CX8F140F

SPEAKER ENCLOSURE CALCULATION — CX8F-140FX8X8-374B
DRIVER IDENTIFICATION
  Code:              CX8F-140FX8X8-374B
  Name:              CX8F140F
  Category:          Coaxial — LF 8" / HF 1.4" with integrated symmetrical aluminum horn
  Brand:             REDCATT

DUAL-VALUE NOTATION:
  Parameters listed as A/B follow the convention: A = LF section, B = HF section.
  Single-value parameters apply to the LF section unless noted.

CONSTRUCTION
  ── LF SECTION (8" woofer) ──
  Nominal Impedance: 8 Ω (Re = 5.6 Ω DC)
  AES Power:         150 W
  Continuous Power:  300 W
  Peak Power:        600 W
  Voice Coil:        50.8 mm (2") diameter, CCAW wire, Glass Fiber former
  L-Winding:         12 mm
  Cone:              Custom paper pulp (Paper CF) — REDCATT-developed
  Surround:          Fabric (woven surround)
  Spider:            Nomex
  T-Plate:           8 mm (heavy motor plate for 150W power handling)

  ── HF SECTION (1.4" dome with integrated symmetrical aluminum horn) ──
  Nominal Impedance: 8 Ω (Re = 5.5 Ω DC)
  AES Power:         30 W
  Continuous Power:  60 W
  Peak Power:        120 W
  Voice Coil:        35.6 mm (1.4") diameter, Kapton former
  L-Winding:         2.5 mm
  Dome:              PEN (polyethylene naphthalate) — high-temperature polymer
  Surround:          PEN
  Horn:              Integrated symmetrical aluminum — rotationally symmetric;
                     provides identical horizontal and vertical dispersion in all
                     planes; CNC machined for dimensional precision (see note below)

  ── SHARED STRUCTURE ──
  Magnet:            Hybrid ferrite-neodymium (combined single magnetic circuit
                     for both LF woofer and HF dome — same topology as CX6F140F)
  Basket:            Steel, dual-gasket front and rear mounting
  Overall Dia.:      207 mm
  Bolt Circle Dia.:  197.2 mm  (8 mounting holes)
  Baffle Cutout:     178 mm
  Depth:             107.5 mm
  Net Weight:        2.8 kg

NOTE ON INTEGRATED SYMMETRICAL ALUMINUM HORN:
  The defining distinction between the CX8F-140FX8X8-374B and the CX6F140FX8X8-361C
  is the integrated symmetrical aluminum horn on the HF section. "Integrated" means the
  horn is assembled as a fixed part of the coaxial driver unit — not a field-replaceable
  waveguide. "Symmetrical" (rotationally symmetric) means the horn's profile is identical
  around the full 360° axis of the driver. Consequences:
  — The driver's coverage angle is the same in all planes (horizontal = vertical);
    there is no preferred orientation for cabinet mounting, simplifying column cabinet
    design.
  — The horn provides acoustic impedance matching from the 35.6mm (1.4") throat down
    to a usable lower frequency limit, allowing the HF dome to operate efficiently
    from approximately 1,200–1,300 Hz.
  — Integration into the basket assembly eliminates the horn-to-driver joint, removing
    a potential acoustic discontinuity and resonance source found in separate waveguide
    designs.
  — The aluminum construction provides thermal conduction away from the HF dome, and
    is mechanically rigid at frequencies where plastic waveguides may flex.
  — The symmetrical horn contributes to the HF Lm = 103 dB (1W/1m) — 2 dB above the
    CX6F's CNC machined waveguide — through more effective throat-to-mouth impedance
    loading.

NOTE ON CCAW VOICE COIL (LF, 50.8 mm):
  The LF 2-inch voice coil uses CCAW (copper-clad aluminum wire). At 50.8 mm diameter,
  a solid copper winding would add significant moving mass to the cone assembly. CCAW
  reduces the coil mass to approximately 40% of solid copper at the same wire gauge,
  which partially offsets the mass penalty of the larger coil diameter. With Mms = 20.2 g,
  the driver maintains competitive sensitivity (92.44 dB 1W/1m) at 150W AES power.
  The CCAW conductivity is sufficient for the 5.6 Ω Re requirement. Thermal expansion
  matching between the aluminum wire core and the glass fiber former is also favorable.

NOTE ON HYBRID FERRITE-NEODYMIUM COMBINED MAGNETIC CIRCUIT:
  Same design philosophy as the CX6F140FX8X8-361C: a single magnetic structure serves
  both the 50.8 mm LF voice coil gap and the 35.6 mm HF dome gap simultaneously. The
  larger T-plate (8 mm vs. 6 mm for the CX6) accommodates the higher flux requirements
  for the 150W LF section while maintaining the HF gap flux for the 30W HF dome.
  Bl = 9.93 T·m for the LF section. Aluminum demodulation ring in the HF section reduces
  Le non-linearity and intermodulation distortion in the HF dome.

THIELE-SMALL PARAMETERS
  ── LF SECTION ──
  Fs   =  86.0 Hz          (free-air resonant frequency — lowest of both coaxials)
  Re   =   5.6 Ω           (DC voice coil resistance)
  Qes  =   0.63            (electrical Q)
  Qms  =   9.06            (mechanical Q — very high; low mechanical loss)
  Qts  =   0.59            (total Q — sealed preferred; see below)
  Vas  =  10.7 L           (equivalent air volume — 2.4× larger than CX6F)
  Sd   = 213.8 cm²         (effective cone area — largest of all drivers processed)
  Mms  =  20.2 g           (moving mass)
  Rms  =   1.2 kg/s        (mechanical resistance — very low; consistent with high Qms)
  Cms  =   0.17 mm/N       (compliance)
  Bl   =   9.93 T·m        (force factor)
  Le   =   0.47 mH         (voice coil inductance — LF section)
  Xmax =   2.0 mm          (one-way linear excursion — LF)
  Xmech=  10.0 mm          (one-way mechanical limit — LF)
  Xprot:   not provided in catalog data

  Consistency check (Qts):  Qes×Qms / (Qes+Qms) = 0.63×9.06 / (0.63+9.06)
                            = 5.708 / 9.69 = 0.589 ≈ 0.59  ✓

  ── HF SECTION ──
  Fs_HF  = 1,000 Hz        (dome resonant frequency; horn loading enables use from ~1,200 Hz)
  Re_HF  =   5.5 Ω         (DC resistance)
  Lm_HF  = 103.0 dB        (1W/1m sensitivity — with integrated symmetrical horn loading;
                             2 dB above the CX6F's waveguide-loaded 101 dB)
SENSITIVITY AND MAXIMUM SPL
  ── LF SECTION ──
  Datasheet Sensitivity:  94.0 dB   (2.83V/1m, per CSV Sensitivity field)
  1W/1m reference (Lm):  92.44 dB  (per CSV Lm field)
  Consistency check:      Re = 5.6 Ω → 2.83V delivers 8.009/5.6 = 1.430W
                          Expected Sensitivity = 92.44 + 10×log10(1.430)
                                               = 92.44 + 1.55 = 93.99 dB
                          CSV shows 94.0 dB — consistent ✓

  LF Max SPL (AES 150W):  92.44 + 10×log10(150) = 92.44 + 21.76 = 114.2 dB at 1 m

  ── HF SECTION ──
  1W/1m reference (Lm_HF):  103.0 dB (with integrated symmetrical horn loading)
  Expected HF Sensitivity:   103.0 + 10×log10(8.009/5.5) = 103.0 + 1.63 = 104.6 dB
  HF Max SPL (AES 30W):      103.0 + 10×log10(30) = 103.0 + 14.8 = 117.8 dB at 1 m

  LEVEL MATCHING NOTE:
  HF Lm (103.0 dB) exceeds LF Lm (92.44 dB) by 10.56 dB — larger than the 7.2 dB
  mismatch in the CX6F140F, owing to the higher acoustic gain of the integrated horn.
  In a passive crossover: an L-pad on the HF section must reduce HF output by ~10.5 dB.
  An L-pad with series resistance ≈ 7.5 Ω and shunt resistance ≈ 6.5 Ω (values
  depend on crossover topology; calculate from nominal 8 Ω HF load after attenuation).
  In a bi-amplified / DSP system: digital gain trim of −10.5 dB on the HF channel.
  After matching, the HF operates well within its 30W AES rating at all drive levels.
DERIVED PARAMETERS (LF section)
  Volume displacement:    Vd = Sd × Xmax = 213.8 cm² × 0.20 cm = 42.76 cm³
  Inductance rolloff:     f_Le_LF = Re / (2π × Le) = 5.6 / (2π × 0.00047) = 1,896 Hz
  Cone radius:            r_cone = √(Sd/π) = √(213.8/π) = 8.25 cm
  Cone beaming onset:     f_beam_LF = c / (π × r_cone) = 34400 / (π × 8.25) = 1,327 Hz
  Zobel (LF):             Rz = 5.6 Ω; Cz = Le / Re² = 15.0 μF (series, across LF terminals)
  Column array limit:     f_array = c / (2 × OD) = 34400 / (2 × 20.7) = 831 Hz ≈ 0.83 kHz
  LF Max SPL:             114.2 dB at 1 m (150W AES)
  Vd = 42.76 cm³:         largest volume displacement of all REDCATT drivers processed

  ⚠ CRITICAL CROSSOVER CONSTRAINT — f_beam_LF vs. HF MINIMUM:
    f_beam_LF = 1,327 Hz is BELOW the HF dome's practical minimum operating
    frequency (~1,200–1,300 Hz with integrated horn loading, vs. Fs = 1,000 Hz).
    This means:
    — An ideal crossover at or below f_beam_LF (≤ 1,327 Hz) pushes the HF dome
      close to its lower operating limit. The integrated horn loading extends the
      dome's low-frequency usability, making 1,200–1,400 Hz crossovers feasible
      but requiring careful crossover slope design to protect the dome below its Fs.
    — A crossover above f_beam_LF (1,400–2,000 Hz) is mechanically safer for
      the HF dome but accepts that the LF cone is beaming before handoff. The
      integrated symmetrical horn broadens the off-axis HF response above the
      crossover to partially compensate, consistent with the manufacturer's claim
      of "good off-axis frequency response."
    — Practical optimum: 1,400–1,600 Hz crossover; 18–24 dB/octave slope to
      protect the HF dome; LF highpass slope to suppress excursion at LF rolloff.

  ⚠ COLUMN ARRAY CONSTRAINT — f_array = 0.83 kHz:
    The 207 mm OD limits coherent vertical directivity in a column array to 831 Hz.
    Above this frequency, individual 8" LF cones radiate independently and vertical
    grating lobes appear in the LF section. For column applications, the LF array
    coherence limit is below even the lowest practical HF crossover frequency
    (~1,200 Hz). This means the column's vertical directivity pattern transitions
    from array-controlled (below 0.83 kHz) to individual-driver-controlled (0.83–1.4 kHz)
    to horn-controlled (above crossover) — three distinct directivity regimes. System
    designers must account for this when defining the coverage specification of a
    column system using this driver.
ENCLOSURE RECOMMENDATIONS (LF section)
  Qts = 0.59 → 0.50–0.70 range: sealed preferred. Vented is a viable secondary
  option where bass extension below Fs (86 Hz) is required in PA applications.

PRIMARY: SEALED
  The Fs = 86 Hz is the lowest of both coaxials processed, giving the best sealed
  bass extension. The Butterworth alignment at 24.55 L is large but practical for
  a professional 8" PA cabinet.

  --- SEALED ALIGNMENTS ---

  Qtc = 0.707 (Butterworth — flattest):  Vb = 24.55 L  |  fc = 103 Hz  |  f-3dB = 103 Hz
    Note: Large enclosure; best sealed bass extension. Practical for floor or
    pole-mount PA cabinets where volume is not the primary constraint.

  Qtc = 0.85 (balanced):                 Vb =  9.95 L  |  fc = 124 Hz  |  f-3dB = 107 Hz
    Note: Recommended. Practical cabinet size for PA and installed sound;
    f-3dB of 107 Hz with a subwoofer handling content below 80–100 Hz.

  Qtc = 1.00 (compact):                  Vb =  5.71 L  |  fc = 146 Hz  |  f-3dB = 115 Hz

  Qtc = 1.20 (very compact):             Vb =  3.41 L  |  fc = 175 Hz  |  f-3dB = 129 Hz
    Note: Suitable for narrow column designs where cabinet volume is constrained;
    subwoofer essential below 120–130 Hz.

SECONDARY: VENTED (PORTED)
  For PA and outdoor applications requiring bass extension below 80–90 Hz without
  a separate subwoofer. The large Vd (42.76 cm³) ensures meaningful acoustic output
  at the tuning frequency.
  Port: 75 mm diameter (Ap = 44.18 cm²).
  End corrections: flanged end 31.9 mm + unflanged end 22.9 mm = 54.8 mm total.

  --- VENTED ALIGNMENTS (75 mm port) ---

  Alignment V1: Vb = 12 L  |  Fb = 70 Hz
    Effective port length:  225 mm  →  Physical port length: ~170 mm
    Port air velocity:      4.26 m/s peak  (well within all limits)

  Alignment V2: Vb = 18 L  |  Fb = 60 Hz
    Effective port length:  205 mm  →  Physical port length: ~150 mm
    Port air velocity:      3.65 m/s peak

  Alignment V3: Vb = 25 L  |  Fb = 52 Hz
    Effective port length:  196 mm  →  Physical port length: ~141 mm
    Port air velocity:      3.16 m/s peak

  Note: Port velocities are very low for all alignments, reflecting the large port area
  (75 mm) relative to Vd. A subsonic high-pass filter at Fb − 10 Hz (42–60 Hz,
  depending on alignment) is mandatory to prevent mechanical over-excursion below
  the tuning frequency, where Xmech = 10 mm limits travel.
COAXIAL FAMILY COMPARISON (2 drivers)
  Parameter                  CX6F140FX8X8-361C           CX8F-140FX8X8-374B
                             (6.5" LF / 1.4" HF)         (8" LF / 1.4" HF)
  ── LF SECTION ──
  LF AES Power               100 W                        150 W
  LF Voice Coil              44.5 mm / Glass Fiber         50.8 mm / Glass Fiber
  LF Voice Coil Wire         CCAR                          CCAW
  LF Fs                      121 Hz                        86 Hz
  LF Qts                     0.47                          0.59
  LF Vas                     4.4 L                         10.7 L
  LF Sd                      141 cm²                       213.8 cm²
  LF Bl                      9.27 T·m                      9.93 T·m
  LF Le                      0.45 mH                       0.47 mH
  LF Xmax                    2.0 mm                        2.0 mm
  LF Vd                      28.2 cm³                      42.76 cm³ ← larger
  LF Lm (1W/1m)              93.8 dB                       92.44 dB
  LF Max SPL (AES)           113.8 dB                      114.2 dB ← higher
  LF Enclosure (primary)     Vented                        Sealed
  LF f-3dB (typical)         70–95 Hz (Fb range)           103–129 Hz (sealed)
  LF f_Le                    1,911 Hz                      1,896 Hz
  LF f_beam                  1,635 Hz                      1,327 Hz ← lower
  ── HF SECTION (shared dome assembly) ──
  HF AES Power               30 W                          30 W
  HF Voice Coil              35.6 mm / Kapton              35.6 mm / Kapton
  HF Fs                      1,000 Hz                      1,000 Hz
  HF Lm (1W/1m)              101 dB                        103 dB ← higher
  HF Max SPL                 115.8 dB                      117.8 dB ← higher
  HF Loading device          CNC machined waveguide        Integrated symmetrical horn
  HF/LF sensitivity gap      7.2 dB                        10.56 dB ← larger gap
  ── SYSTEM ──
  OD                         165.2 mm                      207 mm
  f_array                    1.04 kHz                      0.83 kHz ← lower
  Mounting holes             8                             8
  Crossover range            1,500–2,000 Hz                1,400–1,600 Hz ← lower, tighter
  SELECTION NOTES:
  • Choose CX8F-140FX8X8-374B for: higher power (150W LF), lower Fs (86 Hz),
    larger Vd (42.76 cm³), maximum LF SPL (114.2 dB), integrated symmetrical horn
    (uniform all-axis dispersion), and applications where subwoofer support below
    100–120 Hz is available.
  • Choose CX6F140FX8X8-361C for: smaller enclosure, vented bass extension to
    70–95 Hz Fb without subwoofer, higher LF sensitivity (93.8 dB), higher LF
    f_beam (1,635 Hz) allowing 1,500–2,000 Hz crossover with less beaming conflict,
    better f_array (1.04 kHz) for column coherence above 1 kHz.
  • Both drivers share the same HF dome assembly (140FCD-based), the same hybrid
    ferrite-neodymium combined magnetic circuit topology, the same demodulation ring
    in the HF section, and the same 8-hole dual-gasket basket design.
  • The 8" format's lower f_array (0.83 kHz) is a significant constraint for column
    arrays; the 6.5" driver (1.04 kHz) better suits narrow-column applications.
CROSSOVER AND SYSTEM DESIGN NOTES
  CROSSOVER FREQUENCY — PRACTICAL RANGE 1,400–1,600 Hz:
    Constraints:
    — HF dome Fs = 1,000 Hz; with integrated horn loading, practical minimum ≈ 1,200 Hz
    — f_beam_LF = 1,327 Hz: LF is already beaming at 1,327 Hz
    — f_Le_LF = 1,896 Hz: LF amplitude rolloff above this point
    The narrower practical crossover window (vs. CX6F) arises from the 8" cone's
    lower f_beam. A 1,400–1,600 Hz crossover with 18–24 dB/octave slopes is the
    recommended target. The integrated symmetrical horn's good off-axis response
    (per manufacturer claim) mitigates the LF beaming that occurs just below the
    crossover point. Active DSP crossover with independent LF highpass and HF
    lowpass filters is preferred for accurate slope control and HF dome protection.

  COAXIAL PHASE ALIGNMENT:
    As with the CX6F, the LF cone apex and HF dome acoustic centres are offset along
    the drive axis. Phase alignment correction (all-pass filter or digital delay) is
    required in active systems for a coherent crossover transition. Passive crossover
    designs achieve this empirically through component value selection verified by
    measurement.

  COLUMN ARRAY — THREE DIRECTIVITY REGIMES:
    Below 0.83 kHz:   LF cones operate as a coherent vertical array. Vertical
                       narrowing is array-controlled (number of drivers × spacing).
    0.83–1.5 kHz:     Individual 8" cones radiate independently; vertical coverage
                       widens and grating lobes may appear. This "transition zone"
                       is wider than for the 6.5" coaxial (whose transition zone is
                       1.04–1.5 kHz). System designers should evaluate measured
                       vertical polar data in this region.
    Above 1.5 kHz:    Integrated horn controls vertical (and horizontal) coverage.
                       Coverage pattern is determined by horn geometry; symmetrical
                       horn provides equal H and V angles.

  SUBSONIC PROTECTION:
    In vented alignments (secondary), the cone is unloaded below Fb. With Xmech =
    10 mm and Vd = 42.76 cm³, the 8" cone can produce extremely high excursion on
    subsonic signals or programme material below the tuning frequency. A subsonic
    high-pass filter (Butterworth or Linkwitz-Riley at Fb − 10 Hz) is mandatory.
    In sealed alignments, excursion rises gradually below fc; a rumble filter is
    still recommended at 40–50 Hz for sustained high-power use.

  LF ZOBEL AND PASSIVE CROSSOVER:
    Zobel: 5.6 Ω + 15.0 μF in series across LF terminals. Essential for passive
    crossover; the LF Le impedance rise above 1,896 Hz would shift the crossover
    frequency upward and alter the LF/HF balance without compensation.

  8-HOLE MOUNTING AND LARGE-FORMAT CABINET CONSIDERATIONS:
    The 207 mm OD and 2.8 kg weight require an 8-hole bolt pattern for secure
    baffle attachment in PA cabinets subject to vibration and transport. The 178 mm
    baffle cutout is the primary cabinet dimension constraint; column cross-sections
    narrower than approximately 215 mm cannot accommodate this driver, limiting its
    application in slim column form factors.
SUMMARY
The CX8F-140FX8X8-374B is an 8-inch / 1.4-inch coaxial driver sharing the same hybrid
ferrite-neodymium combined magnetic circuit topology as the CX6F140FX8X8-361C. The LF
section uses a 50.8mm (2-inch) CCAW voice coil on a glass fiber former for high thermal
conductivity and reduced moving mass — supporting 150W AES / 300W continuous LF power
handling — driving a REDCATT custom paper pulp cone with woven fabric surround and Nomex
spider. The HF section uses the same 35.6mm PEN dome assembly as the CX6F, driven by a
Kapton former with an aluminum demodulation ring in the HF magnetic gap to suppress
intermodulation distortion. The principal construction difference from the CX6F is the
integrated symmetrical aluminum horn on the HF section: rotationally symmetric around the
driver axis, it provides identical coverage angles in all planes, eliminates the separate
waveguide joint, and delivers 2 dB higher HF sensitivity (Lm_HF = 103 dB) compared to the
CX6F's separate CNC waveguide (101 dB). The 8-hole dual-gasket basket supports front or
rear baffle mounting in PA and installed sound enclosures.

LF section T/S parameters: Fs = 86 Hz, Re = 5.6 Ω, Qes = 0.63, Qms = 9.06, Qts = 0.59,
Vas = 10.7 L, Sd = 213.8 cm², Mms = 20.2 g, Bl = 9.93 T·m, Le = 0.47 mH, Xmax = 2.0 mm
(one-way), Vd = 42.76 cm³ — the largest volume displacement of all REDCATT drivers
processed. LF 1W/1m sensitivity (Lm) = 92.44 dB, consistent with the 2.83V/1m
measurement (94.0 dB) within 0.01 dB. Maximum LF SPL = 114.2 dB at 1 m (150W AES). HF:
Fs_HF = 1,000 Hz, Re_HF = 5.5 Ω, Lm_HF = 103.0 dB (with integrated horn), AES = 30W,
maximum HF SPL = 117.8 dB. The HF section is 10.56 dB more sensitive than the LF at 1W/1m;
an L-pad (passive) or ~10.5 dB DSP gain trim (active) is required for level matching.
LF cone beaming onset f_beam = 1,327 Hz is the binding crossover constraint — below the
HF dome's lower practical limit with horn loading (~1,200–1,300 Hz) — yielding a narrow
practical crossover window of 1,400–1,600 Hz. LF inductance rolloff at f_Le = 1,896 Hz.
LF Zobel: 5.6 Ω + 15.0 μF. Column array coherence limit: f_array = 0.83 kHz (207 mm OD)
— the lowest f_array of all drivers processed; above 0.83 kHz the 8" LF cones become
independent radiators, creating a transition zone to horn-controlled coverage above the
crossover at approximately 1.5 kHz.

  LF enclosure alignments:
  • Sealed (primary):
      24.55 L / Qtc = 0.707 / f-3dB = 103 Hz  (Butterworth — flattest sealed; large cabinet)
       9.95 L / Qtc = 0.85  / f-3dB = 107 Hz  (recommended for PA/installed sound)
       5.71 L / Qtc = 1.00  / f-3dB = 115 Hz  (compact)
       3.41 L / Qtc = 1.20  / f-3dB = 129 Hz  (very compact; subwoofer support required below ~120 Hz)
  • Vented (secondary) — 75 mm port:
      12 L / Fb = 70 Hz / ~170 mm physical port / 4.26 m/s peak port velocity
      18 L / Fb = 60 Hz / ~150 mm physical port / 3.65 m/s peak port velocity
      25 L / Fb = 52 Hz / ~141 mm physical port / 3.16 m/s peak port velocity
    (Subsonic high-pass filter at Fb − 10 Hz mandatory; all velocities well within PA limits)

  Recommended LF/HF crossover: 1,400–1,600 Hz, 18–24 dB/octave (Linkwitz-Riley or
  Butterworth); active/DSP crossover preferred for slope accuracy and HF dome protection;
  LF Zobel network essential before passive crossover components.

The CX8F-140FX8X8-374B is suited for professional PA cabinet and column speaker systems
requiring the highest LF acoustic output (114.2 dB max SPL) from a coaxial driver, with
a subwoofer or amplifier/DSP system handling content below 100–130 Hz; wide-coverage
PA applications where the integrated symmetrical horn's equal H/V dispersion eliminates
cabinet orientation sensitivity and ensures consistent coverage angle in all planes;
installed sound systems in large venues or outdoors where sustained 150W LF and 30W HF
power handling in extreme weather conditions is required; and bi-amplified column or
cluster systems where the 8" format's 42.76 cm³ Vd, 9.93 T·m Bl, and matched HF
sensitivity (after 10.5 dB attenuation) provide maximum acoustic output per driver bay.