B & C 21DS115_2
Best box: 71.4 L bass reflex tuned to 46.4 Hz · F3 50.2 Hz
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Comparable 21.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the B & C 21DS115_2 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
- Port length (71.1 cm) exceeds a straight internal run; use an elbow bend, slotted vent or 3D folded duct to fit the enclosure.
Recommended Bass Reflex (Vented)
PORT NEEDS ELBOW / 3D| Net Box Volume (Vb) | 71.4 Liters |
| Tuning Frequency (Fb) | 46.4 Hz |
| F3 (-3 dB Cutoff) | 50.2 Hz |
| F6 / F10 Extension | 43.5 Hz / 37.5 Hz |
| Port Inner Diameter | Ø 24.0 cm |
| Port Physical Length | 71.1 cm |
| First Pipe Resonance | 242.0 Hz |
| Estimated MOL @ F3 | 124.9 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 34.8 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 85.6 Hz |
| F3 (-3 dB Cutoff) | 84.7 Hz |
| F6 / F10 Extension | 64.2 Hz / 48.6 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 34.0 Hz |
| Total Q (Qts) | 0.27 |
| Electrical Q (Qes) | 0.277 |
| Mechanical Q (Qms) | 10.2 |
| Equivalent Volume (Vas) | 204.0 Liters |
| Diaphragm Area (Sd) | 1620.0 cm² |
| DC Resistance (Re) | 5.1 Ω |
| Efficiency Bandwidth Product (EBP) | 122.6 |
| Linear Excursion (Xmax) | 16.5 mm |
| Thermal Power (Pe) | 1700.0 W |
| Nominal Diameter | 21.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for B & C 21DS115_2?
Load Forge's calculated alignment puts B & C 21DS115_2 in a 71.4 liter vented enclosure tuned to 46.4 Hz, reaching an F3 cutoff of approximately 50.2 Hz.
Can B & C 21DS115_2 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 34.8 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 84.7 Hz.
What port dimensions should be used for B & C 21DS115_2 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 24.0 cm with a length of 71.1 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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