PHL Audio 7231ND-8
Best box: 276.2 L bass reflex tuned to 33.0 Hz · F3 30.7 Hz
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Comparable 18.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the PHL Audio 7231ND-8 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
- Large enclosure volume (276.2 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 276.2 Liters |
| Tuning Frequency (Fb) | 33.0 Hz |
| F3 (-3 dB Cutoff) | 30.7 Hz |
| F6 / F10 Extension | 27.7 Hz / 24.7 Hz |
| Port Inner Diameter | Ø 20.0 cm |
| Port Physical Length | 17.0 cm |
| First Pipe Resonance | 1011.0 Hz |
| Estimated MOL @ F3 | 121.8 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 121.1 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 57.4 Hz |
| F3 (-3 dB Cutoff) | 59.0 Hz |
| F6 / F10 Extension | 44.2 Hz / 33.3 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 36.0 Hz |
| Total Q (Qts) | 0.42 |
| Electrical Q (Qes) | 0.455 |
| Mechanical Q (Qms) | 5.51 |
| Equivalent Volume (Vas) | 222.0 Liters |
| Diaphragm Area (Sd) | 1250.0 cm² |
| DC Resistance (Re) | 6.4 Ω |
| Efficiency Bandwidth Product (EBP) | 79.2 |
| Linear Excursion (Xmax) | 12.5 mm |
| Thermal Power (Pe) | 1000.0 W |
| Nominal Diameter | 18.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for PHL Audio 7231ND-8?
Load Forge's calculated alignment puts PHL Audio 7231ND-8 in a 276.2 liter vented enclosure tuned to 33.0 Hz, reaching an F3 cutoff of approximately 30.7 Hz.
Can PHL Audio 7231ND-8 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 121.1 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 59.0 Hz.
What port dimensions should be used for PHL Audio 7231ND-8 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 20.0 cm with a length of 17.0 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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