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Since the early 1970s, Backes & Müller has been the technological spearhead of active loudspeakers in hi-fi. In 2023, the Saarbrücken-based company turned 50 and can look back on legendary milestones. But they still have big plans... (Source: Backes & Müller)

50 years of Backes & Müller: always active against the current

50 years of Backes & Müller: In the 70s, 80s and 90s of the last century, there was hardly a name in German (loudspeaker) hi-fi that fascinated fans more than that of Backes & Müller: The active speakers from the Saarbrücken-based loudspeaker manufacturer had a virtual subscription to the reference throne of the most important hi-fi magazine at the time (Audio) and even made it into the living room of Mikhail Gorbachev – the man who enabled Germany to reunify and made the world a better place for a short time with glasnost: So let’s take a long look back

In the early 1970s, engineer Friedrich Müller had a pretty good idea: he added inductive negative feedback to the active technology, which was already working well at the time (but was little appreciated). The term electrified hi-fi fans for years, because it was high-tech that other loudspeaker manufacturers did not have to offer. How did it work? For all diaphragm drivers (i.e. woofers and midrange drivers), Müller placed a coil under the dust protection dome, which – because it was in the force field of an additional magnet – generated a voltage with every excursion. The diagram shows the function:

Backes & Müller negative feedback
The idea of inductive negative feedback: the important thing is the sensor coil, which uses the S/C magnet to induce voltage in a control circuit, which then counteracts in the event of a deviation (graphic: Backes & Müller)

These voltage values are fed to a control system, which compares them with the ideal state and corrects them if there is a deviation. If, for example, the cone resonates for too long, the control in conjunction with the power amplifier provides a corrective in a flash. It is the reason why Backes & Müller speakers have always sounded so crisp in the bass – and still do today. It was so groundbreaking that B&M immediately patented it (patent: PCT/EP2016/053272) and had it renewed in 2015.

Because the mass of a dome tweeter is very small, there would actually be no need for a control at this point. But they were Backes & Müller and also invented a tricky (capacitive) control system for domes. A small grille sits behind the aluminum dome. There is a high voltage (almost 300 volts) between the grid and the dome. At large deflections, the distance changes and with it the voltage – which is then corrected by a special control system. While inductive diaphragm control is still an essential part of B&M’s DNA today, tweeter control has long since been shelved. And indeed, the tweeter control did not really improve the sound either…

Backes & Müller Model 5
With this picture of the Backes and Müller BM5 from 1977 we are reaching a little ahead of history, but on the “naked” BM5 you can easily recognize the massive housing construction as well as the capacitive control (source: Backes & Müller)

50 years of Backes & Müller: the first years

The founding fathers Friedrich Müller and Wolfgang Backes had founded the company together in Saarbrücken, but it was the engineer Friedrich Müller who was in the spotlight. The trail of the businessman Wolfgang Backes was already lost in the 1980s (as if the industry loses anyone…) while Friedrich Müller continued his ideas of active speakers under the Silbersand brand after his departure (at the end of the 1980s).

Backes & Müller Model 3
Excerpt from the DHFI HiFi Yearbook: the first B&M model with order number 3. It was still built with drivers from external suppliers and cost 2,900 Deutschmarks each in the early 1970s – a lot of money back then (source: B&M)

But before the founding fathers left the company, they had a highly successful time. The first market-ready loudspeaker was the Model 3, which was ready in 1972.

While the first models were still sourced from external driver suppliers (Model 3 is equipped with drivers from KEF, Peerless & Co.), the realization quickly set in that it was better to take the complex technology of cone control into one’s own hands: Since the mid-1970s, all drivers have been produced at the headquarters in Saarbrücken – and this is still the case.

Backes & Müller Production
The machine for pulling the metal membranes is also somewhat older, but still does its job perfectly – a fine example of the manual work at Backes & Müller in Saarbrücken (Photo: B&M)

In fact, every Backes sound transducer is currently produced by hand with a high degree of vertical integration. According to current B&M Managing Director Johannes Siegler, you could almost say that each model is unique. This is another thing that makes the Backes models so special. And also a little more expensive…

Backes & Müller Manufaktur
At Backes, one employee is responsible for each speaker produced. He documents the perfect condition with his name (Photo: B&M)

But back to the B&M launch, where the Saarbrücken-based company first sounded out the market with its Model 3 and the BM5. The real breakthrough – also in the perception of the trade press – only came with the BM6, which saw the light of day in 1978. Hannes Scholten, the editor-in-chief of “Audio” at the time, wrote a veritable hymn of praise about a hitherto unheard-of neutrality and sonic honesty.

50 years of Backes & Müller (Photo: R. Vogt)
50 years of Backes & Müller: The picture shows the BM5 (top left) and Model 3 (center). They stand next to a life-size Indian statue that B&M had made in 1990 as an advertisement for their reference power amplifier called “Sitting Bull” (Photo: R. Vogt)

The emergence of Backes & Müller also had a lot to do with the great sympathy of the audio editor-in-chief. Scholten, who launched Audio in 1977, not only wanted to report, but also to shape the market to some extent. An innovative high-tech brand like B&M was just what he needed.


Backes & Müller model BM6
The 3-way compact speaker BM6 from 1978. Three power amplifiers and the controller are located on the (cooling) metal plate on the rear panel. The price at the time was just under 5,400 euros (source: Backes & Müller)

This “will to design” culminated in an audio-inspired “reference” that combined the best that was known at the time: an active concrete bass horn from Phonogen, an ion tweeter from Acapella and, of course, the active midrange of the BM6. The ambitious project probably sounded rather inhomogeneous and never went into series production. But it shows the importance that B&M had at the time.

Audio reference 1980
Reference 1a: a bass horn made of a plastic/concrete mix with B&M midrange plus ion tweeter. All naturally active (Picture: archive)

In terms of sound, it was all quite brisk. I myself tried to live with a BM5 for over a year at the end of the 1990s. Their construction was so robust (wall thickness 3 centimeters!), the technology fascinating. But it couldn’t be tamed: The bass was almost over-precise, the entire mid-high range had so much energy and sounded so present – it just wasn’t for me…

Backes & Müller model 12 and 20
The BM12 5-way speaker (left) was something of a mega-seller for the Saarbrücken-based company. The BM12 was launched in 1980 and cost 11,800 D-Mark/pair at the time. The BM20 came onto the market in 1982, with a pair price of 18,600 Deutschmarks. The BM20 was the flagship for a long time (source: Backes & Müller)

For many fans, however, it was the greatest thing. Building on the excellent reputation of the BM6, the Saarbrücken-based company followed suit: This was followed by legendary speakers such as the BM8, the BM12 and the BM20, the latter of which, as the flagship of the line, was Audio’s reference speaker for many years. They celebrated great successes. And indeed, these three models were still being built well into the 2000s as the “Classic Line” – with occasional refinements, of course.

Backes & Müller Team
A picture from earlier years. It shows the employees of the Saarbrücken-based loudspeaker manufacturer. Compared to today, when the team has just 10 employees, Backes was huge back then (source: Backes & Müller)

And another side story about the status of Backes & Müller at that time. When a spring-like glasnost wind blew around the corners of the world in 1989 and the Federal Republic of Germany truly had many reasons to thank the Russian leader Mikhail Gorbachev, he was presented with a hi-fi system “Made in Germany”. Including, of course, loudspeakers from Backes & Müller…

Supposedly this is not a photo montage. It is said that Mikhail Gorbachev was genuinely pleased with the high-fidelity present (source: B&M)

The years in-between

But despite its good reputation and the enduring fascination with this loudspeaker technology, the company ran into turbulence. Mr. Backes & Mr. Müller stepped down, and musicologist Ingo Knerr became majority shareholder and managing director. He took everything that had gone before to the extreme: the BM30 from 1988 became the largest Backes model in the company’s history and was celebrated accordingly by the trade press. With the BM30, Backes & Müller also caught up with the world leaders in terms of money. The über-flagship remained in the range for 20 years.

Backes & Müller model BM30
The BM30: a 5-way speaker with a height of almost two meters, a weight of 134 kilos and a new price of a good 60,000 marks (source: Backes & Müller)

In 1991, Knerr inspired the developers to create a real reference power amplifier. The Sitting Bull was the first power amplifier ever to break the 100-point mark in the Audio (once again the Audio…). That also made people sit up and take notice. However, Backes pursued this branch only half-heartedly; Sitting Bull remained alone…

Backes & Müller Sitting Bull power amplifier
The Sitting Bull from 1991: 2 x 260 watts or 1 x 750 watts (4 ohms). All this in a rather chic wooden housing (Photo: B&M)

The example of the beautiful reference power amplifier shows the difficulties Backes faced at the time: the company was actually a specialist for highly ambitious active loudspeakers. But the hi-fi fan of that time was into big amplifiers from big names. Knerr tried many things, including the Sitting Bull and passive loudspeakers (which was almost sacrilegious given the Saarbrückeners’ self-image), but the difficulties remained. Knerr stepped down and the Dutch Autosound-Holding joined in, which was not necessarily a specialist for Backes & Müller’s very high-end business.

For example, the WINX loudspeakers were developed. These active speakers, consisting of an ultra-stable continuous cast aluminum housing, were far ahead of their time in terms of design and idea (there were also center and rear speakers) – so far ahead that they should actually be revived…

Backes & Müller WINX
The WINX was an extremely original loudspeaker system with lots of clever ideas and a high female-accept factor (Photo: B&M)

But they too were denied success and the Saarbrücken-based company subsequently focused even more consistently on what they do best: Building incredibly precise-sounding and rather baroque-looking men’s loudspeakers.

I already mentioned the year 1995. Despite the difficult times, it was a milestone year for Backes. In the latest version of the BM30, they used processor-controlled crossovers and digital room adjustment for the first time. B&M has once again succeeded in raising the bar in terms of reproduction quality. Backes has been able to maintain this technological market leadership to this day.

2001: Departure into the new era

Maintaining technological market leadership is primarily down to him: Johannes Siegler. The developer and CEO of the professional loudspeaker manufacturer KS Beschallungstechnik (now KS Digital) was persuaded to take on the same job for Backes & Müller in 2001. He did so and promptly proved to be a real and constant stroke of luck for the Saarbrücken team. He not only brought fresh blood into the somewhat dusty traditional company, but also a great deal of experience in studio technology and – even more importantly – elementary knowledge of DSP programming. In 1996, he developed KSD, the world’s first digitally equalized studio monitor.

Johannes Siegler @ Darmstadt 2022
Johannes Siegler has been CEO at Backes & Müller since 2001: a musician (guitarist) with good ears, lots of ideas and even more knowledge (Photo: R. Vogt)

This knowledge was now also available to the hi-fi supplier Backes & Müller – which took a huge leap forward as a result. Siegler perfected the digital crossover technology through the clever use of FIR filters (Finite Impulse Response Filter), so that the speakers work with absolute timing accuracy – the signal from the individual tweeters, midrange and woofers always reaches the listener’s ear at the same time. This perfection is virtually impossible with passive loudspeakers and analog technology. Siegler cultivated the rather edgy mid-range of the Backes speakers – but in such a way that they naturally retained their honest, straightforward character. Siegler also refined the membrane control, which is part of the DNA, and had it patented again in 2015.

From his experience as a musician and studio professional, Siegler has always had a soft spot for line sources. With the help of many stacked drivers, you don’t create the usual radiation, but a cylindrical wave that produces only a few floor and ceiling reflections. This concept is widely used in sound reinforcement, but rarely in hi-fi. An Infinity Reference Standard is a good example of such a line source. Or a T+A Solitaire S540. Or the larger Backes models.

Because it is not so easy to create the cylindrical wave in the high frequency range so skillfully that it fits perfectly with the wave of the mid and low frequencies, Siegler used his good contacts at the Fraunhofer Institute, which found the perfect approach for him after a long period of research.

Backes & Müller BM Line Horn
Provides cylindrical wave radiation from 800 Hertz: the NExT slot radiator from Fraunhofer research works in all larger Backes models (Source: Backes & Müller)

A thing that looks like a horn but does not amplify sound, but instead produces the required homogeneous, cylindrical radiation in the mid and high frequencies. And a name for this slot radiator was also quickly found: NExT (Nearfield Extension Technology).

Backes & Müller NExt spotlight
How the NExt driver works: many tweeters are cleverly directed into the slotted radiator (Photo: B&M)

With the BMLine 35 from 2006, Siegler then created something like the “mother” of all current Backes models: with membrane control, with phase equalized digital crossover, with cylindrical wave radiation and, of course, equipped with many programmable filters for adaptation to the room acoustics. The enormous reproduction precision was further enhanced because Siegler had at some point chosen the artificial stone Corian as the optimum material for the baffle design. As a reminder: Wilson Audio and, more recently, Lyravox also use similar artificial stone versions for their enclosures. The advantage: nothing deforms, not even a fraction of a millimeter. The disadvantage: It’s just damn hard…

Backes & Müller Model BM Line 35
The milestone BMLine 35 in four different finish variants. But because everything is made by hand in Saarbrücken, many more variations were and are of course possible… (Source: Backes & Müller)

The BMLine 35 cost 60,000 euros a pair at the time. With it and the even larger BMLine 50 from 2008 (starting price: 108,000 euros), Siegler set the pace: extremely impressive sounding, comparatively expensive and technically highly complex loudspeakers, which of course only develop their full potential when they are meticulously calibrated to the owner’s listening room.

At this point at the latest, the specialist trade dropped out. The dealers were either unwilling or unable to provide support for these very special transducers. And so the developers in Saarbrücken had to go out again and again to get their speakers to play perfectly. In 2009, Siegler pulled the ripcord and since then has only been supplying two retailers in Germany: the established Backes & Müller service distribution of Andreas Kühn (Kornwestheim) and the beautiful “Listen” flagship store (Darmstadt), where we have already paid a flying visit.

Rüdiger Schatz and Bernd Hauptmann in the B&M showroom
Rüdiger Schatz (left) and Bernd Hauptmann are the two people behind “Listen”, the B&M showroom in Darmstadt (Photo: B&M)

Siegler was well advised to reduce the number of dealers to just two. After all, he knew what he had in mind and where the dealers would not have gone along: a further enhancement of the BMLine 35 concept – overspeakers in the shape of butterflies.

The history of Backes & Müller is rich in superlatives, but the BMLine 100 tops them all: with dimensions of 100.0 x 230.0 x 125.0 cm (W x H x D), its weight of a quarter of a ton and a price tag of 500,000 euros, it took the cake. It is clear that there were only very few loudspeakers in the world that could offer a similarly precise reproduction, a similar wealth of detail and (hurricane-like) volume at the same time. You can’t imagine better ambassadors for the technologies relevant to Backes.

BMLine 100
The BMLine 100: a very special chapter not only for Backes & Müller, but also in the history of loudspeakers (Photo: B&M)

Or maybe it is. The BMLine 80 and BMLine 60, which are similar in shape, offer almost equally powerful dynamics, but have the advantage of being somewhat more attractive in price. I don’t want to call the BMLine 60 “affordable” – it makes me want to type the word into the keyboard. But at 120,000 euros, they are roughly on a par with the BMLine 50, look much better and can also do a lot more…

50 years of Backes & Müller
A lot of honors have been bestowed over the past 20 years. Quite a few of the certificates were signed by the author himself… (Photo: R. Vogt)

The concept and price of the large BMLine models could raise the question of whether Backes & Müller has finally lost touch with the ground. Here you can throw an explicit “No!” into the room. B&M mastermind Siegler is grounded in terms of price anyway due to his KSD Studio connection. The fact that the noble Backes flagships are so expensive is mainly due to the high degree of individual craftsmanship of the “Made-In-Saarbrücken speakers”. And of course Siegler also knows that you can’t sell speakers of this size and price class as often as you like.

HIGH END 2023 Backes & Müller Jubilee
We raise our glasses: B&M CEO Johannes Siegler at the Jubilee premiere at the HIGH END 2023 (Photo: H. Biermann)

He therefore launched the Jubilee on the market for the company’s 50th birthday. In its highly stable but discreet housing in an almost Bauhaus style, everything that Backes currently stands for came together in terms of technology and sound. And all this with a purchase price of 40,000 euros and cast in a shape that should still fit well in most music lovers’ living rooms. At the HIGH END 2023, I already had the opportunity to listen to this future project from Saarbrücken for a while. Terms like “powerful dynamics”, “brutal clarity” and “spectacular imaging” popped into my head. You would love to have something like that. The price alone… But Siegler cheered me up with a wink: “Oh, I could well imagine presenting a compact Jubilee monitor soon. Wouldn’t that suit us well?”

Half a century after its foundation, Backes & Müller appears to be successfully repositioning itself. There are still the baroque BMLine 12 to 50 models, which still have their fans. But a change towards smarter, more modern, more living space-friendly living is imminent. At the German HiFi Days in Darmstadt, when the production-ready Jubilee was played, it generated a great deal of interest. Or to put it another way: nowhere else at this trade fair was it as full as at Backes…

German HiFi Days 2023 B+M
The Jubilee, priced at 40,000 euros per pair, is set to usher in a new era at Backes & Müller. We couldn’t come to a real assessment of what it sounded like: It was just too crowded… (Photo: R. Vogt)
More from Backes & Müller:

Test Backes & Müller BMLine12: the last of its kind

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Autor: Holger Biermann

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Chefredakteur mit Faible für feinste Lautsprecher- und Verstärkertechnik, guten Wein und Reisen: aus seiner Feder stammen auch die meisten Messe- und Händler-Reports.