Bomber 4″ BBR TOP 120 W RMS 4 OHMS
Best box: 3.0 L bass reflex tuned to 120.7 Hz · F3 120.9 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Bomber 4″ BBR TOP 120 W RMS 4 OHMS 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 120.7 Hz) would need a 23.4 cm port; the recommendation is retuned to 3.0 L at 120.7 Hz so the port can be built.
- Limited linear excursion (Xmax: 1.15 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) | 3.0 Liters |
| Tuning Frequency (Fb) | 120.7 Hz |
| F3 (-3 dB Cutoff) | 120.9 Hz |
| F6 / F10 Extension | 100.0 Hz / 92.5 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 9.9 cm |
| First Pipe Resonance | 1739.0 Hz |
| Estimated MOL @ F3 | 105.6 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 1.62 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 2.291; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 0.7 Liters |
| System Q (Qtc) | 2.291 (above Butterworth: Qtc cannot fall below Qts (1.62)) |
| System Resonance (Fc) | 200.8 Hz |
| F3 (-3 dB Cutoff) | 170.5 Hz |
| F6 / F10 Extension | 152.6 Hz / 131.5 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 142.0 Hz |
| Total Q (Qts) | 1.62 |
| Electrical Q (Qes) | 2.074 |
| Mechanical Q (Qms) | 7.4 |
| Equivalent Volume (Vas) | 0.7 Liters |
| Diaphragm Area (Sd) | 40.7 cm² |
| DC Resistance (Re) | 3.38 Ω |
| Efficiency Bandwidth Product (EBP) | 68.5 |
| Linear Excursion (Xmax) | 1.1 mm |
| Thermal Power (Pe) | 60.0 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 Bomber 4″ BBR TOP 120 W RMS 4 OHMS?
Load Forge's calculated alignment puts Bomber 4″ BBR TOP 120 W RMS 4 OHMS in a 3.0 liter vented enclosure tuned to 120.7 Hz, reaching an F3 cutoff of approximately 120.9 Hz.
Can Bomber 4″ BBR TOP 120 W RMS 4 OHMS be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 0.7 liters with a Qtc of 2.291 (above Butterworth: Qtc cannot fall below Qts (1.62)), the system exhibits an F3 of 170.5 Hz.
What port dimensions should be used for Bomber 4″ BBR TOP 120 W RMS 4 OHMS to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 9.9 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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