LOUDSPEAKERS

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go to: Contents | Features | Bookshelf, Stand-Mount and Desktop | Floorstanding | Editors' Choice Awards Andrew Jones • Technical Audio Devices (TAD) Speaker Designer Roundtable Being born in stereo (Andrew has an identical twin brother who is left handed while he is right—making them a stereo pair from birth!) made a career in audio perhaps pre-destined. Gaining an interest in electronics and hi-fi in his pre-teens informed his decision to study Physics at university, followed by six years of research in audio topics such as computer modeling of crossover networks and active noise cancellation. In 1983 he was invited to join KEF Electronics as a research engineer, progressing to become Chief Engineer. After eleven years at KEF he moved to the USA to join Infinity. In 1997 he was invited to join Pioneer to lead the engineering group in designing speakers. This culminated in the formation, 10 years ago, of the consumer division of TAD, and the exploration of designs without compromise. His spare time (what spare time) is split between travel, tending to his dogs and cats (yes, plural, very), and archery (he recently qualified as a coach and is to be found teaching each weekend when he is home at the local archery range). What are the particular challenges and trade-offs of designing a small loudspeaker Which sonic qualities are you primarily trying to optimize, and which qualities are you most willing (or compelled) to give up Small speakers typically lack the sense of scale and dynamics of large ones, the qualities that give you that sense of reality, effortlessness, and ease. In contrast they can disappear in a way that is difficult to achieve from large speakers. The challenge is in retaining both. Typically smaller speakers are used in smaller rooms, so the designer can take advantage of this to some degree and use the room gain to offset the loss of dynamics in the midbass region. Also smaller speakers are normally equated with lower-cost speakers and that brings its own set of compromises that are independent of size. When cost is divorced from size then the performance loss from small speakers can be made very small indeed, and be confined only to very low, very loud bass. Do you have your own design techniques that maximize the performance of small designs Generally, the first thing to go from small speakers is bass. In order to maximize bass extension, one must necessarily give up efficiency. This means that to get any degree of real-scale dynamics you must put in a lot of power. The speaker not only has to handle this power without damage, it must do so without dynamic compression. Compression in the mids and highs can be dealt with by designing the drivers to have high inherent efficiency, but for the bass driver this is not an option. Piling on more magnet, or using a lighter cone, only gives less low bass. For any size of cabinet and required bass extension there is an optimum set of parameters of mass and magnet strength that will give the correct bass alignment, so the only solution is to design 30 Guide to High-Performance Loudspeakers www.theabsolutesound.com previous page NEXT page
go to: Contents | Features | Bookshelf, Stand-Mount and Desktop | Floorstanding | Editors' Choice Awards Speaker Designer Roundtable voice coils and magnet structures that can take these high power inputs without thermal compression. To solve the issue of high sound level at low frequencies one must also design the bass driver to have large linear excursion to make up for the loss of cone area. A by-product of all of this is that one cannot adequately balance all of these requirements in a two-way design. Has your design work on larger loudspeakers informed your approach to stand-mounted ones The large speaker serves as a reference for the qualities one is seeking from the smaller design. Starting with types of music that do not overly stress the smaller speaker one can listen back and forth to determine how close is the essential sound quality of each. Then listen to more stressful music to explore the limitations of the smaller system. Beyond that, at least for TAD designs, the smaller speakers are very much identical in design and implementation to the larger ones: three-way designs, identical mid/treble drivers, and near-identical bass drivers. This guarantees close sonic signature throughout the TAD family. One other advantage that a small speaker can have is less cabinet vibration. Smaller structures tend to be easier to control than larger ones. What, if any, sonic and technical advantages do small two-ways have over larger multiway systems I hinted at this earlier. I do not blindly believe that simpler is always better. Small two-ways suffer severe limitations and compromises in what they can achieve compared to well-designed three- or four-ways. There is a belief that the greater the number of drivers the more one can hear the transitions and the less homogeneous the sound. I believe the exact opposite. The compromises involved in a two-way make the transitions more likely to be heard, particularly so if we are comparing a small two-way to a large three-way. Large long-throw bass drivers do not do so well in the mids; their off-axis performance is compromised making the transition to the tweeter more variable especially off-axis; their cone colorations are more audible; internal standing waves in the box are more of a problem; cabinet vibration is more audible, and so on and so forth. My ideal high-performance, small two-way speaker is a three-way. 31 Guide to High-Performance Loudspeakers www.theabsolutesound.com 728 third street, unit c, mukilteo wa 98275 usa e: sales@vanaltd.com / www.vanaltd.com previous page NEXT page p: (425) 610-4532 NEXT / f: (425) page 645-7985
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