GRS 4AS-4
Best box: 3.0 L bass reflex tuned to 66.8 Hz · F3 131.0 Hz
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Comparable 4.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the GRS 4AS-4 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
- The textbook alignment (1.5 L at 111.3 Hz) would need a 28.1 cm port; the recommendation is retuned to 3.0 L at 66.8 Hz so the port can be built.
- Xmax is not published, so the port size is an empirical estimate (area ≥ 12 in² per ft³ of net volume, minimum by driver size), not a displacement calculation. Check air velocity in Load Forge Studio.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 3.0 Liters |
| Tuning Frequency (Fb) | 66.8 Hz |
| F3 (-3 dB Cutoff) | 131.0 Hz |
| F6 / F10 Extension | 112.9 Hz / 88.9 Hz |
| Port Inner Diameter ESTIMATED | Ø 5.0 cm |
| Port Physical Length | 40.4 cm |
| First Pipe Resonance | 426.0 Hz |
| Estimated MOL @ F3 | 100.7 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 1.48 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 2.093; 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) | 2.093 (above Butterworth: Qtc cannot fall below Qts (1.48)) |
| System Resonance (Fc) | 185.3 Hz |
| F3 (-3 dB Cutoff) | 154.7 Hz |
| F6 / F10 Extension | 137.6 Hz / 117.8 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 131.0 Hz |
| Total Q (Qts) | 1.48 |
| Electrical Q (Qes) | 1.955 |
| Mechanical Q (Qms) | 6.09 |
| Equivalent Volume (Vas) | 1.4 Liters |
| Diaphragm Area (Sd) | 55.1 cm² |
| DC Resistance (Re) | 3.6 Ω |
| Efficiency Bandwidth Product (EBP) | 67.0 |
| Linear Excursion (Xmax) | N/A mm |
| Thermal Power (Pe) | 25.0 W |
| Nominal Diameter | 4.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for GRS 4AS-4?
Load Forge's calculated alignment puts GRS 4AS-4 in a 3.0 liter vented enclosure tuned to 66.8 Hz, reaching an F3 cutoff of approximately 131.0 Hz.
Can GRS 4AS-4 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 1.4 liters with a Qtc of 2.093 (above Butterworth: Qtc cannot fall below Qts (1.48)), the system exhibits an F3 of 154.7 Hz.
What port dimensions should be used for GRS 4AS-4 to avoid port chuffing?
Xmax is not published for GRS 4AS-4, so the port is an empirical estimate: a 5.0 cm diameter with a length of 40.4 cm (area at least 12 in² per ft³ of net volume). Check the air velocity at your power level in 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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