2-Way Crossover Help

Discussion in 'DIY Discussion' started by JCdenton, Jun 30, 2020.

  1. JCdenton

    JCdenton

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    Hello,

    I was wondering if anyone could help me. I am a music enthusiast, and enthusiasm is what best describes it really, because I have no technical knowledge or education when it comes to setting up audio systems (I am currently trying to learn via youtube videos and internet research, but sometimes it is difficult to grasp some ideas when you come from zero knowledge and have no one to help). I recently got a pair of speakers given by a friend, which I knew didn't work, but since I want to learn about sound and electronics, I thought it was a good project to start my journey.

    The speakers are a pair of Wharfedale W2 Dovedales, which seem to be quite decent, but mine are crackly and failing. I opened them up and found that the drivers and woofers are ok, no apparent issues with wires either, and the problem seems to be with the crossovers (there's a potentiometer which regulates between bass and treble, and the sound turns on and off as I turn the knob)

    This might be sacrilege to some people here, but my main goal is to have them working well, and I don't care about having original parts, so I'm thinking that the best way forward is to get a set of new crossovers, as I don't have the knowledge to fix the originals and most certainly cannot make a new set from scratch. I have no particular interest in having a potentiometer to regulate bass, and treble, so to open up my options I would be happy to replace with something that does not offer this feature.

    I am however really struggling to find something which seems compatible. There is nothing written on the driver and woofer which specifies the wattage. In terms of impedance, the driver (a super 5) says "10 - 15 Ohms" and the woofer shows "12 - 15 Ohms". This implies a range and not an exact impedance, so I can't make sense of which impedance should be in the crossovers. One of the speakers also has a WMT1 transformer, but the other one doesn't. I don't know if this is the way it's supposed to be, or if maybe one is missing from one of the speakers (there are no screw holes to say that there was originally one that was removed)

    I found a document on http://www.troelsgravesen.dk/Wharfedale_cat_files/Wharf_kits.pdf which offers some technical information about Wharfedale speakers, including the aforementioned WMT1 transformer. I know the drives are super 5s because there's a sticker on them, but the woofers have no apparent identification. I did measure them and they are 12 inches with a sticker confirming the impedance to be 12-15 ohms, so my guess is that they are either one of the 12/RS/DDs on the list. This however still leaves a mystery in terms of wattage, and I can't seem to find what the total would be per speaker.

    Would anyone know anything about these speakers or would you be able to suggest replacement crossovers? Have I given enough information or is this insufficient for anyone to help?

    Thanks in advance, and I hope someone out there can help me get somewhere with my project.

    Best Wishes
     
    JCdenton, Jun 30, 2020
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  2. JCdenton

    lawrence001

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    I know these, I used to have the W4s and the Airdales myself.

    The first thing I'd recommend is to buy a contact cleaner spray (I use Servisol) and spray into the potentiometer, turning it about 30-50 times. Then see if it works better.

    Later on you could try replacing the capacitors with like for like values which might improve the sound even more.
     
    lawrence001, Jul 9, 2020
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    Sergeauckland likes this.
  3. JCdenton

    JCdenton

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    Hi Lawrence, really appreciate the advice, I'll try that to see where it takes me. As I mentioned I am completely new to this so am trying to teach myself via google research and youtube videos, so it's hard to do something when you don't have the knowledge to begin with. If the impedance of the cones were lower I think I would have managed to resolve the problem with a modern crossover, but in this case for some reason the impedance is really high, and I can't find anything made nowadays that matches it. I probab;y have a better chance sticking to the original parts.

    Thanks again!
     
    JCdenton, Jul 11, 2020
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  4. JCdenton

    Sergeauckland

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    Bit late to this thread but here goes anyway.

    Lawrence is right that the first thing to try is to clean the tracks of the potentiometer. If that doesn't work, you may be able to replace it, like for like.

    As to replacing the crossover, don't bother, as Wharfedale will have designed the crossover correctly for the drivers. As Lawrence also suggested, after all these years, it will be worthwhile replacing the capacitors in the crossover with like-for-like. Falcon Acoustics are a very good place to get replacement capacitors. They may also do a potentiometer replacement. Very helpful people.

    These crossovers use bipolar electrolytic capacitors, which are made internally as two conventional polarised capacitors back-to-back. After a number of years, they go out of tolerance (usually go high in value) and the crossover doesn't work as designed. Normally, electrolytic capacitors like to see a DC polarising voltage across them. In a crossover, this isn't possible, so the capacitors work without any polarising voltage, and this eventually leads to going out of tolerance. The coils in a crossover won't change value at all, unless they have been grossly abused, so don't need changing. Resistors also tend to have a very long life. I recently changed all the electrolytic capacitors in a pair of 40-year old B&W 801s, and checked the resistor values, and all were still in tolerance. #

    Hope this helps, anyway.

    S.
     
    Sergeauckland, Oct 25, 2020
    #4
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