ResonantLive Sound Archive

Equipment file · End-address dynamic cardioid microphone

Unidyne III / Model 545

Shure · 1960

Evidence status · verified

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

A compact unidirectional microphone lineage that helped define the modern stage vocal mic.

Introduced
1960
Category
End-address dynamic cardioid microphone
Intended use
Handheld vocals, speech, theatre, stadium, and public-address work
Production
1960 onward in successive variants

Equipment photographs · 1

US patent 3,132,713 (1964): microphone diaphragm (Unidyne III)

1 / 1 · US patent 3,132,713 (1964): microphone diaphragm (Unidyne III)

US patent 3,132,713 (1964): microphone diaphragm (Unidyne III)·Charles E. Seeler (Shure Brothers)·Public domain (US patent)

Why it mattered

  1. 01

    Put the Unidyne III single-element cardioid system into the end-address format that became standard for stage microphones.

  2. 02

    Its directional pattern and pneumatic shock isolation improved gain before feedback and reduced handling noise.

Engineering record

Published response
The official data sheet specifies 50 Hz–15 kHz response and selectable low- or high-impedance operation.[1]
Rejection
Shure specified approximately 6 dB cancellation at the sides and 15–20 dB at the rear.[1]

Original pricing

$85 list price

2026 equivalent

≈ $960

United States list price in Shure's 1960 catalogue.[2]

Estimated in August 2026 US dollars using the BLS CPI-U: $85 × 334.980 ÷ 29.6, rounded to the nearest $10.[3]

Use in the field

Shure marketed the 545 specifically for theatre stages, political conventions, stadiums, and public auditoriums.[1]

Professional reactions

Later recollection · 13 September 2016

Shure’s historian reported that Unidyne III designer Ernie Seeler was surprised by the microphone family’s adoption on rock stages, despite his own preference for classical music.

Michael Pettersen (relaying firsthand quotation from Ernie Seeler), Ernie Seeler: Shure acoustical engineer who designed the Unidyne III cartridge used in the 545/SM57/SM58; Pettersen: Shure company historianCompany historian’s retrospective on the Unidyne III family shared by the 545 and later SM microphones; not a preserved 545 launch reaction. · Manufacturer-published case study · Paraphrased account[4]Shure Incorporated · 10 Things You Might Not Know About the SM58

Manuals & original documents

Sources

  1. 1Models 545 and 545S General DataShure · manual
  2. 2The Unidyne storyShure · reference
  3. 3CPI Inflation Calculator methodology and CPI-U dataU.S. Bureau of Labor Statistics · reference · 2026
  4. 410 Things You Might Not Know About the SM58Shure Incorporated · reference · 13 September 2016

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