4FR

SPEAKER ENCLOSURE CALCULATION — 4FRX4-385
DRIVER IDENTIFICATION
  Code:              4FRX4-385
  Name:              4FR
  Category:          Full-Range / Mid-Woofer (dual-use; manufacturer recommends 2-way)
  Size:              4 inch (116 mm OD — wide-flange, outdoor-rated frame)
  Brand:             REDCATT

CONSTRUCTION
  Nominal Impedance: 4 Ω (Re = 3.3 Ω DC)
  AES Power:         30 W
  Continuous Power:  60 W
  Peak Power:        120 W
  Voice Coil:        25.4 mm diameter, copper wire, aluminum former
  Magnet:            Ferrite (sizable magnet; consistent wide Bl field per design notes)
  Basket:            Steel, all parts coated for weather resistance
  Cone:              Polypropylene (PP) with PP dustcap — UV-stabilized, waterproof
  Surround:          NBR rubber, large roll (wide surround for extended physical stroke)
  Spider:            Nomex
  T-Plate:           5 mm
  Overall Dia.:      116 mm  (largest OD in the 4-inch family — wide mounting flange)
  Bolt Circle Dia.:  109 mm
  Baffle Cutout:     94.5 mm
  Mounting Holes:    4
  Depth:             55.9 mm
  Net Weight:        0.78 kg

NOTE ON OUTDOOR / WEATHER-RESISTANT DESIGN:
  The 4FRX4-385 is designed specifically for outdoor and weather-exposed applications.
  Key protections include: UV-stabilized PP cone, PP dustcap, and NBR surround; all
  internal basket and magnetic circuit components are coated against humidity and
  temperature cycling; all adhesive joints use weatherproof formulation to prevent
  delamination under moisture exposure. The wide-flange frame (OD = 116 mm) provides
  additional surface area for gasket sealing against a baffle. The PP cone and dustcap
  resist UV degradation and do not absorb moisture, unlike untreated paper cones.
  This makes the 4FRX4-385 suited for outdoor PA, installed sound, and all-weather
  column speaker applications that would damage standard paper-cone drivers.

NOTE ON POLYPROPYLENE CONE:
  The PP (polypropylene) cone is injection-moulded, providing consistent mass and
  geometry from unit to unit. It is lighter than typical paper cones (Mms = 7.3 g)
  and self-damps mid-band breakup modes differently — PP tends to roll off resonance
  peaks more gradually than paper. The PP dustcap is matched to the cone material
  for compatible thermal expansion and adhesion. The wide NBR surround roll extends
  peak-to-peak physical displacement (Xmech = 4.65 mm) while the linear excursion
  (Xmax = 0.35 mm) is limited by the voice coil gap geometry and coil winding length.

NOTE ON XMAX = 0.35 mm (KEY DESIGN CONSTRAINT):
  The measured linear excursion Xmax = 0.35 mm (one-way) is the smallest value in
  the full-range family by a large margin. This is consistent with the short voice
  coil winding (L-Winding = 4.3, compared to 10.6 for the 4FRX4-322) and reflects
  a design optimised for midrange output and weather durability rather than bass
  excursion. The consequences are:
  — Volume displacement Vd = 1.76 cm³ (lowest in the 4-inch group and near-lowest
    in the full-range family)
  — Bass output capacity is severely limited compared to other 4-inch drivers
  — Port velocity in vented alignments is negligible (< 1.2 m/s) but this does not
    recover the excursion-limited bass output capacity
  — The manufacturer's recommendation for 2-way or multi-way systems is strongly
    reinforced by this constraint; a subwoofer handling content below 100–150 Hz is
    required for music reproduction at meaningful SPL

THIELE-SMALL PARAMETERS (measured, broken-in)
  Fs   =  80.0 Hz          (free-air resonant frequency)
  Re   =   3.3 Ω           (DC voice coil resistance)
  Qes  =   0.58            (electrical Q)
  Qms  =   4.24            (mechanical Q)
  Qts  =   0.51            (total Q — sealed enclosure preferred)
  Vas  =   1.96 L          (equivalent air volume)
  Sd   =  50.3 cm²         (effective cone area)
  Mms  =   7.3 g           (moving mass)
  Rms  =   0.86 kg/s       (mechanical resistance)
  Cms  =   0.54 mm/N       (compliance)
  Bl   =   4.58 T·m        (force factor)
  Le   =   0.29 mH         (voice coil inductance — highest in 4-inch ferrite group)
  Xmax =   0.35 mm         (one-way linear excursion — smallest in full-range family)
  Xmech=   4.65 mm         (one-way mechanical limit)
  Xprot=   6.6 mm          (one-way protection limit)

SENSITIVITY
  Datasheet Sensitivity:  85.13 dB  (2.83V/1m, per CSV Sensitivity field)
  1W/1m reference (Lm):  84.35 dB  (per CSV Lm field — used for Max SPL calculations)
  NOTE: For a 4 Ω driver, applying 2.83V delivers approximately 2.43W (8.009/3.3).
        The expected relationship is Sensitivity ≈ Lm + 3.85 dB, giving an expected
        Sensitivity of approximately 88.2 dB. The CSV shows 85.13 dB — inconsistent
        by approximately 3.1 dB, consistent with the same pattern on the 35FRX4-155
        and 4FRX4-322 (both 4 Ω). Lm = 84.35 dB is used for all calculations.

DERIVED PARAMETERS
  Volume displacement:    Vd = Sd × Xmax = 50.3 cm² × 0.035 cm = 1.76 cm³
  Inductance rolloff:     f_Le = Re / (2π × Le) = 3.3 / (2π × 0.00029) = 1,811 Hz
  Cone radius:            r_cone = √(Sd/π) = √(50.3/π) = 4.00 cm
  Cone beaming onset:     f_beam = c / (π × r_cone) = 34400 / (π × 4.00) = 2,737 Hz
  Max SPL (AES, 30W):     1W/1m + 10×log10(30) = 84.35 + 14.77 = 99.1 dB at 1 m
  Zobel network:          Rz = 3.3 Ω; Cz = Le / Re² = 26.6 μF (series, across driver)
  Column array limit:     f_array = c / (2 × OD) = 34400 / (2 × 11.6) = 1,483 Hz ≈ 1.48 kHz

  ⚠ f_Le = 1,811 Hz IS THE LOWEST IN THE FULL-RANGE FAMILY:
    This is a critical design constraint. The impedance from Le equals Re at 1,811 Hz,
    meaning acoustic output rolls off significantly above this frequency. Even in a
    full-range role, the driver will exhibit −3 to −6 dB or more at 3–4 kHz relative
    to its 1 kHz response, solely from Le. A tweeter or coaxial horn is not optional
    in any application — it is mandatory for intelligible HF reproduction. The Zobel
    network (3.3 Ω + 26.6 μF) compensates the electrical impedance rise but does not
    restore acoustic output that is physically lost at the cone; active DSP treble boost
    can recover some HF output but at the cost of increased voice coil current and heat.

FREE-AIR ANALYSIS (Qts = 0.51 — sealed enclosure preferred, not free-air)
  Free-air f-3dB for reference:
    1/Qts² = 3.845; 2 − 3.845 = −1.845
    u = (1.845 + √(1.845² + 4)) / 2 = (1.845 + √7.404) / 2 = (1.845 + 2.721) / 2 = 2.283
    Ω = √2.283 = 1.511
    Free-air f-3dB ≈ 1.511 × 80 = 121 Hz
  Sealed enclosures provide flatter response and are recommended over free-air use.
ENCLOSURE RECOMMENDATIONS
PRIMARY: SEALED
  Qts = 0.51 is in the sealed-preferred range (0.50–0.70). The sealed box delivers
  the flattest frequency response and is the most appropriate enclosure for this
  driver. Note that the excursion-limited Vd (1.76 cm³) means that regardless of
  enclosure type, maximum acoustic output at bass frequencies is inherently low
  relative to high-Xmax drivers. The sealed box recommendation is based on flat
  frequency response, not bass extension capability.

  --- SEALED ALIGNMENTS ---

  Qtc = 0.707 (Butterworth — flattest):  Vb = 2.13 L  |  fc = 111 Hz  |  f-3dB = 111 Hz
    Note: Large enclosure for a 4-inch driver; lowest sealed f-3dB. Suitable for
    systems with a sub-woofer handling content below 100–120 Hz.

  Qtc = 0.85 (preferred balanced):       Vb = 1.10 L  |  fc = 133 Hz  |  f-3dB = 115 Hz
    Note: Recommended for most 2-way applications. Compact and practically flat
    to ~115 Hz.

  Qtc = 1.00 (compact):                  Vb = 0.69 L  |  fc = 157 Hz  |  f-3dB = 123 Hz

  Qtc = 1.20 (very compact):             Vb = 0.43 L  |  fc = 188 Hz  |  f-3dB = 139 Hz
    Note: Useful for column systems where driver bay volume is tightly constrained
    and the subwoofer or LF section handles content below ~140 Hz.

SECONDARY: VENTED (PORTED)
  Vented enclosures are viable but offer minimal practical advantage here due to
  the very small Vd (1.76 cm³). Port velocities are negligibly low (< 1.2 m/s)
  in all alignments, indicating that the driver's limited excursion — not port
  turbulence — is the binding constraint on acoustic output. Sealed is strongly
  preferred. Port: 30 mm diameter (Ap = 7.07 cm²).
  End corrections: flanged 12.8 mm + unflanged 9.2 mm = 22.0 mm total.

  --- VENTED ALIGNMENTS (30 mm port) ---

  Alignment V1: Vb = 1.5 L  |  Fb = 75 Hz
    Effective port length: 251 mm  →  Physical port length: ~229 mm
    Port air velocity:     1.17 m/s peak  (negligible; well below all limits)

  Alignment V2: Vb = 2.0 L  |  Fb = 70 Hz
    Effective port length: 216 mm  →  Physical port length: ~194 mm
    Port air velocity:     1.10 m/s peak

  Alignment V3: Vb = 3.0 L  |  Fb = 65 Hz
    Effective port length: 167 mm  →  Physical port length: ~145 mm
    Port air velocity:     1.02 m/s peak

  Note: All port velocities are negligible because Vd = 1.76 cm³ is extremely small.
  The vented port provides load relief at Fb but minimal additional bass output
  compared to sealed, given the driver's excursion-limited acoustic output capacity.
CROSSOVER AND SYSTEM DESIGN NOTES
  INDUCTANCE ROLLOFF (f_Le = 1,811 Hz — LOWEST IN FULL-RANGE FAMILY):
    Le = 0.29 mH is the highest Le among the 4-inch ferrite drivers (4FRX4-322:
    0.09 mH; 41FRX8-360B: 0.09 mH) and produces the lowest f_Le in the full-range
    family — even below the 41NFRX16-464A (3,348 Hz, which already required DSP or
    a tweeter below 3 kHz). At f_Le = 1,811 Hz, the acoustic HF rolloff from Le
    begins well within the music band:
      — At 2 kHz: ∼ −0.9 dB from Le alone
      — At 3 kHz: ∼ −2.6 dB from Le alone
      — At 5 kHz: ∼ −5.9 dB from Le alone
    (These are first-order rolloff approximations; actual rolloff depends on cone
    breakup and total impedance. A Zobel network corrects the electrical impedance
    rise but not the mechanical/acoustic rolloff.) Crossover to a tweeter at or
    below 1,500–2,000 Hz is strongly recommended. The manufacturer's recommendation
    for 2-way or multi-way systems reflects this constraint.

  EXCURSION LIMITATION (Xmax = 0.35 mm):
    The maximum one-way linear excursion of 0.35 mm defines the upper limit of
    undistorted acoustic output at any frequency. For reference, to produce 90 dB
    SPL at 80 Hz at 1 m from a sealed enclosure would require approximately 2–3 mm
    of cone excursion from a 50 cm² driver — well beyond the 0.35 mm linear range.
    In practice, the 4FRX4-385 will exhibit increasing THD at frequencies below
    approximately 200–300 Hz at moderate-to-high drive levels. This driver is
    correctly positioned as a midrange/mid-woofer crossed at 100–200 Hz in a multi-way
    system; it is not suitable as a standalone bass driver.

  CONE BEAMING (f_beam = 2,737 Hz):
    Same as other 50.3 cm² 4-inch drivers in the family. Directivity begins
    narrowing above 2,737 Hz. Since the f_Le rolloff (1,811 Hz) is lower than f_beam,
    it is the binding constraint on HF response well before cone beaming becomes
    significant. A tweeter crossover at 1.5–2.0 kHz addresses both constraints.

  COLUMN ARRAY DIRECTIVITY (f_array = 1.48 kHz for 116 mm OD):
    The wide-flange OD of 116 mm — the largest in the full-range family by 10+ mm —
    limits coherent vertical column array directivity to approximately 1.48 kHz.
    This is the lowest f_array in the 4-inch group. In column applications, the
    crossover to tweeter should be at or below 1.4–1.5 kHz to maintain directivity
    coherence. The large OD may require enclosure bay cutout planning for column
    cabinet designs — the 94.5 mm baffle cutout is similar to other 4-inch drivers,
    but the 116 mm overall frame requires wider driver bays or wider spacing between
    drivers in a vertical array.

  4 Ω IMPEDANCE AND WIRING:
    Identical considerations to the 4FRX4-322 — single-driver per channel is standard;
    parallel wiring to 2 Ω should be avoided unless the amplifier is rated for it.

  ZOBEL NETWORK:
    The Zobel network (3.3 Ω + 26.6 μF in series, across driver terminals) is
    particularly important here given the high Le (0.29 mH) and low Re (3.3 Ω).
    The impedance rise from Le is substantial at the crossover frequency region
    (1.5–2 kHz), and a passive crossover network will be significantly affected
    without Zobel compensation. Use a non-polar electrolytic or film capacitor
    rated for the operating voltage.
4-INCH DRIVER COMPARISON (5 variants)
  Parameter              40NFRX16-223       41FRX8-360B        41NFRX16-464A      4FRX4-322          4FRX4-385
                         (Neo, 16Ω)         (Ferrite, 8Ω)      (Neo ring, 16Ω)    (Ferrite, 4Ω)      (Ferrite, 4Ω outdoor)
  Re                     12.3 Ω             5.6 Ω              12.2 Ω             3.5 Ω              3.3 Ω
  AES Power              25 W               20 W               40 W               30 W               30 W
  Voice Coil Wire        CCAW               CCAW               Copper             Copper             Copper
  Former                 Kapton             Kapton             Kapton             Aluminum           Aluminum
  Fs                     115 Hz             134 Hz             98 Hz              79 Hz              80 Hz
  Qts                    1.10               0.75               0.37               0.52               0.51
  Vas                    1.50 L             1.30 L             2.10 L             1.80 L             1.96 L
  Sd                     50.2 cm²           50.3 cm²           56.75 cm²          50.3 cm²           50.3 cm²
  Bl                     5.3 T·m            4.78 T·m           10.0 T·m           4.8 T·m            4.58 T·m
  Le                     0.20 mH            0.09 mH            0.58 mH            0.09 mH            0.29 mH
  Xmax                   0.45 mm            1.1 mm             3.15 mm            2.8 mm             0.35 mm ‼
  Vd                     2.26 cm³           5.53 cm³           17.88 cm³          14.08 cm³          1.76 cm³ ‼
  1W/1m (Lm)             84.39 dB           87.98 dB           89.12 dB           83.66 dB           84.35 dB
  Max SPL (AES)          98.4 dB            101.0 dB           105.1 dB           98.4 dB            99.1 dB
  Enclosure              Free-air only      Free-air (primary) Vented (required)  Sealed (primary)   Sealed (primary)
  Bass −3dB              87 Hz (free-air)   127 Hz (free-air)  65–80 Hz (Fb)      107 Hz (Qtc=0.707) 111 Hz (Qtc=0.707)
  f_Le                   9,785 Hz           9,911 Hz           3,348 Hz           6,189 Hz           1,811 Hz ‼
  f_beam                 2,738 Hz           2,737 Hz           2,577 Hz           2,737 Hz           2,737 Hz
  f_array (OD)           1.66 kHz (104 mm)  1.63 kHz (106 mm)  1.65 kHz (105 mm)  1.63 kHz (106 mm)  1.48 kHz (116 mm) ‼
  Mounting               Standard           Standard           Front or rear      Standard           Standard (wide flange)
  ‼ denotes the lowest value of that parameter in the 4-inch group

  SELECTION NOTES:
  • 4FRX4-385 is the only weather-resistant, outdoor-rated driver in the 4-inch class.
    Its PP cone, UV-stabilized components, and weatherproof adhesive are unique in the
    family. It is the correct choice wherever outdoor exposure or humidity is a concern.
  • The f_Le = 1,811 Hz is the binding HF constraint — lower than f_beam (2,737 Hz)
    and the lowest f_Le in the entire full-range family. A tweeter crossover at or
    below 1.5–2.0 kHz is mandatory in all applications.
  • The Xmax = 0.35 mm and Vd = 1.76 cm³ position this driver as a midrange /
    mid-woofer in multi-way systems; it is not a bass driver.
  • The wide OD (116 mm) lowers f_array to 1.48 kHz — the lowest of the 4-inch group.
    This must be accounted for in column array crossover design.
  • 4FRX4-322 (also 4Ω, ferrite, sealed) is the alternative where weather resistance
    is not required: it has 8× more Xmax (2.8 mm), 8× higher Vd (14.08 cm³), lower
    f_Le (6,189 Hz), and more practical bass extension from a sealed enclosure.
  • Choose 4FRX4-385 for: outdoor rated systems, all-weather column cabinets, and
    2-way or multi-way PA systems where weatherproofing outweighs raw bass output.
FULL-RANGE FAMILY COMPARISON (14 drivers)
  Code              Size  Ω   W AES  Qts   Motor       Fs    Enclosure              −3dB    1W/1m  MaxSPL  OD     f_array
  20NFRX4-345A      2"    4   10     0.52  Neo         185   Free-air / open-back   272 Hz  79.6   89.6    48 mm   3.58 kHz
  21NFRX16-393D     2"    16  10     0.68  Neo         157   Free-air / open-back   164 Hz  85.8   95.8    57 mm   3.00 kHz
  22NFRX8-462A      2"    8   20     0.85  Neo         255   Free-air / open-back   219 Hz  83.5   96.5    61 mm   2.84 kHz
  25NFRX8-279       2.5"  8   20     0.71  Neo ring    123   Free-air / open-back   123 Hz  82.3   95.4    65 mm   2.65 kHz
  30FFX8-264B       3"    8   20     0.78  Ferrite     119   Free-air / open-back   109 Hz  83.6   96.6    79 mm   2.18 kHz
  31NFRX8-229       3"    8   30     0.88  Neo         115   Free-air / open-back    97 Hz  83.5   98.3    79 mm   2.18 kHz
  32NFRX8-463A      3"    4†  30     0.32  Neo ring    118   Vented (75–115 Hz)      75 Hz  89.4  104.1    83 mm   2.07 kHz
  35FRX4-155        3.5"  4   25     0.34  Ferrite      67   Vented (70–80 Hz)       70 Hz  83.1   97.1    93 mm   1.85 kHz
  35FRX8-406B       3.5"  8   20     0.63  Ferrite     128   Sealed                 148 Hz  87.6  100.6    93 mm   1.85 kHz
  40NFRX16-223      4"    16  25     1.10  Neo         115   Free-air / open-back    87 Hz  84.4   98.4   104 mm   1.66 kHz
  41FRX8-360B       4"    8   20     0.75  Ferrite     134   Free-air / open-back   127 Hz  88.0  101.0   106 mm   1.63 kHz
  41NFRX16-464A     4"    16  40     0.37  Neo ring     98   Vented (65–80 Hz)       65 Hz  89.1  105.1   105 mm   1.65 kHz
  4FRX4-322         4"    4   30     0.52  Ferrite      79   Sealed (107–134 Hz)    111 Hz  83.7   98.4   106 mm   1.63 kHz
  4FRX4-385         4"    4   30     0.51  Ferrite      80   Sealed (111–139 Hz)    115 Hz  84.4   99.1   116 mm   1.48 kHz
  † Re = 5.5 Ω
  −3dB: free-air for open-back drivers; Fb range for vented; Qtc=0.85 f-3dB for sealed drivers.

  FAMILY NOTES:
  • 4FRX4-385 is the only outdoor/weather-resistant driver in the full-range family
    and the only PP-cone driver. It is uniquely suited to exposed installations.
  • f_Le = 1,811 Hz is the lowest in the entire family. All other sealed/vented
    drivers have f_Le > 3,300 Hz; the next lowest is 41NFRX16-464A (3,348 Hz).
  • Xmax = 0.35 mm and Vd = 1.76 cm³ are the lowest in the 4-inch group. Among all
    14 drivers, only 20NFRX4-345A (a 2-inch driver) has smaller Vd.
  • The OD of 116 mm gives the lowest f_array (1.48 kHz) in the entire family,
    10–20 mm wider than all other 4-inch drivers. Column cabinet bay planning must
    account for the wider frame.
  • The family now spans f_Le from 1,811 Hz (4FRX4-385) to 9,911 Hz (41FRX8-360B),
    max SPL from 89.6 dB (20NFRX4-345A) to 105.1 dB (41NFRX16-464A), and OD from
    48 mm (20NFRX4-345A) to 116 mm (4FRX4-385) — 14 drivers, 4 enclosure types.
SUMMARY
The 4FRX4-385 is a 4-inch, outdoor-rated mid-woofer / full-range driver featuring
a ferrite magnetic circuit with a consistent wide Bl field, a steel basket with all
components coated for weather resistance, a polypropylene (PP) cone and PP dustcap
with UV stabilizers, a wide-roll NBR rubber surround, Nomex spider, and a 25.4mm
copper voice coil on an aluminum former. The PP cone and dustcap are injection-moulded
for dimensional consistency and do not absorb moisture; waterproof adhesive throughout
ensures the glue joints remain intact under prolonged humidity and temperature cycling.
The aluminum former provides efficient thermal conduction from the voice coil. The wide
mounting flange (OD = 116 mm, baffle cutout 94.5 mm) provides a large gasket sealing
surface suited to outdoor cabinet construction. The manufacturer specifies this driver
for 2-way or multi-way systems in indoor or outdoor, Hi-Fi or professional applications.

Fs = 80 Hz, Qes = 0.58, Qms = 4.24, Qts = 0.51. Vas = 1.96 L, Sd = 50.3 cm²,
Xmax = 0.35 mm (one-way linear excursion), Vd = 1.76 cm³. The Xmax of 0.35 mm is the
smallest in the full-range family and limits the driver's acoustic output at low
frequencies; it is suited for midrange reproduction in multi-way systems crossed above
100–150 Hz, not for high-excursion bass output. Voice coil inductance Le = 0.29 mH
gives an inductance rolloff onset of 1,811 Hz — the lowest f_Le in the full-range
family and a critical constraint requiring a tweeter crossover at or below 1.5–2.0 kHz
in all applications. Sensitivity is 84.35 dB at 1W/1m (Lm); the CSV Sensitivity field
(85.13 dB, 2.83V/1m) is inconsistent with the expected IEC relationship for a 4 Ω
driver, consistent with the pattern on other 4 Ω drivers in this catalog; Lm is used
for all calculations. Maximum SPL is 99.1 dB at 1 m (30W AES). The 116 mm OD limits
coherent column array directivity to 1.48 kHz — the lowest f_array in the full-range
family. Cone beaming onset at 2,737 Hz. Zobel network: 3.3 Ω + 26.6 μF in series
across driver terminals.

  Enclosure alignments:
  • Sealed (primary):
      2.13 L / Qtc = 0.707 / f-3dB = 111 Hz  (Butterworth — flattest)
      1.10 L / Qtc = 0.85  / f-3dB = 115 Hz  (recommended — balanced size and bass)
      0.69 L / Qtc = 1.00  / f-3dB = 123 Hz  (compact)
      0.43 L / Qtc = 1.20  / f-3dB = 139 Hz  (very compact; suited for column bays)
    Note: The excursion-limited Vd (1.76 cm³) means acoustic output below ~200 Hz
    will be modest regardless of alignment; a subwoofer is required for extended bass.
  • Vented (secondary) — 30 mm port:
      1.5 L / Fb = 75 Hz / ~229 mm physical port / 1.17 m/s peak port velocity
      2.0 L / Fb = 70 Hz / ~194 mm physical port / 1.10 m/s peak port velocity
      3.0 L / Fb = 65 Hz / ~145 mm physical port / 1.02 m/s peak port velocity
    Port velocities are negligible (Vd-limited, not port-limited); sealed preferred
    for construction simplicity and equivalent acoustic output.

The 4FRX4-385 is suited for outdoor and all-weather loudspeaker systems where a
weather-resistant 4-inch mid-woofer is required and environmental durability takes
priority over bass excursion — including outdoor column speakers, installed sound
systems in humid or exposed environments, and PA enclosures subject to rain or UV
exposure; 2-way and multi-way active or passive loudspeaker systems crossing this
driver above 100–150 Hz (subwoofer) and below 1,500–2,000 Hz (tweeter) where the
PP cone construction and waterproof adhesive are the primary selection criteria over
the paper-cone alternatives in the family; compact sealed column driver bays (0.43 L
at Qtc=1.20) in multi-element outdoor column systems; and applications where the
widest mounting flange (116 mm OD) provides the largest gasket sealing area for
weather exclusion at the driver/baffle interface.