Vented Specialist

JBL Professional 127H-3

Best box: 78.7 L bass reflex tuned to 38.0 Hz · F3 37.0 Hz

Predicted SPL response of the JBL Professional 127H-3 in the recommended 78.7 L bass reflex box versus the alternative — open it in the simulator Open and tweak this box live ↗

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Recommended Bass Reflex (Vented)

PORT BUILDABLE
Net Box Volume (Vb) 78.7 Liters
Tuning Frequency (Fb) 38.0 Hz
F3 (-3 dB Cutoff) 37.0 Hz
F6 / F10 Extension 32.9 Hz / 29.0 Hz
Port Inner Diameter Ø 6.8 cm
Port Physical Length 4.7 cm
First Pipe Resonance 3646.0 Hz
Estimated MOL @ F3 111.9 dB SPL
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Recommended Sealed (Acoustic Suspension)

MAX TRANSIENT DAMPING
Net Box Volume (Vb) 34.3 Liters
System Q (Qtc) 0.707 (Butterworth)
System Resonance (Fc) 67.5 Hz
F3 (-3 dB Cutoff) 69.6 Hz
F6 / F10 Extension 52.3 Hz / 39.4 Hz
Air Spring Linearity High (Zero port compression)
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Thiele/Small Parameters

Resonance (Fs) 37.0 Hz
Total Q (Qts) 0.37
Electrical Q (Qes) 0.406
Mechanical Q (Qms) 4.18
Equivalent Volume (Vas) 91.0 Liters
Diaphragm Area (Sd) 358.0 cm²
DC Resistance (Re) 5.6 Ω
Efficiency Bandwidth Product (EBP) 91.1
Linear Excursion (Xmax) 6.0 mm
Thermal Power (Pe) 200.0 W
Nominal Diameter 10.0"
Catalog Source Load Forge catalog (manufacturer datasheets and retailer listings)

Frequently Asked Questions

What is the recommended ported (bass reflex) box volume for JBL Professional 127H-3?

Load Forge's calculated alignment puts JBL Professional 127H-3 in a 78.7 liter vented enclosure tuned to 38.0 Hz, reaching an F3 cutoff of approximately 37.0 Hz.

Can JBL Professional 127H-3 be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 34.3 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 69.6 Hz.

What port dimensions should be used for JBL Professional 127H-3 to avoid port chuffing?

Sized from cone displacement (Sd × Xmax), a minimum port diameter of 6.8 cm with a length of 4.7 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.

JBL Professional 127H-3 Enclosure Card
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