KEF 103.2 crossover upgrades
- Thread starter leesonic
- Start date
They're huge, but it's doable. I used a pair of 150uF, but they were Erse PulseX - I have no experience with any other caps on these boards.
Hello friends of the cultivated British sound,
40 years ago I built a KEF CS5 kit (equivalent to Kef Carlton) and am still happy with listening to them today. I have more free time because I don’t have to work any more so I have dedicated some of my time to improve my old speakers. I built the housing a little higher, there is a dead space, which I filled with 5 kg of sand some time ago, the improvement was clear. The image is much more contoured.
Finally, I turned my attention to the crossover. First I replaced the capacitors with Mundorf MKP. The old electrolytic capacitors were still OK from a measurement point, but the improvement with the new MKP was there. Then I removed the two 300 pf capacitors without substitution and the sun came up, I had more and clearer bass.
Encouraged by this significant improvement, I have now completely rebuilt the crossovers and wired them freely without a circuit board. I replaced the MKP capacitors in the tweeter's signal paths with higher quality ones from Mundorf and Jantzen. I installed a stranded air coil in the high frequency range and a high-quality core coil around the low frequency range.
The result is overwhelming for me. The bass is deep and precise, the stage imaging is wide and deep. The instruments and singers are in the room. Female voices now sound the way I always wanted them to. So I am very satisfied. The next speaker project I have in mind will have to wait.
But I don't want to hide one small thing. I've been using Aperion Supertweeter on my speakers for half a year. I had to significantly reduce their efficiency. But without these super tweeters, I don't want to hear the Kef anymore.
kind regards
Franz
40 years ago I built a KEF CS5 kit (equivalent to Kef Carlton) and am still happy with listening to them today. I have more free time because I don’t have to work any more so I have dedicated some of my time to improve my old speakers. I built the housing a little higher, there is a dead space, which I filled with 5 kg of sand some time ago, the improvement was clear. The image is much more contoured.
Finally, I turned my attention to the crossover. First I replaced the capacitors with Mundorf MKP. The old electrolytic capacitors were still OK from a measurement point, but the improvement with the new MKP was there. Then I removed the two 300 pf capacitors without substitution and the sun came up, I had more and clearer bass.
Encouraged by this significant improvement, I have now completely rebuilt the crossovers and wired them freely without a circuit board. I replaced the MKP capacitors in the tweeter's signal paths with higher quality ones from Mundorf and Jantzen. I installed a stranded air coil in the high frequency range and a high-quality core coil around the low frequency range.
The result is overwhelming for me. The bass is deep and precise, the stage imaging is wide and deep. The instruments and singers are in the room. Female voices now sound the way I always wanted them to. So I am very satisfied. The next speaker project I have in mind will have to wait.
But I don't want to hide one small thing. I've been using Aperion Supertweeter on my speakers for half a year. I had to significantly reduce their efficiency. But without these super tweeters, I don't want to hear the Kef anymore.
kind regards
Franz
Hi Gwem,
I removed the 300 pf capacitors without substitution and the improvement was great.
Kind regards
Franz
case310350
New Member
anyone have the crossover schematic with the protection circuitry? 103.2 kefs
I also read the metallized film is not a good option for crossovers>
Film capacitor selection is extremely important to achieve an acceptable quality sound reproduction. Consider the Root Mean Square (RMS) AC rating of the speaker system when selecting the appropriate capacitor since over voltage of a capacitor can result in the premature failure of the component. Additional parameters are the ESR and Dielectric Absorption (DA) of the film capacitors. These values must be as low as possible to avoid distortion.
The board has installed the Electrocube 967D series polypropylene and foil capacitors. Electrocube does not recommend a metallized capacitor for this type of application. The 967D series is designed specifically for audio applications, providing important characteristics of low ESR, low DA, high insulation resistance, and wide temperature range. A high quality, non-polarized electrolytic capacitor, when paralleled with the 967D series, results in the production of quality, premium sound.
I also read the metallized film is not a good option for crossovers>
Film capacitor selection is extremely important to achieve an acceptable quality sound reproduction. Consider the Root Mean Square (RMS) AC rating of the speaker system when selecting the appropriate capacitor since over voltage of a capacitor can result in the premature failure of the component. Additional parameters are the ESR and Dielectric Absorption (DA) of the film capacitors. These values must be as low as possible to avoid distortion.
The board has installed the Electrocube 967D series polypropylene and foil capacitors. Electrocube does not recommend a metallized capacitor for this type of application. The 967D series is designed specifically for audio applications, providing important characteristics of low ESR, low DA, high insulation resistance, and wide temperature range. A high quality, non-polarized electrolytic capacitor, when paralleled with the 967D series, results in the production of quality, premium sound.
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case310350
New Member
what are the resistor values in the 1st schematic?
Thomaswhite
New Member
I had 1 speaker of my pair of 103.2's which had ceased to function, I ended up simply cleaning the corroded traces on the pcb, and soldering small copper wire across areas that were discontinuous. Speaker came back to life. Although the pair sounds quite good, I am certain that a total recap is in order to really do them justice. Falcon Acoustics sells a kit for the 103.2's, but does not include the caps for the protection circuit. I decided to give a go myself at re-capping, and just finished replacing all the caps in my beloved 104/2 speakers with new set from Falcon Acoustics along with new ferro fluid in the T33 tweeters, and I am thrilled with the result.
Philip moses
Member
Hi,
Has anyone got a circuit diagram for the sp2011a board?
All the boards seem different.
Especially the resistors and coils.
Thanks
Has anyone got a circuit diagram for the sp2011a board?
All the boards seem different.
Especially the resistors and coils.
Thanks
Mischa Kool
New Member
Nope, I have a diagram for the SP1144/1143, but it's probably different to what you want?
Have a nice day.
Attachments
Philip moses
Member
Thanks.
I probably don't need it as probably getting my tech to recap and remove the leaking protection circuit parts.
But i had thought about getting him to build new crossovers from scratch.
I'm hoping he can measure the coils and other non marked parts and go from there.
The caps are the same as the diagram but not the resistors.
The resistors and cons seem to vary.
I probably don't need it as probably getting my tech to recap and remove the leaking protection circuit parts.
But i had thought about getting him to build new crossovers from scratch.
I'm hoping he can measure the coils and other non marked parts and go from there.
The caps are the same as the diagram but not the resistors.
The resistors and cons seem to vary.
I have just completed a check and replacement of C3 and C4 of the protection system in my KEF 103.2. They were leaking and corroding the circuit board tracks as you all have found. So thank you all for your advice and tips.
The protection system on one of my speakers tended to operate well before the other. So I chose to remove the relay only on the speaker, which tripped early. With the relay removed this still allows a useful protection alert from the LED. I soldered a shorting link across the normally closed part of the relay circuit. The link shorts out the 680ohm resistor. Alternatively one may remove the 680 resistor and replace with a link. I believe the protection system was required in the 80s as amplifiers were not very powerful and tended to clip early. My amp is one of the new class D designs and clips at over 400watts, which is well beyond comfortable listening. I add below a sketch of the crossover circuit diagram showing the the protection circuit. The crossover diagram includes the detail from previous posts except that I have added the 680ohm protection resistor which is located next to the two 300mfd capacitors.
Above, the crossover prior to modification.
I removed a couple of the original ALCAP capacitors and checked values. they were all closer in tolerance than the replacements that I had purchased from Falcons, so I did not replace the originals.
I'm pleased with the repairs and the 103.2s sound amazing when powered by the modern low distortion class D amps .
The protection system on one of my speakers tended to operate well before the other. So I chose to remove the relay only on the speaker, which tripped early. With the relay removed this still allows a useful protection alert from the LED. I soldered a shorting link across the normally closed part of the relay circuit. The link shorts out the 680ohm resistor. Alternatively one may remove the 680 resistor and replace with a link. I believe the protection system was required in the 80s as amplifiers were not very powerful and tended to clip early. My amp is one of the new class D designs and clips at over 400watts, which is well beyond comfortable listening. I add below a sketch of the crossover circuit diagram showing the the protection circuit. The crossover diagram includes the detail from previous posts except that I have added the 680ohm protection resistor which is located next to the two 300mfd capacitors.
Above, the crossover prior to modification.
I removed a couple of the original ALCAP capacitors and checked values. they were all closer in tolerance than the replacements that I had purchased from Falcons, so I did not replace the originals.
I'm pleased with the repairs and the 103.2s sound amazing when powered by the modern low distortion class D amps .