Tag Archives: Loudspeakers

Q&A: Charlie Hughes

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Charlie Hughes

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

CHARLIE HUGHES: I’ve been involved with designing loudspeaker systems professionally for about 25 years. Prior to that, I worked mixing and recording live music in high school and a little bit in college. I earned a Physics degree from the Georgia Institute of Technology. I was very fortunate to have studied under Dr. Eugene Patronis while I was there. I currently live in Gastonia, NC, about 20 minutes from Charlotte.

SHANNON: How did you become interested in audio electronics?

CHARLIE: My interest isn’t so much electronics as it is loudspeakers. Of course, I have an interest in amplifiers, DSP, mixers, and the like. However, this is secondary to loudspeakers, how to measure their performance, and how to design them to sound good.

SHANNON: Describe your career as a loudspeaker design engineer. What are some of the highlights?

CHARLIE: I started working at Peavey Electronics in Meridian, MS, right after graduating from Georgia Tech. I was there for almost 14 years. After I left Peavey, I spent a short time at Altec Lansing in Milford, PA, as the chief engineer for its pro audio division, which the company was trying to resurrect. In late 2004, when I left Altec, I started Excelsior Audio, a consulting and loudspeaker design and measurement company working primarily with loudspeaker manufacturers.

I did a lot of horn design at Peavey, being the primary horn guy while I was there. I received my first patent (6,059,069) for a horn design concept. Having that patent issued was really cool. I also presented my first Audio Engineering Society (AES) paper on this type of horn design. I remember seeing Don Keele and Earl Geddes in the audience as I began my presentation. That was a bit intimidating at the time, although I had worked with both of them previously.

In 2000, I was asked to be an instructor at a TEF Level II workshop along with Don Eger and Russ Berger. That was a thrill because those guys are acoustical heavyweights! I knew a lot about the TEF platform and time delay spectrometry (TDS) measurement as applied to loudspeaker systems, so I guess I was able to hold my own.

Around the same time, I was programming MATLAB code to help optimize the crossover design for loudspeaker systems. This was mainly done in an effort to make the directivity response more consistent through the crossover region and to reduce the time in doing so by eliminating lots of repeated polar measurements. The resulting program, PolarSum, was very useful in this regard.

More recently I was asked to join the Ahnert Feistel Media Group (AFMG) based in Berlin, Germany, to consult on its software and help with advanced tech support and product training globally. This is the company responsible for the acoustical modeling program EASE. It also produces a couple of measurement programs, EASERA and SysTune. One of its other programs is SpeakerLab. This is an amazing program that, while doing some of the same things as PolarSum, takes loudspeaker modeling and design far beyond what anyone else I am aware of is doing in terms of directivity response.

Being asked to speak as a panelist for two State of the Art of Live Sound Loudspeaker Design seminars at AES conventions in 2008 and 2009 with Tom Danley (Danley Sound Labs), Dave Gunness (Fulcrum Acoustic), Aleš Dravinec (ADR Audio), and Pete Soper (Meyer Sound Labs) was a thrill. In 2010, I was asked to speak at an AES convention workshop with Floyd Toole and Peter Mapp about audio system coverage. To be included in the same company with all these gentlemen was indeed a great honor.

Beginning in 2004, I became the chairman of a CEA standards committee working group, CEA R3-WG1. I’m also active on several AES standards committees.

SHANNON: While working at Peavey Electronics you were responsible for the design and development of many commercially successful products for the musical instrument, cinema, PA, studio monitor, and professional/install markets. Can you share some of the challenges involved with a couple of the most well-known designs? Are they still used today?

CHARLIE: At Peavey, some of the most popular loudspeakers are probably the SP series (e.g., SP-2, SP-3, etc.). I worked on several iterations of a couple of the models in this line. For these, there always seemed to be the issue of improving performance, maintaining reliability, and keeping the cost where it needed to be. Of course, this is probably no different than the challenges facing design engineers at many other companies. There was one instance when it was decided that the horn in the SP line needed updating. I think many of the models were using the older CH-2 at the time. I was tasked with the new horn design (what became the CH-941). Since it would be used across the board on the SP line, I wanted to make sure it was as good as I could make it at the time. There were some challenges to getting the directivity control as consistent as I wanted just above the low end cut-off of the horn. There was some narrowing of the coverage pattern in the midrange. I had to go back and study some of Don Keele’s AES papers as well as the work of Cliff Henricksen and Mark Ureda. Getting the secondary flare angles correct near the horn mouth helped with this.

The Q Wave series (later the QW series) was another line where a new horn design was used. This time it was one of the new Quadratic Throat horns. The same horn was used on several of the models in this line. It worked very well. I was to design a three-way system for the line. This required a new MF horn along with a new HF horn that would use a smaller compression driver. The MF horn required a closed-back 6.5” MF driver. It was difficult getting the right driver for this system. I know I had to have made Tom James (Eminence Speakers) crazy with all of the back and forth to get this driver dialed in to get the right performance, low frequency extension, and power handling. He did it though, and it is the heart of that loudspeaker system.

SHANNON: What made you venture out on your own and start Excelsior Audio?

CHARLIE: The truth is my wife had a lot to do with it. She had been kicking me in the backside for quite some time to start my own business. She had more faith in me than I did! When I left Altec Lansing in 2004 it seemed like the right time to give it a shot.

SHANNON: Can you discuss your best experience thus far?

CHARLIE: That’s a tough one because I’ve been blessed to have so many. If I had to pick one thing, I would have to say it would be getting involved with Synergetic Audio Concepts (SynAudCon). This is an education consortium started by Don and Carolyn Davis to help raise the level of knowledge in the audio industry. When Don and Carolyn retired it was taken over by Pat and Brenda Brown.

I have learned so much from other SynAudCon members: guys like Jay Mitchell, Dave Gunness, Tom Danley, Bruce Olson, Jim Brown, Peter Mapp, Ray Rayburn, Bill Whitlock, and so many others. Without the knowledge, contacts, and friendships I have made stemming from SynAudCon there is no way I would be where I am today.

SHANNON: What was your first personal project? Is it still in use?

CHARLIE: Wow, time to go way back. I think the first personal project I did was the loudspeaker system I designed and built for my senior design project at Georgia Tech. A rather substantial project was required to graduate. Mine was a three-way loudspeaker system. I thought they sounded fairly good at the time, but they looked atrocious! Woodworking was not one of my accomplished skills at the time, nor is it now. I like to think I design them a lot better than I can build them.

I had these and used them from 1987 until about 2001. I made some major changes (complete redesign and rebuild) to the passive crossovers around 1995 that greatly improved the sound. Several years later, the drivers became too deteriorated and they were not worth trying to salvage.

SHANNON: You wrote an article, “Subwoofer Alignment with a Full-Range System” (audioXpress, January 2012). Did you create this project for your personal system? Do you still use the system?

CHARLIE: Not really. This was the result of some work from 2002. I was at a SynAudCon workshop about loudspeaker and acoustical testing and measurement. A question was asked of the instructors regarding the alignment of subs and full-range systems. This sparked a, shall we say, enthusiastic discussion amongst a couple of the instructors. However, the question never really did seem to get answered. I spent a lot of time thinking about this topic and what the right answer should be. By investigating the behavior of individual low-pass and high-pass filters, as well as their summation, I think I found the answer.

I think this is really only an issue when the distance between the subwoofer and full-range system is quite large acoustically (i.e., in excess of one-quarter wavelength in the crossover region). Otherwise, there is not enough phase difference to adversely affect system performance (home systems). In large concert PA systems this distance can be quite large and the cause of substantial problems. I’m hopeful that more people will implement my method and find it to be a useful solution. A video of a talk I gave on this can be found on YouTube and a PDF of the slides downloaded from my website.

SHANNON: Are you currently working on any audio projects? If so, could you tell us a little about them?

Charlie recently finished designing a speaker for SoundTube. The speaker features a line-array point source (LAPS) design.

CHARLIE: Yes, I finished the design work not too long ago for a project I did for SoundTube. This was a three-way fixed, single-box line array with an add-on low frequency directivity extension (LFDE) box. One of the interesting things I was able to do with this design is to frequency shade each pass band (except the HF) to maintain fairly constant vertical directivity control (with respect to frequency) as well as have a fairly short extent of the near-field across the entire operating range of the loudspeaker. Neither of these useful performance aspects is typically embodied in a line array. It is essentially a line array that performs as a point source. Thus, we dubbed the design methodology LAPS (line-array point source).

Charlie recently designed three two-way loudspeakers for Bag End. Each has a 10”, 12”, and 15” woofer.

Another project that is nearing completion for Bag End is a line of three two-way loudspeakers, each with a 10”, 12”, and 15” woofer, respectively. I designed the high-frequency horn, the vented enclosure for each, as well as the internal passive crossovers. We employed a passive all-pass filter in these crossovers to help time align the output from the LF and HF pass bands. I’ve also developed DSP filtering for use as front-end EQ as well as for driving the loudspeakers in a biamp configuration.

An interesting aspect of the EQ used for these loudspeakers is that it is based on the frequency response at multiple listening positions, both on- and off-axis. By post-processing many off-axis measurements we were able to better determine what frequency regions would benefit the best from EQ and which ones to leave alone. Equalizing a loudspeaker based solely on a single frequency-response measurement typically will not yield results as good as this method.

There are some other projects currently in the works but they’re not close enough to completion to be able to discuss them.

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

CHARLIE: I think the TDS measurement method by Richard Heyser was a great innovation for loudspeaker measurement and analysis. There are others methods, such as dual-channel FFT using a log-swept sine stimulus (Angelo Farina) that are also useful.

The realization that the “sound” of a loudspeaker has more to do with its off-axis radiation than the on-axis frequency response is an unassailable truth when listening to loudspeakers in rooms, but it is amazing how many people still don’t get it.

The use of FIR filtering in the DSP available today to make loudspeakers more accurate in terms of the reproduction of the input signal to the system is also a great advance.

SHANNON: Do you have any advice for audioXpress readers who are thinking of building their own sound systems?

CHARLIE: Read Floyd Toole’s book Sound Reproduction, Loudspeakers and Rooms, (Elsevier, 2008). Pay just as much attention to the off-axis response of loudspeakers as the on-axis response. Get the directivity response of the system as consistent as possible across as wide of a frequency range as possible. Avoid abrupt changes in the directivity response. These are most likely to occur through the crossover region. Also, get it right in the time domain. I think that, audibly, this is more important than the frequency domain.

And, have fun! If you don’t enjoy what you’re doing, it’s time to find something else to do. aX

 

Member Profile: Charlie Hughes

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Charlie Hughes

Location: Gastonia, NC (the Charlotte area)

Education: BS, Physics, Georgia Institute of Technology

Occupation: Electro-acoustical consultant/loudspeaker design engineer

Member Status: Charlie said he has been reading Voice Coil since about 1988, and he is a frequent contributor to audioXpress.

Affiliations: Audio Engineering Society (AES), Acoustical Society of America (ASA), Association for Loudspeaker Manufacturing & Acoustics (ALMA) International, Consumer Electronics Association (CEA), National Systems Contractor Association (NSCA), and Synergy Audio Concepts (Syn-Aud-Con)

Audio Interests: Charlie is primarily interested in Constant directivity loudspeaker systems capable of reproducing square waves.

Most Recent Purchase: A set of JH Audio JH13 in-ear monitors

Current Audio Projects: Projects Charlie said he has in the works include a constant directivity line-array loudspeaker and a large format, full-range, high-SPL horn-loaded loudspeaker.

Dream System: Charlie said he hasn’t completed his dream system yet, but he is working on it.

December Products: Ultra Loudspeakers, GAGA Tube Guitar Amp, & More

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The December 2012 issue of audioXpress features product information about a variety of must-have audio gear. Headphones, an amp, a mic, and more are detailed.

SVS Introduces New Ultra Series

SVS recently launched its Ultra series of full-range loudspeakers. The speakers are designed to deliver uncompromised audio performance, boast unsurpassed build quality, and cost-is-no-object performance at an affordable price.

SVS Ultra

The SVS Ultra series loudspeakers were designed by audio enthusiasts with more than 50 years combined experience in the high-end audio arena. The result is a loudspeaker that convincingly conveys the emotion of live music and home theater. The SVS Ultra series delivers a deep, detailed soundstage with incredible resolution, absolute transparency, and rich and articulated bass.

The lineup includes a 45″-tall upswept trapezoidal tower, a bookshelf speaker, a center channel, and a surround speaker. The result is a performance level even more expensive loudspeakers cannot match.

Every other speaker in the Ultra series has been designed to complement the Ultra Tower’s performance, with flush-mounted drivers to reduce diffraction and improve on-axis, high-frequency response, along with rear-mounted bass reflex ports (on the Tower, Bookshelf, and Center speakers) for phenomenal bass output and extension and minimal frequency response degradation.

New Tube Guitar Amp

Milbert Amplifiers introduces the GAGA D-30 tube guitar amplifier, the third in its line of Guitar Artists’s guitar amplifiers. Based on the revolutionary GAGA 90 and offering similar features and functions, the “domestic” model GAGA D-30 provides from 1 W up to 30 W of full-power audio output, is 11 lb total weight, and offers 120-V/240-V mains input.

Milbert GAGA D-30 tube guitar amplifier

The GAGA D-30 may be upgraded to either the domestic GAGA D-60 model, or to the international GAGA 90 model. The upgradeable nature of GAGA amplifiers extends its versatility.

Features common to GAGA amplifiers include: patented technologies; no traditional audio output transformer; light-weight, high-power capability; the ability to play more than 30 kinds of tubes in unlimited combinations, for tonal versatility; adjustable headroom for more distortion at low volumes (down to 1 W); Auto-Everything that auto-biases all tubes; Auto-Impedance and Blow-Proof universal speaker outputs; advanced, regulated power supplies; extended tube lifetimes and Auto-Standby; P3-Ready 9-V high-current phantom power for pedals and active pickups; upgradeability throughout the amplifier series; and it’s made in U.S.

Image ONE Series Gains Bluetooth Model & Product Upgrades

Klipsch now offers its new Image ONE Bluetooth and an upgraded Image ONE. Catering to on-ear enthusiasts, these headphones maintain the same high-quality sound signature and comfort while introducing enhancements in build, functionality, design, and performance. With the launch of these two Image ONE series models, Klipsch introduces upgraded, flat cabling (attached only to the left ear cup) for added durability and tangle resistance, and a flat-folding, collapsible design.

Klipsch Image ONE

The Image ONE Bluetooth serves as Klipsch’s first wireless headphone model. Given its utilization of Hi-Fi Bluetooth (A2DP) audio quality and aptX Codec for lossless streaming, users experience high-performance, uninterrupted listening. The Image ONE Bluetooth’s wireless capabilities are enabled via its built-in rechargeable battery, with wired connection still possible via the included direct-connect audio cable. Large, easily-accessible controls are located on the right ear cup for controlling playlists and phone calls.

Maintaining the same acoustics of the current model, the updated Image ONE provides listeners with flat earpads and an adjustable leather headband for optimal comfort and fit, still providing superior levels of noise isolation. Simplifying cable design, the headphone utilizes only one cable that feeds into the left ear cup. Because the headphone’s ear cups fold flat into the headphone, a smaller carrying case is provided for more compact storage. The same three-button remote and mic is housed on the cable for full call and music control with Apple devices.

 

 

AX December: Speaker Design, Interactive Sound, Power, & More

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audioXpress is all about range—range, in the sense of content diversity. Our international team publishes insightful articles on a wide variety of topics such as speaker design, sound analysis, glass audio projects, and hi-fi product reviews. This month we deliver once again.

First, I suggest you check out the interview with innovative sound designer Andrew Spitz (p. 38). Much of his current work focuses on “interactive experiences.”

Interested in speaker design? We’ve got you covered. Consider starting with the first part of Richard Honeycutt’s series, “Speaker Design School.”

Then  turn to page 8 for the second part of the series “Ribbon and Planar Magnetic Loudspeakers.” Finally, flip to page 14 for the conclusion to Ton Giesberts’s series on his active loudspeaker system project.

The completed PCB for the subwoofer is attached to its heatsink

Ready for a comprehensive transducer test? You can always rely on Vance Dickason’s expert analysis. This month he presents the results of tests he ran on a Morel TiCW 634Nd (p. 30).

The Morel TiCW 634Nd

Once you’ve had your fill of speaker articles, read what Gary Galo thinks about remastered editions of David Hancock’s 1967 recording of the Dallas Symphony’s presentation of Rachmaninoff’s Symphonic Dances (p. 24). What would you choose: vinyl, digital, or both?

If you’re a glass audio enthusiast, head to page 35 to refresh your understanding of power supplies for hollow-state electronics. Transformers and rectifiers are covered in detail.
Lastly, note that the long-awaited amp test page referenced in Richard Honeycutt’s audioXpress November 2012 article—“Differences in Amp Sound: What’s the Truth?”—is now available at www.edcsound.com/amptest.htm.

November Products: Cush Headphones, Measurement Mics, & More

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The November 2012 issue of audioXpress features product information about a variety of interesting, well-designed audio gear. Headphones, an amp, a mic, and more are detailed.

Cush Headphones Offer Sound Quality, Comfort, & Style

KICKER recently unleashed its 39 years of high-performance audio knowledge to offer KICKER Cush headphones.

KICKER’s Cush (Source: KICKER)

Featuring an ultra-lightweight design and thick over-the-ear cushions, Cush headphones offer 54-mm speakers and a 118-dB maximum output to provide the legendary bass response and tonal accuracy for which KICKER is known.

The headphones feature a smooth, soft-touch finish in black gloss or white with monochromatic graphics for a subtle appearance. The breathable, perforated headband cushions the listener’s head.

Cush headphones utilize a 53”, Kevlar-reinforced, flat cable to provide freedom for movement while listening. The flat cable is smooth and less prone to tangles. The angled “L” plug connects into any iPod, iPhone, MP3 player, or KICKER docking system.

Barix Expands Audio Product Range

Barix markets its Annuncicom IP audio and SIP/VoIP devices around the world, bringing bidirectional audio streaming and control solutions to various markets within the commercial, entertainment, private sector, and residential worlds.

Barix’s Annuncicom 60 (Source: Barix)

Barix now offers two low-cost, reliable VoIP and IP Annuncicom audio devices that optimize features and functionality for universal applications.

The new Annuncicom 50 is built specifically for OEM applications. The device delivers Barix’s trademark reliability, open standards design, and multi-format audio capability at a low cost for OEM customers.

Barix also offers the Annuncicom 60, a universal, programmable, and ultra-compact device that offers reliable IP encoding and decoding. It is roughly 40% the size of existing Annuncicom devices, which are known for offering a compact footprint to systems integrators and end users.

The Annuncicom 60 is a single-zone paging interface device that can decode VoIP codecs as well as MP3, AACplus, and PCM audio. Its built-in speaker amplifier, balanced line output and microphone interfaces, serial and contact closure control interfaces, and Power over Ethernet (PoE) support is unique to the market—delivering universal functionality at a competitive price.

Contact Barix for more information at www.barix.com or www.ip-audio.info.

Sennheiser Offers High-End Amp & Headphones

Sennheiser now offers an amplifier for dynamic headphones. The digital HDVD 800 has a fully symmetrical layout and sampling frequencies of up to 24 bit/192 kHz to ensure an unequalled listening experience. It also harmonizes perfectly with Sennheiser’s HD 800, HD 700, HD 650, and HD 600 high-end headphones.

Sennheiser’s HDVD 800 (Source: Sennheiser)

The HDVD 800’s features include its balanced sound image, maximum precision, and impressive spatiality. The high-end headphone amplifier has a fully symmetrical layout for operation with analog audio sources, ensuring symmetrical signal transmission from the source to the headphones. For use with digital sources, the amplifier is equipped with a high-quality Burr-Brown digital/analog converter that converts digital audio data into analog signals, enabling the HDVD 800 to transmit the entire frequency spectrum of high-end audio sources without any frequency loss.

A rotary gain switch at the rear of the unit provides simple adaptation of the amplifier output to the audio input voltage. This ensures that the dynamic range can be used to its full extent.

The HDVD was developed and designed in Germany, which is where the latest member of Sennheiser’s high-end series is also being manufactured.

Sennheiser also offers the IE 800 in-ear earphones, which the company describes as headphones with “the most innovations per square millimeter.”

Sennheiser’s IE 800 (Source: Sennheiser)

The IE 800 offers innovative technology providing brilliant trebles, precise bass response, and a detailed, lifelike sound image with a 5-to-46,500-Hz frequency response.

The IE 800’s interior conceals many small but effective innovations: the centerpiece is Sennheiser’s specially developed extra wide band (XWB) driver. With a 7-mm diameter, it is the smallest wide-band sound transducer available in dynamic headphones. Its functional principle guarantees distortion-free sound even at high-sound pressure levels. It also features a modern design and high-quality materials (e.g., scratch-resistant ceramic housing).

Pro V-Series Speakers Provide High Sonic Accuracy

Pro Audio Technology (PRO), a leader in professional-grade loudspeaker and digital amplifier technology, announced the new V-Series loudspeakers, designed to deliver the high-impact dynamics for which PRO is known, but at a more affordable price. Both new models, the SCRS-210v full-range loudspeaker and the LFC-12v subwoofer, feature 6” enclosures, placing high-output systems in small rooms.

The SCRS-210v loudspeaker (Source: Pro Audio Technology)

The SCRS-210v’s two 10″ woofers provide a high-sound pressure of 102 dB with 1 W of input and combined, can handle 300 W of continuous power. Offering even higher sensitivity, the 1” annular-diaphragm compression driver produces 110 dB/W and delivers detailed and extended highs. Striking a balance of power and accuracy, the SCRS-210v fills nearly any space with cinema-quality sound and concert-caliber music without industrial-grade pricing or space requirements.

For low-frequency support, the companion LFC-12v subwoofer features a high-output 12″ professional-grade woofer with a 4″ voice coil. With sensitivity rated at 96 dB driven with 1 W, and power handling up to 700 W, the LFC-12v has no problem with today’s high-quality recordings.

When paired with the PMA amplifier/processor, advanced digital EQ can be applied to compensate for speaker positions near boundaries or for the effects of placement behind viewing screens or fabric. The PRO V-Series loudspeakers and PMA amplifiers provide a level of sonic accuracy unparalleled at the price.

Acoustic Measurement Microphones

PCB Piezotronics, a leader in the design and manufacture of microphones, vibration, force, torque, load, strain, and pressure sensors, and the pioneer of ICP technology, now offers a 0.25” prepolarized microphone series to complement its line of acoustic products. Models 378C01 and 378C10 are microphone and pre-amplifier combinations designed to measure high frequencies and high amplitudes. The distinguishing features for this series are the microphone frequency capability, which can accurately measure up to 100 kHz, and the 165-dB amplitude range (i.e., 3% distortion limit).

PCB’s Model 378C01 free-field microphone (Source: PCB Piezotronics)

Model 378C01 is a free-field microphone and pre-amplifier suitable for automotive and aerospace noise source location and array applications. Other common applications include biological and medical acoustic analysis, machine monitoring and defect detection, gunshot analysis, cabin noise, and other applications (e.g., testing in anechoic chambers). Model 378C10 is a pressure response microphone typically used in noise absorption applications within impedance tubes or general noise testing in cavities or small enclosures.

PCB carries a full line of prepolarized condenser microphones and pre-amplifiers. The prepolarized designs can also be used with the same constant current source used for ICP accelerometers, minimizing set-up time. PCB also offers the traditional externally polarized microphones that operate from a 200-V power supply.

Expert Audio Reports & Projects

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The redesigned AudioAmateur.com website is now up and running. As you’ll see, it is a more modern, user-friendly website than its predecessor. You can access your digital subscription to audioXpress as well as read feature articles, interviews, member profiles, and news. I encourage everyone to bookmark the site and visit each day. Stay informed!

Now let’s focus on this issue.

Did you attend the 2012 Munich High End Audio Fair? If not, no worries. Ward Maas walked the floor and took copious notes on interesting audio products and systems (p. 12).

Backes & Müller BM100 on display that Munich High-End Audio Fair 2012 (Source. Ward Maas)

In the first part of his series on electrostatic speakers (audioXpress9/12), Richard Mains provided tips for selecting the proper materials for an electrostatic loudspeaker (ESL) project. This month he covers the fabrication process (p. 22).

Electrostatic cell fabrication (Source: R. Mains)

Turn to page 26 for a thoughtful product review. Gary Galo provides an analysis of Monarchy Audio’s SE-100 MK2and SM-70 amplifiers.

Here you see a pair of Monarchy SE-100 MK2 monaural power amplifiers. The rear panel shows the unbalanced RCA and balanced XLR inputs, binding posts for loudspeaker connections, and an IEC AC power connector. The front panel sports new oval handles and a cleaner appearance than the original SE-100 Delux amplifiers. (Source: Gary Galo)

This month’s interview is fascinating (p. 32). Walt Jung’s interesting life and audio-related work will inspire you to learn, design, and write.

On page 8, Mike Klasco and Steve Tatarunis describe what’s behind a speaker cone. They detail the functionality of speaker stuffing.

Are you engaged in the “sound system debate”? On page 18, Richard Honeycutt investigates the differences between hollow-state and solid-state amps.

The last article in this issue is a thorough review of B&C’s new 18” woofer (p. 38). According to Vance Dickason, “the 18TBW100 uses a ferrite motor design, which is probably going to be the trend in pro woofer design until neo’s prices drop to a more competitive level.”

The October issue is now available.

AX September: Speaker Special

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Each year’s “speaker special” issue is a favorite among audioXpress members and clients. It features in-depth articles about speaker technologies and design projects, without completely ignoring other interesting topics (e.g., tube amps).

This year’s special speaker section features informative articles about a detailed loudspeaker design project and an intriguing electrostatic speaker experiment. We also included a third must-read speaker-related article, but it isn’t in the special section because it focuses on enclosures rather than speaker design. Let’s review each article.

On page 23, George Ntanavaras shares his Horizon loudspeaker design. Inspired by Siegfried Linkwitz’s work, Ntanavaras designed an open-baffle active loudspeaker featuring two woofers connected in series used as dipoles, a woofer/midrange used as a dipole, and a dome tweeter used as a monopole. He details everything from the baffle cabinet design to frequency response adjustments.

George Ntanavaras’s Horizon loudspeaker with front grilles (a) and without front grilles (b).

The Horizon loudspeaker’s dimensions

Turn to page 36 to read about Richard Mains’s excellent electrostatic loudspeaker (ESL) project. Although he started experimenting with hybrid electrostatic speakers about two decades ago, Mains hasn’t lost his passion for them. His article covers techniques relating to ESL fabrication, and includes the materials needed to complete your own project.

Richard Mains experimented with electrostatic loudspeakers. This image shows the diaphragm and stator contacts on the back of the cell (a) and on the front of the cell (b).

The third speaker-related article is about enclosures (p. 8). Mike Klasco and Steve Tatarunis cover the practical uses for enclosures, as well as wood alternatives and experimental design techniques.

The rest of the issue’s content is a nice mix of past and present audio technology. We feature an interesting turntable redesign project and the second part of a series on tube sound.

In the article “A Vintage Turntable Revisited,” Ron Tipton explains recent modifications he made to a 2011 turntable restoration project (p. 12). He describes lengthening the tone arm and why he used carbon fiber tubing.

Ron Tipton completed a second Netronics 350D rebuild. The only remaining original parts are the direct-drive DC motor, the platter, the aluminum nameplate with switches, and the 33-1/3 and 45 RPM speed control.

If you’re into tube sound, flip to page 18 for Richard Honeycutt’s insight on distortion. He covers topics such as distortion signatures and testing.