Braun Speaker LE 1 (ex Adventure LE 1)

Teil 1 des Tatsachenberichtes von Burkhard Vogel zum Lautsprecher LE1 von Braun in englischer Fassung. Mit viel Liebe zum Detail beschreibt der Autor die Schönheit und erstklassige Qualität der guten alten Röhrentechnik.  

A factual report0

A test report in a 1982 copy of HIFI-Exclusiv1 magazine caught my eye: as part of a series of articles on electrostatic speakers, the magazine had tested a combination of the Braun CSV 60, PCS 52 and the LE 1.

The fact that the report was far from negative with regard to these venerable products was something of a surprise considering the almost biblical age of the hi-fi system: the author estimated it to be some 20 to 25 years old. In fact, the unprejudiced reader could detect a hint of respect for technology created in the valve age, for a system, which sounded the way one would expect electrostatic speakers to sound: just great!

The discovery of this report marked the beginning of an ‘addiction’, fed still further by an acquaintance in Berlin, the proud owner not only of a pair of LE 1 Speakers but also of a pair of QUAD ESL speakers, the ‘donors’ of the inner workings of the LE 1, manufactured by Braun under QUAD license.

However, a further 11 years were to pass before a collector of Braun products took pity on me and, in late 1993, relinquished two of his treasures, in return for a suitable ransom, to a man thirsty for ‘uniqueness’: product no.’s 2254 and 2940, for the sake of simplicity referred to here simply as A and B.

Once installed in their new home, A and B were connected to a suitable amplifier, a favorite CD (Büdi Siebert, Wild Earth6) was chosen, eyes closed in anticipation and a more or less prone position assured, all human senses trained on the revelation about to take place - but not before shifting the furniture in accordance with the special rules that apply to positioning electrostatic speakers.

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Cover of Design+Design No 32

The collector had naturally allowed the two objects of my desire to be tested, not withstanding a possible sale, and had provided me with his own assessment of the sound quality. The report proved to be accurate, although the statement that one of the two speakers (A) was somewhat higher-pitched than the other had raised an eyebrow even when I made the purchase, but I had put it down to the fact that the speakers were, after all, some 30 to 35 years old.

Unfortunately, it was not that simple. Acoustic analysis of pure sine-wave tones in the low-frequency range showed that the bass panels of speaker A, of which, in addition to a high-frequency panel, there are two in every LE 1, simply did not work.

What a let-down! Opening the speaker up (12 screws) and taking a look was simple enough. But my first impulse was to close it up again very quickly because I was greeted by a stench, redolent of a damp, very mouldy room, so strong that I almost lost any desire to look for the root cause, let alone consider a repair.

The problem was the felt used to dampen the high-frequency sounds at the rear in order to make the position of the dipolar speaker less critical. The source of the revolting smell landed in the bin, but not before having been measured. After all, a suitable replacement had to be found.

If electrostatic speakers do not work, the number of possible causes is limited: either there is a problem with the high-voltage supply, the speaker is not getting any ‘juice’, there is a short-circuit due to corrosion or there is mechanical damage.

A check of the high-voltage unit, which should supply 6,000 volt for the bass panels and 1,500 volt for the high-frequency panel, was a sobering experience. 6 kV was not to be found anywhere, but 1.5 kV was in ready supply; and since there was no frequency-separating filter in the true sense, the entire range was being pushed through the high-frequency panel, so it was little wonder the speaker was high-pitched.

Whatever QUAD2 (the potential supplier of replacement parts; there is also a German distributor, based in Koblenz) can do, I can do it better and quicker - at least, that’s what I thought.

But try finding 3 kV capacitors (10nF), and just a small handful. But that’s what you need, together with several 1kV diodes (1N4007) to create a high-frequency cascade voltage transformer for converting 680 V AC into high-frequency, polarizing direct-voltage.

After countless telephone calls the length and breadth of Germany but after spending less than DM 30,- for the components themselves, two high-voltage units, as a precautionary measure, were installed in A and B; but A’s bass panels remained stubbornly silent. This was because they had been damaged, as closer inspection revealed, by the crime of long-term exposure to a damp environment, leading to corrosion and short-circuiting.

Have you ever tried to order a product directly from Great Britain? No? You should try it! It’s a very educational experience - not just in terms of English language skills but also in terms of the very different way of doing business. The QUAD company, whose grand old ESL was sold approximately 55,000 times over and which is now, unfortunately, no longer manufactured, maintains extremely well organized stocks of all possible spare parts for the ESL, and, as the only supplier of parts known to me at the time, was called upon to provide two replacement bass panels.

However, the march of progress has continued in the form of further development of the ESL and Mr, Peter Walker3, founder of the QUAD company, has now brought out a special protective circuit for the ESL tweeter, limiting maximum voltage at the speaker to approx. 33 volt in order to prevent the popular but destructive habit of using the ESL/LE 1 with extremely powerful amplifiers. When the sound is turned up too far, there is distortion - and the user is alerted to the problem. And there is no need to buy a new high-frequency panel! As a result, the purchase and installment of this device is highly recommended.

Two months and several faxes later, I had everything I needed and all that remained was to carefully mark all cables, draw a circuit diagram (I didn’t manage to find an original from Braun) and remove a large number of screws from the LE 1 frame. Murphy’s Law dictated that after removing 25 screws I discovered it would have been sufficient to have unscrewed the 26th. I had underestimated Braun: each and every screw has its place and purpose. After all screws had been extracted, the central rod, which is under tension and gives the panels their unique rounded form, a form which continues along the front grille, was carefully removed, the frame could be lifted and the panels taken out one by one. But not before first removing the electronic components: power-supply transformer and high-voltage unit, audio transformer and a number of high-voltage cables, all done with the utmost care because the back of the panels is very sensitive, with a waver-thin plastic cover to protect it against dust, and does not forgive rough treatment or blobs of solder.

I mention only in passing that a certain amount of skill as a handyman is required for such tricky mechanical problems, not to mention electronic expertise. In other words, it is not a job for a beginner, particularly as the opportunity presented by such a major overhaul should be seized to introduce the concept of earthed sockets to the LE 1.

As speaker A stood, or more to the point, lay there totally naked, the idea of providing it with a new outfit seemed only natural, especially as the cabinet and body of the speakers showed signs of wear and tear, A call to the ‘inventor’, Prof. Rams, elicited the precise colour codes, but the more I envisaged in my mind’s eye the two speakers after a fresh lick of paint, the less I liked the idea: Somehow, I felt it was better to find a way of adequately presenting these venerable products without resorting to fresh make-up. Instead, I launched into a clean-up campaign of major proportions and the result is certainly no disgrace - however, the use of caustic cleaners should be avoided at all costs, otherwise the paint doesn’t stay where it should, on the speaker.


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Content of Design+Design No 32


A small mechanical device of my own making allowed an earthed socket to be installed, but there was no way to create space for an on-off switch (anyone using a PA 4 as the driver ensuring, admittedly, a very good sound, but please use the protective circuit – could employ the on-off switchable mains power sockets of the CC 4 system; anyone wishing to stick to the CSV 60 or Studio 2, which offers a less satisfying sound, should continue to use the corresponding special cables but does not have to retrofit earthed sockets), but a possible solution would be to simply fit a switch like those used on table lamps to the main power cable. Contrary to popular opinion, the speakers must not be permanently connected to the mains. Any acoustic advantage is wiped out by the wrong kind of amplifier and cable. The reason being that the LE 1 is, unfortunately, quite an electrical challenge: input impedance of 23 Ohm at 20 Hz rising steeply to 100 Ohm at 66 Hz and thereafter dropping rapidly to a plateau around 15 Ohm at between 300 Hz and 3.3 kHz, then falling gently to a highly current-consuming 3 Ohm at 20 kHz. This requires amplifiers, which are almost as stable when in idle mode as they would be at 3 Ohm, or, better still, at 2 Ohm, because a certain variation in performance is normal. It’s also worth noting that the QUAD ESL can do even better: 1.5 Ohm at 20 kHz.

The very special crisp ‘airiness’ of an electrostatic speaker places high demands in terms of hum and hiss on the amplifier. After all, the sound seems to come out of ‘thin air’. The signal-to-noise ratio at the power amplifier output of -86 dBV (limited to a frequency range of 20 kHz) was, in conjunction with high stability and the right current, one of the major preconditions to achieving the level of sound quality I wanted. In other words, it was not good enough to simply restore A and B, I had to develop and construct a corresponding amplifier, something which required a number of attempts before finding a satisfactory solution: so I was able to make good use of the time it took for the parts to arrive from QUAD. And it was really not such a bad thing that one of the bass panels was damaged during transport, allowing me three further weeks of amplifier tests before the replacement arrived.

The wait was made all the sweeter by being told, when filling in the form for compensation for damage, that my application would have to be translated into French, the melodious language of international postal communications. And I now have no doubt whatsoever of the ability of German post office workers to speak French. You learn something new every day, even if you are simply repairing a loudspeaker.

Of course, the restoration work also included removing the carbon-film resistors (8) in the audio transformer and installing 2-Watt metal-film resistors with only 2% tolerance in their place, because the old resistors had drifted by as much as 20% from their rated values.

Once I had cleaned all the parts, removed the dust (using only a very weak vacuum cleaner), installed and soldered them in accordance with the circuit diagram and, accompanied by much anxious perspiration, I had managed to bend and push the panels into place with the central rod, not to mention replacing huge numbers of screws, the great moment arrived: power, voltage and music on! And it worked!

My personal listening ritual was the same as the one described at the beginning of this article, but the choice of music was more critical because this was a test situation: Beethoven’s4 Waldstein Sonata, followed by his Sonata No. 21 were needed to provide the necessary proof that even today a well-maintained LE 1 is not only worth the money paid but, in the right position in the right room, can rival the majority of modern speakers, and in many aspects, is better. The CD, with its wild attacks on the piano, pulls no punches, neither with speaker, nor with the amplifier, and punishes any weakness immediately. The resolution of the LE 1 is phenomenal, some-thing which can easily be demonstrated by listening to Beethoven’s ‘Elise’, a further, extremely well-produced CD5: it is even possible to hear (and one’s immediate thought is that there’s something wrong with the CD, but there isn’t), the sound of the piano stool creaking.

My conclusion: Prof. Rams’ great design, now some 40 years old, is and remains, even today, a yardstick of quality for the demanding listener, a listener who also wishes to enjoy his music in the corresponding interior environment, for which the LE was, after all, created; it is a design which touches the heart strings.

Health warning: extended listening can be addictive!


03 Fig 01
Fig. 1 Casing of LE 1

Fig. 2  A complete studio 2 system with the electrostatic boxes LE 1

Fig. 3  LE 1 Front view


06 Fig 04
Fig. 4 LE 1Side view  


07 Fig 05
Fig. 5 LE 1 Rear view

Pics: Braun AG und Jo Klatt (Figs. 1 & 2)

Additional pics: B. Vogel (Figs. 3 ... 5)



0.  Reproduction of the 'Adventure LE1 'article in Vol. 32, Design+Design, 1995;

     Courtesy Jo Klatt Design+Design Verlag, Hamburg

1.  HiFi Exclusiv, Vol. 1, 1982, p. 48-50

2.  Formerly: QUAD Electroacoustics Limited, Huntingdon PE 18 7DB, UK

     German supplier: QUAD Musikwiedergabe GmbH, www.quad-musik.de

3.  The essential ESL, Hi-Fi-News & Record Review, November 93 S. 68-69

4.  Denon CO-74653, Beethoven: the sonatas for piano vol. 4 with Bruno-Leonardo Gelber

5.  Highlights CD 5 von Stereoplay

6.  Biber Records, Nr. 66461


Abenteuer / Adventure Braun LE1.pdf