PHL Audio 1670NDM-SQ2-16
Best box: 1.9 L bass reflex tuned to 155.5 Hz · F3 259.5 Hz
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Comparable 6.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the PHL Audio 1670NDM-SQ2-16 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 259.2 Hz) would need a 5.9 cm port; the recommendation is retuned to 1.9 L at 155.5 Hz so the port can be built.
- Limited linear excursion (Xmax: 2.5 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) | 1.9 Liters |
| Tuning Frequency (Fb) | 155.5 Hz |
| F3 (-3 dB Cutoff) | 259.5 Hz |
| F6 / F10 Extension | 135.7 Hz / 123.1 Hz |
| Port Inner Diameter | Ø 6.8 cm |
| Port Physical Length | 18.8 cm |
| First Pipe Resonance | 913.0 Hz |
| Estimated MOL @ F3 | 117.2 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.68 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 0.962; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 0.7 Liters |
| System Q (Qtc) | 0.962 (above Butterworth) |
| System Resonance (Fc) | 431.3 Hz |
| F3 (-3 dB Cutoff) | 357.1 Hz |
| F6 / F10 Extension | 291.2 Hz / 231.2 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 305.0 Hz |
| Total Q (Qts) | 0.68 |
| Electrical Q (Qes) | 0.721 |
| Mechanical Q (Qms) | 11.85 |
| Equivalent Volume (Vas) | 0.7 Liters |
| Diaphragm Area (Sd) | 150.0 cm² |
| DC Resistance (Re) | 11.6 Ω |
| Efficiency Bandwidth Product (EBP) | 422.8 |
| Linear Excursion (Xmax) | 2.5 mm |
| Thermal Power (Pe) | 250.0 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 PHL Audio 1670NDM-SQ2-16?
Load Forge's calculated alignment puts PHL Audio 1670NDM-SQ2-16 in a 1.9 liter vented enclosure tuned to 155.5 Hz, reaching an F3 cutoff of approximately 259.5 Hz.
Can PHL Audio 1670NDM-SQ2-16 be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 0.7 liters with a Qtc of 0.962 (above Butterworth), the system exhibits an F3 of 357.1 Hz.
What port dimensions should be used for PHL Audio 1670NDM-SQ2-16 to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 18.8 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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