81FIND

ENCLOSURE RECOMMENDATIONS: 81FINDX8-290
Driver: 81FINDX8-290 (81FIND) — 8" Mid-Woofer
Key T/S: Fs=80Hz, Qts=0.5, Vas=11.3L, Sens=94.7dB 1W/1m
Power: AES 200W / Cont 400W / Peak 800W
Xmax=2.25mm, Sd=213.8cm², Bl=10.2T·m, Re=4.7Ω
Voice Coil: 2" CCAW on glass fiber former (12.5mm winding height)
Magnet: Ferrite | Cone: Glass-fiber loaded paper | Surround: Fabric (M-roll)
RECOMMENDED ENCLOSURE TYPE: Bass Reflex (Vented)
NOTE: With Qts=0.5 and Vas=11.3L, this 8" mid-woofer is well-suited
to compact vented enclosures in the 6–9 liter range. The moderate Qts
provides good cone control while maintaining usable output across the
low-frequency bandwidth. Port velocities remain very low (<9 m/s)
across all alignments due to the modest Xmax, indicating clean port
behavior at all drive levels.
PORT RECOMMENDATION: Round port (65mm diameter) — standard for compact
8" enclosures; provides adequate cross-sectional area with low air
velocity at all alignments.
VENTED ALIGNMENTS:
  a) High SPL
     Net Volume: 6 liters
     Tuning (Fb): 92 Hz
     Est. -3dB: 83 Hz
     HP Filter: 84 Hz (24dB/oct LR recommended)
     Round Port: 65mm dia × 147mm long
     Slot Port: 144mm W × 40mm H × 275mm L
     Port Velocity: 8.4 m/s
     Notes: Compact enclosure, strong mid-bass impact, maximum
     output per cabinet volume. Ideal for small portable 2-way
     systems where cabinet size is the primary constraint.
  b) Balanced Response
     Net Volume: 7 liters
     Tuning (Fb): 85 Hz
     Est. -3dB: 76 Hz
     HP Filter: 75 Hz (24dB/oct LR recommended)
     Round Port: 65mm dia × 148mm long
     Slot Port: 144mm W × 40mm H × 277mm L
     Port Velocity: 7.7 m/s
     Notes: General-purpose alignment, even response through the
     low-frequency range with good transient behavior. Suitable for
     most 2-way portable and installation applications.
  c) Extended Low Frequency
     Net Volume: 9 liters
     Tuning (Fb): 76 Hz
     Est. -3dB: 68 Hz
     HP Filter: 64 Hz (24dB/oct LR recommended)
     Round Port: 65mm dia × 143mm long
     Slot Port: 144mm W × 40mm H × 267mm L
     Port Velocity: 6.9 m/s
     Notes: Maximum low-frequency extension, deeper bass response.
     Requires proper high-pass protection below tuning. Best for
     applications where low-end reach is prioritized over cabinet
     compactness.
SEALED ALTERNATIVE (for reference):
For applications requiring sealed enclosure simplicity (e.g., compact
monitors or bandpass-filtered mid-bass systems):
  Butterworth (Qtc≈0.707): 11L, fc=113Hz
  Compact sealed (Qtc≈0.8): 7L, fc=129Hz
Sealed volumes are larger relative to bass reflex for equivalent LF
extension, making vented the preferred choice for this driver.
DESIGN NOTE: The ferrite motor with weather-coated metalwork and
the proven glass-fiber loaded paper cone make this driver particularly
suitable for portable and semi-outdoor applications. The balanced
cost-to-performance ratio positions the 81FIND as an effective choice
for cost-sensitive product lines without compromising reliability.
--- AI SUMMARY (copy/paste ready) ---
The 81FINDX8-290 is an 8-inch ferrite mid-woofer designed for professional portable and installation loudspeaker systems requiring reliable performance across the 70–3000 Hz operating range. With a sensitivity of 95 dB (1W/1m), a 2-inch CCAW voice coil on a glass fiber former, and a glass-fiber loaded paper cone with M-roll fabric surround, the driver provides a balanced combination of efficiency, power handling, and extended frequency response. The motor-suspension design (Qts 0.5) provides good cone control while maintaining usable output across its operating bandwidth, making it well-suited to compact vented enclosures.
Recommended enclosure alignments (bass reflex) use net internal volumes of 6 to 9 liters with tuning frequencies between 76 and 92 Hz. Smaller volumes (6–7 liters tuned to 85–92 Hz) maximize mid-bass output and cabinet compactness, ideal for portable 2-way systems where size and weight are primary constraints. Larger volumes approaching 9 liters with lower tuning (76 Hz) extend the usable low-frequency response to approximately 68 Hz (–3 dB), suitable for applications where deeper bass extension is required. Port velocities remain well below critical limits across all alignments, ensuring clean port behavior at rated power.
The driver is rated for approximately 200 W AES / 400 W continuous power handling and is intended for use with DSP-controlled amplification. A high-pass filter in the range of 64–84 Hz (24 dB/octave Linkwitz-Riley) is recommended depending on enclosure tuning, along with appropriate limiting to manage thermal and mechanical stress during sustained operation. Typical crossover to a high-frequency driver is in the 1.5–3 kHz region depending on system architecture.