Hertz SX 690 H
Best box: 9.0 L bass reflex tuned to 55.2 Hz · F3 78.8 Hz
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Comparable 8.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the Hertz SX 690 H does not fit your target box volume or tuning. Each entry links to its full enclosure design and Thiele/Small parameters.
Recommended Bass Reflex (Vented)
PORT BUILDABLE| Net Box Volume (Vb) | 9.0 Liters |
| Tuning Frequency (Fb) | 55.2 Hz |
| F3 (-3 dB Cutoff) | 78.8 Hz |
| F6 / F10 Extension | 64.0 Hz / 48.7 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 34.8 cm |
| First Pipe Resonance | 494.0 Hz |
| Estimated MOL @ F3 | 114.8 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.62 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 0.877; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 11.3 Liters |
| System Q (Qtc) | 0.877 (above Butterworth) |
| System Resonance (Fc) | 91.9 Hz |
| F3 (-3 dB Cutoff) | 81.1 Hz |
| F6 / F10 Extension | 65.4 Hz / 51.5 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 65.0 Hz |
| Total Q (Qts) | 0.62 |
| Electrical Q (Qes) | 0.789 |
| Mechanical Q (Qms) | 2.9 |
| Equivalent Volume (Vas) | 11.3 Liters |
| Diaphragm Area (Sd) | 224.8 cm² |
| DC Resistance (Re) | 3.0 Ω |
| Efficiency Bandwidth Product (EBP) | 82.4 |
| Linear Excursion (Xmax) | 5.5 mm |
| Thermal Power (Pe) | N/A W |
| Nominal Diameter | 8.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for Hertz SX 690 H?
Load Forge's calculated alignment puts Hertz SX 690 H in a 9.0 liter vented enclosure tuned to 55.2 Hz, reaching an F3 cutoff of approximately 78.8 Hz.
Can Hertz SX 690 H be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 11.3 liters with a Qtc of 0.877 (above Butterworth), the system exhibits an F3 of 81.1 Hz.
What port dimensions should be used for Hertz SX 690 H to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 34.8 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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