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Interview: Karl Cartwright, Westone

Interview: Karl Cartwright, Westone

Hi-Fi+: How did you become interested in earphone and CIEM design in the first place? What attracted you to this product category?

KC: I love music!  Whether listening to it or playing it, music has always been very important to me. I have many childhood memories of my Dad playing Herb Alpert and the Tijuana Brass albums, or putting together reel-to-reel tapes of choral and orchestral music for the Christmas Holidays.  From the beginning, I tried to get the best stereo equipment my meagre check book could afford, which meant I was playing music in bands and creating sound-on-sound recordings with old reel to reel tape recorders.  When the Sony Walkman revolution hit in the mid-80’s, the way that people listened to music dramatically changed, and as a result, made the entire experience much more personal.  People started listening to music where they could never have enjoyed music before like when jogging, biking, and walking on the beach, etc.  This was great except for one major hitch (besides having to carry all those cassette tapes); the earpieces just would not stay in the ear.

By this time, Westone was a well-established company in the hearing healthcare industry that provided custom ear-molds for hearing instruments, communications, and hearing protection devices.  It wasn’t long before people were asking us for a solution to the portable-music problem and started making custom earpieces that would accept the Walkman style ear buds. Soon after developing the ‘ear bud custom’, I was approached by a local factory that was having communication difficulties on the production line.  Although they were using Westone’s custom earpiece with an ear bud, the lack of attenuation made it very difficult for team to clearly hear their line supervisors. To solve the problem, we discovered the earpiece had to offer more hearing protection than an earbud based system could provide. The solution was an earpiece that acted as hearing protection first and allowed for communication as well.  By using a balanced armature driver from the hearing aid world, and engineering it within a fully occluding earpiece, we were able to combine the two things this factory needed most: a clear audio signal and hearing protection.

Shortly after that, ’90 or ‘91, Bill Chrysler, who was working with Def Leppard and Rush as they were preparing for their world tours, approached me. They each had a unique problem that they were trying to solve before the tour started. With Def Leppard the volume on stage had grown to such a level that it was becoming extremely difficult for lead singer Joe Elliot to hear the vocal monitors over the guitar amplifiers on stage. With Rush, the issue revolved around the milliseconds of delay caused by all the various signal sources on stage like floor monitors, drums, guitar amps, and side-fills.  Using the same principals as we learned in the factory, we were able to sufficiently reduce the level of ambient sound in the ear to a level that the earpiece became the primary listening source. For Joe Elliot, his voice could be turned up enough in his ears that it could compete safely with the volume of the guitar amplifiers simply because the stage volume in his ears was reduced by 25 to 30 dB!  For Rush, the monitor signal provided a clear and precise listening experience as opposed to a smear from all the different signal sources on stage.

A few years later a stage-monitoring gear company, called Leabody Systems, approached me to work with them to help solve some problems Van Halen was having as they were preparing for their 1995 world tour. Leabody introduced me to the monitor engineer for the tour, Jerry Harvey.  The problem was that Alex Van Halen was using earbud style monitors and was consistently blowing them up as he cranked up the volume to compete with the stage monitors.  After describing the solutions that I had developed for Def Leppard and Rush, we decided to give it a try. We built Alex some earpieces that used balanced armature drivers and featured removable faceplates so that if a driver did fail, it could be replaced in the field.    

It was from this early first collaboration that Ultimate Ears by Westone was born!  Originally we offered both moving coil and balanced armature driver earpieces.  However, once we had introduced the UE5 Dual Driver earpiece, the balanced armature driver had proven itself as the ideal source to use within the demanding on-stage environment. A few years later we worked with Shure to create the first fully occluding universal fit in-ear monitor that was primarily planned to be used in the launch of the PSM 600 wireless monitor system.   As you know, much has changed over the ensuing years – some of them firsts for Westone some for other companies.  Through all if this change, one thing has remained the same: a fully occluding earpiece with balanced armature drivers is the first choice for most people in a critical listening environment.


Hi-Fi+: As you work to create new top-tier earphone/CIEM products, what are the top design objectives you try to bear in mind?

KC: For top-tier custom and universal-fit products, the quality of the sound is the most important consideration.  Without that first priority met, no other consideration is relevant.

Hi-Fi+: What technologies and product configurations best enable you to meet your design objectives?

KC: If you look back at the history of Westone, before we created the first universal-fit in-ear monitors for Shure, before there was Ultimate Ears by Westone we were pioneering the use of balanced armature drivers and fully occluding earpieces in critical listening environments. To that end, the balanced armature driver is one of the first tools we would turn to when creating new designs.  That said, I am a huge believer in using the “right tool for the job” and use the best technology that is available, whether balanced armature or moving coil, to solve the problems of a particular design objective.

Hi-Fi+: What is your assessment of the comparative merits of universal-fit vs. custom-fit in-ear designs?

KC: I am a big fan of both and believe each has its place in a discussion about high-end audio.  Westone is one of the few companies that make both types of in-ear designs and I’m proud of what we have accomplished.  The CIEM is a natural extension of the legacy and heritage that Westone developed from the beginning. We have been making custom-fit products for the human ear since 1959 and have developed an intimate understanding of the human ear.  That being said, for some people the purchase of a custom-fit earpiece is not a consideration, which should not preclude them from a high-quality audio experience. The purchase of a CIEM is a very interesting exercise in faith; you read the reviews, you see what the opinion leaders have to say about the different products but unlike a headphone or a speakers system you can’t “try before you buy”.  With universal-fit earphones, the consumer can demo the products to find the one that sounds the best for their needs.  Because our standards are high for all Westone products, our understanding of the human ear is also applied to the design and fit of our universal-fit line. No compromises are allowed for reproducing the Westone sound signature or fit just because it is universal.

Hi-Fi+: Do you favour particular types of drive units for use in your designs and, if so, why?

KC: First the application needs to help drive the decision as to which type of driver technology will be used for a particular design. Is the design going to be used in high noise or low noise environments, and what is the end user expectation for the product? Is it for critical listening, lifestyle, or convenience product?   In addition, there are many physical factors that need to be taken into consideration when designing an earpiece such as insertion loss, canal resonance, internal electrical and acoustic design parameters, to name a few.  However, the overall motivation for me is that the earpiece never sounds harsh or overly aggressive in any one frequency band. The design should be very detailed yet should have a homogenous character with all the frequency bands supporting each other.

I have been fortunate enough to design listening products that are used in space, combat aircraft, by soldiers in the field, musicians on stage, and audiophiles using both balanced armature drivers and moving coil speakers.  The requirements of a F22 Raptor pilot are very extreme with a unique set of design challenges that need to be overcome. While an audiophile will never have to count on his earpiece surviving a 5g combat manoeuvre, the quality of the sound is as important to him as for the pilot.  The varying sizes of balanced armature drivers can offer many advantages from a design flexibility and packaging standpoint.  This gives me many unique opportunities to acoustically and electronically control the output. 

Hi-Fi+: How would you describe the ideal voicing ‘target curve’ for an earphone or CIEM?

KC: The signature Westone sound is warm and detailed, yet spacious without overtly aggressive highs (as this can become fatiguing over a period of time). Having grown up in the end of what I call the “Tube Era” where we were spinning records and listening to tape, this is the kind of warmth that I call home.



Hi-Fi+: What do you consider your top one or two earphone/CIEM product design achievements thus far? What makes those products special from your point of view?

KC: One of the most important realizations was that by treating the earpiece first as a fully occluding product, and understanding the dependence on an acoustic seal in the ear, we could finally realize the full potential of the balanced armature drivers. Without first understanding this concept, a lot of future work would not have been possible either by Westone or other manufactures.

Each product that I have designed is very special to me particularly when the end product has exceeded the original design goals.  Whether it is the communications earpiece used in SpaceShipOne or a universal-fit W60, each product inspires me and allows me to learn a lesson that can be applied to the next design challenge.

Hi-Fi+: When you listen for personal enjoyment, what types of music do you enjoy?

KC: Now this is a tough question!  I really love all music so it might be easier to say what I don’t listen to!  I will often move through Classical, Jazz, Progressive Rock, Rock, Blues, World, and Funk whether they are old or new recordings. The power of a well-recorded classical piece, the intimacy of jazz, and the textures of progressive music always appeal to me.  When I listen, I want to hear the authentic sound of the artist.  Whether it’s someone kicking the bass pedals on a Hammond in an organ trio, the warm saturated fuzz of Mel Schacher’s bass tone on Grand Funk’s Live Album, the bite and spank from a Fender Telecaster, or the saw-tooth wave from an old Mini-Moog, this is what gets me fired up. As a musician, these sounds are something I have become familiar with first hand and this is what I want our earpieces to reproduce.


Hi-Fi+: What do you think the high-performance earphone/CIEM marketplace will be like five years from now?

KC: I believe digital ear scanning will be a big part of getting a custom earpiece made in the future.  Instead of using impression material and injecting it into the ear canal, a digital picture will be sent to us where the earpiece will be manipulated in virtual space for the optimal fit and comfort.  This will greatly increase the availability of custom fit products as digital scanning technology improves and becomes more accessible to the public.  Westone has been on the forefront of this technology and has manufactured earpieces from digital scans of ear impressions for over 10 years.

Also, as wireless technology gets smaller and smaller, earpieces will be asked to perform many functions beyond just listening to music.  The interesting compromise for the consumer may be how much battery life is required, the transmission protocol, the number of functions a consumer wants, etc. versus the sound quality of the earpiece.   I see two distinct consumer segments that will start to converge over time.  One group will be interested in taking their music with them as a convenience or backdrop to their daily lives.  The other listens to music as an immersive experience and desires the best reproduction available.   We have come a long way in the design of IEM’s, but there is still some distance to be travelled.  It will certainly be interesting to see where the road leads us next.


If you enjoyed this interview and would like to see more like it, plus a wealth of additional headphone-related material, download your FREE copy of the Hi-Fi+ Guide to Headphones, Earphones & Related Electronics by clicking here.


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