Sealed Specialist

DS18 PSW8.4D

Best box: 7.5 L bass reflex tuned to 37.5 Hz · F3 47.0 Hz

Predicted SPL response of the DS18 PSW8.4D in the recommended 7.5 L bass reflex box versus the alternative — open it in the simulator Open and tweak this box live ↗

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⚠️ Engineering Notice for Builders

  • The textbook alignment (7.5 L at 35.7 Hz) would need a 109.0 cm port; the recommendation is retuned to 7.5 L at 37.5 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.
  • Port length (98.4 cm) exceeds a straight internal run; use an elbow bend, slotted vent or 3D folded duct to fit the enclosure.

Recommended Bass Reflex (Vented)

PORT NEEDS ELBOW / 3D
Net Box Volume (Vb) 7.5 Liters
Tuning Frequency (Fb) 37.5 Hz
F3 (-3 dB Cutoff) 47.0 Hz
F6 / F10 Extension 37.3 Hz / 30.2 Hz
Port Inner Diameter ESTIMATED Ø 6.8 cm
Port Physical Length 98.4 cm
First Pipe Resonance 175.0 Hz
Estimated MOL @ F3 106.5 dB SPL
⚠️ Port feasibility: a straight 6.8 cm tube needs 98.4 cm of internal length. Use an elbow bend, a slotted vent or a 3D folded duct.
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Sealed (Acoustic Suspension) — compromise

SUITS INFINITE / OPEN BAFFLE

With Qts 0.84 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.188; for a flat response this driver is better used on an infinite (IB) or open baffle.

Net Box Volume (Vb) 9.4 Liters
System Q (Qtc) 1.188 (above Butterworth: Qtc cannot fall below Qts (0.84))
System Resonance (Fc) 59.4 Hz
F3 (-3 dB Cutoff) 64.0 Hz
F6 / F10 Extension 47.0 Hz / 34.9 Hz
Air Spring Linearity High (Zero port compression)
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Thiele/Small Parameters

Resonance (Fs) 42.0 Hz
Total Q (Qts) 0.84
Electrical Q (Qes) 1.058
Mechanical Q (Qms) 4.08
Equivalent Volume (Vas) 9.4 Liters
Diaphragm Area (Sd) 216.0 cm²
DC Resistance (Re) 3.2 Ω
Efficiency Bandwidth Product (EBP) 39.7
Linear Excursion (Xmax) N/A mm
Thermal Power (Pe) 400.0 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 DS18 PSW8.4D?

Load Forge's calculated alignment puts DS18 PSW8.4D in a 7.5 liter vented enclosure tuned to 37.5 Hz, reaching an F3 cutoff of approximately 47.0 Hz.

Can DS18 PSW8.4D be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 9.4 liters with a Qtc of 1.188 (above Butterworth: Qtc cannot fall below Qts (0.84)), the system exhibits an F3 of 64.0 Hz.

What port dimensions should be used for DS18 PSW8.4D to avoid port chuffing?

Xmax is not published for DS18 PSW8.4D, so the port is an empirical estimate: a 6.8 cm diameter with a length of 98.4 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.

DS18 PSW8.4D Enclosure Card
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