PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm
Best box: 6.6 L bass reflex tuned to 100.3 Hz · F3 119.1 Hz
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Comparable 6.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm 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 (3.3 L at 111.4 Hz) would need a 21.7 cm port; the recommendation is retuned to 6.6 L at 100.3 Hz so the port can be built.
- Limited linear excursion (Xmax: 3.5 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) | 6.6 Liters |
| Tuning Frequency (Fb) | 100.3 Hz |
| F3 (-3 dB Cutoff) | 119.1 Hz |
| F6 / F10 Extension | 90.9 Hz / 75.5 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 5.3 cm |
| First Pipe Resonance | 3252.0 Hz |
| Estimated MOL @ F3 | 118.4 dB SPL |
Sealed (Acoustic Suspension) — compromise
SUITS INFINITE / OPEN BAFFLEWith Qts 0.76 a Butterworth (Qtc 0.707) box would be many times Vas. A box equal to Vas reaches Qtc 1.075; for a flat response this driver is better used on an infinite (IB) or open baffle.
| Net Box Volume (Vb) | 4.1 Liters |
| System Q (Qtc) | 1.075 (above Butterworth: Qtc cannot fall below Qts (0.76)) |
| System Resonance (Fc) | 185.4 Hz |
| F3 (-3 dB Cutoff) | 151.9 Hz |
| F6 / F10 Extension | 126.4 Hz / 101.9 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 131.1 Hz |
| Total Q (Qts) | 0.76 |
| Electrical Q (Qes) | 0.782 |
| Mechanical Q (Qms) | 26.61 |
| Equivalent Volume (Vas) | 4.1 Liters |
| Diaphragm Area (Sd) | 150.0 cm² |
| DC Resistance (Re) | 3.4 Ω |
| Efficiency Bandwidth Product (EBP) | 167.6 |
| Linear Excursion (Xmax) | 3.5 mm |
| Thermal Power (Pe) | 400.0 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 PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm?
Load Forge's calculated alignment puts PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm in a 6.6 liter vented enclosure tuned to 100.3 Hz, reaching an F3 cutoff of approximately 119.1 Hz.
Can PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 4.1 liters with a Qtc of 1.075 (above Butterworth: Qtc cannot fall below Qts (0.76)), the system exhibits an F3 of 151.9 Hz.
What port dimensions should be used for PRV Audio 6MR400CF-4 Moto Series 6.5" Carbon Fiber Neodymium Midrange Loudspeaker 4 Ohm to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 5.3 cm is suggested; check the port air velocity at your drive level in the Load Forge Studio.
Shareable Acoustic Card for Forums & Social Media
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.
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