Wednesday, 23 April 2014

Incredible close to music III – The Horn and its Extension into Both Ends

The LM22A/597/Siemens KL405 installation. If we weren't used to the look of such horn installations from Western Electric set ups, these transducers look more common to a professional music instrument than as being loudspeaking units.

When I did listen to Mikes Line Magnetic LM22-A horns the first time, some good three years ago, he just had begun to evaluate the complex issues of driving such a horn together with low frequency coupled woofers. At this very first trials he did perform them for me as well as full range units, just limited by their physical abilities. He just had got the LM-22A-horns with the dedicated LM555 receiver units in very late 2010 from Keith Aschenbrenner. His set up was part of the very first delivery of a handful of Line Magnetic horns ordered to Germany. At this time the LM 597 high frequency horn was not already produced, so the hf-extension needed evaluations for alternative solutions.
In the first step Mike did experimented with Altec stage monitors (15'' biflex drivers) as low end of his installation, later he tried several other speakers in baffles and different enclosure types. At this early stage I do remember listening to the setup, without any HF-extension. Of course it would need some extend into the higher frequencies, but it was with its reduction already better than the most other speakers I had heard in my live.
Original drawing from Western Electric in the 1930ties showing two alternative necks, the single and the double pathed for two receiver units to double the output energy.

In the last couple of years before Mikes interest shifted to such medium frequency horn types, he had already started to listen with modern active studio monitors instead of his Phy salabert baffle speakers. He as well switched from his Shindo amplifying chain to modern professional integrated preamps with RIAA equalization with the words: "I need to get something more neutral, I cannot stay anymore with the tasty colored tube electronics and the limitations of the Phy Salabert full range speakers". I do remember very well, when he showed me his completely new bought set up of studio equipment with these spoken words, – and to be honest, I did not understand his decision. Neutrallity is ok, I thought, but for what reason, when the result is a clean unemotional, uninvolving sound presentation, the typical professional sound. I could not follow on with his ideas and was really irritated about this development. For quite a long time, may be a year or so, he followed on with this concept. Finally his friendship with Norbert Gütte from LignoLab brought him back to the carpets of "tasty audio". He, the famous carpenter of such well known loudspeaker enclosures from A23, like the Rondo, did work out the templates for a double walled, sand filled Sato horn design. He combined it with large Double Onken enclosures, as well double layered and sand filled for the woofers. Mikes auditions at Norberts workshop showed him the tremendous properties of such medium frequency horns. In these days, around early 2010 several people were into such Sato horn concepts and a lively discussion about these set ups took place in a German web community. Mikes experience with Norbert Gütte's set up did lead directly into the decision to build up a similar concept for himself. It was right the time when Keith Aschenbrenner came up with the distribution of the Line Magnetic speakers, so it matched well prepared ground...

Schematic of the Sato horn published in the magazine L'Audiophile in 1983

In difference to the original designs from Western Electric (WE12A, WE13A, WE15A), the Sato horn is made completely from ply wood, even the neck is made from wood, which makes the build a little bit easier, if you are planning to do it as project. I am sure this difference will have a not unimportant effect on its general sound attitude, where the Western Electric originals incorporate casted metal necks (mostly made of bronze) in combination with wooden mouse openings. Only the WE22A and The WE16A are made from welded sheet metal and with casted metal necks.
The Line Magnetic horn replica offers two different casted aluminum necks, one for the LM555W receiver  (of course as well the original WE555A) and a another one to adapt other drivers like common Altec types or, if money does not matter, modern japanese equivalents like the Goto range. There are not so many alternatives, which will be able to cover the same wide frequency range, in particular at the lower end of the 22A's physical design (around 250 hz), so you either extend to four or more paths or you stay with a handful drivers to cover the medium frequencies. Here the very first compression driver design from Western Electric, the WE555A sets the pace, even by todays standards. Since this unit was designed as a universal receiver unit for even bigger horn types like the WE12A, but as well for a lot smaller types like the WE14A, used it in these days. Where the big horn designs do start around 100 hz and the the smaller designs will end up at 6000-7000 hz, the WE555A had cover them all. The most of the later designed compression drivers do not cover the half of this range, in particular at the lower end. I have been told, this is a result of the damped chamber behind the diaphragm, other drivers don't have, I do not know.

Of course there are drivers made today, which can even perform lower frequencies (Goto). Isn't it remarkable, that the very first design of the early 1930ties outperforms almost anything made with improved knowledge today? Is there no alternative way than to accept the rifts as a result of a advanced stage of mass production and profit expectation? – Again, a next example for the formerly in several of my articles named "staircase of technical progression" which always leads down.

When I did visit Mike the next time, he had made several improvements in his set up. After testing other hf-drivers from Siemens and other brands, he introduced the common known JBL 075 driver, together with different woofers to his horns. He now did accept the use a frequency dividing crossovers with three paths. The man who told me for almost 20 years about the advantages of crossover less homogenous full range drivers, the merits resulting from the absence of any phase degradation or time delays, was now using a three way separated signal. His experience with Norbert Güttes set up made this change possible. And now it even comes better, he did use a digitally delayed crossover unit and active amplification. Now all signals got converted into digital in order to be digitally separated, equalized, room customized, time aligned, even the already digital ones!  Again, and a bit slower,  c o n v e r t e d  i n t o  d i g i t a l  t o  b e  d i g i t a l l y  p r o c e s s e d  t o  b e  r e c o n v e r t e d  i n t o  a n a l o g u e!
I could not imagine a higher category of worst case scenario than this decision, when I heard about it the first time. At this point I did spend almost eight years to incorporate the wonderful merrits of transformer coupling and directly heated triodes into any of my pre- and amplification stages, and now this!? I had stored away my cd-player around 1995, when I got my Verdier and never missed it again. I do remember years of endless evaluations when Mike started with Shindos pre and power amplifiers, I do remember bronze parts around the tonearms and in combination with his Verdier, silver connections, every step was done after clear evaluation with good money. And now all signal got processed through a 300 EUR unit as a 'jack of all trades' solution with the words: "it is not listenable, may be almost not, – I think, but its hard to compare really…"? And: "electronic components are highly overrated within audio. The most important component is the speaker. If this will do right, electronics have to do the job?"I was more than skeptical about all this new "perspectives", since my experience of 20 years did tell me a different story.

He did in this early beginning, what lots of people were doing with their Sato horn's, they correct all frequency deformation and time delays together with additional room alignments to shape the sound stage to an ideal form in a tremendous matter. The three active channels are forwarded to three separate power amplifier stages per side, all were modern smps amps. Wit this set up Mike found a best possible solution in his room and if you would have asked him, he would have said: "I cannot get it any better at this stage". With digital correction systems you always have a toy to play out several curve shapes, as a result you will have ten or twenty curves, were each seem to better the next one, if you don't get lost on the way.

I do remember in his history a never ending evaluation of preamplifiers like the Kaneda, but mainly tube amplified designs with lots of different design topologies like SRPP, standard triode cathode followers or vintage pentode circuits, before he settled down with a first Shindo preamplifier.  In the first step he got the classic beginner menu served as "Claret" somewhere in the early 1990ties, shortly afterwards extended with a Shindo Concertino stereo power amplifier. More complex designs from the Shindo line followed, since it ended up in the late 1990ties were it is today with the Monbrison preamp and the 300B Mono Amps. I do remember listening evaluations of original 300b tubes from the fifties (engraved base), from the 1960ties (yellow printed base), reissues from 1990ties, were the best tubes was heaven, all others went into the second choice spares box. But with the new verdict "electronics are overrated", all these experiences were obsolete! Really?

To look at it from a different angle: For more than 20 years Mike followed an idea, where audio representation was defined by physical sensation, other than ingenious superficiality. We did learn, that a acoustic instrument succeedes by its harmonic properties, rather than its measured frequency spectrum. We were able to transmit this experiences to audio components with some success. With this idea all components have been evaluated through their harmonic properties, finally choosen for their musical superiority.

My irritations and skepticism about his new philosophy did reduce my interest a bit in 2011, so it took a year that I came back to have a look at the new advantages. Mike had completed with the smps amps, instead he reinstalled his classic tube amplification chain from Shindo. The digital correction was rejected, were now passive crossovers had taken place. He did use a Isophon 15'' woofer in a dipole enclosure and he had the new Line Magnetic LM597 high frequency horn installed, were the JBL did work before. The only adjustment was now a auto former were the energy for both horns got reduced at -3db to match the woofers output.

Again we did listen to digital program material, but this time even without the typical familiarization process to his new chain the resolved sound quality struck my down. Almost pure warm music attracted me in a way I never had heard before. Almost a holographic soundstage of widest possible dynamics and pure harmonic refinement surrounded me in the listening position, a level of naturalness I could not imagine before. Completely overtaken and deeply impressed I did drive home, knowing that I did hear something today, which opened my eyes for the advantages from big horn developments. I did learn that such a horn can do somethings, other designs are just not physically able to perform. Outstanding!

Line Magnetic 15'' field coil bass LM-BA5

Since that experience a good year ago, the Isophon woofers got exchanged to other woofers, like the dedicated Line Magnetic 15'' field coil driver. But finally Mike did end up with a "historic matching" solution how he said. The Siemens Klangfilm KL405's are permanent magnet units and got integrated in a double stacked array within his new made dipole enclosure to match physically the width of the LM22A. With this doubling principle they can as well double their output level, so that the autofomer for the horns can can be set out of service. I would not be able to clarify between the Isophons and the Siemens by remembrance, but I can say it is the best low frequency performance I did hear so far, completely fast, deep and three-dimensional, in a perfect balance of energy and transparency. It was so good, that it changed my longtime evolved ideas for my Tannoy enclosures, were I did realize a similar design idea now with a before unbelieved success.

Mike told me about the LM597 Loud Speaking Telephone which he got as newest extension now, I did read a lot about the supposed qualities of the originals to be the best hf-frequency driver available. But now I could not say anything about it, I just did visually realize that they were there. Right, that is exactly the point. This high frequency driver has a rare attitude, it is unobtrusive, completely invisible in acoustic terms, almost all other designs are not. I am personally very sensitive with tweeters, in particular with horn tweeters. It does not take long, when more conspicuous drivers are on play, that their dominance bring me into a feeling of unease. I never did like to listen to the most Altec drivers in longer terms in the past, even when their performance is very attractive at the first glance. This is one reason I personally prefer the Tannoy Dual Concentric, its integrated hf-unit is one of the best horn tweeters ever made, it is very similar in character to the LM597, – invisible and perfectly refined. Is that driver the key to the perfection of harmonies in Mikes set up. Yes and no!

In difference to himself I would judge several things like the complete chain for that reason, with its perfectly matching components, in particular the majestic analog front end, has a enormous influence to this harmonic presentation. With other words: I believe about the influence of built quality of electronics and do rate them as important for audible harmonic qualities. I still believe in all these little adding inexplicable effects from several components, like paper-in-oil-capacitors throughout the signal, as well now the new analogue crossover. The absence of switched power supplies and integrated circuits towards selected elaborated tube amplification, as well the rely to wooden materials in corporation with physical resonances and all the little forgotten improvements, which were long term approved in order to harmonize the audio signals as a chain. I think at this actual state his chain has reached attributes of performance, were musical harmonies dominate the character of audio perception and make the technical process of its origin completely forgettable. I did warn Mike several times just to settle down now with what he has, after more than 30 years of expedition the nirvana of audio, but Mike would not be him, if he will not start the next stage of examination. I know already what it will be. There are still some white areas on the map of the 1930ties to go. I would fear to destroy the rare grown tender plant. I do not know another audio set up of this stage of refinements, were the illusion of naturalness in tonality and performed dynamics is so perfectly present…

Read on about the final part soon, Volker