The Calvini is a classical dynamic loudspeaker.
The extraordinary tube amplifiers of KR-Audio work in single-ended triode mode. A type of amplifier which is a sonic dream, but terribly inefficient.
Even the smallest model, delivering mere 12W of power is a giant within this class of amplifiers. So a fitting speaker needs to be very efficient.
The HighEnd fair took place in Munic the first time in 2005. The listening cabins were tiny. Therefore I was requested to develop a a compact, efficient Loudspeaker, for small rooms and close listening distances.
I designed a 2-way loudspeaker with two midbass drivers placed symmetrically above and below the tweeter. To achieve a high efficiency I chose 6.5" divers from Vifa.
It´s not without reason that the 17WN225-8, the senior, was listed for many years in Vifas portfolio till recently. A lightweight and lowloss moving system and a virtually free-of-resonances coated paper diaphragm work in a small sized cast aluminum basket. A similar clean rolloff could be found with Seas drivers featuring unfilled Polypropylen diaphragms, like the WP170. However, in combination with lossy surrounds those drivers sounded indeed clean but also lame.
The parameters qualify the driver exquisitely for small bassreflex cabinets.
The driver shows a very smooth amplitude response even beyond 3kHz and such a clean rolloff, that one might omit with a crossover alltogether.
More modern and pricy drivers couldn´t perform any better.
The BR-alignment is chosen to give a lower bandwidth limit of 60Hz in 12.5L volume. The raised lower limit goes together with a smooth rolloff towards lower frequencies. Placed in close proximity to a wall, the wall assists the low bass down to approximately 40Hz. The usual lower-F alignments lead to a boosted boomy bass if the speaker is placed close to a wall.
One single lowloss foil-inductor limits the working frequency range of the two parallel connected midbass drivers to 2kHz. This way the Calvini achieves a efficiency of true 90dB@1m at 1W/4Ohm. At 2.83V it achieves 93dB@1m. The amplitude response is very smooth with a perfect rolloff.
Another Vifa-driver serves as tweeter. The XT25TG30-4 ring-radiator has meanwhile gained considerable fame. Without support it is just a bit to low in volume compared to the midbass dual. The support comes in form of a small tractrix-horn, turned out of massive aluminum.
The horn offsets the tweeter diaphragm backwards by 38mm. The time behaviour profits from this measurement. The step response appears very clean.
The horn is designed with a lower working frequency range limit of 2kHz.
Above 2kHz the amplitude response peaks at close to 100dB, followed by a steady and smooth descent up to 20kHz. With the electrical crossover frequency designed a bit ´too high´ using a small capacitor one can smooth out the amplitude response. Additional filter parts guarantee sufficiently steep filter flanks at the desired crossover frequency.
Above 15kHz the amplitude response drops swiftly because the driver can´t load the horn any higher.
Over the important range up to 5kHz the horn unburdens the driver alot.
The sound becomes more dynamic and less distorted compared to the naked driver. The horned driver sonics remain smooth and silky and doesn´t show even the slightest tendency of the naked driver to skirl.
The SPLs of the midbass drivers and the horned tweeter fit perfectly. No damping resistor networks are required.
The external crossover is housed in a clear transarent acrylic casing. It consists of just a handful of highquality parts. A series resonance network, connected in parallel to the speaker terminals, flattens the impedance response to easen the amplifiers life and to prevent high impedance outputs of tube amplifiers to spoil the amplitude response.
The cabinets of the speakers are manufactured from a mix of materials.
The large sized sides are made from simple rectangular sheets of granite. You see a Labrador Blue Pearl.
The frame out of the lid, front, bottom and backside are made from easy-to-work-with wooden chipboard coated with a brushed true aluminum foil. The bassreflex channels are formed as small slots opening to the front. The channels also stiffen the cabinets.
A speaker stand out of the same mix of materials lifts the 24" high speaker to the right listening height.
The sonic performance of the speakers is very lively with lots of ´body´, combined with highly dynamic, still though smooth and silky highs. It´s really fun to listen at elevated volumes levels.
Because of the high directionality the sweet spot is small.
Standing freely in a room of more than 30m² floor space, a subwoofer should be added.