About the Company
Brüel & Kjær — Reel-to-Reel Tape Recorder Production History
Company: Brüel & Kjær (B&K)
Country: Denmark
Founded: 1942 (by Per V. Brüel and Viggo Kjær)
Reel-to-reel production: Mid-1950s – late 1970s
Market: Scientific, acoustic measurement, vibration analysis
Recording focus: Precision signal storage, not music
Brüel & Kjær is one of the most respected names in measurement science, and their reel-to-reel tape recorders were designed as laboratory instruments, not entertainment or studio equipment.
Origins and Context
Brüel & Kjær specialized in:
Acoustic measurement
Vibration analysis
Structural testing
Noise research
By the early 1950s, these fields required a way to:
Store measurement signals accurately
Replay them without time or amplitude distortion
Analyze data repeatedly under controlled conditions
Conventional audio tape recorders were not accurate enough, prompting B&K to develop their own precision tape machines.
Entry into Tape Recording (Mid-1950s)
Purpose of B&K Tape Recorders
B&K reel-to-reel machines were designed to:
Record wideband, linear signals
Maintain extremely stable tape speed
Minimize wow, flutter, and phase error
Preserve amplitude accuracy
They were often used alongside:
Microphones
Accelerometers
Frequency analyzers
Oscillographs
Key Reel-to-Reel Models
B&K Type 700 Series (Late 1950s–1960s)
Early precision analog tape recorders
Mono or multi-track measurement channels
Valve (tube) electronics initially
Later transistorized
Speeds commonly included:
7½, 15, and 30 ipsDesigned for constant-speed accuracy, not convenience
These machines were large, heavy, and rack-mountable, often installed permanently in laboratories.
B&K Type 7005 / 7007 / 7008 (1960s–1970s)
Fully transistorized
Improved frequency response and signal stability
Designed for compatibility with B&K analyzers
Some models optimized for:
Time expansion
Speed-change analysis
Environmental noise logging
Many models supported FM (frequency-modulated) recording, essential for low-frequency vibration analysis that standard audio recorders could not handle accurately.
Technical Characteristics
Transport Design
Extremely high-precision capstan systems
Servo-controlled motors
Minimal tape tension variation
Gentle tape handling to preserve data integrity
Electronics
Flat, calibrated frequency response
Known amplitude accuracy
Low phase distortion
Not voiced or “sweetened” for listening
Tape Formats
Open reel, typically ¼-inch tape
Occasionally multi-channel formats for instrumentation use
Often used instrumentation tape, not consumer audio tape
B&K tape machines were never sold to consumers, studios, or broadcasters.
Peak Usage (1960s–Early 1970s)
Brüel & Kjær reel-to-reel machines were used globally in:
Aerospace research
Automotive noise testing
Civil engineering
University research laboratories
Government acoustics labs
They became a de facto standard for analog signal storage in scientific environments.
Transition Away from Tape (Late 1970s)
By the late 1970s:
Digital data recorders emerged
FFT analyzers reduced reliance on analog storage
Computer-based measurement systems took over
Brüel & Kjær gradually phased out reel-to-reel production in favor of:
Digital analyzers
Data acquisition systems
Software-based analysis tools
Legacy
Brüel & Kjær reel-to-reel recorders are remembered as:
Among the most accurate analog tape machines ever built
Purpose-built scientific instruments
Technological benchmarks in speed stability and signal integrity
Today they are:
Rare
Mostly found in laboratories, universities, or technical museums
Occasionally repurposed by experimental audio engineers, though this was never their intended use