Red House


Construction: 3-way open baffle loudspeaker
Measured frequency response: 18Hz-50kHz (+/-3dB)
Dimensions HxWxD: 153x40x18 (cm)
Weight: 90 kg
Recommended amplifier power: 450 W
Nominal impedance: 4 Ohm
Measured sensitivity: 91 dB (2.83V/1m)
Availability: Available
Retail price: 37500 EUR/pair (including 23% VAT)
Download PDF


In the world of high-end audio, it becomes more and more difficult to get brand new, yet still reasonable ideas. Emerging projects, however impressive, merely reinterpret already known concepts (although often long forgotten) or, what seems even worse, follow false leads, sacrificing rationality on the altar of flashy design and ambition of flaunting own inventiveness. It is not uncommon that significant breakthroughs remain unnoticed, while superficial details are acclaimed milestones. One time it reminds opening an open door, some other time it's nothing more than reinventing the wheel. On the other side, clients expect not only good sound, but also dazzling design and the technical progress.

Producers and constructors function therefore under the pressure of clients' expectations and competitors' actions, which often lead them to undertake projects not necessarily perfect from the acoustic point of view; following super-devices are more and more impressive, becoming at the same time more and more a compromise dictated by the market. Large companies, with serious technological background, can do more...and less at the same time – each and every new project has to be a 'safe bet', with all other success factors calculated just as precisely as acoustic parameters. There is no room for concepts overly controversial or... too ordinary. Apart from that, every renowned company strives to keep its style and solutions to underline its image and sustain market recognition.

All those political-marketing aspects influence companies' operations proportionally to its size, scope and market position; for the smaller ones, fortunately, this influence is less disturbing. As a result, ESA, despite its more humble background and support, may freely develop projects, in which it is acoustics which plays the first part, and not extravagant form, luxurious materials or complex high-tech solutions with barely noticeable impact on the final sound experience. One may sprinkle speaker cones with star dust, but... what for?

Red House is not a conventional project, which is to be noticed right away, but nothing in this device was implemented 'for show'. We neither invented the wheel, nor an open baffle; we did not uncover any rules of physics – we just (and foremost) applied them skilfully. Correctly designed open baffle does not leave much room for interpretation for graphics and designers, imposing specific construction dimensions and drivers arrangement, thus shaping the ultimate concept. An open baffle has, however, one indubitably positive feature – as its name indicates, the case is not a massive box, but a middle-thick panel, which may be perceived attractive as such, but vaguely disturbing at the same time.

Relatively simple construction of an open baffle induces an acoustic setup needing more complex calculations and trials than typical 'box' cases, whose appropriate attuning is much easier. High quality open baffle poses therefore a challenge, demanding technical knowledge and experience. Bearing this in mind, Red House is not the first open baffle concept in ESA's portfolio, with its construction team mastering and designing dipole loudspeakers no less than twenty years. What made us follow this unusual concept were not only promising sound characteristics achieved by similar constructions available on the market, but also the theory, indicating unwavering advantages of a dipole construction, opening a vast potential for fascinating studies and experiments for a constructor. Open baffle is an adventure for the designer, a pleasure for the user, and for all – an indisputable satisfaction.

From the sole construction of a dipole loudspeaker stems however a challenge of its miniaturisation, as the low-range section has to be much more powerful than in a conventional box speaker of similar parameters. As a result, open baffle constructions, especially high-end ones, cannot be placed on a low-budget shelf; from their very nature, they belong to the high-end, similarly to electrostatic constructions. There are numerous conventional loudspeakers equipped with massive speaker power, able to handle hundreds of watts giving back over 100 dbs. In case of dipole speakers – that's not the purpose – here quantity lets the quality to emerge.

Seeing a construction with three 13” woofer drivers, one might get the impression that such a project is designed to create a bass-storm even in the biggest spaces. Indeed – such a setup enables Red House to achieve everything that a high-end loudspeaker should achieve, in the sense of power, dynamics and the bass range; beating records is not one of its purposes, however. From the idea of an open baffle construction stems low electrical efficiency – in order to compensate for that, and to be able to achieve satisfying results in the end, it is vital to provide a system with high efficiency and significant power reserve (seen from the perspective of a conventional system). In other words, three 13” speakers of the Red House create acoustic pressure comparable to only one such speaker, mounted in a conventional bas-reflex case. What is then the purpose of using such an expensive, speaker-hungry setup?

Limiting the case to an open baffle lets us to grasp benefits being out of reach for any other loudspeaker case, even those most advanced in a battle against inevitable resonances. In our case, this problem simply does not exist – lack of the back case wall equals no inner-resonances, and thus no static waves induced between the case walls, no wall vibrations due to the acoustic pressure inside the baffle, etc. The pressure is freely released at the back of the cone, not closed, suppressed or used to induce any resonance system. Not surprisingly, there are also no problems with the impulse response, which overload mostly bass-reflex systems – in an open baffle setup only the speaker plays, at its output parameters (fs, Qts).

A special feature of an open baffle design is also creating an octal directional characteristics (hence its name – 'dipole'), being an effect of contradictory radiation phases of a front and back side of a cone. Consequently, half of the total energy generated by the setup is aimed directly to the listener, while in case of the vast majority of typical constructions with omni-directional low-frequency radiation, most of the energy spreads in various directions, gets reflected, generates resonances and reaches the listener distorted and delayed. Thanks to a radical eradication of this phenomenon, bass generated by a dipole is much more detailed; it characterizes with a better attack, definition, decay, and additionally it comes from specific directions of the sound stage, instead of humming indefinably over everything. The objective precision goes hand in hand with the sense of sheer authenticity.

In the low-frequency section of the Red House system we used best Scan-Speak woofers – the 13” Revelators. Those are one of the most brilliant low-range drivers, designed with a typical for this Danish producer accuracy and consideration. A special composite cone, with cellulose outer layers and foam core, characterizes with a great stiffness and ability to suppress own vibrations. A powerful magnetic system, equipped with Symmetric Drive solution, keeps optimal values of key parameters. 3 inch coil with a titanium carcass accepts high power without compression, while low-loss suspension does not induce any interference to the cone movements, thus not dimming even most subtle impulses. Such a speaker, although powerful, does not move like a bull in a china shop – true dynamics mean full control and conveying both strong impulses and those most ephemeral ones. In a construction where such a refined woofer meets the most noble case type – an open baffle – achievable becomes the projection of fascinating, near-ideal low frequencies.

The mid-range section is based on a system of closed chambers; in this range of frequencies, applying an open baffle would also be possible, but also would not prove that beneficial as in case of low frequencies; on the other hand, it would result in specific problems stemming from entering a wave length range similar to the baffle width; closed case design facilitated setting the cut-off frequency with the woofer section, with application of previously chosen drivers of a moderate diameter; attenuation of the mid-range frequencies and preventing its resonances in a closed case in not as troublesome as in case of low-frequency waves. However, also here an innovative approach was taken, since the mid-frequency chamber is designed in a way preventing the stationary waves to appear (through a system of specific carving on particular layers of the baffle).

Two mid-range speakers, placed with the tweeter in a symmetric configuration (d'Appolito) are also best Scan-Speaks from the Illuminator series. Their finitely ideal construction covers a neodymium magnetic system, along with a custom-made carcass (undistorted radiation from the back side of the cone with a pressure way-out from the lower suspension), under-hung voice coil (lowest distortions), two-layer cellulose cone with resonance-dispersing crease (each of two glued together layers is made out of a single cellulose piece – the convex central part, the so called dust-proof cap, is not a separate element), lastly an extremely low-loss suspension (made of a specific kind of foam instead of rubber).

Something more than an icing on a cake is the beryllium tweeter. Also here Scan-Speak showed its mastery. This speaker, used in a few most expensive loudspeaker systems in the world, is a masterpiece not only owing to the meticulous work of Danish engineers, but also thanks to best quality raw material; there are several methods of beryllium dome production, with various content of 'beryllium in beryllium', which conspicuously affects the final parameters and sound quality. Beryllium Illuminator sets a reference level – neodymium magnetic system with large-dimension slice shape (but little depth) and precisely shaped suppressing chamber do not let for any parasite resonances inside the speaker to appear.

The crossover is the 'brain' of a speaker system. Audiophiles focus on the quality of its components, which is reasonable, as those should be adequate to the quality of the whole construction; however, what is most crucial about it is its topology and adequate parameters of its components, ultimately affecting successful composition of all parts of a loudspeaker, which cannot be assessed based merely on its looks. There are no universal two-way, three-way, etc. crossovers, for which application of better and more expensive components would result in a better sound quality. Each crossover has to be tailored to the particular speaker set, taking into account applied types of speakers, their arrangement and the influence of the loudspeaker case – which, in case of an open baffle, is most significant. In this case, the crossover not only splits the sound into ranges adequate for particular speakers, but also corrects their characteristics; the choice of the cut-off frequency, filters' slope, shape of characteristics within pass bands, have to be immensely precise. It cannot be based on simple equations – in the tuning process, significantly more factors has to be taken into account than in case of closed case speakers, which renders a well-tuned crossover of a dipole construction a piece of art. Thus, it should be well protected – in case of Red House, the crossover was hidden in the chamber carved in the lower part of the baffle, closed with the plinth.

In typical loudspeakers, depending on their size and class, case walls are made of different materials, have various widths, while the front panel, to which they are mounted, is usually 'privileged'. In Red House, the whole case boils down to the 18cm-thick front panel (and stabilizing plinth). It consists of four layers of plywood and four layers of MDF, to which it owes its firmness and ability to attenuate vibrations – all speakers get a solid support and isolation. The thickness of 18 cm allowed to fit within the close chamber mid-range speakers, as well as magnetic systems of the woofers – all components fit inside the baffle, which is neatly finished with a grille aligned with the back facet of the baffle.

The shape of a spindle results from acoustic and mechanic reasons, while its attractive looks is an additional reward for a consequent advance towards reaching the ultimate goal – the sound of an extraordinary precision and naturalness, giving a special perspective for projecting and perceiving low frequencies, as well as ease of adaptation in not necessarily spacious rooms. Dipole, thanks to its unique and highly beneficial directional characteristics, reducing the problem of static waves, may function in various conditions in which other types of loudspeakers, even high-end ones, would lose substantially. Base guidelines regarding dipole speakers suggest creating the stereo system lengthwise the room, as dipole bear staying sidewise close to the walls well (in the plane of the baffle, the acoustic energy is the smallest); on the other hand, we should leave more space behind them – at least a meter, while in an ideal setup they should be placed in 1/4 – 1/3 of the room's length.