January 1968 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
It is doubtful that as many people today build their own stereo speaker enclosures as was the case back in the 1950s through about the 1970s. During those decades stereo equipment was a really big deal, as evidenced by the large number of articles in technical and hobby magazines. I have posted a couple dozen articles on the subject here on RF Cafe. Topics included equipment reviews and feature comparisons, troubleshooting and alignment, modifications to commercial units, build-it-yourself projects, optimized room layout and construction, and even advice on how to best enjoy your stereo system. Lots of comics appeared in the magazines as well poking fun at how a stereo enthusiast's family members and neighbor might not appreciate the ear drum-busting power capability of your system. There were also quizzes like this one on speaker enclosure baffle design to challenge the stereo buff's technical knowledge (search the list below).
A Baffling Quiz
By Robert P. Balin
Speaker enclosure designs differ mainly in the way they employ baffles, ports, tubes, columns, ducts, and horns to control the sound radiated from the front and back of the speaker. To see how much you are baffled by enclosures, try matching the cross-section drawings (A-J) of commonly used enclosures with the names by which they are known (1-10).
1 Acoustic labyrinth ___
2 Air coupler ___
3 Baffle ___
4 Ducted-port phase inverter ___
5 Folded horn ___
6 Helmholtz resonator ___
7 Horn-loaded reflex ___
8 Infinite baffle ___
9 Klipschorn ___
10 Resonant column ___
<see answers below>
Popular Electronics published many quizzes over the years
- some really simple and others not so simple. Robert Balin created many of the quizzes.
This is a listing of all I have posted thus far.
- A Baffling Quiz
- January 1968
- Electronics IQ Quiz
- May 1967
- Plug and Jack Quiz
- December 1967
Switching Quiz - October 1967
Angle Quiz - September 1967
Electronics Quiz - July 1967
- Bridge Circuit
Quiz -December 1966
- Diode Function
Quiz - August 1965
- Diagram Quiz, August
- TV Trouble Quiz,
- Electronics History Quiz,
- Scope-Trace Quiz,
Circuit Analogy Quiz, April 1973
Your Knowledge of Semiconductors, August 1972
- Ganged Switching
Quiz, April 1972
- Lamp Brightness
Quiz, January 1969
- Lissajous Pattern Quiz, September 1963
Quizoo, October 1962
- Electronic Photo Album Quiz, March 1963
- Electronic Alphabet Quiz, May 1963
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960
- Vector-Circuit Matching Quiz, June 1970
Quiz, September 1961
- RC Circuit
Quiz, June 1963
- Diode Quiz,
- Electronic Curves Quiz, February 1963
- Electronic Numbers Quiz, December 1962
- Energy Conversion Quiz, April 1963
Function Quiz, June 1962
Quiz - February 1967
- Unknown Frequency
Quiz - September 1965
Metals Quiz - October 1964
Measurement Quiz - August 1967
- Meter-Reading Quiz,
Geometry Quiz, January 1965
Factor Quiz, November 1966
Math Quiz, November 1965
- Series Circuit Quiz,
Quiz, March 1966
- Electronic Analogy
Quiz, November 1961
Coupling Quiz, August 1973
- Electronics Analogy Quiz, August 1960
- Audio Quiz,
Unit Quiz, May 1962
Capacitor Circuit Quiz, June 1968
- Quiz on AC Circuit Theory, December 1970
- Magnetic Phenomena Quiz, February 1962
- Electronics Geography Quiz, April 1970
Electronic Menu Quiz, August 1963
- Electronic Noise Quiz, August 1962
- Electronic Current Quiz, October 1963
- Electronic Inventors Quiz, November 1963
Function Quiz, January 1962
- Electronic Measurement Quiz, January 1963
Tube Quiz, February 1961
- Kool-Keeping Kwiz, June
- Find the
Brightest Bulb Quiz, April 1960
Baffling Quiz Answers
1 - D) An Acoustic Labyrinth is a form of bass-reflex enclosure which uses a folded rear air column designed to be one-quarter wavelength at the low-frequency resonant point of the speaker. The resonant column dampens the resonant peak of the speaker and extends the low-frequency response.
2 - I) An Air Coupler is an air column designed to be one-quarter wavelength at the speaker's low-frequency resonance point to minimize the resonant peak and provide improved speaker-to-room (free air) acoustic impedance-matching.
3 - G) The Baffle, box baffle, or Hartley-Turner enclosure, uses a series of vented, sound-absorbent baffles to absorb back radiation and minimize back loading.
4 - A) A Ducted-Port Phase Inverter is a form of bass-reflex enclosure in which a duct provides additional acoustic inductance to resonate with the acoustic capacitance provided by the volume of the enclosure. The reduced acoustic capacitance requirement permits a more compact cabinet for the same speaker resonant frequency.
5 - F) A Folded Horn offers the advantages of speaker-to-room acoustical impedance matching in a more compact cabinet than an otherwise impractically large straight horn design.
6 - B) The Helmholtz Resonator, or R-J enclosure, is a form of bass-reflex enclosure in which the port, in the form of a narrow, circular slit surrounding the speaker, supplies additional acoustical resistance for improved low-frequency damping of the speaker.
7 - E) The Horn-Loaded Reflex enclosure is a form of ducted-port phase inverter having the increased radiation resistance and higher efficiency provided by the horn-shaped duct.
8 - C) An Infinite Baffle enclosure is not really infinite in the sense that all of the front radiation will go forward without refraction, but back-enclosed cabinets do prevent the back radiation from interfering with the sound radiated from the front of the speaker and, in that sense, are considered a practical form of infinite baffle.
9 - H) A Klipschorn enclosure is a folded, exponential horn which uses the corner of the room as the final flare of the horn mouth, and thereby, in effect, places the listener within the horn.
10 - J) A Resonant Column is a cross between an infinite baffle and a tuned pipe coupler that provides the large air volume of an infinite baffle in an enclosure design which requires less floor space.
Posted September 5, 2019