I am planning to upgrade the filter of my old Kef 105.2 speakers. The original filter is build with ferrite coil inductors, bipolar inductors and a couple of wire wound resistors. The circuit also has four large (120 uF) capacitors and a relay into the signal path. I presume this is intended to protect the speakers against dc on the input line.
All components are all > 30yr old, on first sight in good shape.
- The first thing I want to do is to forget about the dc protection circuitry (C1, C2, C2, C4, relay and 680 Ohm resistor on the original scheme). I think it is safe to do, since the amps I use have dc-protection circuitry. Am I right on this?
- I will internally rewire the units, probably with Kimber 4TC (mid/high) and Kimber 8TC low.
- I would like to remove the old foam insulation and replace it with something better. What is the best material to use in a closed cabinet? Wool? Pritex?
I intend to keep the original filter intact, and to build a new filter, hard wired with high quality modern components:
- for the low pass section I would like to use transformer core inductors, or maybe even Mundorf Zero Ohm inductors. The problem (?) is, that dc-resistance of the new components will be much lower than the old ones. I am pretty sure that Kef engineers calculated the dc resistances of the components they used into their design. So, is this a problem or not? Will the lower resistance of the transformer core inductors improve the impulse performance, as I would hope? Or will the altered dc-resistance change the characterics, resulting in just the opposite (poor performance)? Or doesn't it matter, since the dc resistance of the woofer itself (6.9 Ohm) is much higher than the components?
- Are transformer core inductors as good as is told? Or would any decent thick wire ferrite coil do the job? Or should I consider Tritec air coils to be a better choice? Tritec foils have a very good match with the original components in terms of dc-resistance.
- For medium and high section, I would use band foil air intuctors. Or should I use Tritec air coils her too?
- Capacitors will be MKP's, Clarity Caps or Audyn Cap. For the C's in series with the tweeter, I'm thinking of Jantzen Audio Silver Caps.
Well, at least this is what I'm dreaming of. Problem is, this is becoming some kind of 'cost no object' project (1000 USD??)
I would very much like to hear from people who have more experience than I do, about the choice of components I described above, and about the result I may expect by doing this.
Are my Kef 105.2 worth the investment?
All components are all > 30yr old, on first sight in good shape.
- The first thing I want to do is to forget about the dc protection circuitry (C1, C2, C2, C4, relay and 680 Ohm resistor on the original scheme). I think it is safe to do, since the amps I use have dc-protection circuitry. Am I right on this?
- I will internally rewire the units, probably with Kimber 4TC (mid/high) and Kimber 8TC low.
- I would like to remove the old foam insulation and replace it with something better. What is the best material to use in a closed cabinet? Wool? Pritex?
I intend to keep the original filter intact, and to build a new filter, hard wired with high quality modern components:
- for the low pass section I would like to use transformer core inductors, or maybe even Mundorf Zero Ohm inductors. The problem (?) is, that dc-resistance of the new components will be much lower than the old ones. I am pretty sure that Kef engineers calculated the dc resistances of the components they used into their design. So, is this a problem or not? Will the lower resistance of the transformer core inductors improve the impulse performance, as I would hope? Or will the altered dc-resistance change the characterics, resulting in just the opposite (poor performance)? Or doesn't it matter, since the dc resistance of the woofer itself (6.9 Ohm) is much higher than the components?
- Are transformer core inductors as good as is told? Or would any decent thick wire ferrite coil do the job? Or should I consider Tritec air coils to be a better choice? Tritec foils have a very good match with the original components in terms of dc-resistance.
- For medium and high section, I would use band foil air intuctors. Or should I use Tritec air coils her too?
- Capacitors will be MKP's, Clarity Caps or Audyn Cap. For the C's in series with the tweeter, I'm thinking of Jantzen Audio Silver Caps.
Well, at least this is what I'm dreaming of. Problem is, this is becoming some kind of 'cost no object' project (1000 USD??)
I would very much like to hear from people who have more experience than I do, about the choice of components I described above, and about the result I may expect by doing this.
Are my Kef 105.2 worth the investment?
