Impedance
Before developing the actual filter, the impedance response of the drivers was smoothed with the help of exactly calculated circuits. This not only influences the optimum functioning of the crossover, but it also enhances the cooperation between amplifier and loudspeaker. Even the tweeter's impedance rise above 15 kHz is audible if the drive unit is precise enough to accurately reproduce these frequencies. Because we take so much care in creating a steady impedance response of the driver combination, the phase correction circuit can respond close to its theoretical potential.
First Order Filters
Dynaudio developments are based to a great extent on the application of 6 dB, or first order filters.
Often in promotional literature, the impression is given that the use of filters with a high slope, 12 to 24 dB per octave, is a quality feature of loudspeaker systems. This approach has some validity when using drivers of standard construction and a narrow frequency range. Here crossovers with a high slope may help to maintain a smooth frequency response. But on the other hand, the higher the slope of the filter, the worse the pulse response of the drive unit. Since music consists of dynamic signals with many pulses and few pure sine waves, reproduction suffers from filters with a high slope. Therefore, Dynaudio uses only first order filters. Even if this requires highly optimized drive units that are difficult and expensive to manufacture, the musical result shows that it is worth our efforts.
Phase
By means of carefully directed structural parameters the phase response of Dynaudio drivers is optimized.
The remaining difference around the overlap of woofer and tweeter are balanced by a very sensitive compensation circuit. This circuit uses only high quality components with narrow tolerances and very fast recovery. Long term stability is also a significant factor in the overall design of the compensation circuit. Until recently academic researchers as well as most system manufacturers have discounted the influence of phase on the sound of a loudspeaker system. But from the very beginning, Dynaudio has considered the phase response of a loudspeaker to be just as important as any other aspect, because it has been a known fact that stereo imaging and rear channel information in quadraphony are based to a large extent on differences in phase. A loudspeaker may have an accurate frequency response, but if its phase response is irregular, the consequence will be blurring, exaggerated musical sounds, or harsh tonalities.
Impedance Correction
Even if all of the aspects discussed above have been carefully observed, the impedance response will still have ripples which can only be controlled by an impedance compensation network. When properly constructed and employed, the impedance response between 100 Hz and 1.000.000 Hz is linear at 4 ohms. The connected amplifier is presented a nearly pure resistive load. The power amplifier can be operated under ideal conditions. Usually a loudspeaker is a difficult load for an amplifier, because complex signal portions generated by the capacitors and inductors require high circuit stability. But in the Dynaudio engineering approach, the loudspeaker system presents the ideal load for the amplifier and the sonic combination is always as good as the potential of the electronics.
Subjective And Objective Evaluation
Most audio enthusiasts have encountered components that share almost identical structure, design, and performance levels yet exhibit very different sonic properties.
It is the fuel that fires the quest for audio excellence. This is a phenomenon that we have often confronted in crossover design. There are several paths that will yield a similar response measurement, but in listening tests the products will have a personal signature that seems out of proportion to the design differences. In the design of the Special One two different technical approaches were followed, and then each was refined for precise measurable fidelity to the original signal. At each step there were extensive listening tests. These tests were performed independently, but as they progressed the two designs began to resemble each other in ways the design team had not foreseen. For example, for the first time ever we used a PC board layout that had no conductor paths. All components are connected directly or with large cable diameters. Inductance coupling of the coils on the copper coating was carefully avoided as well. This was an important experience because we recognized that many results cannot be generalized beyond the immediate experiment. Dynaudio products will continue to be designed experimentally; the designs will be ratified through patient critical listening.
Inductors
Well designed inductors with large wire diameters can often clearly improve the accuracy of response.
During the design of the Speacial One systematic tests with different coil formulation were made. We were able to learn that "The thicker the wire, the better the results" was often not the case. We found that the Q (or quality) of the inductor influences the sonic results at high frequency range, is an important contributor to the fidelity of the system. Owing to this experience, Dynaudio developed coils which have several conductors with different diameters in parallel, an advancement we have named CWC coils. Application of these coils makes possible a precise bass reproduction with more dynamic range and less coloration. We believe CWC coils will play an important role in all future Dynaudio products, though they must be part of the original filter design and loudspeaker project in order for the improvement to be maximized.
The Result
The Special One sounds like no loudspeaker has in the past. It has no special musical material but allows you to enjoy all music to its fullest potential. It is unobtrusive but intense. For those audio enthusiasts who are looking to improve the chain of high fidelity reproduction, the Special One will certainly stand up to a detailed evaluation; for those who love music the Special One will be a joyful experience.
