RAAL Ribbon Tweeters
In an effort to recreate a sound that happened in some other place, in some other time, audio engineers are constantly trying to find the best means to record and reproduce the sound as exactly as possible. If we could have absolutely accurate replica of recorded sound at the end of an audio equipment chain, than the sensation that we would have, would be the same as we actually participated in the recorded event.
Of course, absolute accuracy is not possible. Fortunately enough, it has been proven that it takes a certain level of reproduction accuracy to make the human or animal ears experience no difference to original. Impressive achievement, but with ridiculously expensive and impractical laboratory equipment and conditions.
Our goal is to bring the most of that experience to everyday life
Buy a RAAL ribbon tweeter today: 70-10D or 140-15D.
- Special FLATFOIL® pure Aluminum ribbon
- Special SYMMLEAD® low inductance signal path
- Special EQUAFIELD® NdFeB magnetic structure
- Special “non-wave-guide” INOX front plate
- Exceptional vertical dispersion
- Super-fast settling time
- Flat frequency response
- Low nonlinear distortion
- High signal power handling
- Highest reliability
70-10D Ribbon Tweeter
140-15D Ribbon Tweeter
Optional: Amorphous Core
Recently, we finished development of Amorphous C-cores transformer application in our ribbons. We are
the first to use AMCC's in ribbons for absolutely uncompressed high power transient transfer and, at the same
time, even further improving already the best low-level performance in the world today, by decreasing the
width of hysteresis compared to HF ferrite cores. For direct coupled tube SE-ribbon, we successfully
developed 175:1 ratio, -3dB at 120kHz Amorphous C-core transformers that can carry DC idle current of
SET. Impedance conversion is about 30000:1, bringing the 0.1 Ohm ribbon up to 3kOhm, good for plate
loading of most triodes in HF.
RAAL is a company based in Zajecar (Zayechar), eastern Serbia. It is 100% owned and managed by its founder and director, solely creating the company's policy, products, development and strategy.
Now, RAAL has more than 11 years of very extensive experience in ribbon loudspeaker research and production. That includes 13 different models of various ribbon speakers for different applications, from home high-end to professional PA solutions. Many of the two and three-way custom high-end loudspeakers, some with very radical solutions regarding ribbon drivers. Interesting thing is that not one pair of loudspeakers changed hands. If the customer wanted something to be improved, it was always the RAAL’s upgrade to a bigger ribbon driver, but not the new loudspeaker of another brand. The consequence was the vast experience gained in building real, usable designs, that fit to people, not just scientific exercises which couldn’t have “real life” usable value, or if they could, they would be very cost-ineffective. All that was, in fact, the serious R&D that had been done and finally, RAAL’s goal is made, and that is to have the cost-effective transducer, but with a performance and reliability that can not be matched.
Recently, after 11 years of small, handmade quantities, the company have started a serial production of two true ribbon models that sublimed the RAAL’s present know-how, in a new production facility. Still, there is a lot of work done by hand, but that’s what true ribbons are like. No machine can do what a skilful hand can. Nearby is construction in progress of the anechoic chamber and very much elaborated listening room, to have daily access to such tools. Extensive use of FEM analysis methods, complex acoustic measurement methods, laser and water-jet cutting, CNC machining, etc. helps in bringing new ideas to life and keeps the pace up with large manufacturers, furthermore, makes us superior to them regarding production of specialized, dedicated to purpose, custom made drivers in small quantities.
EQUAFIELD® technology: The magnetic field in RAAL ribbons is homogenous. Regarding the width of the gap, it is designed to have the same strength at the ribbon edges, as well as at the ribbon middle portion. It reduces the stress at the ribbon foil dramatically. The distortion, too. To get the precisely shaped field, through the gap width and depth, we’ve extensively used the FEM and BEM magnetic circuits analysis software. In order to obtain such a field in real magnetic circuit, very strong NdFeB magnets have been precisely machined, prior to magnetization, in very special shape. Making the magnetic field homogenous, sacrifices the strength of it, but efficiency should easily be changed for low stress and low linear and nonlinear distortion.
FLATFOIL® technology: Homogenous field has one, much more interesting result and that is the possibility to use non corrugated, thin, no-excess-weight-sandwich, flat aluminum ribbon. We are using just slightly structurally shaped pure aluminum foil, of just 0.004 mm of thickness, to yield the best possible performance. FLATFOIL®, although very thin, is much more resistant to high signal input, and unable to go out of optimum magnetic field, thus providing the non compressed dynamic output and much lower distortion at high SPL output, achieving the dynamic capabilities of horn loaded drivers with incomparable neutrality.
SYMMLEAD® technology: Very important part of signal handling is its path to the ribbon ends. Almost all of today’s ribbon drivers are using the layout which loops around the whole magnetic structure, which is, in fact, the single winding solid iron core inductor, connected in series with ribbon. This is effectively depriving the ribbon of high frequency signal. The solution for this problem is, RAAL’s unique signal leads path, which doesn’t put the signal leads around the iron. The signal is fed to the ribbon through two symmetrical leads above the iron yoke, which effectively widens the bandwidth considerably. This layout also acts as a RF signal canceling circuit, to stop the power amplifier being fed with radio frequency signals which might be picked up by ribbon acting as an antenna.
TRANSFORMER: The impedance matching transformer is made to transfer the real power without distortion. Not just the shaped noise signal for power measurement methods, but real high-power signal peaks can be transmitted to the ribbon, which preserves the natural dynamics recorded. The primary inductance of the transformers in RAAL ribbons is set to a value which corresponds to the second coil of 4th order L-R high-pass filter at the appropriate cut-off frequency, depending on the model in question.
Recently, we finished development of Amorphous C-cores application in our ribbons. Some years ago, we were the first to introduce large gap approach in building ribbon transformers and now we are the first to use AMCC's in ribbons for absolutely uncompressed high power transient transfer and, at the same time, even further improving already the best low-level performance in the world today, by decreasing the width of hysteresis compared to HF ferrite cores. For direct coupled tube SE-ribbon, we successfully developed 175:1 ratio, -3dB at 120kHz Amorphous C-core transformers that can carry DC idle current of SET. Impedance conversion is about 30000:1, bringing the 0.1 Ohm ribbon up to 3kOhm, good for plate loading of most triodes in HF.
FACE PLATE: One of the big existing problems is the use of thick front plates, so common in true ribbon designs, which are then beveled to minimize their acoustical influence. On the other hand, beveled front plate act as a wave guide somewhere in higher kHz range, ruining the linearity, so that has not solved the problem yet. RAAL’s unique front plates are very thin with no bevels, and our research brought us to the making of the zigzag “acoustically invisible” front plate ribbon opening. The benefit is “non-wave guide”, seamless coupling or ribbon air loading to the open space, because of the “distributed parameter” edges of the opening. By that, we achieved the unmatched linearity in the upper kHz region and exceptionally “clean” impulse response.
FOAM DEFLECTOR PADS: Wide angle polar response is of great importance for the natural reproduction, therefore using the larger ribbon drivers bares a problem, since they are showing very intensive “beaming” of high frequencies, as they are line sources far bigger than the wavelengths of high frequencies in audible range. For model 140-15D, we found the solution for that problem in using the specially shaped foam pads in front of the ribbon. The dispersion pads are working as an acoustic lens, by slowing down the velocity of sound and thus shaping the sound wave front from cylindrical to spherical. The parasitic effect of partial sound absorption is inevitable, but acceptable. The pads are magnetic and they can slide on the front plate. By adjusting the distance between the pads, sliding them toward or apart each other, it is possible to shape the on-axis linearity vs. wide angle vertical polar response. In this way anyone can adjust the high frequency output by his-hers own liking. If the pads are completely removed, 15 kHz on-axis response is increased in level of about 7 dB.
BACK CHAMBER: sub-critically damped compression chamber of ideal proportions provides the exceptional amplitude linearity and impulse response.
RIBBON REPLACEMENT KIT: ribbon replacement is made easy by our ribbon replacement kit, which is easily replaced by the user. This “kit” is in fact our SYMMLEAD® signal leading frame, holding the stretched ribbon, allowing it to snap into perfect position between the magnets.
This feature might be an obsolete one, because RAAL ribbons are destructible only by really extreme abuse or curiosity. In two years, we sent away only 3 replacement kits to customers who destroyed the ribbons by opening the drivers out of curiosity. Aside from that, our reliability record is 0% failure rate.