18FIND

ENCLOSURE RECOMMENDATIONS: 18FINDX8-036
Driver: 18FINDX8-036 (18FIND) — 18" ferrite pro woofer, 8 ohm
Key T/S: Fs=36Hz, Qts=0.42, Qes=0.44, Qms=8.4, Vas=203.4L, Sens=97.24dB
Power: AES 1000W / Cont 2000W / Peak 4000W
Xmax=5.85mm (linear), Xmech=17.85mm
Sd=1257cm², Bl=23.6T·m, Le=1.74mH, Re=5.2Ω
Voice coil: 101.6mm (4"), copper winding, Polyimide former (250°C rated)
Cone: carbon fiber loaded paper
Surround: fabric, triple roll constant geometry
Spider: Nomex silicone (long-term shape memory)
Depth: 184mm | Baffle cutout: 426mm | Ferrite motor | Aluminum basket

COMPARISON — 18FIND vs 182FIND:
  The 18FIND (18FINDX8-036) and 182FIND (182FINDX8-127) share the 18-inch
  ferrite platform — identical Sd, baffle cutout, and power class — but
  differ substantially in motor design and acoustic character:

  | Parameter | 18FIND   | 182FIND    |
  |-----------|----------|------------|
  | Qts       | 0.42     | 0.23       |
  | Bl        | 23.6 T·m | 35.4 T·m   |
  | Le        | 1.74 mH  | 4.92 mH    |
  | Fs        | 36 Hz    | 31 Hz      |
  | Mms       | 211.8 g  | 281 g      |
  | Coil      | standard | inside/out |

  The 182FIND uses an inside/outside wound coil to achieve extreme Bl=35.4T·m
  at the cost of very high Le=4.92mH, restricting its use in 3-way and 2.5-way
  topologies only. The 18FIND uses a conventional winding, producing a lower
  but still competitive Bl=23.6T·m, a moderate Le=1.74mH (inductance rolloff
  at ~475Hz), and a higher Qts=0.42 that requires larger enclosures. The 18FIND
  integrates into standard two-way PA systems with crossover at 800Hz–1.5kHz
  without Le-related penalties, making it the more versatile and
  system-integration-friendly of the two 18-inch ferrite options.

ENCLOSURE TYPE RATIONALE:
  Qts=0.42 is within the vented design region for an 18-inch professional
  woofer. Vented (bass reflex) enclosures are the appropriate and only
  recommended alignment. The moderate Qts requires somewhat larger
  enclosures than the 182FIND (Qts=0.23) for equivalent tuning frequencies,
  but the vented alignment remains highly efficient and produces excellent
  bass output and extension across the 90–180L cabinet range.

DISPLACEMENT:
  Vd = Sd × Xmax = 1257 cm² × 0.585 cm = 735.3 cm³ (peak, one-way)

PORT SIZING NOTE:
  Vd=735.3cm³ requires a minimum port aperture of 125mm round or
  250×80mm slot. A 100mm round port produces velocities exceeding
  25 m/s at all alignments — do not use.

INDUCTANCE NOTE:
  Le=1.74mH → inductance rolloff onset at approximately 475Hz.
  Standard two-way integration with a compression driver or coaxial
  HF unit at 800Hz–1.5kHz is fully compatible without inductance
  compensation. No Zobel network or Le equalization is required for
  typical professional two-way crossover designs.
VENTED (BASS REFLEX) ALIGNMENTS
Ports: 125mm diameter round tube (Ap=1.227×10⁻² m²)
       OR 250×80mm slot port (Ap=2.000×10⁻² m²)

DO NOT use 100mm round port — velocity exceeds limits at all alignments.

Port velocity limit (pro PA / touring): ≤22 m/s
Port velocity limit (install / theatre): ≤17 m/s
ALIGNMENT A — COMPACT TOURING (90 L net internal)
  Box volume:        90 L (net internal)
  Tuning freq (Fb): 55 Hz
  125mm round port:  134mm long
    Port velocity:   20.7 m/s (peak, at Xmax)
  Slot port (250×80mm): 219mm long
    Port velocity:   12.7 m/s (peak, at Xmax)
  System f-3dB:      ~53 Hz
  HP filter:         42 Hz, 24 dB/oct DSP (mandatory)
  Max SPL (1000W, 1m): ~127 dB
  Application:       Compact 18" two-way touring PA cabinet, bass
                     module in mid-large format line array, high-SPL
                     club and festival bass cabinet.
  Notes: Maximum output from the most compact practical enclosure.
         The 125mm round port velocity of 20.7m/s is within the pro
         PA limit for touring applications; for installation use the
         250×80mm slot at 12.7m/s is strongly preferred to remain
         within the 17m/s install limit. At 53Hz -3dB the driver covers
         bass guitar, kick drum, and the full sub-bass programme range.
         The 90L cabinet at approximately 590×560×330mm external is
         consistent with compact 18" PA formats. The 134mm round port
         is particularly short — a consequence of the larger box
         volume at this tuning — fitting any panel position easily.
ALIGNMENT B — STANDARD PA (130 L net internal)
  Box volume:        130 L (net internal)
  Tuning freq (Fb): 46 Hz
  125mm round port:  133mm long  ← virtually identical to Alignment A
    Port velocity:   17.3 m/s (peak, at Xmax)
  Slot port (250×80mm): 217mm long  ← virtually identical to Alignment A
    Port velocity:   10.6 m/s (peak, at Xmax)
  System f-3dB:      ~44 Hz
  HP filter:         35 Hz, 24 dB/oct DSP (mandatory)
  Max SPL (1000W, 1m): ~127 dB
  Application:       Standard two-way touring and installation bass
                     cabinet, installed main LF in HoW, theatre, arena,
                     outdoor stadium PA, flyable 18" bass enclosure.
  Notes: The recommended general-purpose alignment. At 44Hz -3dB the
         system resolves bass guitar open E (41Hz) and covers the full
         music programme with high acoustic output. The 125mm round
         port velocity of 17.3m/s is within installation limits, and
         the slot at 10.6m/s is appropriate for theatre and critical
         environments. The 130L cabinet at approximately 640×610×360mm
         external is a standard professional 18" two-way format.

  PORT NOTE: The 125mm round port (133mm) and slot port (217mm) for
  alignment B are virtually identical in length to alignment A (134mm,
  219mm). A single common port tube specification covers both alignments;
  cabinet volume alone determines the tuning frequency. This property
  simplifies production of a two-box range sharing the same port hardware.
ALIGNMENT C — EXTENDED LF (180 L net internal)
  Box volume:        180 L (net internal)
  Tuning freq (Fb): 38 Hz
  125mm round port:  141mm long
    Port velocity:   14.3 m/s (peak, at Xmax)
  Slot port (250×80mm): 229mm long
    Port velocity:    8.8 m/s (peak, at Xmax)
  System f-3dB:      ~36 Hz
  HP filter:         28 Hz, 24 dB/oct DSP (mandatory)
  Max SPL (1000W, 1m): ~127 dB
  Application:       Extended bass two-way cabinet, cinema LF section,
                     large-venue installed main woofer, festival and
                     outdoor event main bass cabinet.
  Notes: The deepest alignment. At 36Hz -3dB the driver reproduces the
         low B fundamental of 5-string bass guitar (31Hz within 5dB) and
         the full cinema LFE bandwidth. The 180L enclosure at approximately
         700×660×440mm external is the upper limit of a standard flyable
         18" bass cabinet; fixed-install versions accommodate this volume
         more readily. Internal cross-bracing and damping treatment are
         required. Port velocity of 8.8m/s on the slot is very low —
         suitable for library-quiet studio and theatre environments.
SYSTEM SUMMARY TABLE
  | Alignment   | Volume  | Fb    | f-3dB | 125mm Port | v      | 250×80 Slot | v      | HP     |
  |-------------|---------|-------|-------|------------|--------|-------------|--------|--------|
  | A Compact   | 90 L    | 55 Hz | ~53Hz | 134mm      | 20.7   | 219mm       | 12.7   | 42 Hz  |
  | B Standard  | 130 L   | 46 Hz | ~44Hz | 133mm *    | 17.3   | 217mm *     | 10.6   | 35 Hz  |
  | C Extended  | 180 L   | 38 Hz | ~36Hz | 141mm      | 14.3   | 229mm       |  8.8   | 28 Hz  |
  All velocity figures in m/s (peak, at Xmax).
  * Port lengths A and B are virtually identical — common port hardware applicable.

  Sensitivity:     97.24 dB (1W/1m)
  Max SPL (1000W): ~127 dB at 1m
  Impedance:       8 ohm nominal (Re=5.2Ω)
  Le:              1.74mH — rolloff onset ~475Hz; no Zobel network required
  Voice coil:      101.6mm (4"), copper, Polyimide former (250°C rated)
  WARNING:         Do not use 100mm round port — velocity exceeds limits.