Vented Specialist

BRAX CI22512

Best box: 3.7 L bass reflex tuned to 75.6 Hz · F3 110.1 Hz

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Comparable 5.5" Drivers

Drivers with similar piston area, resonance and Qts — useful alternatives when the BRAX CI22512 does not fit your target box volume or tuning. Each entry links to its full enclosure design and Thiele/Small parameters.

Goldwood

GW-205/8S 5-1/4" Shielded Poly Woofer 8 Ohm

5.25" · Fs 86.1 Hz · Qts 0.82 · Vas 5.1 L

Telefunken

Breitband 13cm L6423

5.5" · Fs 80.0 Hz · Qts 0.5 · Vas 5.0 L

Goldwood

GW-205/4S 5-1/4" Shielded Poly Woofer 4 Ohm

5.25" · Fs 83.1 Hz · Qts 0.68 · Vas 5.4 L

Hertz

MILLE PRO MPK130 3

5.25" · Fs 90.0 Hz · Qts 0.64 · Vas 3.0 L

HELIX

Ci3 W130-S3

5.0" · Fs 89.0 Hz · Qts 0.74 · Vas 4.6 L

LaVoce

CSF051.21

5.5" · Fs 110.0 Hz · Qts 0.64 · Vas 4.1 L

Compare them in the same box → Browse all 5.5" drivers → All BRAX drivers →

⚠️ Engineering Notice for Builders

Limited linear excursion (Xmax: 3.2 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)	3.7 Liters
Tuning Frequency (Fb)	75.6 Hz
F3 (-3 dB Cutoff)	110.1 Hz
F6 / F10 Extension	91.7 Hz / 70.8 Hz
Port Inner Diameter	Ø 5.0 cm
Port Physical Length	24.3 cm
First Pipe Resonance	709.0 Hz
Estimated MOL @ F3	108.4 dB SPL

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Sealed (Acoustic Suspension) — compromise

SUITS INFINITE / OPEN BAFFLE

With Qts 0.74 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.047; for a flat response this driver is better used on an infinite (IB) or open baffle.

Net Box Volume (Vb)	4.6 Liters
System Q (Qtc)	1.047 (above Butterworth: Qtc cannot fall below Qts (0.74))
System Resonance (Fc)	125.9 Hz
F3 (-3 dB Cutoff)	105.5 Hz
F6 / F10 Extension	87.4 Hz / 70.3 Hz
Air Spring Linearity	High (Zero port compression)

Simulate This Sealed Box in App →

Thiele/Small Parameters

Resonance (Fs)	89.0 Hz
Total Q (Qts)	0.74
Electrical Q (Qes)	0.971
Mechanical Q (Qms)	3.11

Equivalent Volume (Vas)	4.6 Liters
Diaphragm Area (Sd)	98.0 cm²
DC Resistance (Re)	3.1 Ω
Efficiency Bandwidth Product (EBP)	91.7

Linear Excursion (Xmax)	3.2 mm
Thermal Power (Pe)	N/A W
Nominal Diameter	5.5"
Catalog Source	Load Forge catalog (manufacturer datasheets and retailer listings)

Frequently Asked Questions

What is the recommended ported (bass reflex) box volume for BRAX CI22512?

Load Forge's calculated alignment puts BRAX CI22512 in a 3.7 liter vented enclosure tuned to 75.6 Hz, reaching an F3 cutoff of approximately 110.1 Hz.

Can BRAX CI22512 be used in a sealed box?

Yes. In a sealed (acoustic suspension) enclosure of 4.6 liters with a Qtc of 1.047 (above Butterworth: Qtc cannot fall below Qts (0.74)), the system exhibits an F3 of 105.5 Hz.

What port dimensions should be used for BRAX CI22512 to avoid port chuffing?

Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 24.3 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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