Kef Cresta 2s SP3303 second hand.
Original crossover.
A nutty sculpture of all the ferrous magnetic parts in the binding posts. Usefully the posts themselves are not ferrous.
The crossover board with all but one of the components removed showing the factory inductances.
Actual inductor measurements
L1 850uh 0.5 ohm dcr
L2 247uh 1.8 ohm dcr
L3 2.49mh 0.9 ohm dcr
Original capacitor measurements, quite good mostly in tolerance but slight upward trend that might indicate age. Who knows they might have carried on for decades more.
C1 10.8uf 0.08 ESR (should be 10)
C2 4.9uf -0.2 ESR (4.7)
C3 7.8uf -0.06 ESR (7)
C4 28.4uf 0.08 ESR (25)
ESR readings not that reliable.
So a further step might be to change L1 for an air core for less distortion in the bass (as it's in series with the woofer and the crossover point is a high 3000hz so well into mid frequencies) but it would be a lot bigger. The standard inductor seems to be high quality so going with that for now. The tweeter air core inductor is good, it could be changed for a baked varnish version.
The modified crossover with Jantzen lecap electrolytics and cross caps polypropylenes on the HF. Jantzens standard model capacitors, really very good value the parts cost including shipping was £32.
A mundorf metal oxide resistor for more detail in the HF, value increased by 0.4ohms to 2.2 ohms, hopefully enough to compensate for brighter mkp caps, it might need adjusting in practice.
The original ceramic resistor left in place for LF, wire-wound for sheer power delivery and inductance doesn't matter so much on the bass.
The HF air core inductor wrapped in self amalgamating tape and moved so it isn't pointing into the middle inductor, the drawback is that, it's now in the same axis as the bass inductors albeit separated a bit. Alternatively I could wrap it in foam and mount it off the side for better separation and or upgrade it, but for now it'll do.
Underside, converted from 4 terminal biwire to 2 terminal single wire with brass nuts and washers, the ring terminal is also copper so nothing ferrous in the signal path.
100nf Panasonic ecwfs bypassing the film caps.
There's a lot there to run in, after 10 hours it was sounding really good, lively, and capable of fairly clear very high volumes, which the original electrolytics couldn't do, it might improve further. The amount of detail and texture is beyond what I'm used to.
Thank you for viewing, comments, suggestions welcome and I hope this helps if anyone is doing their own mods.
(Dear Jantzen, if you could make the legs of cross caps 1cm longer to reach the board when mounted end on, it would be much appreciated)
Original crossover.
A nutty sculpture of all the ferrous magnetic parts in the binding posts. Usefully the posts themselves are not ferrous.
The crossover board with all but one of the components removed showing the factory inductances.
Actual inductor measurements
L1 850uh 0.5 ohm dcr
L2 247uh 1.8 ohm dcr
L3 2.49mh 0.9 ohm dcr
Original capacitor measurements, quite good mostly in tolerance but slight upward trend that might indicate age. Who knows they might have carried on for decades more.
C1 10.8uf 0.08 ESR (should be 10)
C2 4.9uf -0.2 ESR (4.7)
C3 7.8uf -0.06 ESR (7)
C4 28.4uf 0.08 ESR (25)
ESR readings not that reliable.
So a further step might be to change L1 for an air core for less distortion in the bass (as it's in series with the woofer and the crossover point is a high 3000hz so well into mid frequencies) but it would be a lot bigger. The standard inductor seems to be high quality so going with that for now. The tweeter air core inductor is good, it could be changed for a baked varnish version.
The modified crossover with Jantzen lecap electrolytics and cross caps polypropylenes on the HF. Jantzens standard model capacitors, really very good value the parts cost including shipping was £32.
A mundorf metal oxide resistor for more detail in the HF, value increased by 0.4ohms to 2.2 ohms, hopefully enough to compensate for brighter mkp caps, it might need adjusting in practice.
The original ceramic resistor left in place for LF, wire-wound for sheer power delivery and inductance doesn't matter so much on the bass.
The HF air core inductor wrapped in self amalgamating tape and moved so it isn't pointing into the middle inductor, the drawback is that, it's now in the same axis as the bass inductors albeit separated a bit. Alternatively I could wrap it in foam and mount it off the side for better separation and or upgrade it, but for now it'll do.
Underside, converted from 4 terminal biwire to 2 terminal single wire with brass nuts and washers, the ring terminal is also copper so nothing ferrous in the signal path.
100nf Panasonic ecwfs bypassing the film caps.
There's a lot there to run in, after 10 hours it was sounding really good, lively, and capable of fairly clear very high volumes, which the original electrolytics couldn't do, it might improve further. The amount of detail and texture is beyond what I'm used to.
Thank you for viewing, comments, suggestions welcome and I hope this helps if anyone is doing their own mods.
(Dear Jantzen, if you could make the legs of cross caps 1cm longer to reach the board when mounted end on, it would be much appreciated)
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