Electro-Voice 1824M

A phenolic-diaphragm midrange compression driver built for horn systems that need to stay intelligible at the back of the room.

Overview

The 1824M is a midrange compression driver. It never got its own magazine cover, but it shows up in every serious horn-loaded system of its era. It was designed to be loud and clear rather than lush and romantic, and that's what it does.

Period coverage of the 1824M specifically is thin. The driver appears in the broader conversation around University Sound and Electro-Voice horn-loaded systems. Modern Recording (September 1981, p.21) fielded a reader question about Electro-Voice HR60/DH1012 horn-driver combinations running 30 watts at 8 ohms with a 60-degree coverage pattern. That's the same family of design thinking the 1824M belongs to, where crossover points and impedance matching dominate the practical concerns. This driver lived in sound reinforcement and studio monitoring, where the question wasn't "how does it sound" but "will it survive the gig and stay intelligible at the back of the room."

None of that design guidance is glamorous, and neither is the 1824M. It does a job: midrange compression, high output, flat from 300 to 4,500 Hz. It has a minimum impedance that won't scare an amplifier and a sensitivity that makes the most of whatever power you feed it. Collectors chasing a Western Electric or an Altec will pass it by. Anyone building or maintaining a horn system from the University Sound parts bin will know it on sight.

Key Features

Phenolic Diaphragm with Aluminium Voice Coil on Kapton Former

The diaphragm is phenolic, a material chosen for its ability to survive high temperatures and hard use without the fragility of some exotic alternatives. The voice coil is aluminium wound on a Kapton former. That combination keeps weight down while handling the thermal load of continuous high-output operation. Sources describe the 1824M as having "phenolic diaphragms and simple phasing plugs," which points to a design that favors durability and predictable behavior over exotic materials or complex phase-correcting geometry.

The phenolic diaphragm is also why the 1824M has a reputation for smoothness rather than bite. One source describes it as "a smoother-sounding version of the 1823m," which suggests the 1824M traded some of the 1823M's aggressive character for a more relaxed midrange. Whether that's an improvement depends on what you're asking the driver to do.

Two-Inch Voice Coil

The two-inch voice coil diameter matters in a midrange compression driver. A larger coil has more surface area for heat dissipation, which helps power handling and thermal stability under sustained output. It also means the driver can be crossed over lower without running out of excursion. That's useful when the 1824M covers the 300 to 4,500 Hz range in a three-way system.

It means the 1824M needs very little amplifier power to reach serious output levels, and it means the driver will reveal every bit of noise and distortion upstream of it. Pair it with a quiet amplifier or don't bother. The sensitivity figure is single-sourced and should be treated as approximate until corroborated, but even allowing for measurement conditions, this is clearly a high-efficiency design.

300 to 4,500 Hz Frequency Response

The rated response of 300 to 4,500 Hz puts the 1824M squarely in the midrange, above the woofer's territory and below where a dedicated tweeter takes over. The driver is described as a good choice for midrange duty in three-way systems where a separate tweeter handles the higher frequencies.

Horn-Loaded Design with Simple Phasing Plugs

Like all compression drivers, the 1824M mounts on a horn. The "simple phasing plugs" mentioned in the literature are the internal geometry that aligns the sound waves as they exit the diaphragm and enter the horn throat. Simpler phasing plug designs trade some high-frequency extension for smoother response through the midrange, which fits the 1824M's role as a midrange specialist. The driver is part of the broader University Sound and Electro-Voice horn-loaded ecosystem, where crossover points and impedance matching are the practical concerns that dominate system design.

Historical Context

The 1824M belongs to the University Sound line that Electro-Voice absorbed and continued producing. The exact production years are not documented in the available sources, and no original price has survived in the record. The driver was part of a family of components, including the 1823M, 1824S, and related models, that shared diaphragm technology and design philosophy.

By the early 1980s, the 1824M was still relevant enough that Modern Recording (September 1981, p.21) was fielding reader questions about similar Electro-Voice horn-driver combinations in sound reinforcement applications. The magazine's response focused on crossover points and impedance matching, the details that determined whether a horn system would actually work in a real room.

Collectibility & Value

The 1824M occupies an odd position in the collector market. It's not a Western Electric or an Altec, the names that command serious money. Collectors chasing those will pass the 1824M by without a second glance. But for anyone building or maintaining a horn system from the University Sound parts bin, it's a known quantity: reliable, repairable, and capable of doing what it was designed to do.

Current market activity is sparse but not nonexistent. A pair of 1824M drivers with copy 8HD horns has been listed on Reverb with an asking price of $570.31. That's an asking price for a specific pair with horns, not a reliable indicator of market value for the drivers alone. Individual drivers and pairs surface on Craigslist and eBay with some regularity, often described as being in "great working condition," which suggests that surviving examples have held up well. Replacement diaphragms are available, which helps anyone who finds a pair with tired or damaged units.

The 1824M is also listed among driver models recommended for talkbox use, a niche application that points to the driver's midrange presence and durability.