JBL 4345

Commentary

Professional series large speaker system using newly developed 46 cm woofer.

The low band is equipped with a 46 cm cone type Woofer 2245H developed by fusing traditional technology and the latest technology.
Compared to the conventional 38 cm cone type woofer, this woofer is not only an expanded cone paper, but also has improved efficiency, linearity, low distortion rate, and other characteristics, enabling superior low-frequency reproduction.
The cone section is made of carefully selected materials. In order to optimize mass and rigidity, JBL's original damping agent (Lansa-Plus) is applied to the back side. In addition, JBL's original SFG structure is adopted for the magnetic circuit. The magnetic field in the voice coil gap is symmetrical, and combined with the flux stabilizing ring wound around the pole piece, second harmonic distortion is reduced. In addition, the voice coil has a wide piston motor cortex area of 100 mm diameter and 25 mm length. The linear peak displacement reaches 20 mm. In addition to the heat sink capacity, compression of output at high power is reduced.

It is equipped with 2122H of 25 cm cone type woofer in the middle and low range.
It uses new cone paper with reduced distortion outside the crossover frequency, and is equipped with 75 mm diameter copper ribbon voice coil, SFG magnetic circuit, etc.
The 2122H has a sealed back cavity to prevent interference from other units.

The mid-range area is equipped with a horn type mid-range that combines an acoustic lens 2308, horn 2307 and driver unit 2420.
The 2308/2307 is a horn lens to be used in combination with a driver with a throat diameter of 2.5 cm. It has the same performance as the 2311/2308 except for the difference in the suitable driver. The mounting dimensions to the baffle and the crossover frequency are also the same. When this horn / lens is mounted on a baffle 30 cm wide x 30 cm high or more, the directivity of horizontal 80 ° x vertical 45 ° is obtained.
Slant Plate 2308 is secured to the front of the baffle by the provided Velcro tape.

A horn type tweeter 2405 is installed in the high range.
This horn tweeter was developed for wide-range studio monitors. While inheriting JBL's high-efficiency and high-input-resistance characteristics, it realizes a linear response of up to 21.5 kHz and directivity of 140 ° horizontal x 40 ° vertical (10 kHz).
In addition, new technology is incorporated into the ultra-thin ring diaphragm to improve the top-end response.

The network section was developed based on JBL's new high-isolation network design. By adding a small-capacitance capacitor to a carefully selected high-capacitance capacitor, the connection of sound is smoothed and transparency is improved.
In addition to the 2-channel multi-amp drive at 290 Hz (using channel divider 5234), it is also possible to drive by built-in network.

The enclosure uses a 21 mm thick rigid particle board and an asymmetric internal reinforcement to prevent unwanted vibrations such as standing waves. The vertical mirror image pair system enhances sound image localization and sound field reproducibility.

Model Rating

Method	4-Way, 4-Speaker, Bass Reflex System, Floor Type
Unit	For Low Band : 46 cm Cone Type (2245H) For Medium Low Band : 25 cm Cone Type (2122H) For Middle and High Area : Horn Type (2420 + 2307 + 2308) For High Pass : Horn Type (2405)
Frequency characteristic	32 Hz to 20 kHz ± 3 db
Directional	Horizontal 60 ° x Vertical 30 ° (-3dB, 16 khz)
Output sound pressure level	95dB/W/m
Impedance	8 Ω
Allowable input	120W (network) 200W (Multi-Amp Lo) 100W (Multi-Amplifier Hi)
Crossover frequency	Network : 320 Hz, 1.3 kHz, 10 kHz Bi-amplifier : 290 Hz, 18dB/oct.
Enclosure volume	253L (Woofer) 14L (mid-woofer)
External dimensions	Width 765x Height 1096x Depth 470 mm
Weight	104kg