Wharfedale W60 crossovers

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Good morning,

I have a pair of very early Wharfedale 2-way W60s. The crossover is composed of an inductor, 12uf cap and 50 ohm l-pad. I have replaced both speakers' caps with 12uf motor runs.

When I received these, one of the speaker's tweeter wasn't putting out sound. When I opened the back up to replace the cap, lo and behold, I found that the 50 ohm l-pad had been replaced with a 50 ohm 1W or 2W potentiometer!

Obviously this needs to be replaced, but I'm wondering with what? It appears that the 50 ohm l-pads were unique to Wharfedale. I have seen crossovers on epay, but I don't want to fork over $60 for a single l-pad.

I had read elsewhere that it is possible to replace these with 8 ohm 50W mono l-pads. Does anyone have experience doing this? Will this change the response of the speakers or do incremental damage to the drivers over time?

Thanks for any help!
 
I'm surprised no-one has helped you here, Ggizzy!

What most of us do when faced with a crackly old level adjusting potentiometer on a tweeter is to hard wire it at a fixed level with two 10W wirewound resistors.

523587d1452211614-pioneer-cs-77-speaker-mod-suggestions-simple-crossover.jpg


These things go by various names like ceramic, wirewound and sandcast, but are cheap as chips at around £1 a pop.

There's even calculators, for 16 ohms, in your case:
LPad Driver Attenuation Circuit Designer Calculator

Not rocket-science. Come back to me if you are still struggling with Ohm's Law an all that! :D

I'd really need to see the circuit to be more exact, but it's probably fairly straightforward. Resistors are resistors at the end of the day.
 
Good morning,

I have a pair of very early Wharfedale 2-way W60s. The crossover is composed of an inductor, 12uf cap and 50 ohm l-pad. I have replaced both speakers' caps with 12uf motor runs.

When I received these, one of the speaker's tweeter wasn't putting out sound. When I opened the back up to replace the cap, lo and behold, I found that the 50 ohm l-pad had been replaced with a 50 ohm 1W or 2W potentiometer!

Obviously this needs to be replaced, but I'm wondering with what? It appears that the 50 ohm l-pads were unique to Wharfedale. I have seen crossovers on epay, but I don't want to fork over $60 for a single l-pad.

I had read elsewhere that it is possible to replace these with 8 ohm 50W mono l-pads. Does anyone have experience doing this? Will this change the response of the speakers or do incremental damage to the drivers over time?

Thanks for any help!

+1 to just replacing an L Pad it with regular resistors. There's nothing special abut an L Pad. Easy to measure with meter.

If you want to do something nice, I'd suggest the M&M combo. Mills 5 watt resistors and Mundorf MKP caps or M&A - Mills and Audyn

Oops, I guess Audyn doesn't make a 12uF cap, but you can get there by adding in parallel, or get another brand.

Or you can just spend as little as possible. :) But you may learn something.

Best,


Erik
 
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Those are really great, Steve! It is amazing what technology we now take for granted, when once-upon-a-time it was an innovation.

I wonder if I can use the use of solder, or electron flow as a marketing tool.

"The SNR-1, featuring silver content solder longitudinally aligned with each connection for more vibrant sound. "
 
I like revisiting memory lane sometimes, Erik.

The tools available to engineers in the 50's and 60's were quite basic, but if you knew what you were doing with them, you could get good results. Smith Charts worked with antennas and filters. AVO meters were ace! And we could all do calculation stuff in seconds on a slide rule. :D

I miss the old Decade Boxes, where you could just dial in capacitor, coil and resistor values without needing to unsolder components and fit new ones. You really could tune by ear, which is what Gilbert Briggs and others did.

But really most of those old engineers could just do mental arithmetic and other stuff in their heads. :cool:
 

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I apologise for not responding earlier. I had gotten caught up with another project and missed all the great responses. I have a few pictures here of the inside of the crossover. They are from the good speaker. I hope the quality is legible enough. I do not have a great camera on this computer.

The l-pad just appears to be a brightness control? I usually keep it almost nearly "up" or to the right/clockwise. I like more treble than bass for what I listen to. It's 50 ohm as stated before.

I also have a bunch of 10W value ceramic resistors laying about to use up!
 

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If we are to trust this wiring diagram...and it ought to be a simple coil on the bass with yours...

414882d1398504911-wharfdale-airedale-cross-over-wharfedale-tweeter.jpg


A 20R pot might be replaced by two 10R resistors for a middle setting.

A 50R pot might be replaced by 10R and 40R, if that is the setting you like.

A saw what looks like an old pair of Wharfedale Melton 2 in a local shop tonight. It was dark, but they were either Celestion or Wharfedale 12" bass and tweeter.

Will check them out tomorrow. My second ever speakers! :)
 

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The Meltons are £45. With 10" bass I guess. Interesting transparent dustcap, through which you could see the voicecoil former. Probably AlNiCo magnets at that vintage.

Must be very old from the look of them. Later sixties with the brown grilles, probably. But the tweeters were some sort of black 1" soft dome, which I don't think is original at all. They usually came with the purple plastic cones in a little cup-type enclosure, which fried rather easily.

Back to your question. Yes it does matter what order the resistors go. Boxsim came up with this for another 10" bass and cone tweeter. But your speakers may work entirely differently. You can only try to get back to the original layout and hope for the best.
 

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You've gotta trace the wiring from the inputs to the outputs. Draw a diagram.

526597d1453427632-wharfedale-w60-crossovers-wharfedale-w60.png


I can't really guess what the polarity on the tweeter is or even the impedance of the drivers. I'm usually quite cautious about avoiding amplifier blowup though. Keep it above 4 ohms in the shunt path.
 
Well, I am snowed in for the time being, so I went ahead and diagramed the Wharfedale crossover. I am not sure of the inductor's value or the specifics of the woofer and tweeter in these 2-way speakers. They do not appear to be labeled other than with the Wharfedale brand and their country of origin. There is a patent number on the back of the tweeter, if that would help.

I'm guessing that if I were to use the 40/10ohm combination, I'd play the 10 ohm in the shunt? I am still a bit confused on the issue. I appreciate your kindness and patience.
 

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Thanks for the reply.

So I would just substitute two resistors where the lpad is in circuit? The 10 ohm going to ground through the shunt and the 40 ohm before the inductor between that and the cap? Or should I place the resistors in the positions indicated in Steve's diagram?
 
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That circuit you drew makes no sense at all. The 50 ohm potentiometer is seeing full amplifier output. It will fry. It must come after the capacitor, like in the Wharfedale original print. Adding a coil to the bass path is trivial.

414882d1398504911-wharfdale-airedale-cross-over-wharfedale-tweeter.jpg


The full 50R strip shorts the live point after the capacitor to earth, and the slider adjustable tag connects to the tweeter +ve, and earth is earth for the tweeter. Then it behaves like a volume control. The two resistive arms of the potentiometer add up to 50 ohms, by, er, Ohm's Law. :eek:

Of course it won't measure that way with a 4-16 ohm tweeter adding a contribution to a multimeter measurement. But the idea is you set up the pot the way you like it, measure the two legs and replace with hardwired resistors.
 
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