Rockford Fosgate P1S815
Best box: 137.6 L bass reflex tuned to 21.2 Hz · F3 30.1 Hz
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Comparable 15.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Rockford Fosgate P1S815 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 (137.6 L) requires extensive internal matrix bracing to prevent panel resonance.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 137.6 Liters |
| Tuning Frequency (Fb) | 21.2 Hz |
| F3 (-3 dB Cutoff) | 30.1 Hz |
| F6 / F10 Extension | 24.8 Hz / 19.0 Hz |
| Port Inner Diameter | Ø 10.0 cm |
| Port Physical Length | 30.9 cm |
| First Pipe Resonance | 556.0 Hz |
| Estimated MOL @ F3 | 110.1 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.68 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 0.962; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 172.0 Liters |
| System Q (Qtc) | 0.962 (above Butterworth) |
| System Resonance (Fc) | 35.4 Hz |
| F3 (-3 dB Cutoff) | 29.9 Hz |
| F6 / F10 Extension | 24.4 Hz / 19.4 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 25.0 Hz |
| Total Q (Qts) | 0.68 |
| Electrical Q (Qes) | 0.751 |
| Mechanical Q (Qms) | 7.2 |
| Equivalent Volume (Vas) | 172.0 Liters |
| Diaphragm Area (Sd) | 860.0 cm² |
| DC Resistance (Re) | 7.2 Ω |
| Efficiency Bandwidth Product (EBP) | 33.3 |
| Linear Excursion (Xmax) | 9.5 mm |
| Thermal Power (Pe) | 200.0 W |
| Nominal Diameter | 15.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Rockford Fosgate P1S815?
Load Forge's calculated alignment puts Rockford Fosgate P1S815 in a 137.6 liter vented enclosure tuned to 21.2 Hz, reaching an F3 cutoff of approximately 30.1 Hz.
Can Rockford Fosgate P1S815 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 172.0 liters with a Qtc of 0.962 (above Butterworth), the system exhibits an F3 of 29.9 Hz.
What port dimensions should be used for Rockford Fosgate P1S815 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 10.0 cm with a length of 30.9 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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