AR-112/64

 

The Enclosure

AR-112/64 is a 2-way, 2-element full range speaker.

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 be 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. (See Figure 63)

Figure 63

High-frequency section is a horn loaded design, 60 o (H) X 40 o (V) constant directivity horn is specially designed for AR-112/64 which is relatable (See Figure 64), making its directivity always 60 o (H) X 40 o (V) no matter it is in up-right position or laid flat. The geometry of the horn is so designed that the dispersion angle will not be narrowed with the raise of operating frequency.

As compared to direct radiator type speaker, the advantage of horn loading is:

 

The sound wave radiated from the diaphragm (cone) to free space, the wave front changes (expanding) rapidly. The radiating resistance is low, so does the efficiency.

 

As the cross section of a horn changes (expanding) gradually,as well as the wave front of the sound wave radiated from the diaphragm (cone) that coupled to the horn. The radiating resistance is high, the amplitude of the vibrating diaphragm is reducedso does the efficiency of transformation. (See Figure 65)

Figure 65

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 Speaker NL4MP connectors for amplifiers and for loop-in and loop-out to additional enclosures. (See Figure 66)

Figure 66

The components

The LF unit is a L12/75/09Z 12-inch cone type driver which is developed by iBO.

• The cone of L12/75/09Z is light and rigid, the surround is soft, has better LF response.
• The materials of the cone is specially formulated pulp with fiberglass and wool
• Magnet is made from high flux y30 strontium ferrite and the magnetic structure weights 6.15kgs
• The diameter of the voice coil is 3-inch (75mm) edge wound with flat aluminum wire on a Kapton former. (See Figure 67)

Figure 67

The HF 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,the diameter is 3-inch (75mm)
• The diameter of the throat is 1.4-inch (35mm)
• The slits pattern of the phase plug is circumferential (see Figure 70)
• y30 high flux strontium ferrite is employed and the magnetic structure weights 6.05kgs.(see Figures 68 and 69)

Figure 68 Figure69

Without the phase plug, the radiation from the center of the diaphragm or cone and the radiation from of the edge reach the throat at different time as the distances are different, and there are therefore phase difference (See Figure 86).

Figure 86

With the phase plug, the radiations from the center and from the edge are traveling at equal distance. When these radiations reach the throat, they are in phase.

 

Crossover Network

The sensitivity of AR-112/64’s high frequency component (110 dB w/m) is much higher than the low frequency component (97 dB w/m). The difference is more than 10 dB. If a build-in passive crossover network is employed, the sensitivity of AR-112/64 can only be 97 dB w/m. It does not make sense to sacrifice the 10 dB of the high frequency component. Besides, any passive crossover network have an insertion loss. The actual sensitivity of AR-112/64 would be less than 97 dB w/m. We decided not to employ passive crossover network for AR-112/64 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

AR-112/64 may be used in conjunction with any of AR-112/45, AR-115/64, AR-115/45 or AR-153 plus AR-215B or AR-218B to make up a 3-way or 4-way array for fixed installation sound reinforcement system of any scale such as theaters, multi-function hall and large disco or used individually as stage side fill.

 

Technical Specifications and diagrams (See below)

FREQUENCY RESPONSE	50 Hz ~ 18 KHz (± 3 dB )/35 Hz ~ 20 KHz(-10 dB)
SENSITIVITY (1W/1m)	HF:110 dB(1.5kHz~16kHz) LF:97dB(50Hz~1.5kHz)
NOMINAL IMPEDANCE	HF/LF:8/8 Ohm
POWER RATING	HF/LF150/400 W (AES)
CROSSOVER FREQUENCY	1.5 KHz
LF COMPONENTS	1×12〞woofer (3″voice coil)
HF COMPONENTS	1×2〞exit compression driver(3″voice coil)
NOMINAL COVERAGE	60゜(H) ×40゜(V)
CALCULATED OUTPUT (MAX)	HF:131 dB SPL, 137 dB SPL peak LF:123 dB SPL, 129 dB SPL peak
DIMENSIONS (H×W×D)	670×420×420 (mm)
WEIGHTS	34 (kg)
CONNECTORS	2 Neutrik NL4MP connectors
SUSPENSION HARDWARE	Flying tracks (side) Flying hardware set (rear)

Rigging

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