cm |
| First Pipe Resonance | 523.0 Hz |
| Estimated MOL @ F3 | 99.5 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.656 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 0.927; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 3.4 Liters |
| System Q (Qtc) | 0.927 (above Butterworth) |
| System Resonance (Fc) | 128.6 Hz |
| F3 (-3 dB Cutoff) | 110.0 Hz |
| F6 / F10 Extension | 89.3 Hz / 70.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 90.9 Hz |
| Total Q (Qts) | 0.656 |
| Electrical Q (Qes) | 0.772 |
| Mechanical Q (Qms) | 4.35 |
| Equivalent Volume (Vas) | 3.4 Liters |
| Diaphragm Area (Sd) | 73.9 cm² |
| DC Resistance (Re) | 5.73 Ω |
| Efficiency Bandwidth Product (EBP) | 117.8 |
| Linear Excursion (Xmax) | 1.8 mm |
| Thermal Power (Pe) | 20.0 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 Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm?
Load Forge's calculated alignment puts Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm in a 2.7 liter vented enclosure tuned to 77.3 Hz, reaching an F3 cutoff of approximately 109.1 Hz.
Can Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 3.4 liters with a Qtc of 0.927 (above Butterworth), the system exhibits an F3 of 110.0 Hz.
What port dimensions should be used for Coast Buyouts CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 32.9 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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Not sure if CW-125B20U 4-1/2" Paper Cone Woofer 8 Ohm fits your physical space?
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