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Author:Admin     Click:586     Time:2018-01-03 09:40:00

AR-153 is a 3-way, 3-element full range speaker.

The Enclosure
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 97)

Figure 97
The shape of AR-153 enclosure is trapezoidal instead of rectangular. It is easier for arraying as well as helping in reduction of standing wave (See Figure 98)

MF and HF sections are horn loaded with an integrated MF/HF horn specifically designed for AR-153 (See Figure 99)

Figure 99
The HF horn is a constant directivity horn as the dispersion angle would 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, and so does the efficiency.

As the cross section of a horn changes (expanding) gradually, and as does the wave front of the sound wave radiated from the diaphragm (cone) that couple to the horn. The radiating resistance is high, the amplitude of the vibrating diaphragm is reduced and so does the efficiency of transformation. (See Figure 100)

Figure 100
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 total 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 101)

Figure 101
The components
LF unit is a L15/75/12Z 15-inch cone type driver which features.
Light and rigid cone with high compliance surround and soft spider. The bandwidth is wide and better reproduction of extended low frequency
The materials of the cone are specially formulated pulp, fiberglass and wool
The magnet is made from y30 high flux strontium ferrite. The magnetic structure weight 6.15kgs
The diameter of voice coil is 3-inch (75mm) which is edge wound with flat aluminum wire on a Kapton former. (See Figure 102)

Figure 102
The horn for MF and HF is integrated but the drivers are independent.

MF unit is a M6/50/01Z 6.5-inch cone type driver specifically designed and developed for AR-153.
The cone is very thin and very light but extremely rigid as well as the surround and the spider. It is specifically designed for reproduction of mid range similar to a driver with 4-inch titanium diaphragm
As it is intended for the reproduction of 400HZ to 3.5KHZ range and is coupled to the horn without phase plug similar to LF horn loading
The magnet of M6/50/01Z is made from y30 high flux strontium ferrite weight 313kgs
The diameter of voice coil is 2-inch (50mm) edge wound with flat aluminum wire on a Kapton former. (See Figure 103)

Figure 103
HF unit is a H1/34/05Z compression driver.
The diameter of the diaphragm is 1.25-inch and made is of ultra thin titanium plus the edge wound flat aluminum wire is also very light. The whole mess of the diaphragm/voice coil assembly is very small, efficiency is very high. The high frequency can be extended to 22KHZ
The diameter of the throat is only 1.0-inch, the cross section is much smaller than that of the area of the diaphragm. There is a high pressure zone built up between the diaphragm as the phase plug whose total cross sections of the slits are about equal to the cross section of the throat
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, as well as phase difference.
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. (See Figure 104,105 and 106)


Figure 105

Figure 106
The horn that coupled to the H1/34/05Z driver is made of fiberglass reinforced plastic

Crossover Network
The horn of MF/HF sections of AR-153 is an integrated unit. The sensitivities of MF and HF are very close. There is a built-in passive crossover between MF and HF. However, The sensitivity of AR-153’s high frequency component (103 dB w/m) is much higher than the low frequency component (98 dB w/m). The difference is more than 5 dB. If a build-in passive crossover network is employed, the sensitivity of AR-153 can only be 98 dB w/m. It does not make sense to sacrifice the 5 dB of the high frequency component. Besides, any passive crossover network have an insertion loss. The actual sensitivity of AR-153 would be less than 98 dB w/m. We decided not to employ passive crossover network for AR-153 and recommend using external speaker processors that incorporate delay and equalization functions such as iBO D-26 (2 in, 6 out) digital speaker processors.

Applications and Technical Specifications
AR-153 may be used in conjunction with any of AR-112/45, AR-115/64, AR-115/45 or AR-112/64 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)

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