Hi, I have a set of used Kef 105 (first version) and they've been sounding a bit flat. I did a sweep of frequencies and it turns out that the mid range driver in one of the units isn't sounding at all.
I opened it up and skipped out the cross over and played some mid frequency tones and it works. Great! I've not blown any more drivers and don't have to start searching for a matched pair.
I checked the crossover and it has clearly been recapped and more over modified. (I was told it was recapped when I bought it, got receipts too). It was done by a very well known company. Not sure if I should name them or not.
First thing I did was disconnect the tweeter and subwoofer and play a tone through the crossover and lightly tap on the caps. When tapping on one of them the mid range driver started sounding.
Removed the crossover to find that the one of the legs of the cap wasn't solder to the board at all, it was a completely dry joint. I resoldered that and reassembled.
The driver is now sounding, but is way quieter than the other. I am a bit of a loss as what to do. Because the crossover has been modified I am not really sure whether I should go around testing all of the caps and just replace the ones that are out of spec - I mean the speaker is working, right? Or whether I should return the crossover to the original design.
I found this schem for the cross over online
The new values are:
The ones I've not filled in are on a separate daughter board that looks unmodified.
This is a picture of the cross in its current state, also a picture of the dry solder joint before I resoldered.
Any advice as to how to proceed is welcome, my gut says cut my losses and restore them to original.
I opened it up and skipped out the cross over and played some mid frequency tones and it works. Great! I've not blown any more drivers and don't have to start searching for a matched pair.
I checked the crossover and it has clearly been recapped and more over modified. (I was told it was recapped when I bought it, got receipts too). It was done by a very well known company. Not sure if I should name them or not.
First thing I did was disconnect the tweeter and subwoofer and play a tone through the crossover and lightly tap on the caps. When tapping on one of them the mid range driver started sounding.
Removed the crossover to find that the one of the legs of the cap wasn't solder to the board at all, it was a completely dry joint. I resoldered that and reassembled.
The driver is now sounding, but is way quieter than the other. I am a bit of a loss as what to do. Because the crossover has been modified I am not really sure whether I should go around testing all of the caps and just replace the ones that are out of spec - I mean the speaker is working, right? Or whether I should return the crossover to the original design.
I found this schem for the cross over online
The new values are:
| R1 | ||
| R2 | ||
| R3 | Missing | 47ohm |
| C1 | ||
| C2 | ||
| C3 | ||
| C4 | ||
| C5 | 30mfd | 30uF 100V |
| C6 | 10u J 400 | 10uF |
| C7 | Value not visible | 100uF |
| C8 | 6u8 J 400 | 7uF |
| C9 | Missing | 30uF |
| C10 | 2u2 J 400 | 3.3uF |
| C11 | Missing | 0.22uF |
| C12 | 3u3 J 400 | 7uF |
| C13 | Missing | 2.2uF |
The ones I've not filled in are on a separate daughter board that looks unmodified.
This is a picture of the cross in its current state, also a picture of the dry solder joint before I resoldered.
Any advice as to how to proceed is welcome, my gut says cut my losses and restore them to original.
Back in ther day, when we first got the KEF 105s, we removed the isolating thingies on th emidrange for an improvment in DDR/resolution.
dave
dave
If it's way quieter than the other mid, you'll have to check those two drivers against each other for sound output at some reasonable input level. If they match there, then go after the crossover components. Or maybe it's easier to just measure all the caps, if you have the tester that can do so.
Interesting how they pulled the Zobel off the tweeter. Being a KEF crossover, some components are there just to help present an overall "resistive" load to the amplifier. Burner components; but you can hear them because the amplifier "feels" them in the speaker load. Gets expensive to replace with better than stock quality.
Interesting how they pulled the Zobel off the tweeter. Being a KEF crossover, some components are there just to help present an overall "resistive" load to the amplifier. Burner components; but you can hear them because the amplifier "feels" them in the speaker load. Gets expensive to replace with better than stock quality.
Good point, I'll do that - issue is that the 105 is a bit of pain to work on. Lots of screws and panels.
I don't have one, but I've been meaning to get one. Don't the caps need removing from the board to test them?
Right, okay.
This is C13 and R3 right?
Sometimes they can be done in circuit - depending on their connection. If not, it's just one leg.
Yeah, C13 with R3. What that does is make the tweeter look more stable in impedance to the upstream crossover component network. Someone must've listened to it and decided it sounded more "airy" or something without these parts. I'd replace them, give the original design a chance; see how you hear it.
Thanks.
I think I am going to go back to the original design.
I am just going to get some electrolytic axle caps for them.
Ive heard that it's worth getting foil caps for the tweeter is that right and would that be for C9, C10, C11, C12 & C13?
I think I am going to go back to the original design.
I am just going to get some electrolytic axle caps for them.
Ive heard that it's worth getting foil caps for the tweeter is that right and would that be for C9, C10, C11, C12 & C13?
If in doubt, restore to original and use an equaliser to make your tonal changes instead of modifying the crossover.
I am going to do the tests we spoke about tonight, but if I conclude the driver is fine would this capacitor set be a decent enough deal:
https://www.falconacoustics.co.uk/kef-1051-replacement-capacitor-set.html
https://www.falconacoustics.co.uk/kef-1051-replacement-capacitor-set.html
Okay I just checked and it seems the driver is totally fine. Whilst it's open I'll see if I can find any glaring differences in resistances between the two crossovers.
Otherwise I'll just go for that falcon cap set.
Otherwise I'll just go for that falcon cap set.
A Chinese component tester can be bought for £ 20. The accuracy is acceptable for capacitors and resistors and it can measure the ESR of electrolytic capacitors, to see if these are still OK. Such testers are not usable for inductors - at least mine shows values which are 20 % off.
I am onto that too, I just bought a new multimeter with capitance. It doesn't do ESR but I am not sure what those ESR values should be anyway.
My question is really whether I should try and fix this crossover design or just restore it to original.
My question is really whether I should try and fix this crossover design or just restore it to original.
KEF, being a fairly renowned speaker manufacturer - I'd trust them. Which suggests "restore to original". Then if you think you can do better, like Mr "tear out the tweeter Zobel to make it sound better"... Maybe. But start at the baseline, then (hopefully) move up in performance.
All the same it takes a lot of care to modify a crossover without upsetting the blend of the drivers, and to know that you're not doing it to suit some problem in the current room, rather than for the good of the speaker. Therefore unless you know better, it's safer to return to original and keep your EQ settings separate to get the tone you need and to help with your room, since that won't change the blending of the crossover.
Thanks for the input.
I've got the cap meter on the way, should be with me by weds. I'll try and diagnose what's wrong for my own curiosity.
But I think the game plan is to return it to stock.
If I need to by lots of new caps, then I'll buy that kit from Falcon. But if I can cobble something out of what I have plus a handful of new ones the I'll do that. Definitely need to clean up the board and soldering though!
I guess there is no harm in having caps with an unnecessarily large voltage rating - as the current caps do?
I've got the cap meter on the way, should be with me by weds. I'll try and diagnose what's wrong for my own curiosity.
But I think the game plan is to return it to stock.
If I need to by lots of new caps, then I'll buy that kit from Falcon. But if I can cobble something out of what I have plus a handful of new ones the I'll do that. Definitely need to clean up the board and soldering though!
I guess there is no harm in having caps with an unnecessarily large voltage rating - as the current caps do?
I've bought the falcon kit. Just going to restore it to original. At least if nothing else, I'll have an idea what these speakers were supposed to have sounded like new.