W-3F

W-3F is a two-way, two-element full range speaker, its LF unit and HF unit is of coaxial configuration (See Figure 31).

Figure 31

It is a better configuration to form a virtual point source. As the back of the HF horn is sealed that has little or nothing to do with the size or design of the enclosure.

 

For the LF unit, the front radiation is horn loaded and the back radiation is bass reflex.

 

The enclosure is of phase inverted (or vented) design. The advantage of this design is that sound wave radiated from the rear of the speaker is in phase with the sound wave radiated from the speaker front by proper phase adjustment after passing through the vent. The vent itself functions as an additional radiator is this case, and its radiation can add constructively to that of the speaker over certain frequencies. It requires less speaker excursion and therefore reduced amplitude distortion for a given acoustic output in the lowest portion of its usable bandwidth. This effect is most noticeable for frequencies in the neighborhood of the system lower cutoff frequency.

 

For the same lower cutoff frequency, the enclosure can be made smaller and due to this reason, the air within the enclosure acting as an air cushion at very strong transient signals.

 

The enclosure is trapezoidal (See Figure 32) for easier arraying.

 

The enclosure is made of 18mm (11-ply) birch plywood. All joints are tenon and mortise of Chinese tradition plus screws and adhesive to ensure the rigidity and durability.

 

Many domestic and imported speaker enclosures using medium density fibre (MDF) board to reduce cost, but MDF has a fatal weakness. It soften when moisten and loss its rigidity. iBO rather uses expensive birch plywood to build the enclosures to ensure its strength and rigidity no matter used indoor or outdoor, rain or fine.

 

The enclosure is heavily braced internally and a black powder-coated steel mesh grille protects the drivers from damage. The finishing is in black semi-matt textured environmental friendly paint. A rear connector plate fitted with two Neutrik Speakon NL4MP connectors for amplifiers and for loop-in and loop-out to additional enclosures (See Figure 33).

Figure 33

The Components

The LF unit is L12/75/03Z, 12-inch in diameter. This unit is specifically developed by iBO for W-3F.

  • The cone is a special formulated pulp and carbon fiber, very light and very rigid
  • The shape of the cone is straight and deep with a better mid frequency and transient response
  • The diameter of the voice is 3-inch edge wound with flat aluminum wire on a Kapton former (See Figure 34)

Figure 34

  • Magnet is made from high flux y30 strontium ferrite. The weights is 6.15kgs (See Figure 35)

L12/75/03Z

Figure 35

  • Loaded horn is made from glass fiber reinforced plastic

 

Mid/high –frequency unit is a H3/75/03Z

Compression driver

The H3/75/03Z is developed by iBO featuring:

  • The diaphragm is made of titanium and its surround is Mylar. The voice coil is edge wound with flat aluminum wire, (See Figure 36 and 37) the diameter is 3-inch (75mm)

Figure 36 and 37

  • The diameter of the throat is 1.4-inch (35mm)
  • The slits pattern of the phase plug is circumferential .
  • y30 high flux strontium ferrite is employed and the magnetic structure weights 6.05kgs.

 

 

A conical exponential horn called conical wave guide is coupled to the H3/75/03Z for the mid/high frequency band. The directivity is 45 o X 45 o. The exponential horn was chosen due to its minimal changing rate of cross section.

 

We expect the acoustic impedance of a horn be kept constant pure resistance for a widest possible frequency band. Exponential horn fulfilled this requirement. The materials of the horn is fiberglass reinforced plastic.

 

The Crossover Network

The sensitivity of W-3F’s high frequency component (110 dB w/m) is much higher than the low frequency component (103 dB w/m). The difference is more than 7 dB. If a build-in passive crossover network is employed, the sensitivity of W-3F can only be 103 dB w/m. It does not make sense to sacrifice the 7 dB of the high frequency component. Besides, any passive crossover network have an insertion loss. The actual sensitivity of W-3F would be less than 103 dB w/m. We decided not to employ passive crossover network for W-3F and recommend using external speaker processors that incorporate delay and equalization functions such as iBO D024 (2 in, 4 out) or D-48 (4 in, 8 out) digital speaker processors.

 

 

Applications and Technical Specifications

Maximum (not the peak) SPL of a single W-3F is 132dB (HF), 131dB (LF). Several W-3F or mixed with W-6F and/or W-8F plus subwoofer W-218B to form a 3-way or 4-way array enough to handle any large scale activities such as large touring, large concert, arenas and stadiums, large theaters etc., suitable for either indoor or outdoor.

 

Technical Specifications and diagrams (See below)

FREQUENCY RESPONSE

170 Hz ~ 19 KHz (± 3 dB )/ 132 Hz ~ 21 KHz(-10 dB)

SENSITIVITY (1W/1m)

HF:110 dB(1.5 kHz~20 kHz)

LF:97dB(170 Hz~1.5 kHz)

NOMINAL IMPEDANCE

HF:8 Ohm/ LF: 8 Ohm

POWER RATING

HF:150 W (AES)/ 400 W(AES)

CROSSOVER FREQUENCY

1500 Hz

LF COMPONENTS

1×12〞horn-loaded (3″voice coil)

HF COMPONENTS

1×2〞exit compression driver(3″voice coil)

 

NOMINAL COVERAGE

45゜(H) ×45゜(V)

CALCULATED OUTPUT (MAX)

HF:132 dB SPL, 138 dB SPL peak

LF:131 dB SPL, 137 dB SPL peak

DIMENSIONS (H×W×D)

540×580×550 (mm)

WEIGHTS

45 (kg)

CONNECTORS

2 Neutrik NL4MP connectors

SUSPENSION HARDWARE

Flying tracks (front)

Flying hardware set (rear)