W-218B

For simpler functions in small venue where only a couple of speakers are required the full range speaker used may be needs to extend its frequency response to 50HZ or even lower to cope with the functional requirement. Not in the case of speakers as part of an array. An array usually consists of many speakers, each individual speaker or a group of speakers serving specific purpose. There is no need for any speaker or part of the array to cover the entire frequency range. The full range speaker need not extend down to very low frequency as it would be covered by subwoofers. Besides, the full range speakers in an array can not be made very large due to physical and acoustic limitations. As part of an array, the W-218B is designed to handle to low end of the frequency response down to around 40HZ.

 

Enclosure

The enclosure of W-218B is of front horn loaded and rear vented design (See Figure 64). Two LF units are mounted on the bass horn that is farthest inside the cabinet. The front radiation is “squeezed” out of the horn. The rear radiation passes thru the phase inverted passages that would be in phase with the front radiation augmenting the low frequency response.

This design combined the advantages of horn loading and bass reflex enclosures. The enclosure need not made very large. 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. (See Figure 65)

Figure 65

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 .

The Component

Two L18/100/11Z drivers are used in W-218B 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.
• The magnet is made from y30 high flux strontium ferrite weights 10.75kgs

(see Figures 66 and 67).

Figures 66

Figures 67

The Crossover Network

Normally there is no built-in passive crossover network in a subwoofer or perhaps only a built-in low pass filter, but even a low pass filter could cause phase problem and there is insertion loss. For these reasons, the W-218B has no built-in passive crossover network nor low pass filter. It is recommended that all W series speakers should be used in conjunction with external speaker processor with delay and equalization functions such as iBO D-26 (2in6 out) digital speaker processor.

 

Applications and Technical Specifications

W-218B can be used in conjunction with W-3F, W-6f or W-8F to form a three-way or four-way system for any large scale activities and venues such as outdoor concerts, touring, arenas, stadiums, large theaters and large discos. It works well both indoor and outdoor.

 

Technical Specifications and diagrams (See below)

 

FREQUENCY RESPONSE	40 Hz ~ 170 KHz (± 3 dB )/ 30 Hz ~ 200 Hz(-10 dB)
SENSITIVITY (1W/1m)	104dB(40 Hz~150 Hz)
NOMINAL IMPEDANCE	4 Ohm
POWER RATING	1200 W(AES)
LF COMPONENTS	2×18〞monifolded (4″voice coil)
CALCULATED OUTPUT (MAX)	135 dB SPL, 141 dB SPL peak
DIMENSIONS (H×W×D)	916×620×750 (mm)
WEIGHTS	91 (kg)
CONNECTORS	2 Neutrik NL4MP connectors

 

Chick here for product W-218B