8FR

ENCLOSURE RECOMMENDATIONS: 8FRX4-551A
Driver: 8FRX4-551A (8FR) — 8" Full-Range (Hi-Fi / Open Baffle)
Key T/S: Fs=53Hz, Qts=0.378, Vas=36.8L, Sens=93dB 1W/1m
Power: AES 30W / Cont 60W / Peak 120W
Xmax=5.8mm (one-way linear), Xmech=11.8mm (protection at 9.8mm)
Sd=213.8cm², Bl=7.86T·m, Re=3.8Ω (4-ohm nominal), Mms=18.38g
Le=0.08mH (extremely low — wide-bandwidth motor design)
Voice Coil: 1.6" aluminum on Kapton former (17.6mm winding height)
Magnet: Ferrite with copper shorting cup | Basket: Aluminum
Cone: Bamboo fiber reinforced paper pulp with whizzer cone
Phase plug: Bullet style | Surround: Fabric
NOTE: This is a dedicated hi-fi full-range driver with a whizzer
(secondary) cone for extended high-frequency response to 15 kHz
and a bullet-style phase plug for controlled off-axis dispersion.
The extremely low voice coil inductance (0.08 mH) and copper
shorting cup ensure flat impedance and clean response through the
upper midrange and treble. Designed primarily for open baffle (OB)
applications, but also suitable for sealed and vented enclosures.
  PRIMARY — Open Baffle (OB)
Open baffle mounting is the intended application for this driver.
In OB, the driver radiates as a dipole — front and rear waves are
in opposite polarity and partially cancel at low frequencies. Above
the baffle frequency (fb), the response is essentially flat. Below
fb, the response rolls off at approximately 6 dB/octave due to
dipole cancellation.
BAFFLE FREQUENCY vs BAFFLE WIDTH:
  Baffle Width       fb (Hz)    Notes
  40 cm              273        Small desktop/nearfield
  50 cm              218        Compact stand-mount OB
  60 cm              182        Medium floor-standing OB
  80 cm              136        Large floor-standing OB
  100 cm             109        Very large statement OB
  Formula: fb = 343 / (π × baffle_width_in_meters)
RECOMMENDED OB CONFIGURATIONS:
  a) OB — Compact (50 cm wide baffle)
     Baffle Frequency: 218 Hz
     Dipole rolloff below 218 Hz at ~6 dB/octave
     Usable bass (no EQ): ~120–150 Hz
     With DSP bass EQ (+6 dB/oct shelving): usable to ~60–70 Hz
     EQ boost at Fs (53 Hz): ~12 dB
     Baffle suggestion: 50 × 70 cm minimum, 18–25mm birch plywood
     Notes: Compact OB for nearfield/desktop or small room use.
     Requires significant DSP bass boost to achieve flat response
     below 200 Hz. The small baffle allows excellent imaging and
     disappearing soundstage. Best paired with a dipole subwoofer
     (OB sub or H-frame) for full-range reproduction.
  b) OB — Standard (60–70 cm wide baffle)
     Baffle Frequency: 156–182 Hz
     Dipole rolloff below 156–182 Hz at ~6 dB/octave
     Usable bass (no EQ): ~100–120 Hz
     With DSP bass EQ (+6 dB/oct shelving): usable to ~50–60 Hz
     EQ boost at Fs (53 Hz): ~9–11 dB
     Baffle suggestion: 60–70 × 90–100 cm, 18–25mm birch plywood
     Notes: The recommended starting point for most OB builds.
     Moderate DSP bass boost achieves a musically satisfying
     full-range response. Good balance between bass extension,
     imaging, and practical room placement. Can work as a
     stand-alone full-range system in smaller rooms, or paired
     with a subwoofer for larger spaces.
     *** RECOMMENDED FOR MOST OB APPLICATIONS ***
  c) OB — Large (80–100 cm wide baffle)
     Baffle Frequency: 109–136 Hz
     Dipole rolloff below 109–136 Hz at ~6 dB/octave
     Usable bass (no EQ): ~80–100 Hz
     With DSP bass EQ (+6 dB/oct shelving): usable to ~40–50 Hz
     EQ boost at Fs (53 Hz): ~6–8 dB
     Baffle suggestion: 80–100 × 120–140 cm, 18–25mm birch plywood
     Notes: Large baffle provides the deepest bass without
     requiring excessive EQ. Less DSP boost means less excursion
     demand at low frequencies, improving dynamic headroom. The
     large baffle provides more acoustic loading but begins to
     narrow horizontal dispersion at higher frequencies. Best
     for dedicated listening rooms where room placement allows
     large panels.
OPEN BAFFLE DESIGN NOTES:
- Baffle should be made from acoustically inert material (birch
  plywood, MDF, or bamboo laminate — 18mm minimum, 25mm preferred)
- Bracing behind the driver cutout is recommended to minimize
  baffle vibration
- Driver offset from center (both horizontally and vertically)
  reduces edge diffraction artifacts
- Room placement: OB speakers require distance from rear wall
  (minimum 50–80 cm) to avoid comb filtering from rear wave
  reflections
- The dipole radiation pattern provides a natural, spacious
  soundstage with minimal room excitation compared to monopole
  (boxed) speakers
- The whizzer cone handles frequencies above approximately
  3–5 kHz; its integration with the main cone provides the
  wide-bandwidth single-point-source characteristic
- DSP bass equalization: a 6 dB/octave shelving boost below the
  baffle frequency restores flat response. Monitor excursion —
  the driver's 5.8 mm Xmax limits maximum output at low
  frequencies under heavy EQ boost
  ALTERNATIVE — Sealed Enclosures
For listeners who prefer a traditional boxed speaker, sealed
enclosures provide smooth, predictable rolloff and are simpler to
build than OB. The Qts of 0.378 produces overdamped sealed
alignments in practical volumes — the gentle rolloff integrates
well with room gain in domestic environments.
  d) SEALED — Compact (Qtc ≈ 0.7)
     Net Volume: 15 liters
     System Resonance (fc): 98 Hz
     Qtc: 0.70
     Response: Butterworth, maximally flat sealed response
     Notes: Most compact practical sealed alignment. The fc of
     98 Hz is relatively high — the speaker will roll off below
     100 Hz and rely on room gain for usable response into the
     70–80 Hz range. Best when paired with a subwoofer for bass
     support, or for nearfield desktop use where proximity gain
     assists low-frequency extension.
  e) SEALED — Balanced (Qtc ≈ 0.6)
     Net Volume: 25 liters
     System Resonance (fc): 83 Hz
     Qtc: 0.60
     Response: Overdamped, smooth gentle rolloff
     Notes: Good balance between cabinet size and bass extension.
     The overdamped response provides a natural, warm rolloff
     that sounds musical without excessive resonance. With room
     gain, in-room response extends usably to ~55–60 Hz. A good
     starting point for a full-range bookshelf or stand-mount
     speaker without a subwoofer.
     *** RECOMMENDED SEALED ALIGNMENT ***
  f) SEALED — Extended (Qtc ≈ 0.5)
     Net Volume: 50 liters
     System Resonance (fc): 70 Hz
     Qtc: 0.50
     Response: Heavily overdamped, very gradual rolloff
     Notes: Large enclosure providing the lowest sealed fc. The
     heavily overdamped alignment rolls off very gradually,
     providing usable response well below fc with room gain
     (estimated in-room -3 dB around 45–50 Hz). Suitable for
     a floor-standing full-range speaker in a medium to large
     room. The large cabinet volume makes this a substantial
     piece of furniture.
  ALTERNATIVE — Bass Reflex (Vented) Enclosures
Vented enclosures provide deeper bass extension than sealed in the
same volume, but introduce port-related artifacts (chuffing, resonance
at tuning frequency). For a hi-fi full-range driver, sealed or OB is
generally preferred for purity of reproduction, but vented is an
option where maximum bass extension from a compact enclosure is
required.
  g) VENTED — Compact
     Net Volume: 27 liters
     Tuning (Fb): 61 Hz
     Est. -3dB: 56 Hz
     HP Filter: 51 Hz (24dB/oct recommended)
     Round Port: 65mm dia × 51mm long
     Port Velocity: 14.3 m/s
     Notes: Higher tuning for stronger upper-bass output and
     compact cabinet. Good for a vented bookshelf-sized
     full-range speaker.
  h) VENTED — Balanced
     Net Volume: 31 liters
     Tuning (Fb): 55 Hz
     Est. -3dB: 51 Hz
     HP Filter: 45 Hz (24dB/oct recommended)
     Round Port: 65mm dia × 58mm long
     Port Velocity: 12.9 m/s
     Notes: General-purpose alignment with good extension
     relative to cabinet size. Usable bass response to ~50 Hz
     with room gain extending further.
  i) VENTED — Extended
     Net Volume: 37 liters
     Tuning (Fb): 48 Hz
     Est. -3dB: 41 Hz
     HP Filter: 38 Hz (24dB/oct recommended)
     Round Port: 65mm dia × 68mm long
     Port Velocity: 11.3 m/s
     Notes: Maximum bass extension, reaching into the low
     40s Hz anechoic. A compelling option for a vented
     floor-standing full-range speaker. Port velocities are
     moderate and well-controlled.
VENTED NOTE: Port lengths are short (51–68 mm) and velocities are
moderate (11–14 m/s), making port design straightforward. A simple
rear-mounted 65 mm round port is sufficient. Consider a flared port
for lowest noise in critical listening applications.