GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer
Best box: 8.4 L bass reflex tuned to 58.6 Hz · F3 86.4 Hz
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Comparable 6.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the GRS 6PR-8 6-1/2" Poly Cone Rubber 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: 3.0 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) | 8.4 Liters |
| Tuning Frequency (Fb) | 58.6 Hz |
| F3 (-3 dB Cutoff) | 86.4 Hz |
| F6 / F10 Extension | 73.4 Hz / 57.7 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 16.8 cm |
| First Pipe Resonance | 1022.0 Hz |
| Estimated MOL @ F3 | 105.7 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.87 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.23; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 10.5 Liters |
| System Q (Qtc) | 1.23 (above Butterworth: Qtc cannot fall below Qts (0.87)) |
| System Resonance (Fc) | 97.6 Hz |
| F3 (-3 dB Cutoff) | 79.2 Hz |
| F6 / F10 Extension | 67.0 Hz / 54.8 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 69.0 Hz |
| Total Q (Qts) | 0.87 |
| Electrical Q (Qes) | 1.157 |
| Mechanical Q (Qms) | 3.51 |
| Equivalent Volume (Vas) | 10.5 Liters |
| Diaphragm Area (Sd) | 140.0 cm² |
| DC Resistance (Re) | 7.1 Ω |
| Efficiency Bandwidth Product (EBP) | 59.7 |
| Linear Excursion (Xmax) | 3.0 mm |
| Thermal Power (Pe) | 60.0 W |
| Nominal Diameter | 6.5" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer?
Load Forge's calculated alignment puts GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer in a 8.4 liter vented enclosure tuned to 58.6 Hz, reaching an F3 cutoff of approximately 86.4 Hz.
Can GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 10.5 liters with a Qtc of 1.23 (above Butterworth: Qtc cannot fall below Qts (0.87)), the system exhibits an F3 of 79.2 Hz.
What port dimensions should be used for GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 16.8 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
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