HELIX Ci5 S200FM-D2
Best box: 10.8 L bass reflex tuned to 46.8 Hz · F3 69.6 Hz
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Comparable 7.0" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the HELIX Ci5 S200FM-D2 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) | 10.8 Liters |
| Tuning Frequency (Fb) | 46.8 Hz |
| F3 (-3 dB Cutoff) | 69.6 Hz |
| F6 / F10 Extension | 58.5 Hz / 45.5 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 41.2 cm |
| First Pipe Resonance | 418.0 Hz |
| Estimated MOL @ F3 | 109.8 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.8 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.131; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 13.5 Liters |
| System Q (Qtc) | 1.131 (above Butterworth: Qtc cannot fall below Qts (0.80)) |
| System Resonance (Fc) | 77.8 Hz |
| F3 (-3 dB Cutoff) | 65.2 Hz |
| F6 / F10 Extension | 54.6 Hz / 44.3 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 55.0 Hz |
| Total Q (Qts) | 0.8 |
| Electrical Q (Qes) | 0.885 |
| Mechanical Q (Qms) | 8.31 |
| Equivalent Volume (Vas) | 13.5 Liters |
| Diaphragm Area (Sd) | 194.0 cm² |
| DC Resistance (Re) | 3.6 Ω |
| Efficiency Bandwidth Product (EBP) | 62.1 |
| Linear Excursion (Xmax) | 7.5 mm |
| Thermal Power (Pe) | 200.0 W |
| Nominal Diameter | 7.0" |
| Catalog Source | Load Forge catalog (manufacturer datasheets and retailer listings) |
Frequently Asked Questions
What is the recommended ported (bass reflex) box volume for HELIX Ci5 S200FM-D2?
Load Forge's calculated alignment puts HELIX Ci5 S200FM-D2 in a 10.8 liter vented enclosure tuned to 46.8 Hz, reaching an F3 cutoff of approximately 69.6 Hz.
Can HELIX Ci5 S200FM-D2 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 13.5 liters with a Qtc of 1.131 (above Butterworth: Qtc cannot fall below Qts (0.80)), the system exhibits an F3 of 65.2 Hz.
What port dimensions should be used for HELIX Ci5 S200FM-D2 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 41.2 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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