JBL 435Be (2002)
The JBL 435Be is a professional compression driver released in 2002. It's best known as the midrange head of the flagship K2 S9800 loudspeaker system. It has a 1.5-inch throat and a forged pure beryllium diaphragm - a 3-inch (75 mm) unit, and the first of its kind for JBL in a compression driver. The diaphragm weighs less than 0.5 grams, with a total moving mass around 1 gram. That was a big break from earlier materials. Beryllium's density of 1,850 kg/m³ is roughly a third that of titanium (4,500 kg/m³) and well under aluminum (2,700 kg/m³). The driver also has a high-flux neodymium magnet, an aluminum ribbon wire voice coil on a heat-resistant bobbin, and a rapid-flare phase plug borrowed from JBL Professional units to reduce second-harmonic distortion. The aluminum die-cast back cover doubles as a rib-type heat sink.
Specifications from the period record: 5 Ω impedance, 40W allowable input, 110 dB/2.83V/m output, frequency response from 500 Hz to 15 kHz, and a recommended crossover of 800 Hz. The driver measures 108 mm in diameter by 91 mm deep and weighs 1.4 kg. Its original price was ¥150,000 per unit. The diaphragm has JBL's Aqua Plus coating to control split vibration. The company said this extended piston motion past 15 kHz and let the driver work as a high-frequency unit in two-way systems.
Documentation on the 435Be outside of Japanese spec databases is thin. Most of what exists is forum discussion and secondhand sale listings. In 2011 a French forum member sold a 435Be with its matching H9800 horn, noted the pair was the midrange section of a K2 S9800, and asked €2,500. Another French forum thread, about upgrading the JBL 4430, cautioned that the 435Be was not a drop-in replacement. As one user put it, it's a 1.5-inch driver that requires very particular equalization. The same thread recommended the TD2001 as the better upgrade for the 4430, noting it adapts to the 2344 horn without issue. An audioheritage.org poster observed that by the late 2000s the 435Be was no longer used in any current production system. He suggested that fitting Truextent beryllium diaphragms into newer 4-inch JBL drivers was arguably a better route. A Japanese repair shop has documented servicing 435Be neodymium drivers, and at least one owner has reported a K2 S9800SE coming back from service sounding better than original.
No formal professional reviews of the 435Be have surfaced. What's known comes from JBL's own published specifications and the scattered word of owners and sellers. Used pairs are occasionally listed in the low four figures.
- Type: Compression driver, 1.5" (38 mm) throat
- Impedance: 5 Ω
- Allowable input: 40W
- Output: 110 dB/2.83V/m
- Frequency response: 500 Hz – 15 kHz
- Recommended crossover: 800 Hz
- Diaphragm: 3" (75 mm) forged pure beryllium, Aqua Plus coated
- Dimensions: 108 mm dia. × 91 mm deep · Weight: 1.4 kg
- Original price: ¥150,000 (1 unit, 2002)
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