I have a pair of KEF Cantor speakers that I bought new in 1975. They sound OK but after 41 years they must be tired and probably not sounding as good as they used too. On the PCB there are 3 components: Large white cylinder with many windings around an iron core; another but smaller wrapped in yellow plastic tape, and a much smaller black cylinder with a wire from each end. This is stamped N.P. 93-7432. (I've Googled this with no results). I guess this is either a capacitor or resistor?
So, what exactly have I got here, and should I replace anything?
You may guess (correctly) that I'm new to electronics, but I can solder and I'm willing to have a go.
Cheers, Mike
So, what exactly have I got here, and should I replace anything?
You may guess (correctly) that I'm new to electronics, but I can solder and I'm willing to have a go.
Cheers, Mike
Sounds like the first is an inductor, don't know about the 2nd and the third sounds like a non-polarized capacitor.
Can you post a pic or two for us?
Can you post a pic or two for us?
Anything like these:
KEF DN13 Crossover Type SP1036 hifiloudspeakers.info
If so then the black part is a cap, the yellow looks like an iron cored inductor and the white an airspaced inductor.
Edit... not sure on the white one. Has it an iron core ?
KEF DN13 Crossover Type SP1036 hifiloudspeakers.info
If so then the black part is a cap, the yellow looks like an iron cored inductor and the white an airspaced inductor.
Edit... not sure on the white one. Has it an iron core ?
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Hope this is it.
An externally hosted image should be here but it was not working when we last tested it.
Hope this is it.
Hope the picture got through OK.
Both the white and yellow components seem to have an iron core.
My seconds question was: do I need to replace any of these? If the capacitor (black one?), do you have any idea of the ohms/watt value based on the number NP 93-7432?
Supplimentary question: I was expecting to see a resister somewhere, but then, what do I know 🙂
Thanks, Mike
Both the white and yellow components seem to have an iron core.
My seconds question was: do I need to replace any of these? If the capacitor (black one?), do you have any idea of the ohms/watt value based on the number NP 93-7432?
Supplimentary question: I was expecting to see a resister somewhere, but then, what do I know 🙂
Thanks, Mike
Most probably the white one has an iron core too. The capacitor is an electrolytic, replace it with a film type (for example MKP) of same value and same or higher voltage. The inductors will last forever.
Coils don't degrade, electrolytic caps yes, pull it off, you should see a value mark somewhere. Replace with same spec electrolytic, or higher voltage value, reason see below.
The ESR of the electrolytic cap provides the resistance needed, so a good reason not to change with a film cap (much lower ESR).
Ralf
If any of the capacitors in the crossover are electrolytic, then they must be bi-polar.
Ordinary polar electrolytic do not like reverse voltage.
The electrolytic capacitor/s are the only items that could wear out.
Plastic dielectric capacitors can wear out if subjected to repeated severe over-voltage interference spikes, but in a crossover this is extremely unlikely to ever occur.
Ordinary polar electrolytic do not like reverse voltage.
The electrolytic capacitor/s are the only items that could wear out.
Plastic dielectric capacitors can wear out if subjected to repeated severe over-voltage interference spikes, but in a crossover this is extremely unlikely to ever occur.
Just desolder one leg of that black thingy and lift it to see if there is any value marking on the underside. The number you are seeing is probably a manufacturing batch number.
Actually the cap looks like a film to me - but if it is a NPE, follow Sam's suggestion and desolder it to look for a value, and replace with a film. Depending on the sensitivity of the individual drivers for which this XO was intended, the DCR of the iron cored chokes could well supply any required attenuation - indeed, careful selection of drivers might eliminate the need for any further R.
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Yes non polarised. What value is it ?
The picture in my link showed 4MFD (that's 4 uF or microfarad) at 50 volts working.
The picture in my link showed 4MFD (that's 4 uF or microfarad) at 50 volts working.
Thank you all for your help. I will take out the capacitor, look for a value and replace.
Incidentally, which of the three components is responsible for splitting the signal to the two drivers?
Mike
Incidentally, which of the three components is responsible for splitting the signal to the two drivers?
Mike
The components all work together to make a crossover.
Huge and massive oversimplification...
The capacitor will pass higher frequencies.
The inductor will pass lower frequencies.
So I would guess that one inductor will be in series with the bass unit allowing low frequencies through. The capacitor will be in series with the tweeter letting high frequencies through. The third inductor could be placed across the tweeter where it will 'short out' remaining lower frequencies. Working in conjunction with the capacitor and the tweeters own characteristics will enable the manufacturer to get the response they want.
Huge and massive oversimplification...
The capacitor will pass higher frequencies.
The inductor will pass lower frequencies.
So I would guess that one inductor will be in series with the bass unit allowing low frequencies through. The capacitor will be in series with the tweeter letting high frequencies through. The third inductor could be placed across the tweeter where it will 'short out' remaining lower frequencies. Working in conjunction with the capacitor and the tweeters own characteristics will enable the manufacturer to get the response they want.
Special crossover caps are available although you will have to search what is available in your area. Don't pay over the odds for so called boutique parts either.
Alcap 50V Standard Electrolytic capacitors for all audio and hi-fi loudspeaker crossover applications.
Alcap 50V Standard Electrolytic capacitors for all audio and hi-fi loudspeaker crossover applications.
Bit of a classic, the old 9L KEF Cantor. Looks like a simple 2mH coil to the bass and 4uF/0.3mH tweeter filter. Or thereabouts. 😀
Anatomy of KEF Cantor
KEF got a lot of mileage out of the 8" B200 and 5" B110 bextrene bass/T27 mylar tweeter. Lots of variations. I think there were a couple of versions of the bass, designated by SP numbers.
Falcon Acoustics and Wilmslow Audio do a lot of reconstructions of the various old KEF filters. The 104ab was one. And they aren't expensive. Once you've identified the exact bass, there's nothing stopping you fitting some of the later, more sophisticated filters. 😎
Anatomy of KEF Cantor
KEF got a lot of mileage out of the 8" B200 and 5" B110 bextrene bass/T27 mylar tweeter. Lots of variations. I think there were a couple of versions of the bass, designated by SP numbers.
Falcon Acoustics and Wilmslow Audio do a lot of reconstructions of the various old KEF filters. The 104ab was one. And they aren't expensive. Once you've identified the exact bass, there's nothing stopping you fitting some of the later, more sophisticated filters. 😎
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As suggested, I have de-soldered the black component (see photo above). The wording on it is as follows:
+ ELCAP +
+ 4MFD +
+ 50V +
+ N.P. +
It is 2cm (3/4") long, black with red ends and a wire at each end.
It seems to be of hard plastic.
I presume that ELCAP means Electrolytic Capacitor but from what I've read EC's are all polarised. The PCB gives + & - at the holes, but I'm confused by all the + signs on the cap. No mention of any minus. So is this a non-polarised cap as indicated by the N.P.?
Should I get an exact replacement (if poss) or a more modern equivalent?
Thanks again
Mike
+ ELCAP +
+ 4MFD +
+ 50V +
+ N.P. +
It is 2cm (3/4") long, black with red ends and a wire at each end.
It seems to be of hard plastic.
I presume that ELCAP means Electrolytic Capacitor but from what I've read EC's are all polarised. The PCB gives + & - at the holes, but I'm confused by all the + signs on the cap. No mention of any minus. So is this a non-polarised cap as indicated by the N.P.?
Should I get an exact replacement (if poss) or a more modern equivalent?
Thanks again
Mike
Yes, its non polarised. There is no plus and there is no minus... I guess the two plusses are meant to mean you can connect either end to the most positive point in a circuit. They could just as easily be two minuses.
Electrolytics can be either polarised (the most common) or non polarised. You can also make a non polarised cap by connecting two normal polarised ones in series and back to back but the 'real deal' is better for a crossover cap.
Electrolytics can be either polarised (the most common) or non polarised. You can also make a non polarised cap by connecting two normal polarised ones in series and back to back but the 'real deal' is better for a crossover cap.
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