|Vifa Vivace '94 modifications|
Modifying the crossover, part 1
In phase one the MKP capacitors in the high-section have been replaced by tinfoil KP-SN parts and the MKTs in the mid-section by MKPs. The inductors in these sections have been replaced by types with a larger wire diameter and the standard wirewound resistors by MOX metaloxide types. The internal wiring has been replaced by silver-plated solid copper wire with teflon insulation.
After the first tones: it sounds terrible! The mid/high is rough, unrefined and shrill. But after a burn-in of a number of weeks the pleasant character of the silver and the tinfoil capacitors comes forward: the sound gains in detail and spacing and eventually it sounds a lot better than before the procedure.
This upgrade is highly recommended, but patience is mandatory!
After listening to the 'new' sound for a while it's noticable that things are not running smoothly in the high section yet. Instruments like cymbals and s-sounds have an annoying sharp edge that doesn't sound right.
There is some suspicion towards the metaloxide resistors, so they are replaced by the original wirewound ones. That's better: the sharpness has become considerably less (but hasn't disappeared...). Lesson learned: oxide does not belong in the audio-chain, but actually that's old news :-)
Modifying the Vifa tweeter
Found an article on the internet about damping the bore in the tweeter's pole piece. This should decrease unwanted resonances and make the high-end sound more pleasant. It's a relatively simple job: the bore can be accessed by removing the front plate and the dome assembly from the magnet, and then it can be stuffed with some damping material. And it works! The high-end has become more clear and the sharpness has disappeared almost completely.
Modifying the crossover, part 2
With the purchase of a Marantz SA8400 SACD player and a Nordost Blue Heaven interconnect the resolution of Super-Audio CD enters the livingroom. But this also clearly reveals that things are not yet running smoothly in the high-section. It lacks a certain focus, it sounds a bit smeared, messy. Hard to explain.
Found on the internet that the Vifa tweeter can be replaced by a D2905/9300 from Scan-speak. This is a higher quality tweeter and more attention has been given to damping of the resonances in the back chamber. The characteristic and parameters largely match those of the HT-275, so they are directly interchangeable. In the filter the electrolytic in the low-section will be replaced by an MKT and the inductor in the high-section by a CFI copper foil inductor. The resistors will be a Mills non-inductive MRA-12 for the mid and a nice 5W Kiwame carbon film in the high-section. So this is not going to be a problem anymore, that's for sure.
The result is a completely different Vivace '94! In a positive way, to be exact. The sound is so much cleaner and detailed, and then the soundstage, the depth. What a detail, what a space! Apologies for the euforic part :-). This tweeter is very suitable for this speaker. Anyone considering to build it would be better off to take this into account when purchasing the components, together with the improved filter. It will save a lot of tinkering (and costs) afterwards.
Time to listen to the CD-collection all over again... :-)