SEAS L0021-04S RM 120
Best box: 2.8 L bass reflex tuned to 77.8 Hz · F3 78.5 Hz
Open and tweak this box live ↗
Will it fit your requirements?
Check the SEAS L0021-04S RM 120 against your space and targets — instant, no sign-up.
Estimated retail 3052.00 NOK · Check price & availability ↗
Free, no sign-up to simulate · a free account saves your design
Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the SEAS L0021-04S RM 120 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: 1.7 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) | 2.8 Liters |
| Tuning Frequency (Fb) | 77.8 Hz |
| F3 (-3 dB Cutoff) | 78.5 Hz |
| F6 / F10 Extension | 69.0 Hz / 60.5 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 31.2 cm |
| First Pipe Resonance | 552.0 Hz |
| Estimated MOL @ F3 | 103.2 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 1.2 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 142.5 Hz |
| F3 (-3 dB Cutoff) | 148.0 Hz |
| F6 / F10 Extension | 110.8 Hz / 82.7 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 72.0 Hz |
| Total Q (Qts) | 0.35 |
| Electrical Q (Qes) | 0.403 |
| Mechanical Q (Qms) | 2.66 |
| Equivalent Volume (Vas) | 3.8 Liters |
| Diaphragm Area (Sd) | 50.0 cm² |
| DC Resistance (Re) | 3.0 Ω |
| Efficiency Bandwidth Product (EBP) | 178.7 |
| Linear Excursion (Xmax) | 1.7 mm |
| Thermal Power (Pe) | 400.0 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 SEAS L0021-04S RM 120?
Load Forge's calculated alignment puts SEAS L0021-04S RM 120 in a 2.8 liter vented enclosure tuned to 77.8 Hz, reaching an F3 cutoff of approximately 78.5 Hz.
Can SEAS L0021-04S RM 120 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 1.2 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 148.0 Hz.
What port dimensions should be used for SEAS L0021-04S RM 120 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 31.2 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.
Not sure if L0021-04S RM 120 fits your physical space?
Don't force a driver into the wrong box. Use Bass Match to calculate which of 8,000+ catalog drivers delivers the highest SPL, lowest F3, and cleanest port air velocity for your exact trunk or room dimensions.
Run Bass Match for Your Space