DIY Audio: Seek and You’ll Find in Santa Clara

This week, while visiting Santa Clara, CA-based HSC Electronic Supply, I came across a book display featuring a few of our best-selling titles: Loudspeaker Design Cookbook, Glass Audio Projects, and Loudspeaker Recipes.

Book display at HSC Electronic Supply in Santa Clara, CA

If you happen to be in the Santa Clara area, I encourage you to visit HSC. It has a wide variety of electronics components, audio parts, and test equipment. Audio enthusiasts will be particularly excited to browse HSC’s superb stock of tubes.

Tubes at HSC Electronic Supply

HSC Electronic Supply of Santa Clara
3500 Ryder Street
Santa Clara, California 95051
Mon – Fri: 8 am – 7 pm, Sat: 9 am – 5 pm



Industry Watch: April

Brown Named Thiel Audio’s Interim COO

Bob Brown, former longtime president/CEO of Lenbrook America (an exclusive US distributor of NAD and PSB brands), has been appointed to Thiel Audio’s board. He has also been hired as Thiel’s interim COO. Bob’s appointment follows Thiel’s recent acquisition by a Nashville-based private-equity firm that includes Thiel’s new CEO Bill Thomas, an audio enthusiast who until now has not been involved in the loudspeaker industry.

Brown will provide the company’s new owners with a complete analysis of the existing operation, including manufacturing, domestic and international sales, and marketing. Brown’s mission is to provide the guidance and market awareness necessary to maximize future opportunities. The new owners seem aware of the necessity to maintain the legacy aspect of Thiel Audio and appreciate the pitfalls that have plagued other investor-led high-end audio acquisitions. As Lenbrook America’s president/CEO, Brown distributed NAD Electronics and PSB Speakers. Brown has also been president/COO of Tivoli Audio. He is currently ZVOX Audio’s international sales manager, a position he maintains.

One of Brown’s first decisions was to hire former NAD National Sales Manager Stephen DeFuria as Thiel Audio’s new full-time National Sales Manager. DeFuria was most recently employed by Tempo High Fidelity as its North American sales manager for Musical Fidelity, the UK-based manufacturer of audio electronics. For more than 10 years beginning in 2001, DeFuria was national sales manager for NAD Electronics. At NAD, DeFuria was responsible for all aspects of US sales and marketing, including direct management of independent representatives, training initiatives, and trade show management. Previously, DeFuria was the principal of Audio Vision, a Boston-area hi-fi retailer that he acquired in 1984. DeFuria remained in audio retailing for approximately 19 years, selling Thiel products for 15 of those years. Thiel Audio manufactures 10 products ranging in cost from $1,090 each to $14,700 per pair.

Photo 1: Jeremy Berkhardt

Burkhardt Acquires Soundcast

Less than a year after leaving Nortek, a SpeakerCraft subsidiary, former SpeakerCraft CEO Jeremy Burkhardt has acquired Soundcast, a wireless outdoor-powered speaker manufacturer (see Photo 1).

Burkhardt sued Nortek in January 2013, alleging the parent company threatened to enforce a non-compete agreement that Burkhardt says is invalid. Joining Burkhardt at Soundcast is longtime SpeakerCraft alumni Jeff Francisco. Francisco will be taking over the position of Soundcast’s Chief Technology Officer, the same position he held at SpeakerCraft for approximately 24 years.

Photo 2: Startup menu for the THX home theater tune-up app

THX Releases Its First Mobile App

Photo 3: Adjustment and Extras menu for the THX home theater tune-up app

THX has released its first mobile iOS app, titled THX tune-up, for adjusting customers’ THX systems (or any other system). The new iPhone/iPad app will enable users to adjust their TVs, projectors, and speakers for maximum performance. Shown in Photo 2, the THX tune-up is being offered in the iTunes App Store for $1.99.

THX tune-up guides users through picture and sound adjustments to provide the best possible entertainment experience, plus it includes links to THX cinema trailers, the THX signature “THX Deep Note,” “Moo Can,” which plays the classic “moo” sound from a THX cinema trailer, and “Ask Tex,” which provides answers to any questions about home THX theater equipment and the setup process (Photo 3).

Custom-designed video patterns and audio test tones are provided to help users check for optimal video equipment settings based on both equipment capabilities and the room lighting environment. External speakers can also be measured for correct phase and connection.

Color and tint settings are often difficult to properly adjust without special glasses or other unique equipment. But, THX tune-up uses the iPad or an iPhone camera and a THX-designed built-in color filter to help consumers ensure colors are accurate and that skin tones appear natural.

The interactive app provides step-by-step instructions via narration and text and a detailed guide on how to use all its features.

Tests sequences available on the THX app include video adjustments and audio adjustments. The video adjustments feature:

Aspect ratio—Ensures your TV displays shapes and        sizes correctly

Brightness—Adusts shadow details and night scenes so the picture is clearly visible

Contrast—Controls white detail

Color—Modifies colors so they are bright and vibrant but not overly saturated or cartoonish

Tint—Alters skin tones appear natural and are not too green or red

The audio adjustments feature:

Speaker assignment—Ensures that speakers are connected to the correct audio video receiver (AVR) output and intended sound is coming from the correct speaker

Speaker phase—Confirms that positive and negative speaker wires are correctly connected and all speakers are in phase

Although the new THX app is “pretty good,” the company said the tune-up app is not intended to provide full-calibration capabilities. It refers users to professional installers and calibrators for optimal fine-tuning results. THX plans to release an Android version of the tune-up app this spring.

New York Audio Show Set for April

This year’s New York Audio Show (the second ever) is scheduled for April 12–14, 2013, at the Palace Hotel in midtown Manhattan, NY. There will be demonstrations from more than 75 companies. Loudspeaker companies exhibiting at the New York Audio Show include Audio Engine, Coincident Speaker Technology, Dupuy Acoustique, Martin Logan, MBL North America, Naim Audio, PMC, Quad Musik, Raidho Acoustics, Robert Lighton Audio, Sanders Sound Systems, Sony, Spendor Audio Systems, TAD, Venture Audio, Waterfall Audio, Wilson Audio, and Zellaton.

Special events include a sneak-preview screening of Last Shop Standing, a film that charts the rise of record shops in the 1960s through 1980s, the impact of the best-sellers chart, vinyl’s demise, and the introduction CDs and other technologies had on music stores. The show will also host Classic Album Sundays, a record club that will hold listening sessions that feature songs from classic albums (e.g., Talking Heads’ Remain in Light, Kraftwerk’s Autobahn, and Love’s Forever Changes). Attendees will learn the history behind the featured albums and hear them on vinyl on a state-of-the-art, hi-fi system. Michael Fremer, editor of AnalogPlanet, will host daily workshops, including demonstrations on how to set up a turntable and how various pressings of the same album can sound radically different.

A series of clinics and seminars is also under development. The exhibits and demo rooms will be located on the conference center’s fourth and fifth floors and the hotel’s ninth, 10th and 11th floors.

Produced by the UK-based Chester Group, this second annual show is designed to share the wonder of music through quality audio. “Our inaugural US event last year confirmed there is a strong desire in the New York area to experience music beyond MP3 players,” said Roy Bird, Chester Group’s chairman. “We are building upon that success with special events that will create even more excitement, and we are thrilled that the New York Audio Show has been selected to preview the Last Shop Standing.”

NAMM’s Award Winners

The following products received the National Association of Music Merchants (NAMM) 2013 Best of Show Awards for loudspeaker design:

Photo 4: The Electrovoice ZLX PA speaker

Electro-Voice ZLX Portable PA—Available in 12” and 15” two-way versions, Electro-Voice’s new ZLX line of portable powered loudspeakers are intended for use as either mains or monitors (see Photo 4). The ZLX portable, powered loudspeakers include a 1,000-W Class-D amplifier, a single-knob DSP control with an LCD and application/location presets, input level meters, independent amplifier control, and a patented split-baffle design. With pole-mounted capabilities, the loudspeaker enclosures feature composite construction with high/low grip design.

Photo 5: The JBL M2 mastering monitors

JBL M2 Master Reference Monitor—The largest speaker in JBL’s studio monitor line, the M2 Master Reference Monitor, integrates new JBL transducer technologies in a free-standing, two-way system (see Photo 5). The M2 design includes JBL’s new D2 compression driver, which uses two annular diaphragms and two voice coils; JBL’s new 2216ND differential drive 15” woofer, with dual voice coils; and a patented wire application said to reduce power compression and enable linear output regardless of the playback level. The M2 Master Reference Monitor delivers 20-to-40-kHz extended in-room response, and 123-dB SPL at 1 m. The M2 also utilizes JBL’s patent-pending waveguide “Image Control,” said to enable neutral frequency response, both on- and off-axis in the vertical and horizontal planes down to the M2’s 800-Hz crossover point.

Photo 6: The M Audio M3-8 three-way studio monitors

M-Audio M3-8 Studio Reference Monitor—M-Audio’s M3-8 three-way studio reference monitor features an 8” woven Kevlar low-frequency driver, 5” woven Kevlar mid-frequency driver, and a 1” silk dome tweeter with an integrated guard (see Photo 6). The speaker comes in an attractive, wooden mahogany case with wooden internal baffling and delivers 220-W of tri-amp Class A/B power. It has a three-band EQ with bypass, a switchable low-cut filter, an XLR and 0.25” balanced and RCA unbalanced input are provided.

Photo 7: The PreSonos S6 and S8 coaxial studio monitors

PreSonus Sceptre S6 & S8 Studio Monitor—Released in partnership with Fulcrum Acoustic, PreSonus’s Sceptre CoActual Series studio reference monitors include an 8” low/mid-frequency driver and a 1” (25-mm), horn-loaded, high-frequency transducer within a single coaxial unit with aligned voice coils (see Photo 7). The Sceptre S6 CoActual studio monitor’s coaxial speaker integrates a 6.5” low/mid-frequency driver and a 1” (25-mm), horn-loaded, high-frequency transducer. Both models have acoustic ports. The monitors incorporate TQ algorithms, and a four-position Acoustic Space switch controls a second-order shelving filter centered at 100 Hz, with four attenuation settings (no attenuation, –1.5, –3, and –6 dB) so users can account for the bass response relative to room dimensions and speaker placement. VC

Member Profile: Howard Ferstler

This is a reclad left speaker for one of Howard’s dream systems. The speaker is shown here without its grill.

Location: Tallahassee, FL

Education: BA in history and philosophy; electronics (bomb-navigation systems technician) training in the United States Air Force

Occupation: Howard is now retired. He worked for 35 years as a library technical assistant.

Member Status: Howard said he has been a longtime subscriber to both audioXpress and Voice Coil.

Audio Interests: Howard is intrigued by all traditional aspects of audio including speakers, amps, receivers, and players.

Most Recent Purchase: He listed two Crown XLS1000 stereo power amps, a Pioneer VSX-1122-K receiver, and several Dayton subwoofer drivers among his recent purchases.

Current Audio Projects: For years, Howard fiddled with audio gear, reviewed products, and wrote articles and books. However, he said he finally has systems he appreciates and has no desire to upgrade. However, he is layering redwood over one final speaker to cosmetically match it with the others.

Dream System: Howard has two dream systems, both of which are in operation. He is an “amps are amps” kind of guy. With speakers, he is considerably more critical. He uses several Allison speakers, and he has been friends with Roy Allison for decades.

Howard’s main system (music only), features Allison IC-20 loudspeakers as his left and right channel speakers. His center speaker (in a custom-built solid-cedar cabinet) has Allison drivers and a crossover based on Allison designs. The surround channels are four refurbished Allison Model Four loudspeakers, and he has dual cylinder subwoofers, with Dayton Reference Series 12” drivers (home designed and built, with a smooth extension to 18 Hz) a Yamaha DSP-A1 integrated surround amplifier, a Crown XLS1000 power amplifier, a Rane THX-44 equalizer #383038 that handles the three front channels, plus the subwoofers, and an Onkyo DV-S939 DVD player, used only for CD playback.

His second system, which features almost as many components, is used mainly as his home theater. This system includes a Samsung 56” DLP TV (down the line he hopes to upgrade to a 70” LED set), and a home-built speakers with  Allison, Tang Band, RadioShack, Dayton Audio, and NHT drivers. The three front systems use vertical MTTM mid/tweeter arrays, with dual woofers at the bottom, a Pioneer VSX-1122-K receiver, dual cylinder subwoofers, with Dayton Titanic Series 12” drivers (home designed and built, with redwood top and bottom panels), a Crown XLS1000 power amplifier, an ART EQ351 mono equalizer for the subwoofers, and a Panasonic DVD/VHS recorder,  a Sony BluRay player, and a RadioShack mini TV (used to program the recorder).

Audio Crossword Answers (April 2013)

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


3. ABHENRY—Centimeter

6. STRAY—Unwanted capacitance

7. UNBALANCED—Single-ended

9. UNOBTANIUM—A nonexistent metal that has every physical property needed for a specific application

10. ACTIVEDEVICE—Electron tube or transistor [two words]

13. DIBIT—Specifies one of four values

14. PICOAMPERE—A unit of current equal to 10-12 A

15. HEADER—Mounting plate

16. DINA—Radar jamming transmitter that operates in the 92- to 210-mHz band

17. WHITEALICE—Nickname for Alaskan network of radio stations that link early-warning radar stations [two words]

18. HALLEFFECT—Proof that electric currents in metals are carried by moving electrons [two words]



1. VALVE—A British tube

2. CRYSTALRECTIFIER—Semiconductor diode [two words]

4. INDUCTANCE—L is its symbol

5. TYMPANUM—The eardrum

8. VARISTOR—Often used to suppress AC-line spikes

11. REPEATER—A remote indicator

12. CHROMATIC—Includes semitones and whole notes

14. PVDF—1,1-difluorethene, polyvinyleden

15. HASH—Garbage or gibberish

Q&A: Geoff Boyd

Geoff Boyd is the managing director of Coleridge Design Associates.

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

GEOFF BOYD: I have lived in San Jose, CA, since 2006. But, I hail from the Caribbean and spent most of my life living in UK. I am a 1970 Commonwealth Scholar and Physics and Chemistry graduate of the University of Leeds, West Yorkshire, England,  with post-graduate and post-doctoral research experience in Material Science at the Oxford University, Oxford, England. Leaving academia in the early 1980s I co-founded Memotech, one of the UK’s leading first-generation PC companies. I then led NXT, the company that introduced the world’s first computer interactive Videowall display systems, which included marketing and selling these high technology display systems into Japan.

In 2010, after more than 10 years at NXT specializing in new business development, technology innovation, and intellectual property licensing, I rekindled my entrepreneurial activities and founded Silicon Valley-based Coleridge Design Associates, which has the objective of building a team of designers, scientists, and engineers who specialize in creating intellectual property (IP) by invention and innovation aimed primarily at the consumer electronics (CE) and green energy (GE) markets. At its core is “Invention by Design” rather than “Invention by Serendipity” with the skill and experience to recognize the difference between a trip to Brighton (the seaside) and a trip to Mars.

SHANNON: What was your first personal project? Why did you build it? Is it still in use?


GEOFF: My exposure to electronics was as a postgraduate student in the
Department of Metallurgy, Oxford University, where those so inclined built their own electronics equipment for lab experiments. I took to this like a duck to water and became quite proficient at electronics design and construction as well as sheet metal work for enclosures. My first personal project was to build a functioning version of Peter Walker’s Quad 405 current dumping amplifier. The design with full schematics was published in a December 1975 issue of Wireless World. I was fascinated with the concept of the reactive bridge balancing technique used in the design. In fact, I remember doing a second-order calculation to fine tune the inductor’s resistance of the bridge. I added Douglas Self’s advanced preamplifier with discrete LED-biased op-amps, which was also published in Wireless World in 1976 as well as a discrete Class A headphone amplifier also published at the time. I laid out the PCBs using the “pen and tape” method and etched it in the lab. No purchased kits here! I fabricated the sheet metal enclosure under the expert tutelage of John Short, who ran the student workshop in the Department of Metallurgy at Oxford for many years. This integrated amplifier had a pride of place in my living room for many years. It eventually gave way to a Yamaha AV receiver over 10 years later.

SHANNON: You have more than 30 years of experience in technology and audio visual innovation. How did you get started?

GEOFF: In 1978 I moved from the Department of Metallurgy to the Engineering Department at Oxford University as a post doctorate researcher in mechanical properties of materials at elevated strain rates. This required recording data for tests lasting a few milliseconds with data rates at tens of MHz. Though my passion for music and interest in audio electronics remained, my electronics interest and expertise shifted to computer and memory electronics design.

SHANNON: What made you venture out on your own and start Coleridge Design?

GEOFF: I started as an entrepreneur during those heady days of the first personal computers in 1979. I plotted to start a hardware and software business with another researcher at Oxford, Robert Branton, who worked with the programming research group at Oxford. It wasn’t a difficult decision to branch out because at the time Margaret Thatcher had just become prime minister and the cushy jobs at the universities were disappearing fast. By 1981, the writing was on the wall and tenure was going to end, so I decided to forget about an academic career and start my own tech business. Our first business, Memotech, was making add-on memory packs for the Sinclair ZX81. Initially, I designed the products while still at the Engineering Department and then I jumped ship as soon as the business roared to a massive success.

The story of Memotech is interesting. The ZX81 came with 1 KB of memory, and the first thing the user needed was a 16-KB memory pack. When dynamic random access memory (DRAM) ICs were purchased, they needed to be fully tested in circuits with demanding tests, which typically lasted 3 to 4 min. In the UK, there were two contract manufactures who made Sinclair’s add-on packs—Thorn EMI and AB Electronics. They used GenRad testing machines that cost over $1 million each. You couldn’t speed up the test, so the throughput of these machines was limited. Memotech couldn’t afford these machines to test its MemoPaks, as they were called, so we built our own testing rigs using Intel 8048 8-bit microcontrollers with a complete memory test system that cost us less than $500! The MemoPaks were housed in black anodized extrusion enclosures and had a reputation for quality. Needless to say, Memotech cornered the market on Sinclair ZX81 memory add-ons, and we were able to build a multimillion-pound business within one year. I remember that we had UK retailers WH Smith, Boots, and others on allocation, and we could sell everything that we could make. In the US, the ZX81 was launched as the Timex 1000, and we experienced explosive growth and success. I hastily left the university and never had the time to submit my D-Phil thesis from the work in the Metallurgy Department at Oxford, although my research was peer reviewed and published at the time.

At Memotech, we thought all we had to do was produce a first-class product with a great design and specifications, and the buyers we had on allocation would come to us. So, we designed and manufactured the Memotech MTX 512 home computer, which was launched in 1983. We were competing against BBC Microcomputer System and never stood a chance in the UK. The buyers never came and the level of marketing required was beyond our resources, so our backers eventually pulled the plug in 1986. That was a huge lesson. I bought what was left of the business and relaunched Memotech Computers using high-resolution digital video technology that had been developed at Memotech to a new market of videowall technology. We dominated the supply of videowall controllers for nearly 10 years, from 1986 to 1995.

Another lesson I learned from 1995 to 1999 was that “things change.” We miscalculated, thinking that to have large LCD-TVs one would need to “tile” smaller displays. In 1995, it was generally accepted in the display industry that one could never manufacture LCDs larger than approximately 23” diagonal because of glass-handling issues. Another bit of wisdom at the time was that LCDs would quickly transition from amorphous silicon active matrix LCD (AMLCD) to low-temperature polysilicon technology (LTPS), which would mean the driver electronics used with AMLCD would be eliminated. And a further bit of wisdom at the time was that the yield of LCDs would never exceed about 70%. I launched Coleridge Design in 1996 to create a business to tile partially defective LTPS 23” to 25” LCD panels into 100” very large screen flat panel displays (VLS-FPDs) based on these false assumptions.

Needless to say, the business never took off as technology changed making all three assumptions on which the business was based wrong. And in 1999, I joined NXT, the UK flat-panel speaker IP company, as a display consultant to launch SoundVu where “the screen is the speaker.” For 10 years, I worked at NXT with a fabulous team of colleagues all passionate about music and sound reproduction. I worked primarily in IP business development and sales. It was a valuable experience that brought me in contact with all the great audio and consumer electronic companies of the world. I did contribute on the technology side and have a number of NXT patents to my name, but it wasn’t my day job. In 2006, the bulk of the NXT business moved to Hong Kong to be closer to its licensees and I moved to Silicon Valley to be closer to the OEMs that were licensee targets. By 2010, NXT was retrenching, having failed to make a lasting impact with its IP licensing business model, and started moving back to UK. This was my cue to relaunch my entrepreneurial career in Silicon Valley. Coleridge Design in San Jose, CA, was launched at the beginning of 2010.

SHANNON: Tell us about your work. Do the models you used 30 or even 20 years ago still function today?

GEOFF: The Coleridge Design plan is to develop IP mainly in consumer electronics audio and sound reproduction as well as in printed electronics and green energy with the “user experience” as the guiding force. I call it “inventing by design,” where I call on my extensive experience in science, technology, engineering, and mathematics (STEM) to lead a team charged with addressing neglected technology needs.

The entrepreneurial model we used in the past was based on gut feelings. We make a design and a product then put it out there to see how it sells. If the product and price was great then it would sell with moderate PR and marketing. The marketing was entirely business-to-business (B2B) or business-to-consumer (B2C), depending on the product and the target market. The Internet changed the model slightly in the last 20 years but not significantly. Today, we have a fundamental shift with the advent of social media, which in effect means that our marketing effort is dominated by consumer-to-consumer (C2C). Another significant change is the advent of Kickstarter and crowdfunding. In the context of making and taking products to market, I view it as an extension of C2C where you can test the market before you build your product. Our case with Coleridge Design and the aCUBE is a classic case of using Kickstarter to test the market and fail early.

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

SHANNON: Your most recent innovation is the aCUBE. How did this design come to be? What makes it so unique?

GEOFF: In about 2004, Dr. Graham Bank, a colleague at NXT, made a breakthrough in loudspeaker technology inventing the balance mode radiator (BMR) loudspeaker. The BMR is a full-range loudspeaker driver, which provides outstanding performance. My personal view is that this is the most significant advance in loudspeaker technology since 1925 when Rice & Kellogg invented the loudspeaker as we know it today.

BMR technology has appeared in many stand-alone loudspeaker products. However, these have largely been in either expensive Hi-Fi or in performance compromised speaker systems. The advantages of BMR speaker technology are many, but primarily relate to its pinpoint accuracy yet wide dispersion and extended frequency range. Together this allows the design realization of a high-performance, single-drive system such as the aCUBE.

This project takes the 4.5” BMR full-range loudspeaker drivers from CSS, a company owned by my former NXT colleagues, Dr. Graham Bank and Jon Vizor, and marries these drivers with beautiful handmade clear-cast acrylic 6.5” cube enclosures and the latest Class-D amplifier technology from Maxim Integrated. The result: The best in-class performance speakers optimized as near-field active loudspeakers that are stylish, exceptional quality, affordable, and convenient.

The use of acrylic is quite by accident. I have tended to use aluminum extrusions in most of my designs. The MemoPak 64K, the Memotech MTX 512 computer, and the Memotech DDFS videowall controllers were all made with black anodized aluminum preferably brushed. So we designed and prototyped a range of BMR speakers in anodized aluminum enclosures. However, before we made the protototypes, we built some acrylic enclosures as proofs of concept to test the BMR drivers from Cotswold Sound Systems. They sounded fabulous. However, when we used the aluminum prototypes, the enclosures rang like a bell and we had to take drastic measures to dampen the sound. Due to my materials science background, I realized that the acrylic sounded fabulous because of the material’s high internal damping over the entire audio bandwidth due to viscoelasticy. That was the reason the relatively thin walled enclosures sounded so well. Once we decided to make the aCUBE out of acrylic sheet, we had to find a supplier who could make perfect cubes using CNC and the latest techniques in bonding and polishing. The beauty in cast acrylic sheet is how it renders the light through perfect edges.

I have to confess, the aCUBE Kickstarter project was a bit of a Trojan horse in an attempt to gauge whether the consumer electronics market has an appetite for a new audio brand in quality sound reproduction and whether crowdfunding is a viable route to launching such a brand. It didn’t take long to see that in its present form, the Coleridge Design brand will not be a viable vehicle for launching the groundbreaking, disruptive audio technologies as I envisaged. Another valuable lesson learned from this early failure is that very little has changed and launching a new brand is still all about marketing, albeit nowadays C2C social media marketing.

The Lunatik Touch Pen, available in several different colors, is currently in prototype development. The accessory can be used both as a regular ink pen and as an implement for your tablet

SHANNON: Describe your touch-pen technology and how it works.

GEOFF: A couple of weeks after I got my first iPhone in 2007, I designed and built a capacitive-touch pen using conductive silicone rubber to emulate the finger. There are two requirements for a capacitive touch pen. The first is that it must form a flat conductive area of about 0.5 to 1 cm2 on the touch glass surface. The second is that this conductive area must be electrically connected to an electrical “sink” such as the human body or “large” lump of metal. The first touch pen that we built had a mild steel core of about 100-mm long × 3-mm diameter embedded in a silicone rubber “pen” about 110-mm × 8-mm diameter. We built a few hundred prototypes, but it wasn’t viable because there was no IP protection.

So we came up with a design in which the rubber grip of a gel pen was made out of conductive silicone rubber and modified so that when the pen refill was retracted the silicone rubber tip would collapse and could be used as a touch pen even when the pen body was plastic because the grip would conduct through the fingers.

Coleridge Design licensed the technology exclusively to Scott Wilson at who launched it on Kickstarter, his second project after his very successful TikTok project that created the Lunatik Brand. (For more information, visit

This is the licensing business model that we generally want to use for the IP we develop. The key is to make a whole product that is ready for market. Most of the time it is not that easy because the technology is not a “whole product” and needs one or more entities in the supply chain to complete the product. In many cases, it might be an OEM or brand to take the product to market as well as suppliers to change the way they make products. That is very hard and needs to be driven by the OEM. That was the reasoning behind trying to make Coleridge Design an audio brand. If one cannot take it to market then one has to make it worth the while of the OEM or brand to get on board. That generally means some degree of exclusivity. Say a time-limited exclusivity or even an outright sale or fully paid up license.

SHANNON: What do you see as some of the greatest audio innovations of your time?

GEOFF: In the last 40 years, we have come a long way in improving the user experience but only if we use convenience as the main metric. To speak to that, I would say three of the great innovations of “my time” include: The Digital Audio revolution, which has led to surround sound and iTunes; the Class-D filterless audio amplifier; and distributed mode loudspeaker (DML) culminating in Dr. Graham Bank’s BMR. However, in so many ways, we have gone backward in the user experience of audio, mostly in the name of convenience. I recall valve amplifier systems from the 1960s and 1970s with very large speakers, some of them built into the users’ homes, which outperform most systems I have heard in the last 20 years.

How do we get great-sounding audio out of relatively “small” enclosures? I clearly remember an encounter I had with Michael Gerzon, who it would be reasonable to say invented surround sound. It was sometime in 1975, just after he had published his work on surround sound in Wireless World in December 1974. I was invigilating as a student’s part-time job on Friday evenings at the Radcliffe Science Library in Oxford and Michael, who was at the Oxford Mathematics Institute, had reserved some books on Matrix theory. I spotted his name on the ticket and when he came to collect his books I pumped him with questions on surround sound. I came away with two pieces of information, which I clearly remember to this day. The first was that the minimum number of speakers required for full surround sound would be six at the corners of an octahedral arrangement. Two at the top front, one at the bottom center, two at the bottom back, and one at the top center. But the bad news, he said, was that for the equations to work they all had to be full-range speakers (i.e., including bass). This has remained with me for 40 years.

SHANNON: Are you currently working on or planning any other speaker-related projects?

GEOFF: Coleridge Design has been developing IP on three audio related projects:

A personal surround-sound headphone system (PX3) based on design work we did on motorcycle helmet audio ( The new development seeks to achieve the same Helmet-Blaster unbelievable surround-sound performance in similar form factor and power requirements as conventional headphones.

The magnetless voice coil actuator (M-LVCA), which is a green initiative to eliminate rare earth magnets in loudspeaker motors at reduced cost without loss in performance and increase in weight. This is based on recent advances in insulated iron soft magnetic composites (SMCs) coupled to audio digital signal processing. It is scalable to all sizes of loudspeaker motor. There are possible spin off applications in electric vehicle technology

The extended range flat-panel bass (flatBASS) loudspeaker with active shallow enclosure technology. My 1975 encounter with Michael Gerzon makes this what I consider the holy grail of loudspeaker technology!

SHANNON: Can you recommend any useful new parts or promising technologies to audioXpress readers? Anything you’re using now that you think readers should know about?

GEOFF: I would recommend Graham Bank’s BMR loudspeaker drivers from Cotswold Sound Systems mounted in naturally damped “thin-walled” acrylic enclosures. Thin-walled clear cast acrylic sheet typically 4-mm thick for 3” to 4” cubes, say 6-mm thick up to 6” to 8” cubes and say 10-mm thick up to 12” to 15” cubes.

There has been rapid improvement in lowering the cost and increasing the performance of the latest filterless class-D amplifiers from Maxim Integrated and Texas Instruments (TI). They are very efficient and worth evaluating in new designs but good quality power supply design is critical. Also the bridge tied load (BTL) output configuration of modern Class-D is pretty much mandatory but care must be taken to switch both ends when using speaker switch boxes.

Another new technology worth considering in modern audio designs is the use of supercapacitors from, say, Maxwell and PowerStor, particularly for battery designs, which are now really viable with the new super-efficient filterless Class-D amplifiers. Audiophiles love the concept of a battery-powered audio amplifier! Quiescent current of these amplifiers is the key efficiency metric. Supercapacitors have drawn much attention in recent years due to their high power density, reversibility, and long cycle life. They are found in a wide range of applications from smart phones to electric vehicles and the rapid price reduction in recent years has made them affordable in applications like this.

These low-cost supercapacitor devices are typically 2.5 to 3 V maximum so one needs to incorporate active balancing when these devices are used in series. For example, AA batteries would be configured in series for relatively high peak powers into 4-Ω loads from typically 15 or 12 V (primary or rechargeable respectively). However, particularly when partially discharged, these battery stacks are very poor at delivering the intermittent heavy-power transients required for high quality audio. A series bank of active balanced supercapacitors can supplement the battery pack and completely counteract this.

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

GEOFF: In the words of Nike, “Just do it.” I don’t mean to be flippant, but I firmly believe that you really learn when you make stuff. I include circuit simulations in “making stuff.” I tend use TI’s TINA-TI and other free tools for analog simulation. I don’t breadboard until I have it working in simulation. But, in the end, it has to be prototyped and tested. In analog audio electronics, this is getting really hard as we move to smaller fine-pitch ICs. My advice is to make use of manufacturer’s reference board designs and take a stab at laying out your designs using the many free tools available from PCB fabricators. I tend to use old fashioned axial and radial devices for breadboarding small sections, but more often than not, the working simulations allows one to go straight to SMD PCBs, typically 0603 passive devices for prototypes and preproduction only moving to 0402 if board space is an issue. Another golden rule I have for analog audio is to always use full differential designs, particularly when interfacing to digital ICs with analog outputs. aX

April New Products and News

AmpliVox Wireless PA Supports many Media Devices

Amplivox SW720 Wireless PA system

The updated SW720 Wireless PA system includes several practical accessories.

AmpliVox Sound Systems has unveiled its newly updated SW720 Wireless PA system, a versatile PA package that supports all types of external media. The SW720 PA enables audio or video to be played from MP3s, CDs, DVDs, or any iDevice from Apple (e.g., iPhones, iPads, or iPods), complemented by a wireless handheld mic for voice amplification. For audiences of up to 500 people and rooms as large as 2,500 ft2, the SW720 is an all-in-one solution for multimedia presentations.

The revamped SW720 Wireless PA system with a remote-controlled DVD player now includes AmpliVox’s S1732 cable and adapter, enabling iPads and other Apple devices to be simultaneously played and charged. The unit also contains an integrated DVD/CD/MP3 disc player with a USB/SD card reader and video output that enables DVDs to be viewed with a projector or other video display. For voice amplification, the SW720 features a built-in UHF selectable 16-channel wireless receiver with a 300’ range wireless handheld microphone.

The SW720’s straightforward controls customize presentations. A voice priority switch mutes music when the mic is in use, and separate bass/treble controls enable easy sound adjustments. Weighing 11.5 lb, the molded plastic enclosure is durable and portable. A protective cover offers many pockets for accessory storage. The SW720 can run for up to 6 h on its built-in rechargeable battery, or it can be powered with the included AC power cord.

For more information, visit

Dayton Audio’s DVC Subwoofer

Dayton Audio Ultimax DVC

Dayton Audio’s DVC subwoofers are designed to improve power handling and reduce power compression.

Dayton Audio’s Ultimax Series DVC subwoofers are purpose-built to move air and create clean, articulate, and fast bass. To improve power handling, increase thermal management, and reduce power compression, Dayton Audio designed the Ultimax Series with large black anodized formers and vented pole pieces, under-spider ventilation, and two-layer copper voice coils.

The Ultimax’s “Tall-Boy” rubber surround is intended for extra-long linear excursion without reducing the Nomex honeycomb/woven glass-fiber laminated cone’s surface area. Copper shorting rings and a pole piece cap reduce inductance and distortion, while the Ultimax’s dual spiders maintain linearity at high drive levels.

Dayton Audio’s Ultimax Series dual voice coil subwoofers are engineered and built using the latest in subwoofer technology. They are now available in 10”, 12”, and 15” sizes. Dayton Audio products can be purchased in the US through Parts Express (

For more information, visit


Danley Sound Labs SH-96 HO

Danley raises the sound pressure level (SPL) on its Synergy Horns SH Series

Danley Sound Labs recently announced improvements to many of its already highly-regarded SH Series full-range loudspeakers. The new versions are identified by the suffix “HO,” which stands for “high output.” For example, if someone wants to get the most performance out of the Danley SH-96, order the Danley SH-96 HO.

The new designs use a more powerful two-way high frequency. As a result, the low- and mid-frequency drivers can be used to their full potential yet maintain Danley’s characteristic frequency response, phase response, and fidelity. In conjunction, the HO designs use a new crossover and have additional options for bi-amping and for changing the low-frequency impedance. Because the cabinets themselves haven’t changed, the new versions retain the coverage and frequency loss patterns of the originals. The new models include the SH-95 HO, the SH-96 HO, and the SH-64 HO.

Because the new switch panel cannot operate reliably if left exposed to the elements, weatherized versions of the new high-output loudspeakers must be pre-ordered with specified biamping and impedance settings.

For more information, visit

B&K Precision Launches “pwrApp” for Apple Products

B&K Precision pwrApp

B&K Precision’s new “pwrApp” can be used on an iPad, an iPhone, and an iPod touch.

B&K Precision launched its new “pwrApp” for iPad, iPhone, and iPod touch. Adding greater value to its DC power solutions, B&K Precision’s pwrApp enables full monitoring and control of a network-connected (via WLAN) XLN-GL series of power supplies over local wireless networks.

The pwrApp’s primary function is remote operation of all XLN-GL power supplies’ functions. The pwrApp’s features include live visual monitoring and interactive power supply control, visual data graphing, audible trigger alarms within the app, and data export.

Fully functional in-app demos of devices, monitoring, and programs are available with or without a connected XLN power supply. B&K Precision’s pwrApp for iPad and iPhone offers full interface control in English, French, German, Portuguese, Spanish, and traditional Chinese via a simple selection menu. Future versions of pwrApp will offer control of additional select WLAN-enabled B&K Precision power supplies. Available for immediate download via iTunes, pwrApp is free of charge to all users.

For pwrApp and XLN information, as well as hardware/software requirements, visit

NUGEN Audio offers Stand-Alone LM-Correct Loudness Tool

NUGEN Audio LM Correct

NuGen Audio now offers a new stand-alone version of its LM-Correct loudness analysis and correction tool.

NUGEN Audio, a creator of intuitive tools for audio professionals, has released a new stand-alone version of its LM-Correct loudness analysis and correction tool, which was originally only available as an AudioSuite plug-in. For the first time, LM-Correct is available as a file-based program, taking its speed and simplicity beyond the Avid digital audio workstation (DAW) environment. LM-Correct provides EBU R128|ATSC A/85 (CALM Act)-compliant loudness correction with unmatched simplicity, providing users with a rapid two-click solution for loudness normalization and conformance.

Part of NUGEN Audio’s range of innovative and easy-to-use loudness correction tools, LM-Correct is a faster-than-real-time tool that calculates and corrects for integrated program loudness and short-term maximum loudness. LM-Correct includes an internal true-peak limiter that transparently handles any intersample peaks.

LM-Correct’s settings include presets for current loudness standards, short-term loudness, overall integrated program loudness measurement and correction, maximum true-peak level targeting, and “EBU Mode.” The software also supports mono through 5.1 audio.

LM-Correct is available immediately for OS X and Windows operating systems. For more information about LM-Correct and other NUGEN Audio products, visit

Saelig Introduces Handheld RF Spectrum Analyzer

Saelig PSA2702

Saelig’s PSA Series II RF spectrum analyzers feature long, rechargeable battery life.

Saelig Company has introduced the PSA Series II RF spectrum analyzers. Available in 1.3- and 2.7-GHz versions, these new instruments are smaller, lighter, and have a longer battery life than other more expensive handheld RF products. PSA Series II analyzers incorporate a 4.3” (11 cm) backlit thin-film transistor (TFT) color touchscreen display, with a high-capacity rechargeable Lithium-ion battery to produce more than 8-h operation per charge. The PSA Series II PSA1302 has a 1-to-1,300-MHz frequency range, while the PSA Series II PSA2702 operates up to 2,700 MHz. Dynamic range is 80 dB with a noise floor at –100 dBm. Resolution bandwidth is selectable down to 15 kHz.

The PSA Series II’s features include sweep modes (e.g., continuous, single, peak hold, and sweep average), AM/FM audio demodulation with built-in speaker, and data logging for traces, data points, or screen images (with storage for 10,000 entries per file triggered from a key press, internal timer, external trigger, or the limits comparator). Traces or complete screen images can be saved to file and compensation tables for antennae or other external transducers can be created and loaded. USB host and device connectors enable the use of USB flash drives or direct connection to a PC.

PSA Series II analyzers are controlled via finger-operated touchscreen soft keys in a hierarchical menu system that provides rapid access to menu functions. All functions can also be operated using just the hard keys.

The ruggedized casing incorporates a rubber protection buffer, a bench stand, and screen protection. For bench-top use, the instrument can be operated from its AC charger. For portable use, its 8-h battery life can be further extended by selecting auto-off, which turns the instrument off (retaining all data) after a selectable delay of 5 to 60 min. from the last key press. The compact, handheld PSA Series II RF Spectrum analyzers weigh 20 oz, making them suitable for any portable RF service kit. For more information, visit