JBL 2446H

Name: JBL 2446H
Brand: JBL

A 30.5-pound compression driver that turns a few watts of amplifier power into a wall of sound. Cross it over at 500 Hz or higher.

Overview

The 2446H is a large-format compression driver with a 49 mm (2 in) exit, built around a 100 mm (4 in) pure titanium diaphragm and an aluminum ribbon voice coil. It is the 8-ohm "H" version of the 2446 platform. The "J" variant is the 16-ohm sibling. JBL's own literature documents them together as the 2446H/J.

The big difference from smaller-format compression units is the magnet assembly and the efficiency that comes with it. JBL rates sensitivity at 111 dB, measured at 1 W, 1 m and averaged across the 2 kHz octave band. Feed it a single watt and it produces a sound pressure level that most hi-fi speakers need dozens of watts to approach. That means a lot of headroom. A few watts of clean amplifier power go a very long way, and the driver is still coasting while the rest of the system is working hard.

The frequency range is specified as 500 Hz to 20 kHz at -10 dB, with a recommended crossover of 500 Hz or higher. This is not a tweeter in any conventional sense. It carries the upper midrange and the treble together, which is why it turns up in large two-way and three-way professional systems and not in domestic bookshelf cabinets. The 500 Hz crossover recommendation is a floor, not a suggestion. Run it lower and the diaphragm pays for it.

Flux density is listed at 1.9 T (19,000 gauss) for the 2446H/J. The diaphragm is pure titanium at 100 mm (4 in), and the voice coil is aluminum ribbon. The driver measures 235 mm (9.25 in) in diameter and 131 mm (5.2 in) deep, and weighs 13.8 kg (30.5 lbs) each. That is over thirty pounds for a single compression driver, and nearly all of it is magnet structure. It is the kind of figure that decides whether a cabinet needs bracing or a whole new design.

JBL's own description of the 2446H/J and its 2450H/J stablemate credits the Coherent Wave phasing plug design with coherent summation of acoustical power up to much higher frequencies than previous large-format drivers. The 2450H/J is the neodymium version. The same literature describes it as providing equivalent electromechanical conversion efficiency at two-thirds the size and one-third the weight of previous large-format designs. The 2446H is the ferrite-magnet member of the pair, and the weight difference between the two is plain.

The driver's power capacity is rated at 100 W above 500 Hz and 150 W above 1 kHz. The rating climbs with frequency, so the further above the crossover the driver operates, the more power it will take. That comes from diaphragm excursion limits, and it is why the crossover recommendation is stated as a hard floor.

Because the 2446H is a 49 mm (2 in) exit driver, it mates with JBL's larger horns rather than the 25 mm (1 in) throat models. JBL's documentation lists the 2446H/J as a compatible driver for the 2380A, 2382A, and 2385A Bi-Radial horns, all of which share a 49 mm (2 in) throat. The 2380A is a 90° H x 40° V design with a usable low-frequency limit of 400 Hz and a minimum recommended crossover of 500 Hz. The 2382A offers 120° H x 40° V coverage. The 2385A narrows the horizontal pattern to 60°. The 2380A and 2385A are molded structural foam. The 2380A carries a sensitivity figure of 112 dB, the 2382A 110 dB, and the 2385A 114 dB. Each of those horns weighs between 1.62 kg (3.5 lbs) and 2.2 kg (6 lbs), which is a rounding error next to the driver bolted to it.

The 2446H also appears as the high-frequency driver in JBL's 4670D and 4675C system configurations. In the 4670D it is paired with a 2380A horn and two 2035H low-frequency drivers in a 4-ohm system rated 600 W with a 500 Hz crossover. The 4675C uses the same driver with a 2360B horn and 2506C lens, also 600 W and 500 Hz. The 4675C-4LF and 4675C-8LF variants use the 2446H with the same 2360B/2506C combination, rated 1200 W on the low-frequency section and 100 W on the high-frequency section. In every one of those systems, the crossover lands at exactly 500 Hz, the driver's stated minimum.

For anyone comparing period documents, the 1993 Sound and Communication (December 1993, p.26) coverage of a church installation describes a central cluster built from JBL systems. That is the kind of large-format, high-output application this driver was designed for. Coverage of that sort is thin on measurement detail for the driver in isolation, so most of what is known about the 2446H comes from JBL's own system documentation and not from independent bench testing.

The available documentation supports no domestic hi-fi application for this driver. It is a professional component, sold to be installed in clusters and system cabinets.