REDCATT 61FHM
Best box: 21.6 L bass reflex tuned to 33.3 Hz · F3 34.1 Hz
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Comparable 6.5" Drivers
Drivers with similar piston area, resonance and Qts — useful alternatives when the REDCATT 61FHM 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
- 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) | 21.6 Liters |
| Tuning Frequency (Fb) | 33.3 Hz |
| F3 (-3 dB Cutoff) | 34.1 Hz |
| F6 / F10 Extension | 28.6 Hz / 25.2 Hz |
| Port Inner Diameter | Ø 5.0 cm |
| Port Physical Length | 21.0 cm |
| First Pipe Resonance | 819.0 Hz |
| Estimated MOL @ F3 | 102.1 dB SPL |
Recommended Sealed (Acoustic Suspension)
MAX TRANSIENT DAMPING| Net Box Volume (Vb) | 17.0 Liters |
| System Q (Qtc) | 0.707 (Butterworth) |
| System Resonance (Fc) | 58.8 Hz |
| F3 (-3 dB Cutoff) | 60.9 Hz |
| F6 / F10 Extension | 45.4 Hz / 34.1 Hz |
| Air Spring Linearity | High (Zero port compression) |
Thiele/Small Parameters
| Resonance (Fs) | 44.0 Hz |
| Total Q (Qts) | 0.52 |
| Electrical Q (Qes) | 0.577 |
| Mechanical Q (Qms) | 5.27 |
| Equivalent Volume (Vas) | 14.4 Liters |
| Diaphragm Area (Sd) | 132.7 cm² |
| DC Resistance (Re) | 3.2 Ω |
| Efficiency Bandwidth Product (EBP) | 76.3 |
| Linear Excursion (Xmax) | 3.2 mm |
| Thermal Power (Pe) | 100.0 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 REDCATT 61FHM?
Load Forge's calculated alignment puts REDCATT 61FHM in a 21.6 liter vented enclosure tuned to 33.3 Hz, reaching an F3 cutoff of approximately 34.1 Hz.
Can REDCATT 61FHM be used in a sealed box?
Yes. In a sealed (acoustic suspension) enclosure of 17.0 liters with a Qtc of 0.707 (Butterworth), the system exhibits an F3 of 60.9 Hz.
What port dimensions should be used for REDCATT 61FHM to avoid port chuffing?
Sized from cone displacement (Sd × Xmax), a minimum port diameter of 5.0 cm with a length of 21.0 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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