W-8F is a three-way, four-element full range speaker. its LF unit and HF unit is of coaxial configuration.
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 the 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 experiential 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. (See Figure 48)
Covering the MF band is two 8-inch drivers in horizontal configuration. (See Figure 49) are coupled to a horn
The horn is a constant directivity 60 o (H) X 40 o (V) horn
A specially designed phase plug to minimize the interference between the two 8-inch drivers. In frequency band where human voice is concentrated performs outstandingly with enough power reservation.
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 perforated 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 50)
LF unit is a L15/100/06Z 15-inch driver.
L15/100/06Z is developed by iBO specifically for horn loading
Frame is die cast alloy
The cone is a special formula of pulp and glass fiber. The depth of the cone is rather shallower with reinforcement ribs for better reproduction of low-frequency
Surround and spider are stiffer to increase the mechanical stiffness
The cone is treated with inflammation resistant agent
The diameter of the voice coil is 4-inch edge wound with flat copper wire on a Kapton former.(see Figures 52 and 53)
The magnet is made from y30 high flux strontium ferrite weights 8.54kgs. Two M8/50/05Z handle the mid-frequency band;
Frame is die cast alloy
The cone is a special formula of carbon fiber, glass fiber and wool
The cone is light and thin but very rigid
Magnet is of high flux y30 strontium ferrite weights 3145kgs
The diameter of the voice coil is 2-inch edge wound with flat aluminum wire. The coil former is of Kapton.( see Figures 54 and 55)
Figure 54 Figure 55
Operating range is 250Hz to around2KHz. The crossover frequency of low to mid is 400Hz and mid to high is 1.4KHz,well within operating range.
HF unit is a H3/75/03Z compression driver loaded with a 60 o (H) X 40 o (V) horn.
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 feat afumimium wire, the diameter is 3-inch (75mm)
The diameter of the throast is 1.4-inch (35mm)
The slits pattern of the phase plug is of circumferential type
y30 high flux strontium ferrite is employed and the magnetic structure weights 6.05kgs (See Figures 56,57 and 58)
Figure 56Figure 57 5 Figure 8
The sensitivity of W-8F high frequency component (110 dB w/m) is much higher than the low frequency component (104 dB w/m). The difference is more than 6 dB. If a build-in passive crossover network is employed, the sensitivity of W-8F can only be 104 dB w/m. It does not make sense to sacrifice the 6 dB of the high frequency component. Besides, any passive crossover network have an insertion loss. The actual sensitivity of W-8F would be less than 104 dB w/m. We decided not to employ passive crossover network for W-8F and recommend using external speaker processors that incorporate delay and equalization functions such as iBO D-24 (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-8F is 132dB (HF), 131dB (LF). Several W-8F or mixed with W-6F and/or W-3F 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.