Here is a 2-way satellite and subwoofer system that was published 1978 in Wireless World. I was aiming for a small box size to obtain wide dispersion. The woofer is flush-mounted to radiate into half-space. The satellites hang from strings and away from reflecting surfaces. The satellites transition from full-space, omni-directional radiation to increasingly forward radiation above 500 Hz, though with a broadening again as the tweeter takes over. Equalized for flat on-axis response, this system is an early attempt at reducing the off-axis frequency response variation which is typically summarized by the 'power response' of a loudspeaker. |
1) A small 2-way closed-box speaker with 8' and 1' drivers crossed over at 3 kHz. 2) The KEF 107 as a 3-way speaker that was typical for good speakers of the time. 3) The L-07 was 3-way dipole speaker with front and rear firing tweeter and a wall mounted closed-box subwoofer. |
Its W-M-T/T-M-W arrangement of drivers narrows the vertical dispersion somewhat and reduces total power output further. The increasing beaming of the front tweeter with higher frequencies and shorter wavelengths is compensated power-wise by a rear tweeter. The surface mounted subwoofer has 3 dB lower total power output than in free-space for the same on-axis SPL. The above power response estimate for the L-07 is an improvement over the 2-way satellite/subwoofer system. This was clearly audible as a smoother and more open sound. |
The Quad ESL-63 electrostatic loudspeaker has been a strong inspiration to me. I loved the neutrality and realism of its sound the first time I heard it. Peter Walker designed it to act as a dipole point source by breaking up the large radiating surface into circular rings which were then driven from a tapped delay line. Besides having exceptionally low non-linear distortion, this is a speakers which has a minimum phase response. This should be of particular interest to audiophiles who consider 'transient perfect response' - as much as that is physically possible in a band-pass system - to be of importance for their music enjoyment. The ESL-63 has two prime weaknesses: Its tweeter disc is acoustically large which leads to beaming and a tight sweet spot. It has limited low frequency output volume and overall dynamic range. I like to listen at near realistic sound levels and so my goal was to design a speaker that preserves the admirable characteristics of this one and some other planar speakers, but without their shortcomings. |
This goal set me on a journey from which the L-07 is an early example. This design became simplified, and was described as a 'compact dipole speaker' in one of my AES papers, using M-T-M main-panels and separate dipole woofers. From this I developed a line of Audio Artistry loudspeakers, the Dvorak, Vivaldi and Beethoven. The PHOENIX project belongs to that family. With the availability of improved drivers it became possible to build an even more compact open baffle speaker, to improve the uniformity of the polar response, to extend low frequency response and volume while maintaining a very large dynamic range. This is the ORION. |
The total SPL capability of the ORION can be further increased by adding two closed box, monopole THOR subwoofers. This might be needed for home theater applications or where extremely high volume levels of music can be tolerated in a domestic environment. This turns ORION into a 4-way system with added crossover at 40 Hz. Now the tweeter becomes the system component that ultimately limits the maximum SPL. |
Similarly, it is the tweeter that ultimately limits the maximum sound output capability of the Audio Artistry Beethoven-Grand. This open baffle speaker, though, was designed for much larger rooms. The symmetrical driver arrangement on the physically very tall main panel maintains a more constant acoustical size of the source and gives increased vertical directivity. Thus the speaker reaches deeper into the room for greater listening distances. The large number of drivers keeps non-linear distortion very low.The dipole woofers employ eight 12' drivers each. |
A loudspeaker of completely different size, cost and shape is PLUTO. It approximates an acoustic point source, an almost perfect monopole. Being omni-directional it has a power response that is essentially flat from 60 Hz to about 3 kHz where it begins to roll off as the speaker becomes increasingly forward aiming due to the increasing acoustic size of the tweeter with increasing frequency. PLUTO illuminates the room very uniformly and thus the response from an acoustically neutral room adds no coloration to the direct sound. Tonality and openness are almost indistinguishable from the ORION when set up corresponding to their reverberation distance. Imaging is superb. The small drivers limit, of course, the maximum low frequency SPL. THOR subwoofers could be added, but that would defeat the speaker's small size and easy portability for optimum placement in small rooms. |
Over the years I have had stimulating email exchanges with its designer, Kolja Willimzik. |
'Where is the acoustic center for a driver in a baffle? Joerg Panzer, Stan Lipshitz, Jim Hayward, Laurie Fincham, SL | Wolfgang Klippel and John Vanderkooy |
Don Naples, Wood Artistry, demonstrates his ORION creation in Bubinga wood with Ebony trim. | ... as people listen and Janet Naples looks on |
J - Burning Amp Festival, October 2009Just like last year this was a fun event and a great opportunity to meet interesting people, to talk audio stuff - some of it far out for me - to see unfamiliar products and to do some listening. All this in a relaxed, slightly chaotic happening, but free flowing and with a welcomed absence of 'audiophile neurotics' and in a good spirit. My interest is, of course, loudspeakers and so I looked forward to hearing two exotic full-range drivers that would be mounted in Nelson Pass's large open baffle loudspeakers right on location. The first was a new Feastrex pair, the only one in existence and build with paper cones by a Japanese master craftsman using centuries old techniques for making archival papers. The drivers had very large diameter field coils. So did the Lowther pair, except these were in long cylinders. Both needed magnet supports since the baskets obviously could not hold the weight. The large 15' woofers had their own amplification and there was no shortage of bass output. The full-range drivers were straining and rather colored, though the Lowthers sounded more neutral. It was like viewing a slightly abstract painting when I wanted to see a photograph of the landscape. I did not hear anything that would have given me an incentive to investigate such drivers or to re-evaluate what I am doing. I was quite surprised to learn the retail prices of around $48,000 for the Feastrex pair and $4,400 for the Lowther pair. Nelson showed and used a clever power amplifier with a single depletion mode MOSFET device that he had designed and built the day before the Festival. With a slight amount of FET linearization and about 5W output capability and it was used for the Lowther pair. It all seemed to me an invitation to experiment with audio and to have fun with it. http://www.diyaudio.com/forums/clubs-events/ |
The Burning Amp Festival - 2008 in nearby Sausalito, California, gave me the opportunity to talk about my current preoccupation with phantom images in 2-channel audio playback and how they relate to how our brain has been wired to function for survival over millions of years. This has definite implications upon loudspeakers, rooms and recording techniques. The professional and DIY exhibitors for this one day festival came from a rich variety of backgrounds in amplifier, loudspeaker, turntable and electronic design. Their audience were dedicated audiophiles and each other. This was an opportunity for enthusiasts to meet as they pursue their passion. I briefly demonstrated Pluto-2, driven from an Oppo DV-980H, which generated a welcomed surprise and comments of musicality, imaging and warmth of sound. I had a good time at the event and returned home tired but satisfied from talking with many attendants. |
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