What is the recommended ported (bass reflex) box volume for SB Acoustics MR13P-4?

According to electroacoustic alignment calculations, SB Acoustics MR13P-4 performs optimally in a 4.3 liter vented enclosure tuned to 64.8 Hz, reaching an F3 cutoff of approximately 75.2 Hz.

Can SB Acoustics MR13P-4 be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 2.3 liters with a Qtc of 0.707, the system exhibits an F3 of 116.8 Hz with tight transient response and natural roll-off.

What port dimensions should be used for SB Acoustics MR13P-4 to avoid port chuffing?

To keep vent air velocity below turbulence limits at rated power, a minimum port diameter of 5.0 cm with a length of 29.0 cm is recommended.

Reflex Optimized

SB Acoustics MR13P-4

Complete Thiele/Small parameters, optimized ported (bass reflex) and sealed enclosure designs, F3/F6/F10 cutoffs, and vent turbulence analysis calculated by Load Forge.

Estimated Retail

179.95 EUR

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⚠️ Engineering Notice for Builders

Limited linear excursion (Xmax: 3.0 mm); set a high-pass subsonic filter at 25–30 Hz when driven with high power.

Recommended Bass Reflex (Vented)

OPTIMIZED EXTENSION

Net Box Volume (Vb)	4.3 Liters
Tuning Frequency (Fb)	64.8 Hz
F3 (-3 dB Cutoff)	75.2 Hz
F6 / F10 Extension	63.7 Hz / 54.3 Hz
Port Inner Diameter	Ø 5.0 cm
Port Physical Length	29.0 cm
First Pipe Resonance	593.0 Hz
Estimated MOL @ F3	100.0 dB SPL

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Recommended Sealed (Acoustic Suspension)

MAX TRANSIENT DAMPING

Net Box Volume (Vb)	2.3 Liters
System Q (Qtc)	0.707 (Butterworth Q=0.707)
System Resonance (Fc)	123.0 Hz
F3 (-3 dB Cutoff)	116.8 Hz
F6 / F10 Extension	89.6 Hz / 67.8 Hz
Air Spring Linearity	High (Zero port compression)

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Verified Thiele/Small Parameters

Resonance (Fs)	41.0 Hz
Total Q (Qts)	0.23
Electrical Q (Qes)	0.25
Mechanical Q (Qms)	2.8

Equivalent Volume (Vas)	19.4 Liters
Diaphragm Area (Sd)	70.0 cm²
DC Resistance (Re)	3.3 Ω
Efficiency Bandwidth Product (EBP)	164.0

Linear Excursion (Xmax)	3.0 mm
Thermal Power (Pe)	30.0 W
Nominal Diameter	5.0"
Catalog Source	Manufacturer Official Datasheet

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[b]SB Acoustics MR13P-4[/b] — 4.3L Bass Reflex tuned to 64.8Hz (F3: 75.2Hz). Designed with [url=https://loadforge.io]Load Forge[/url].

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