What makes Cessaro horn speakers different to ALL other horn speakers?

I used to have a love/hate relationship with horn speakers. The usual descriptions people use to describe horns …’speed, clarity, lack of distortion, dynamics…’ are pretty accurate but beyond the audiophile language, I feel there’s just something amazing about how a horn speaker charges the air in a room. They have a way of making the music palpable, like ‘sit up, pay attention and feel it!’ I like that. I don’t like boring, and horn speakers are never boring.

But at some point in my experience, my attention has been drawn to something in the sonic presentation that just doesn’t feel right. For me, it’s usually the integration of the non-horn lower bass frequencies with the horn loaded mids and highs. I happen to be sensitive to that aspect and it snaps me out of the illusion of the artist performing in front of me. Some people refer to a specific colouration that can sound a bit aggressive, or ‘honky’.

Nevertheless, the allure of horns has seen me return time and time again to having them as my speaker of choice. Over the years, I felt with some conviction that I had a reasonable understanding of the ‘horn speaker sound’. Then one day I sold an amplifier to a guy, decided to deliver it and help him install it in his system. He told me that he had a pair of German horn speakers so I was looking forward to installing the amp and having a quick listen before going home.

His speakers were a pair of Cessaro Horn Acoustics Beta’s with a walnut cabinet and pearl white horn. I had read about Cessaro speakers but had never actually heard them. I was struck by their presence and by the quality of their finish. That paled into insignificance when I heard them playing music. They did not sound anything like what I had come to expect a horn speaker should sound like. It was one of those unforgettable experiences.

I can’t believe that some years later, I became the Australian distributor for Cessaro and delighted in facilitating that same experience for other people. After recently spending some time with Ralph Krebs (the founder), I feel compelled to share with you some information that can shed some light on why his products are so special.

So, make a cup of tea, relax and read on…

Horns are the original loudspeaker design

Horns made of the real horn of a cow, sheep or other animal or out of wood have been used to amplify sound since antiquity within many cultures. The European alphorn, the Jewish shofar and the Aboriginal digeridoo also use horn principles to amplify sound. The first horn loudspeaker was invented in 1877 by Werner von Siemens, which he named a “mobile coil transformer”. In the ensuing decades, horn loudspeaker designers such as Gustavas, Webster, Klipsch and Voigt (amongst others) pioneered horn technology and horn loaded designs became the first mass-produced loudspeakers, gracing cinemas, studios, concert halls and eventually personal hi-fi systems.

The first acoustic systems were horn speakers. This is a gramophone from 1899.

How do horn speakers work?

Speakers produce sound waves when a radiating diaphragm (membrane) moves back and forth to push air. The larger the radiating diaphragm, the more air will be moved and the greater the sound energy produced. Ideally, diaphragms need to be as low mass (light) as possible to respond to the electrical signal accurately. They must also be as stiff as possible to avoid changing shape during movement and creating distortions. Unfortunately, as a radiating diaphragm increases in size, it becomes heavier and slower, which affects its accuracy and its practicality.

By using a flared transmission channel (a horn), the effective radiating area of the source of sound can be increased to that of the mouth, thus creating greater air coupling (louder sound) and making it possible to use smaller, lighter & stiffer radiating diaphragms. Because of the gradual change of the diameter of a horn, the source of sound at the throat engages all the air in the horn. We can think of a horn as having an imaginary, massless diaphragm at the mouth.

The horn allows the mechanical power capabilities of the source to be tapped much more efficiently. In the case of horn-loaded speakers, neither the electromechanical efficiency nor the power capability of the speaker itself is changed, but the transfer of mechanical to acoustic energy is greatly increased. Horns can therefore be considered to be ‘acoustic transformers’ or ‘sound amplifiers’.

Due to the significantly reduced membrane excursion, a horn speaker is extremely quick both in its acceleration & deceleration capacity with considerably reduced amplitudes of post-oscillations. In addition, the reduced membrane excursion and the acoustical attenuation through the horn avoid critical partial oscillations of the membrane. Thus, distortions are nearly non-existent and dynamic compression is virtually negligible.

So horn speakers can provide the following advantages:

• High efficiency (efficiency is the percentage of electrical energy emitted into the room by the loudspeaker as sound pressure).
• Clear and distortion-free sound even at very high levels.
• Precise and almost instantaneous level differences (dynamics).

If horn speakers are so efficient, why are they so rarely found in Hi-Fi?

With their significant advantages in efficiency, distortion-free clarity and dynamics, you would imagine that logically, most speakers should be using horn technology, right? Well, not in practice. Why?

As simple as the principle is in theory, the implementation is actually rather complicated and building a high-performance horn speaker is difficult, and expensive.

One challenge is the tuning of horn speakers to certain frequency ranges. A large horn is particularly important when it comes to reproducing tones from the low frequency range. The sound wavelength should not be less than the circumference of the horn opening. A 50Hz-bass tone for example, spreads at a wavelength of 6.80 metres. To produce this frequency purely from a horn, it would require a horn with a 6.8m mouth opening! For this reason, horns are sometimes used for the high and mid-level frequencies and then traditional dynamic cone drivers are used for the lower frequencies. Seamlessly integrating ultra-fast, dynamic horns with slower cone drivers then becomes a challenge.

In addition, the individual loudspeaker components must be precisely matched to the horn. These include the nature and size of the speaker diaphragm and the design of the electromagnetic drive. Horns are very good at revealing the quality of the drive unit that they are coupled with, revealing imperfections in driver performance. Therefore, the drivers used must be very high quality and coupled with great care.

The horn shape has to be extremely precise so that it doesn’t introduce any colourations to the sound. Furthermore, the horn must be constructed from a high density, sonically inert, heavy material with the perfect damping characteristic otherwise it can add its own sonic flavour (resonance) to the sound. For these reasons, the considerable cost and engineering expertise required to overcome these issues has resulted in a relatively small number of horn speaker manufacturers in the hi-fi market.

With so many other cheaper, more room friendly options, why bother with horns?

There is one very good reason that pursuing a horn speaker design has merit. Put simply, when they are ‘done right’, they are absolutely amazing. If you are searching for the ultimate loudspeaker to faithfully reproduce a live musical event in your listening space, you should listen to a properly implemented horn speaker system.

Unfortunately, there are plenty of poorly implemented horn speakers in the market which exhibit some of the advantages of horn design however are let down by critical flaws.

If you were to find a horn speaker that is well designed & engineered, is constructed from the very best materials, uses the very best perfectly matched drive units and is built with extreme attention to the finer details, your listening experience could very well be revelatory. For those looking for such an example, let me introduce you to Cessaro Horn Acoustics from Germany.

What makes Cessaro horn speakers different to all other horn speakers?

Cessaro Horn Acoustic aim to produce the best horn loudspeakers possible by ensuring a totally uncompromising approach to design, components and construction of their speakers. No corners are cut, the technology is cutting edge, the quality is heirloom and the attention to detail is extreme. They are designed to be the last pair of loudspeakers you will ever buy, unless of course you upgrade to another Cessaro.

There are 6 reasons why Cessaro are different to all other horn speaker designs:
1. Horn technology
2. Drive units
3. Time alignment system
4. Crossover
5. Cabinets quality and weight
6. Cable

Cessaro Horn Technology

The design and implementation of the actual horn is fundamental to horn speaker designs and is critical to achieving ultimate sound quality. Every single detail matters. If the shape, weight or the softness of the inner damping material changes slightly, the sound quality is affected. It has taken Cessaro many years of research, experimentation, working with experts in specific fields and ultimately…. simply listening to get these details right.
The horn shape, the inner damping polymer, the construction technique and the composition of their horns contain technologies that cannot be found on ANY other loudspeaker systems in the world. Unfortunately, producing such designs comes at a cost with the cost of one Cessaro horn alone often costing more than some other complete high-end speaker designs. However, there is no other way to achieve these results.

Horn shape

The horn shape is one of the foundations of horn loudspeaker design. There are many different horn shapes used in audio, including exponential, radial, tractrix, constant directivity, bi-radial, LeCleac’h, quadratic…just to name a few. Cessaro developed their own software which simulated the performance of every possible horn shape and spent 2.5 years researching and developing their horn designs. Ultimately, they developed a custom designed spherical horn shape with some modifications at the horn mouth to create a softer wave at the edge. This produces fewer secondary waves and results in a more accurate, cleaner, more open sound.

Horn construction and inner damping

Cessaro manufacture their horns with a double shell, internally filled with a heavy polymer. The special composition of the polymer is critical as it has a specific density that is not too soft or too hard in order to provide perfect inner damping characteristics.

No adaptors

The horn throat is made from an one inch thick solid aluminium ring. Within the throat ring is another aluminium ring which is inserted to keep the driver in position and the compression driver is fixed directly at the horn throat, directly coupling the driver with no adapter in use.

Horn weight

Due to these construction methods, Cessaro horns are very heavy. The horn alone (without the driver) is 7kg for the Wagner, 60kg for the Alpha, over 100kg for the Beta and over 250kg for the bigger horns.

Cessaro Drive Units

Why is driver quality so important with a horn? Put simply, if the drive unit has poor sound characteristics or a specific sonic character, those attributes will be amplified by around 10dB by the horn. Once you have unwanted driver-induced sonic artefacts, you really can’t fix the sound. You will always hear it. Since horns are so revealing of the driver quality, sourcing and matching the drivers correctly is paramount.

Cessaro predominantly use custom made TAD drivers however in the last five years, Cessaro have found it more difficult to source compression drivers and paper cone drive units that meet their requirements. In response, they have embarked on custom collaborations and increasingly more in-house development and production of drive units. This has improved flexibility, quality control and has ensured sustainability and future support.

Cessaro Time Alignment System

Since so many factors can affect the final sonic performance of a driver coupled with a horn, then it is undesirable to simply have the horns in a fixed position. Furthermore, adjustability is also required to account for seating position, room shape and other acoustic space influences.

Cessaro has built a special time alignment system for all of its modular horn systems and for some other models. This incorporates a very strong base plate where the heavy horns with drive units can be fixed. On top of each base plate is a CNC-machined linear element mechanism including a spindle to rotate the moving plate towards the front or back of the speaker. This enables the ability to make precise adjustments of the horn position to within one tenth of a millimetre! For those customers who desire it, a digital display inside the rotating knob can be ordered as an option.

The adjustability does not end there. Cessaro also provide a solid stainless steel mechanism to acutely control the firing angle of the horns. Only with the ability to make fine adjustments are you able to find the correct position for proper driver time alignment and adjustment for listening position & room influences.

Cessaro Crossover

When you have high quality drivers coupled with well designed horns, the slightest imperfections are revealed, so crossover technology is vital. It is relatively cost-effective to make a crossover that simply fulfils the role of dividing an audio signal into multiple frequency bands. However, to make a crossover that performs at a very high level sonically is difficult to do.

An appropriate analogy is comparing a fast food cook to a Michelin star winning chef. The quality of the products are very important but knowing how to use the ingredients, at what time, in what place and in which portion is the key and can result in wildly different results.

Aside from using high value capacitors based on pure silver MICAS technology, Cessaro design their filter networks with a focus on the psychoacoustic properties that are most important for human ears. Together with their time alignment system, their speaker systems can be individually adjusted at each client’s listening space to suit the client’s electronics, room behaviour or personal tastes.

Cessaro Cabinet Quality and Weight

Cessaro cabinets are constructed to function effectively as the structural backbone of the speaker. Aside from lasting a lifetime, they also must also look great to complement the overall product quality and to provide a pleasing aesthetic ownership experience for the client. To that end, Cessaro employ the most accomplished artisans in Germany to finish their cabinetry to coach-building standards. The exceptional craftmanship is evident in every speaker, perhaps most obvious in the ArtDeco model which exhibits the most exquisite wood crafting perhaps of any speaker in the world. Each cabinet is hand made by one master craftsman using old woodcraft techniques and takes months to finish.

Cessaro speakers are also notorious for being very heavy. For example, their smallest speaker the Wagner weighs 220Kg per pair and their most advanced speaker, the Omega is almost 5,000kg per pair. Cessaro owner Ralph Krebs recently commented on this:

“I know that we are well known for heavy products but it’s not because we like to carry heavy things! Believe me, we wish we could achieve the same results at a much lower weight, but it’s just not possible.”

Even from the weight of their components, it is easy to see how distinctive Cessaro are from ‘standard’ high end speakers.

Cessaro Cable

Cessaro have developed their own pure silver cable to use throughout their speaker models based on what they believe is the best match. For perfect continuity, the same cable strands run through from the input terminal to the crossover and from their output to the drive unit. Active bass units also have the same cable. The whole speaker system is wired with pure silver cable – consistent wire technology. Clients can even purchase the same cable to use externally for perfect system matching if they wish.

What about integration?

Many horn speaker designs suffer from poor integration of the bass driver units with the horn midrange. There are a number of reasons why this phenomenon happens. For example, trying the integrate a front loaded low-mid bass horn with a conventional bass cabinet with very low efficiency makes seamless integration impossible however it seems to be evident in high end speaker designs.

Other designs use a long-travel bass driver in a cabinet with an extremely short front horn. Due to the short horn, this design is very limited in its ability to produce low frequencies so to compensate, the design incorporates an equalizer and a boost at lower FQ to produce the lower bass notes. Although this design succeeds in producing lower bass notes, the bass is slow and ‘heavy’ and sounds different to the notes produced by the higher frequency horns. The difference in the nature of the bass is immediately noticeable and perceived as poor integration.

With the Cessaro Liszt, Beta, Gamma, Zeta and Omega, the speed of the drivers integrate seamlessly at the carefully selected crossover points so it is not possible to hear any integration issues in that range. The Alpha II’s cross their 16“driver with the compression driver at around 500Hz and achieves the best performance of a speaker of that design in its class.

Summary

Driven by the uncompromising passion of their founder Ralph Krebs, Cessaro have patiently applied research, technology, materials science an evolutionary thinking to address all the challenges that face high end horn speaker manufacturers. The result is a totally unique range of some of the most musically thrilling loudspeakers ever created. After spending some time with Ralph Krebs, I have never forgotten a comment he made to me which sums up his ethos:

“Every little detail makes a difference. Quality matters even if the client can’t see it.”

So, I urge the audiophile and music lovers among us to forget about what you think you know about horns, forget about what you have heard in the past… and organise to listen to a PROPERLY implemented horn speaker system from Cessaro Horn Acoustics. You will never forget it.

Cessaro products
Cessaro website
Our visit to Knox Audio
Cessaro demonstrated at Knox Audio