GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer
Best box: 1.4 L sealed · Fc 229.1 Hz · F3 189.0 Hz
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Comparable 5.25" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer 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: 2.5 mm); set a high-pass subsonic filter at 25–30 Hz when driven with high power.
Textbook Bass Reflex — not recommended (8.1 dB bass hump)
PORT BUILDABLE| Net Box Volume (Vb) | 1.5 Liters |
| Tuning Frequency (Fb) | 137.7 Hz |
| F3 (-3 dB Cutoff) | 205.0 Hz |
| F6 / F10 Extension | 185.3 Hz / 157.3 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 17.1 cm |
| First Pipe Resonance | 1005.0 Hz |
| Estimated MOL @ F3 | 111.2 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 2.04 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 2.885; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 1.4 Liters |
| System Q (Qtc) | 2.885 (above Butterworth: Qtc cannot fall below Qts (2.04)) |
| System Resonance (Fc) | 229.1 Hz |
| F3 (-3 dB Cutoff) | 189.0 Hz |
| F6 / F10 Extension | 171.7 Hz / 150.3 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 162.0 Hz |
| Total Q (Qts) | 2.04 |
| Electrical Q (Qes) | 3.102 |
| Mechanical Q (Qms) | 5.96 |
| Equivalent Volume (Vas) | 1.4 Liters |
| Diaphragm Area (Sd) | 75.2 cm² |
| DC Resistance (Re) | 7.3 Ω |
| Efficiency Bandwidth Product (EBP) | 52.2 |
| Linear Excursion (Xmax) | 2.5 mm |
| Thermal Power (Pe) | 90.0 W |
| Nominal Diameter | 5.25" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer?
A simple ported box is not recommended for GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer: the textbook alignment (1.5 liters tuned to 137.7 Hz) needs a 17.1 cm port, and no nearby retune stays buildable without a bass hump. A sealed box, a passive radiator or a folded duct is the practical choice.
Can GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 1.4 liters with a Qtc of 2.885 (above Butterworth: Qtc cannot fall below Qts (2.04)), the system exhibits an F3 of 189.0 Hz.
What port dimensions should be used for GRS 5PF-8 5-1/4" Paper Cone Foam Surround Woofer to avoid port chuffing?
A straight 5.0 cm port would need 17.1 cm of length, which does not fit a practical cabinet. Use a passive radiator or a folded/3D duct instead of a straight tube.
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