Preparing a trip to the USA for the CES and a bit of R&R with my family beforehand, I stumble upon an audio site that I didn’t know about and which was going into a great deal of details about open baffle and point source speaker design: www.linkwitzlab.com
I have been researching open baffle speakers for my blog after reconnecting with my friend Alain Wacquet who designed such speakers in the 80s under the AW Audio brand and with whom I shared many a hifi show in France at the time.
His designs were really “out there” at the time and he had just shared with me a review of his penultimate design: the EA-16, released in 1987. (His last design in 1995, the Transparence, was produced in very limited quantities, and cannot be called a production model, really...)
I was also trying to find out if it would be possible to listen to the Emerald Physics speakers at the CES. They use digital filtering and equalization to produce amazing results as I read in many a review. Unfortunately, this didn’t happen...
The funny thing is that the name of Linkwitz Lab should have been an instant hit, but it took me a couple of emails with the owner of the website for the penny to drop: I was indeed talking to Siegfried Linkwitz, who made himself famous by teaching the KEF engineers about group delay and transient response together with his colleague Russ Riley in the 70s when KEF was shopping around to buy a state-of-the-art FFT analyser and ended up with Hewlett-Packard in California, where Siegfried and Russ were working at the Microwave Division in Santa Rosa.
I encourage you to read an interview that recounts the story in quite a humoristic fashion: http://www.linkwitzlab.com/AX%20interview.htm
Interestingly enough, one, I was designing a speaker system at the time using second order Linkwitz-Riley filters, and two, I was working at HP, and met Siegfried in Amsterdam in 1985, we think, not realising who he was and obviously missing out big time on an opportunity to pick his brains!
So, this time around I was not going to miss the chance to meet with him, as I was in San Francisco for a few days and he lives just up the road in Marin County. He was generous enough to spend the whole morning of Boxing Day with me, showing me his lab/home office, talking shop nonstop for a couple of hours and then sitting down to listen to his unusual creations: the open-baffle system Orion and the point-source system Pluto. We had a great time!
Before we go any further, let me explain where his Orion system seats in my experience of electrodynamic open baffle systems (which excludes my beloved MartinLogans...):
AW Audio used a quite complex passive filtering and some physical time alignment between drivers. It mainly used a series of 12cm drivers and one tweeter in a two-way arrangement.
Jamo is the only mainstream manufacturer to have wandered successfully in this genre, although my last listening session at the Melbourne Show was quite a disappointment, but I believe it was a case of the room not being at all suitable for such a design.
At the other end of the design complexity, we find the Emerald Physics which uses a Berhinger DCX2496 as a digital filter and equaliser and several amplifiers to get the job done, or Kyron as seen at the Melbourne show, an even more extravagant foray into the “box less” adventure (10 drivers per channel each driven by their own amp – 700 watts of them per channel)!
Siegfried Linkwitz has a more middle-of-the-road approach with his Orion system now in its rev4 avatar, using only 5 drivers per channel all from SEAS, each equalised and 3 way electronic filter ( which he calls an ASP, Analogue Signal Processor), driving your own amps (Bryston 9B SST anyone???).
If you are prepared to build a pair yourself, then the budget is less than 4000$ for a pair. Just add your own amps, preamp and sources (Siegfried uses an OPPO BDP-95 Blu-ray Disc Player as his primary source, and audio files stored on his computer or digital radio).
Before I tell you about my listening impressions, let’s first talk about the Pluto speakers...
Another favourite acoustic topic of mine has always been the elusive “point source” speaker, one that is supposed to solve a lot of our listening problems, i-e stable image, absence of “sweet spot”, coherent phase, time aligned response and so on.
Cabinet size, shape and driver positions are all part of the equation and it is believed that all these limitations would disappear if (and it is a big “if”...) we could design a single driver, very small, full range, with high efficiency and power handling. I guess you could call it the Nirvana of speaker design!
Many attempts have been made and the coaxial driver “a la Tannoy” or more recently the Uni Q from KEF and their recently introduced “Blade” are good example of these tribulations.
A bad example, although a commercially successful one could be the Acoustimass from Bose...
The Elipson spheres back in France in the 70s were another elegant solution to this problem. Triangle and Microphase in the 80s attempted the miniaturisation of the Elipson 4050 with their 1180 and SAT+SWS or Triton designs, trying to put some WAF into an acoustically well designed satellite/subwoofer system and both had some commercial success.
More recently, the “Cube” by Vismes in France, Audel in Italy or the i90 from VAF in Australia are good examples of small point speakers.
But we were all unaware that Siegfried Linkwitz had designed a similar system in the 70s and abandoned it to concentrate on the open baffle variety.
Fast forward to 2002, and Siegfried, in the course of another assignment, discovers a 2” tweeter (from Aura) that can reproduce frequencies down to 200Hz! He also was toying with 5” drivers as a woofer (now from SEAS) and this is the result: an omnidirectional speaker system, very close to be a point source, with built-in amplifiers, 2-way electronic crossover (1kHz) et equaliser called the Pluto, now in its 2.1 revision.
“My goal was to obtain an acoustically small source with wide and uniform sound dispersion over most of its frequency range. Next to dipole radiation, as with the ORION, I consider omni-directional behavior desirable, provided that either the room has neutral acoustics or that one listens to such speakers from a close distance.” says Siegfried on his website.
Yes, I know their WAF is appalling, apart from the small size and light weight, which means one could tuck them away in a cupboard and have them deployed when needed, but put a blindfold on, and listen...
Also, many DIYers around the World have come up with more “spouse friendly” designs...
These are mind blowing little marvels. The only time you notice them at Siegfried’s place is when there is a bit too much bass and the piped woofer excites the floor boards.
I have not had a chance to listen to them on a concrete floor. My guess is this problem could disappear, although remember we are talking about a 5” driver in a closed box...
As an aside, I am generally suspicious of speakers with a crossover at 1kHz or so, but there is NO WAY you can feel this if you don’t know, and even knowing, the integration between the two drivers is astonishing, the image very stable and the so-called “sweet spot” fairly wide.
We even found my favourite test track on Siegfried’s hard drive: “Private Investigations” from the Dire Straits album Alchemy – clearly not what Siegfried listens to sipping coffee...
Now, moving on to the Orions, we managed to listen to some of the same tracks we had used on the Plutos, and what was already quite extra-ordinary on the Plutos became almost miraculous on the Orions. It was like there were no speakers, as we were transported into the recording venue: no distortion, wide and stable image, high dynamics, in a word, pure music.
I can only compare this experience to my recent audition of the Ocellia speakers in Paris recently as well as listening to hi-res digital recording by AIX Records via Oppo BDP95, Bryston amplification and Thiel speakers at the CES: same absence of “HiFi-ness”, same impression of being there, same sheer musical pleasure...
Merci beaucoup Siegfried, for spending some time with me and let me in your world: it will feed some long lasting memories and maybe some more speaker designs on my part...
PS: You can find a lot more information on these amazing speakers and how to build them here: www.linkwitzlab.com
PS: for my Australian readers, a printed (and edited...) version of this article has been published by Australian HiFi Magazine in its March 2012 issue and posted online here: http://www.avhub.com.au/index.php/Video/Audio-Interviews/Hi-Fi/siegfried-linkwitz-an-afternoon-with-a-legend.html