AX April: Improving a Classic

Editors’ note: Just prior to printing this issue, we learned that Ed Dell, founder of Audio Amateur, had passed away. He was 90 years old. Ed was a remarkable man whose talents ranged from DIY audio to publishing to writing. We’ll celebrate Ed’s work in the May issue of audioXpress. Our thoughts are with his family and friends.

Recently, Patrick Brunner found a pair of Dynaco ST70s—once known as the best-selling tube power amplifier—in good condition. As an engineer, he couldn’t resist adding some tweaks to the old classic. In this issue, learn how he installed a new 6GH8 driver board to the ST70 and updated its relatively weak bias supply (p. 12). You can do the same for $25 or less.

There is a dizzying array of tubes out there. But if your interest is in audio amplifiers, you need detailed knowledge of only a few models—including critical audio preamplifier tubes. Find out more in Richard Honeycutt’s article (p. 22).

Mike Klasco and Steve Tatarunis call high-polymer piezoelectric film “the lost technology.” In the first of a two-part article, Klasco and Tatarunis introduce you to the often-overlooked technology and its promises and drawbacks for audio applications (p. 8).

Also in this issue, Vance Dickason reviews Scan-Speak’s D2908/714000, the company’s second 30-mm beryllium dome tweeter (p. 18).

In another review, Victor Staggs looks at the Spin-Clean Record Washer System MKII. He says the affordable system enables you to expand the lifetime of irreplaceable LPs (p. 25).

Geoff Boyd, co-founder one of the UK’s first personal computer companies, relaunched his entrepreneurial career in the Silicon Valley, establishing Coleridge Design Associates to develop innovations in consumer electronics audio and sound reproduction. Check out our interview (p. 28).

Finally, David J. Weinberg provides his full take on the 2013 International CES trade show in Las Vegas (p. 33).


Mary Wilson

Q&A: Chuck Hansen

Electrical Engineer Finds “Joy in Audio Electronics”

Chuck Hansen

Chuck Hansen began his engineering career in 1966.

SHANNON BECKER: Tell us a little about your background and where you live.

CHUCK HANSEN: I have always lived in Monmouth County, NJ. I took college prep courses at Middletown High School, and I was fortunate that one of the high school guidance counselors found me a college we could afford. I graduated from Newark College of Engineering—now New Jersey Institute of Technology (NJIT)—with a BS in Electrical Engineering and took some grad courses at Fairleigh-Dickinson. My Dad and two uncles were tool and die makers, and my grandfather was an engineer. We all eventually retired from the same Bendix Red Bank division in New Jersey. My dad was very supportive of my interest in science and technology.

SHANNON: How did you become interested in audio electronics?

CHUCK: When I was a kid, I bought a book about the story of a boy who became interested in ham radio and got his license, built his own radio transmitter and receiver, and had all kinds of interesting adventures on the air. I never got a ham license, but it sparked (no pun intended) my interest in electricity, science, and electronics, and I do belong to the American Radio Relay League (ARRL).

When I was young, I built an AM radio kit that used a cap, a tunable slug inductor, and a germanium detector diode, with a transistor to drive headphones. With a wire antenna and ground, I was able to receive the larger AM stations in New York City. From that experience, I subscribed to as many electronics magazines as I could find (e.g., Radio Electronics, Popular Electronics, etc.). I kept modifying the audio amplifier section of the kit radio hoping it would sound better (but I didn’t perform any AB testing). I also took apart every dead radio and TV I could find, keeping the electronics parts for my “junk box.”

During high school summers, I worked for a German couple at a local amusement park. When they replaced their sound system in 1960 they gave me their old Telefunken AM receiver-amplifier and a wire recorder. I used the receiver-amplifier chassis for many electronic audio projects. My dad helped me build a nice cabinet for a donated turntable and a used Dynaco PAS-2 preamp. I built a 10-W stereo power amplifier, using a design from the RCA RC-19 tube manual, reusing the old Telefunken chassis. I used mediocre 4” and 8”  Lafayette Radio drivers at each end of the cabinet. Later, we added a Pentron tape deck since the wire recorded wasn’t good for audio. I guess it would be a valuable antique now.

During college, I learned to play electric bass (just in time for the Beatles invasion). I built a guitar amplifier from a Gromes hi-fi amplifier kit, then made a speaker cabinet from plywood and two cheap 12” bass guitar loudspeakers. It worked fine as long as I didn’t expect to get any fundamental bass notes from the 41-Hz low E string. North Jersey was rich in jazz musicians, and I took jazz guitar lessons from some of the pro players, while playing bass in college rock bands to earn money for my tuition. I also worked college summers at the old Electronic Associates, in West Long Branch, NJ. It made precision analog computers and two-axis plotters. It even made its own precision film capacitors for the integrator and differentiator plug-in amplifier modules. I learned all I could about analog electronics from the engineers there.

Chuck in Bendix Lab

Chuck worked on the Boeing 747’s electrical system in the Bendix Systems Lab in 1968.

SHANNON: Describe your career as an electrical engineer and your work as a consultant in the aerospace industry.

CHUCK: I always worked in the electric power field, starting at Bendix Electric Power Division in 1966, working on 400-Hz aerospace power. My dad and two uncles had worked there since World War II. After a couple years, I headed up the electrical system test group for the new Boeing 747 jumbo jet, which had a 60-kVA generator on each of the four engines. The main AC system could be run isolated, in full-parallel, or split-parallel. Two independent 90-kVA generators were mounted on the auxiliary power unit (APU). It was the most complex aircraft electrical system ever designed at that time. I also designed the generator control units for the hydraulic-powered emergency generators used on the F-14 and F-15 fighters.

Back then, we had to use military-approved parts. There were no integrated circuits, so that meant all-discrete transistor designs. There were no MOSFETs, and the diffused-junction bipolar power transistors that were available were far too slow to switch the highly inductive exciter field with our generator voltage regulators. Not much was known about safe operating areas at the time. Bendix had its own semiconductor division, but it was more interested in small-signal transistors. To ensure high reliability, we used a very expensive Westinghouse gold-doped alloy Darlington transistor that, while slow, had a huge avalanche energy rating. I learned a lot about discrete analog design from the Bendix engineers who grew up in the vacuum-tube era.

Next, I went to work for PSEG, a New Jersey-based electric utility, in a newly formed group tasked to add gas-turbine generation units to the grid in the early 1970s to meet New Jersey’s increasing power demand. It took years to make a steam-generating plant, while the turnkey modular gas turbine units were a quick install. I designed a very accurate solid-state underfrequency unit that triggered selected fast-responding gas turbine units (64 MW in total) to go into what was termed “area regulation mode” to prevent loss of the system in the event of a transmission line overload.

This was in response to the 1965 Northeast Blackout, where loss of a generating station in Ontario, Canada caused cascading transmission line overloads that tripped off one power area after another down into the US. I also helped design the area regulation controller topology. Large steam-powered generators just can’t change load quickly enough to respond to system instabilities. The gas turbine area regulation control system gave the system the needed control algorithm to restore stability.

My next PSEG assignment was to head the Instrumentation and Controls section of the Salem Nuclear Generating Station Startup Group. Soon after we formed, we were caught up in the confusion during the Energy Reorganization Act of 1974, when the agency that had control over commercial nuclear power changed from the Atomic Energy Commission (AEC) to the Nuclear Regulatory Commission (NRC). The reorganization and rule changes delayed Salem by a few years and added greatly to the cost of Salem and every subsequent nuclear power project in this country, as I recall.

Next, I went to work for an erstwhile company in New York City that specialized in international nuclear power design. However, when the Three Mile Island accident occurred in 1978, I felt it was best to return to Bendix Electric Power Division. I became the Systems and Controls Supervisory Engineer. The company I left went out of business when nuclear power generation design and construction came to a virtual halt.

When analog and digital ICs first came out, we needed a lot of hand-holding and the IC manufacturer’s experts came to our rescue. I am indebted to many folks including: Bonnie Baker, James Bryant, Martin Giles, Gerald Graeme, Walt Jung, Walt Kester, Ron Mancini, Bob Pease, Jim Williams, and the others who guided me through the practical application of their company’s analog ICs. I was lucky enough to meet some of them in person at seminars held in New York and New Jersey venues.

Bendix was taken over by Allied Chemical in the late 1980s, which then became Allied-Signal (A-S) with the purchase of the Signal companies. I retired from A-S in 1998 when our division was moved to Tucson, AZ. A bit later A-S bought Honeywell and then took the Honeywell name.

I currently work for a small startup company that does work in the aerospace electric power field. The old Bendix/A-S/Honeywell plant in Eatontown, NJ is now a Lowes, ironically located right behind the building in which I now work. I design custom lab and calibration equipment and design all the current transformers we produce. I also participate in engineering design reviews, helping to ensure the analog designs and aircraft interfaces are robust and reliable.

SHANNON: Tell us about your first personal project.

CHUCK: My first personal project was the aforementioned AM radio kit. I built it when I received it as a Christmas present, with no idea how it worked. It is long gone. It probably came to grief from all my modifications. I replaced it in 1961 with a Lafayette transistor AM radio.

SHANNON: You have written two books for Audio Amateur and you have published more than 260 magazine articles. What compelled you to start writing? Are you planning to submit more articles to audioXpress?

CHUCK: First, a little back story: To ensure uniform design requirements for our electronic design engineers, I compiled the derating requirements from MIL-HDBK-217, MIL-STD-1547, DO-160, and all of our commercial aircraft customers’ standard parts manuals into one worst-case design requirements manual that could be used for every customer. We called it “Bendix Electrical/Electronic Parts Selection, Application and Derating.”

The first paid article I wrote was for the Gernsback publication Popular Electronics in 1980. It was based on the idea of high reliability through derating the voltage, current, and power applied to electronic parts, using the information I researched for the design requirement manual. “For Projects That Last—Derate Your Components” was published in Popular Electronics, January 1982. I wrote a total of 10 articles for Popular Electronics through 1998. In 2001, I wrote “Choosing and Using Electronic Parts: A Survival Guide,” a three-part expanded version of my derating article for audioXpress.

A colleague and I wrote feature articles about Bendix equipment for the Bendix Eatontown Output and the Local Focus newsletters at work. Then, to help the people in production test, I started writing documents that explained how our equipment worked and how to troubleshoot the various electronic units. I created schematics for the testers that were similar to the ones provided with Heathkits and Howard W. Sams PhotoFacts. They were well received and helped add objectivity to what they had termed “black magic” electronics testing.

I first got in touch with Ed Dell in 1997 to propose a preamp construction article based on the HeadRoom headphone amp module. Not only did he graciously accept an article from a perfect stranger, he came down to visit me a few months later. (His son Chad teaches at Monmouth University, and it turned out Chad was the faculty adviser for my niece’s future husband.) I utilized the chassis from my old Heathkit AA-1214 integrated amp. I adapted a Walt Jung design for the phono preamp section. My article appeared in the June 1997 issue of Audio Electronics, and thus began my long association with Ed Dell and The Audio Amateur (TAA), leading to almost 250 more articles, reviews, test reports, and “New Chips on the Block” article columns in the various TAA publications. Through TAA I have become friends with many of the true experts in the audio field, for which I am very grateful.

While my engineering background is primarily in aerospace electric power, audio is a synergistic fit for my work in analog design. During the time I served as the ad-hoc test editor for the Audio Amateur audio equipment reviews, digital audio was achieving higher and higher resolution, and it became clear that my modest 16-bit test equipment could no longer keep up with the rapid progress in audio technology. I learned a lot about audio testing from John Atkinson at Stereophile magazine, and the Audio Precision Audio.TST newsletters. It is also interesting to realize how far publishing has come since 1980, when I reviewed my first article from the print galleys. Now, we do everything on computers and submit articles by e-mail. More and more magazines are becoming online only and no longer provide print versions.

My most recent submission to audioXpress (February 2012) was a new book review, on Helmuth Lemme’s book, Electric Guitar—Sound Secrets and Technology (Elektor, 2012).

SHANNON: Are any of the designs that appeared in audioXpress still in use today?

CHUCK: Oh, yes, many of them are still in use since I sometimes wrote articles based on practical circuits I needed for a work application or my own lab. I also use much of the test equipment discussed in audioXpress articles and other electronic publications. Topics included: a multi-tone IM signal generator, a precision sine wave oscillator, a transformer polarity tester, audio passive loads, an audio balun, a semiconductor curve tracer, a noise meter amplifier, a phase meter calibrator, a power quality monitor (my current source for measuring loudspeaker impedance and phase versus frequency), the AES17 22-kHz low-pass filter for PWM audio amplifier tests, and oscilloscope calibrators.

Chuck in workshop

Chuck is surrounded by his equipment in the home workshop he constructed.

I still use my HeadRoom-based preamp as my headphone amplifier, my modified Adcom GFP-55 II preamp, my modified Rotel RCD 970BX CD player, my modified Scott 222C tube-integrated amp, and my scratch-built LM3875 IC power amplifier with a quad-pod circuit

I also use the modified Peavey TKO-80 bass guitar amp that was the topic of a 2003 two-part audioXpress article, and I  designed a simple modification for my Evans 80 Jazz Amp that minimizes the crossover distortion. Evans incorporated this change in the production amplifier boards starting in 2003. I really enjoyed our collaboration.


SHANNON: Tell us about your book, The Joy of Audio Electronics (Audio Amateur Publications, 1999). Why did you write it specifically for beginners? After 14 years, is there anything you would explain differently?


CHUCK: After I retired in 1998, Ed Dell asked me if I wanted to write a book for beginners who were interested in audio electronics. It took a number of false starts and rewrites before I was able to distill his concept into the book he published. Old Colony book sales were pretty slow so he contacted RadioShack to see if it might be interested in featuring the book on its in-store sales racks (Forrest Mimms did quite well with his notebooks and project designs in RadioShack stores). RadioShack wasn’t really interested in a book about such a narrow topic.

The other book I wrote for Audio Amateur was A Brief History of Bendix Red Bank Tubes. It started out as an article for Vacuum Tube Valley magazine, but it never got published for a variety of reasons. Ed obtained the rights to the article and had me expand it into the book in 2006. My grandfather and an uncle were vacuum tube engineers before the depression, and my father developed a lot of the specialized tooling at Bendix for the internal parts of the Red Bank tubes. Many of the employees who worked in the “tube section” were getting on in years, and I felt compelled to document as much about Red Bank tubes as possible while they and my family were still around. Much of the tube work was done for the military during the cold war, so there wasn’t a lot of public information available.


SHANNON: In your book, The Joy of Audio Electronics, you discuss setting up a workshop. Can you describe your own workshop?


CHUCK: My workshop lab is located in a spare bedroom, while I do the metal work and machining in my basement shop. I get lots of exercise running up and down the stairs when I am building a project. Most of my equipment is 1970s era HP, Fluke, and Tektronix, along with Heathkits that I have modified for improved performance. Then, there is also my home-brew test equipment.

If I find 1970s test equipment on eBay that is “untested, for spare parts,” I will buy it for the custom semiconductors that I might be able to use to repair my own equipment in the future. Tektronix used a custom dual JFET in its scope amplifiers that has a high- and low-transconductance JFET in the same multi-pin package. Those are just not available anymore. I have three Tektronix 7603 oscilloscopes (two are not fully functional) and lots of 7000-series plug-ins. I also collect Tektronix TM-50x power modules and its 500-series plug-ins. I recently purchased a “not working” HP-339A distortion test set that had a defective power switch actuator rod. When I fixed that it worked fine, although the front panel lettering is not in the greatest condition. One of my projects is to fix at least one of my three Tek AM-503 current probe amplifiers.


SHANNON: Tell us about the five engineering patents you hold.


CHUCK: They are all related to the electrical power industry in which I worked for 46 years (so far).

In 1980, another engineer and I devised a method of detecting diode failures in multi-diode rectifier bridges. Bendix had developed a brushless 28-Vdc generator for two-engine business jets (the same basic concept as an automotive alternator) that used two three-phase ac windings that were displaced by 30 electrical degrees and rectified. This offset enables each peak-phase voltage its own time slot and results in a 24-pulse DC ripple with fairly low AC-ripple voltage magnitude. If any of the 12 diodes shorts out, it severe distorts the DC waveform and, if allowed to persist, will cause partial-phase shorts across the dc bus that could also cascade into additional diode failures. The original machines used fusible links that allowed the short-circuited diode to clear, but also allowed higher DC-bus ripple and reduced output power. Our “apparatus,” as they say in patent parlance, used two additional three-phase bridges made up of small diodes in the generator control unit. We compared the ideal ripple from the small diodes to that of the generator’s DC output ripple, and if the generator ripple exceeded a specified voltage difference at any point in the two waveforms, we would trip the generator off line and enable the remaining good generator to supply the aircraft power. The trick was to set the sensing circuits to allow for the different temperature dependant forward drop between the 70-A power diodes and the small-signal diodes in the control unit, as well as the ground voltage drop in the aluminum fuselage.

Again, in 1980, one of the best rotating machine designers in the world, Al Wohlberg, and I came up with a way to wind the exciter field of the above brushless dc generators to enable generator self-buildup without the help of any outside DC power. The steel housing (back-iron) and silicon iron laminations in a conventional brush-type dc starter-generator retains enough residual magnetism to provide the minimum 0.7-Vdc residual voltage required to initiate generator build-up. The newer brushless machines, however, use aluminum housings and exotic and expensive permandur laminations that do not retain enough residual magnetism. Our invention used the new rare-earth samarium cobalt (SmCo) permanent magnet material in conjunction with a startup winding in the exciter to provide the needed residual. We electromagnetically cancelled the startup winding flux after the generator built up. This only worked because of the high coercive (Hc) force of SmCo magnets, which would not be demagnetized by the cancelling flux. If we didn’t do this, the magnets would continue to produce output voltage even if the flight crew shut off the generator switch. Our invention was then obviated by our metallurgists who came up with a way of annealing the permandur so it would provide the necessary residual magnetism. This saved the weight of our magnets and startup winding.

My third invention in 1983 was my own. I needed to find a way to detect unbalance currents in the three-phase power going to large 20-kVA motors in the new 747–400 aircraft using only current transformers. If one phase of the motor opened, the motor would not start and the heavy locked-rotor stall current would flow in the two remaining phases. This would severely unbalance the aircraft three-phase power and might even burn out the motor. These motor windings are not neutral-grounded in order to prevent a large fault current from flowing in the aircraft aluminum fuselage ground if a winding shorted to the motor housing. The problem lies in the fact that, even with an open winding, all the current entering and leaving the windings is equal and opposite, much like the leakage current sensing in a household ground fault circuit interrupter (GFCI) outlet. Since I didn’t have access to the phase voltages, I concentrated on sensing the nature of the motor ripple current change when various unbalanced current conditions existed. The detector I came up with three-phase rectified the current transformer secondary output signals across a single common burden resistor in the current transformer (CT) neutrals. With all three phase currents balanced, the three-phase ripple frequency (for 400-Hz aircraft AC power) was 2,400 Hz rather than the 1,200 Hz I had expected. This was an empirical revelation, since there were no spectrum analyzers available and no Fortran version of SPICE yet. I used a conventional time-domain oscilloscope to determine the resulting frequency-domain ripple content of all combinations of unbalanced phase currents. I then used a high-pass filter that enabled me to detect the normal condition and trip the motor contactor when the lower frequency fault condition occurred. This simple circuit allowed the heavy three-phase 75-A circuit breakers to be removed from seven motor circuits.

Invention four was also my own. In 1990, Motorola Semiconductor announced it was ceasing all production of injunction transistors. We used unijunction transistors (UJTs) for the time delays in our older control units. Unlike commercial products, you can’t just stop making equipment for airliners and military aircraft as long as they are in service, without a viable replacement. Bendix had a semiconductor division that used Raytheon’s fabrication facility. I came up with a three-terminal replacement circuit for the UJTs that could be implemented in either a hybrid or monolithic integrated circuit (IC). The added advantage was precise control over all the UJT variables in all combinations and permutations.

My last invention was another collaboration. Solid-state DC-AC power converters have failure modes that, while rare, could result in DC content in the AC voltage. This can cause saturation and other electromagnetic (EM) havoc in motors and transformers. The circuit used a high-pass filter and all-pass phase compensator combination to detect any DC content in the AC waveform.


SHANNON: Are you currently working toward obtaining new patents for any ongoing projects?


CHUCK: Not any more. Only two of my patents were developed alone, the other three were collaborative efforts. Not all my disclosures became patents. Some were nullified by discovery of prior patents during the search period or were filed too long after the “first disclosure” within Bendix engineering.

The aerospace companies I worked for specialized in power conversion, a complex design expertise that I have been fortunate enough to avoid. I always described their development process as “one microsecond away from disaster.” They now also use lots of FPGA-based digital controllers whose programming is another specialty in which I have no interest. My particular specialty is analog design.


SHANNON: Do you have any advice for audioXpress readers who want to build their own sound systems?

CHUCK: There are three main ways to build your own audio equipment. One is to buy a kit. You can also design and build everything from scratch (Gary Galo and Bob Cordell are quite good at this), and I recommend that the builder use a CAD program for mechanical layout. I do this with my test equipment designs since an attractive front panel is not a priority for me.

The third method is to buy older commercial equipment and modify it to your liking. That’s the approach I generally use, because all the difficult chassis work has been completed by the manufacturer. You need to make sure the front panel is in good condition, but to me the condition of the electronic internals is less of an issue. My system preamp is a modified Adcom GFP-55 II. My computer audio system uses a modified Lafayette Radio receiver and modified Lafayette Criterion 50A loudspeakers that GR Koonce helped me redesign. I have also purchased and resold older commercial audio equipment on eBay after changing all the aluminum caps, re-soldering the switch contacts, and testing it to make sure it is working to specification. aX

Audio Crossword Answers (March 2013)

The answers to audioXpress’ March audio crossword puzzle are now available.


5.    CERAMICPLATE—Capacitor type used due to its low inductance and low cost [two words]
6.    BUTTERWORTH—Produces a maximally flat amplitude response
11.    SUSPENSIONSYSTEM—A loudspeaker’s weakest mechanical part [two words]
13.    GASSY—Tube types that can draw excess current and generate static in the output signal
14.    HAPTIC—Sense of touch
16.    SHORTED—Power transformer that has a metallic or burnt varnish smell
17.    KLYSTRON—Used as an oscillator
18.    STRUCK—CJS Labs’ CEO and chief scientist
19.    COCHLEA—Senses vibration


1.    ACOUSTICRESEARCH—Company credited with being the first to commercialize the dome tweeter [two words]
2.    SYNCHRONOUSAVERAGING—Analyzes the vibration signature of rotating machines or gearboxes [two words]
3.    VACUUMTUBE—Makes amplification and radio possible [two words]
4.    TWEETER—An electrodynamic driver
7.    CROSSOVERNETWORK—Single-driver speakers cancel the need for it [two words]
8.    NOISECANCELLATION—Eliminates out-of-phase information [two words]
9.    RECTIFIER—Passes current in only one direction
10.    PINK—Noise with a continuous frequency spectrum and equal power per constant percentage bandwidth
12.    MASERATI—Recently teamed with Bowers & Wilkins to make limited-edition, co-branded audio products
15.    PRESBYCUSIS—Causes include noise exposure and aging

March New Products & News

Coleridge Design Associates Introduces the aCUBE

Tech start-up, Coleridge Design Associates (CDA), has launched a new transparent speaker system that combines balanced modal radiator (BMR) sound quality technology with stylish looks, convenience, and affordability. The aCube BMR speaker design features an audio drive unit with an extended frequency.

The aCUBE uses 4.5” BMR full-range loudspeaker drivers inside clear-cast acrylic 6.5” cube enclosures.

The aCUBE uses 4.5” BMR full-range loudspeaker drivers inside clear-cast acrylic 6.5” cube enclosures.

The aCUBE uses 4.5” BMR full-range loudspeaker drivers, beautiful handmade clear cast acrylic 6.5” cube enclosures, and the Maxim Integrated Product’s latest Class-D amplifier technology.

The aCUBE’s use of clear-cast acrylic is more than aesthetical. It relates to the material’s functional capabilities: Acrylic possesses an inherent acoustic benefit, offering great sound quality and high internal damping that does not resonate and radiate sound as much as other materials (e.g., most plastics, wood, and aluminum).

Convenience is one of the main reasons users are turning to monophonic speakers. Although there are times when solo speakers are beneficial, the aCUBE proves that sound does not have to come at the cost of convenience.

Optional adaptors (e.g., Bluetooth, Apple Airplay, USB, and optical S/PDIF) enables the aCUBE to be used with a variety of smartphones, TVs, and PCs. An auto-off feature puts the system into Sleep mode after 1 to 2 min., waking instantly when audio appears.

Volume level control can be set once and left alone enabling the sound level to be controlled by the source device. This makes the aCUBE remote-control redundant. A portable option contains a travel case and battery back that uses supercapacitors. Pricing for aCUBE starts at $180. Visit for more information.

Leslie Named Renkus-Heinz President

Renkus-Heinz selected Scott Leslie as its next company president.

Renkus-Heinz selected Scott Leslie as its next company president.

Renkus-Heinz has appointed Scott Leslie to the position of President. Leslie comes to Renkus-Heinz from JBL Professional, where he served as Vice President of Engineering. His deep industry background includes stints at a wide range of technology leaders including Sun Microsystems, Tektronix, and Altec Lansing. Leslie is also founder of Evidant Corp., providers of Business Intelligence for IT solutions, where he has held executive-level positions since 2002.

Leslie joins Renkus-Heinz as the company is experiencing unprecedented growth. Despite the economic downturn, Renkus-Heinz has seen a substantial surge in sales and has significantly grown its engineering staff. Leslie’s new position will see him spearheading the company’s continued expansion, working closely with company founder and chairman Harro Heinz.

SONEX Rondo Baffles Featured in sculpture

SONEX Rondo cylindrical baffles—designed to reduce reverberation and echo within indoor pools and other loud, noisy spaces—are the key component in a unique sculpture titled Splash!

The Splash! sculpture uses 972 multicolored SONEX Rondo baffles.

The Splash! sculpture uses 972 multicolored SONEX Rondo baffles.

The unprecedented sculpture was commissioned as part of the City of Miami Gardens’ Art in Public Places Program, a program which aims to bring art into the community. Artist Xavier Cortada originally envisioned a design composed of scattered pool noodles to resemble a splash of water on the ceiling of the Betty T. Ferguson Recreation Center Aquatic Facility, Miami Gardens, FL. The facility offers aquatic classes and swimming lessons where participants need to hear and understand instruction. Acoustical issues—common in most indoor pools—were addressed with the sculpture, which features 972 colored pinta acoustic SONEX Rondo baffles.

Class 1 fire-rated, SONEX Rondo baffles absorb sound across all frequencies, which prevent noise build up that interferes with speech intelligibility. pinta acoustic’s baffles are resistant to fungal and microbial growth and can withstand humid conditions characteristic of indoor swimming pools.

Vertical or horizontal applications are possible and provide design flexibility. SONEX Rondo cylindrical baffles are available in standard 24” (610-mm) lengths with 6” (152-mm) diameters or custom size. SONEX Rondo baffles are lightweight and easy to install with cork-screw hangers. pinta acoustic offers baffle products in natural white, light-gray,  standard, and custom colors.

To make the Splash! sculpture, the baffles were individually suspended from stretched cables within custom-made aluminum frames. The frames were suspended below an exposed metal roof deck. Each baffle was hung at a predetermined height to simulate an overall, 3-D sound wave effect. Visit for more information. aX

Industry Watch: March

Passing of a Loudspeaker Pioneer

Clifford B. Digre

Clifford B. Digre

It is with regret that Voice Coil notes the passing of a pioneering colleague. Clifford B. “CB” Digre, one of the audio industry’s stalwart loudspeaker manufacturers, died November 25, 2012, at age 89. More than 60 years ago, Cliff founded what is today known as MISCO—a manufacturer of loudspeakers and related products serving dozens of markets and industries. Cliff was a past president of the Association of Loudspeaker Manufacturing and Acoustics (ALMA), and he was awarded three patents for loudspeaker-related inventions:

  • US Patent 3,492,443 (January 27, 1970)—A dust seal and pressure element for the magnet assembly of a loudspeaker
  • US Patent 3,898,393 (August 1975)—This invention was designed to shield and center a voice coil and pole piece, within the magnet, from foreign matter (e.g., pieces of ceramic material).
  • US Patent 4,293,741 (October 6, 1981)—This design relates to sound transducer assemblies and attachments of a ceramic magnet assembly to a loudspeaker basket. The invention enables the front plate and basket to be securely connected without any space between them.

Cliff was the kind of innovator who could turn problems into business opportunities. Case in point: In 1947, Cliff’s wife bought a small radio with “horribly distorted” sound. When the fault turned out to be a rubbing voice coil, Cliff, then a student at the National Radio School in Minneapolis, MN, decided to recone the speaker himself and save $3. That fix inspired a loudspeaker repair and reconing business—Minneapolis Speaker Reconing. When television’s popularity in the early 1950s meant fewer radio speakers to recone, Cliff actively pursued other markets, including drive-in theater speakers. His decisions made Minneapolis Speaker Reconing the largest reconing service in the country.

In 1956, a customer asked Cliff to design and manufacture an 8” speaker with the same high quality as his reconed speakers. The initial 200-speaker production run was a huge success; however, just as Cliff’s team began to assemble the second order for 1,000 speakers, the customer died and his company canceled the order. Cliff didn’t panic. He contacted other sound contractors, trying to sell the 1,000 speakers. They did sell, sometimes out of sympathy for Cliff’s predicament. Then, repeat orders poured in as buyers discovered the speakers’ high quality. The line expanded to automotive speakers and 12” speakers for hi-fi sets. Cliff’s reconing company transformed itself into a full-time speaker manufacturing company—MISCO.

While Cliff knew he had a superior product, MISCO speakers needed to attract more attention in the marketplace. Early on, one customer even referred to MISCO as a company with “me, too” products. Cliff decided in addition to MISCO speakers high audio quality, they also needed to stand out visually. At the time, all speaker cones were black with gray-felt dust caps. After considerable development, MISCO rolled out speakers with red molded cones—the legendary Red Line. Cliff got product recognition, as his company was one of the first to develop brand retention based on cone color.

Cliff’s career in the audio industry was bookended by his service as a World War II combat veteran—first, as a B-17 ball-turret gunner and radio operator based in England. Then, 64 years later, as author of the memoir Into Life’s School. Cliff believed once you left school, you entered life’s school and learned valuable lessons your entire life.

Cliff’s industry legacy, however, is MISCO. Now managed by his son, Dan Digre, MISCO operates out of a new manufacturing facility in Minneapolis. The company’s markets include pro sound, gaming, home theater, aerospace, medical, military, transportation, and audio. Dan said, “Cliff’s speakers have touched the ears of nearly everyone in the United States.” He will be missed. For more information, visit

CES Draws 150,000 Plus

It’s possible (we won’t know until the official audit is released), that 2013 was the largest International Consumer Electronics Show (CES) in its history. The show held in Las Vegas, NV, drew more than 150,000 attendees, including more than 35,000 from at least 170 foreign countries, according to the Consumer Electronics Association (CEA), which produces CES. The official attendance number will be audited this spring. In 2012, CES set an attendance record of 156,153 industry professionals.

CES 2013 was physically the largest in the show’s 45-year history, with 1.92 million net square feet. The previous record was 1.86 million net square feet in 2012.

ALMA Symposium a Success

The ALMA Symposium was another successful event. This year’s loudspeaker engineering gathering attracted 16 exhibitors and 110 attendees. Exhibitors included ACO Pacific (measurement microphones), Audiostar Electronics (voice coils), BeStar Technologies (microspeakers, microphones), Dr. Kurt Müller & Co. (cone assembly parts), Dyne Analytics (FEA transducer software), Earthworks (measurement microphones), Ferrotec (magnetic fluid), Globe Plastics (OEM plastic loudspeaker parts), Klippel (test equipment), Listen (test equipment), Loudsoft (loudspeaker design software and test equipment), Materion Electrofusion (Truextent beryllium diaphragms), Menlo Scientific (audio consulting), MSC Software (Actran acoustics simulation software), Phase Group (OEM QA analysis), Pulsus Technologies (OEM electronics), and Voice Coil (an OEM loudspeaker manufacturing publication). Companies represented by the 110 attendees included: Accusonic Voice Systems, American Ally Company, Audio Limited (New Zealand), Audiostar Electronics, Apple, Arrow Acoustics, Atlantic Technology, Beats Electronics, BeStar Technologies, Bogen Communications, Bomatec International, Cabasse, Cisco Systems, CJS Labs, Core Brands, Corning, DB Design, DJB Enterprises, Dyne Analytics, Estron A/S, Far North Electroacoustics, Fujitsu Ten, Globe Plastics, Google, G.R.A.S., Harman International Industries, JBL Professional, HiWave Technologies, Jawbone, Jaguar, Land Rover, Klipsch Audio Technologies, KSC Industries, LAGO Acoustics, LifeSize, Listen, Logitech, Loudspeaker Component, Maeden International, Materion Electrofusion, Matrix Advisors, Menlo Scientific, Merry Electronics (USA), MISCO, Morel, MSC Software, Ole Wolff Electronics, Outsource Services, Parts Express, Paradigm Electronics, Polk Audio, Proficient Audio, Pulsus Technologies, Psychotechnology, QSC, Rockford College, Samsung Electronics, Scan-Speak, Sonos, Texas Instruments, Triad Speakers, True Technologies, THX, VUE Audiotechnik, Warkwyn Associates, and York Lake Partners.

Jim Hunter presents “The Life and Times of Paul Klipsch” at the ALMA Symposium.

Jim Hunter presents “The Life and Times of Paul Klipsch” at the ALMA Symposium.

The ALMA Banquet featured an outstanding presentation by Jim Hunter, Klipsch Group historian, titled “The Life and Times of Paul Klipsch.”. This year’s Driver Awards were as follows:

Paul Klipsch was posthumously awarded the year’s ALMA Beryllium Lifetime Achievement Driver Award.

Paul Klipsch

The Beryllium Lifetime Achievement Driver Award was presented by Dr. Floyd Toole to Paul Klipsch, posthumous, and Vance Dickason, industry consultant, editor of Voice Coil magazine, and author of the Loudspeaker Design Cookbook.

Vance Dickason, editor of Voice Coil magazine, received this year’s ALMA Beryllium Lifetime Achievement Driver Award.

Vance Dickason

Dr. Sean Olive, Harman International’s director of acoustic research, received the ALMA Titanium Driver Award.

Dr. Sean Olive

The Titanium Driver Award (recognizing a specific technical contribution) was presented by Dr. Floyd Toole to Dr. Sean Olive, director of acoustic research at Harman International, and Doug Button, former vice president of engineering at JBL Professional.

Phil Bunch, president of Phase Group, received the ALMA Gold Driver Award from Stu Lumsden, vice president of engineering at Polk Audio.

Phil Bunch

Mike Oslac, of York Lake Partners, received the ALMA Gold Driver Award from Dan Degre, CEO of MISCO.

Mike Oslac

The Gold Driver Award (recognizing contributions to the ALMA organization) went to Phil Bunch, president of Phase Group, presented by Stu Lumsden, vice president of engineering at Polk Audio (see Photo 6); and Mike Oslac of York Lake Partners and ALMA board member emeritus, presented by Dan Degre, CEO of MISCO.

If you missed this year’s ALMA Symposium, you missed a lot. If you are not an ALMA member, you can join by visiting

AX March: What’s Your Passion?

Many years ago, a children’s book inspired Chuck Hansen’s interest in audio electronics. Soon, the clever kid from New Jersey was listening to New York City AM stations on a kit-built radio and disassembling every dead TV and radio he came across—for the parts.

Hansen went on to become an electrical engineer, aerospace industry consultant, patent holder, and author. In an interview on page 27, he discusses his careers and his lifelong enthusiasm for audio projects.

Chuck Hansen in his workspace

On page 8, Mike Klasco and Steve Tatarunis focus on the piezo ceramic tweeter, in their third installment of “Tweeter Talk.” Their article looks at the history and technology of a tweeter that never reached its full potential.

This month’s edition also examines the most common subsystem to fail in audio equipment—the power supply. Many things can disrupt it—from electrical surges to lightning.  How do you know when power supply problems are causing blown fuses or even a complete shutdown of your audio equipment? On page 32, Richard Honeycutt answers that question and more.

Are you an audiophile who has wanted to work with the FINEMET-core transformer in your own DIY project? On page 12, Tadaatsu Atarashi tells us how he utilized an affordable FINEMET-core transformer in his small output amplifier project.

Tadaatsu Atarashi’s project (Source: Radio Technology magazine, 2011, reprinted with permission)

Turn to page 23 for a look at the Apollon speaker system, designed by German engineer Gerd Lommersum. Utilizing a chassis from the Scan-Speak Illuminator series, the freestanding unit includes a subwoofer that “packs a punch.”

Gerd Lommersum’s Apollon speaker system

In this month’s “Test Bench” on page 36, Vance Dickason reviews the 12FHX76 from B&C Speakers, a driver in the company’s new line of pro sound coaxial speakers.


Mary Wilson

Edward T. Dell, Jr.: In Memoriam

February 12, 1923–February 25, 2013

Edward Dell, founder and former publisher of Audio Amateur Inc., died Monday, February 25, 2013, at the age of 90.

Dell, a legendary audio guru, developed his taste for publishing and audio as a teenager. He became a veteran builder of audio hi-fi speakers and was a longtime full member of the Audio Engineering Society and the Boston chapter of the Acoustical Society of America. He published magazines and books on all areas of audio for more than 35 years.

Edward Dell

After launching the company’s flagship publication, The Audio Amateur, in 1970, Dell published a number of specialized titles covering a wealth of subjects in audio. Proud to lead a force of some 700 authors worldwide—experts and enthusiasts in audio technology—he started audioXpress 32 years later, in 2002. Dell propelled audioXpress to its position as the audio technology authority and, in 2011, he sold his company’s assets—which included audioXpress, Voice Coil, and the annual directories Loudspeaker Industry Sourcebook and World Tube Directory, as well as several books and CDs—to the Elektor group, which publishes Circuit Cellar and the North American version of Elektor.

Dell corresponded with many longtime readers and authors after his retirement, maintaining a connection to the audio world he loved. His literary legacy continues to inspire a new generation of audiophiles as they design and build their own “dream” systems.