ResonantLive Sound Archive

Equipment file · Constant-directivity horn

HR9040 constant-directivity horn

Electro-Voice · 1975–1976

Evidence status · verified

Claims in this file are tied to item-specific sources.

A large-format constant-directivity horn developed from Don Keele's mid-1970s horn research.

Introduced
1975–1976
Category
Constant-directivity horn
Intended use
Controlled mid/high-frequency coverage in touring and installed reinforcement
Production
Mid-1970s professional product line

Equipment photographs · 1

Electro-Voice HR9040 constant-directivity horn

1 / 1 · Electro-Voice HR9040 constant-directivity horn

Electro-Voice HR9040 constant-directivity horn·Electro-Voice·© Electro-Voice; used for identification and historical commentary

Why it mattered

  1. 01

    Addressed the frequency-dependent narrowing of conventional exponential horns.

  2. 02

    Helped make predictable coverage a stated loudspeaker-system design objective.

Engineering record

Coverage method
Its geometry combines a diffraction section with a conical flare to maintain substantially constant angular coverage through the operating band.[1]

Original pricing

No reliable period price located

2026 equivalent

Not calculated without a reliable original price.

No dated Electro-Voice price list was located.

Use in the field

Constant-directivity horns became building blocks for large multiway touring systems that required defined audience sectors.[1]

Manuals & original documents

Sources

  1. 1What's So Sacred About Exponential Horns?Audio Engineering Society · technical paper · 1975

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