Restoring Wharfedale W3 speakers

[Dr Smith]

Hi,
I live in the Golden Triangle of Yorkshire Hi Fi home of Sugden, Wharefale, Richard Allen, Castle...and others. I'm fascinated with their products from the 60's and 70's. I recently picked up a pair of W3's and today I dessembled them intent on restoration. Please could somebody help me by telling me:

1. why the 12" drivers have polystyrene glued into the cones - see picture? Should I remove this?

2. The Super 5 and Super 3 drivers have felt annuli. Should I replace like for like or 'upgrade' to foam or rubber?

Thanks in advance.

 

[Galu]

Welcome to the forum!

The polystyrene diaphragm both lowers the resonance frequency of the driver an acts an an acoustic filter to reduce enclosure resonances heard through the cone.

You shouldn't remove the polystyrene.

In addition, the upper frequency response of the 12" driver shown in your post will be limited to around 1,000 Hz by the polystyrene.

If the felt has not deteriorated with age, I would leave well enough alone. A different material will change the response of the Super 5 and 3.

 

[Galu]

Super 5

For the record, the Wharfedale literature does not mention a Super 5 in relation to the W3 speaker.

The lineup is given as a WLS/12 woofer, a 5" W3 midrange and a Super 3 tweeter.

The 5" W3 midrange is described as having a cloth surround and a heavy cone which is chemically treated to reduce resonance.

This driver lineup is in accord with the crossover frequencies of 1,000 Hz and 5,000 Hz.

 

[Galu]

Actually, Dr Smith, your woofers are W/12/RS/PST units (RS = Roll Surround, PST = Polystyrene), which would have superseded the WLS/12.

Forgive me for going on so, but I too am a fan of early Wharfedale loudspeakers!

P.S. Dr Smith - are you also a Lost in Space fan? 🤓

 

[Dr Smith]

Hi Galu, I really appreciate your incite and expertise. You have already helped me a lot. So I'd like to ask you, what's your view on the polystyrene cone inserts? was this a standard option? Importantly, what's the thinking behind it? You mentioned the baffle acts like a hi pass filter and limits the frequencies, is this a desirable thing?

As for the mid range 5" W3 and the Super 3, the felt has deteriated in all the drivers so I'm set to replace it. Do you know where I can source appropriate felt?

Thanks for your help so far

p.s. I grew up with Thunderbirds and Lost in space. I haven't revisited these in many years, but on your prompt I shall. I'm a fan of si fi in general, Dark Star and Bladerunner (Mk1) being absolute favs.

 

[Stuey]

Oh, the pain!

 

[Galu]

I now read that the WLS/12 woofer was fitted with a thick expanded polystyrene diaphragm, known as a 'bung', which provided a degree of acoustical filtering. It also sported an inverted roll surround as is clearly shown in your image.

So, contrary to what I said in post#4, I'll go with your woofer as being the WLS/12! The 'bung' is therefore a standard fitting.

I believe that the 'bung', acting as a low pass acoustical filter, permitted the use of a simple electrical low pass filter.

 

[Galu]

Do you know where I can source appropriate felt?

Black melton wool cloth as used for clothing would do the job.

https://www.etsy.com/listing/1125794365/100-wool-black-melton-great-fabric-for

 

[Galu]

what's your view on the polystyrene cone inserts?

I'll add that the 'bung' provides extra stiffening of the paper cone, thus promoting pistonic motion.

 

[Dr Smith]

Thanks Galu. I see the crossover you poted differs from mine. I'll renew the caps with polypropylene from Wilmslow audio: https://wilmslowaudio.co.uk/monacor-mkp-polypropylene-capacitors/12-fd-monacor-mkp-capacitor

In the schematic I have it shows a 4mfd cap, yet I don't see one incorporated into the crossovers I have. I've tested the inductors for continuity and they seem fine so I intend not to replace these - is this wise?

 

[Dr Smith]

Re wool, I'll buy some, what glue do folk recommend to attach the wool annuli to the cones and frame?

Thanks,
Craig

 

[Galu]

I've tested the inductors for continuity and they seem fine so I intend not to replace these - is this wise?

I would keep them as inductors don't deteriorate or change in value (unless they have been severely overloaded - unlikely in this case).

In the schematic I have it shows a 4mfd cap, yet I don't see one incorporated into the crossovers I have.

Strange, it should surely be there. I shouldn't think the 3" would be comfortable simply piggybacking on the 5" without the 4 uF for protection.

what glue do folk recommend to attach the wool annuli to the cones and frame?

I suggest Anita's Tacky PVA Glue.

 

[Galu]

In the following thread, a W3 renovator mentions two capacitors, a 12 uF and a 2 uF:

https://audiokarma.org/forums/index.php?threads/wharefdale-w3-help.770054/

 

[Galu]

In the following W3 crossover, the cylindrical capacitor is a 12 uF electrolytic one and the rectangular block is a 2 uF paper in oil one.

 

[Galu]

Since you haven't commented on my findings, I should like to assure you that I have verified by calculation that the component values of 2.5 mH, 12 uF and 2 uF (or equally 2.2 uF) are correct for this crossover.

If you can't find the 2 uF paper in oil capacitor, it may be that someone has removed it for another purpose believing it to have special musical qualities.

 

[AllenB]

I've tested the inductors for continuity and they seem fine so I intend not to replace these - is this wise?

Normally it's a lower risk assumption to keep them as is. Measuring resistance isn't a bad thing to do, not only to see that they have continuity, but also the requisite resistance.

That said, if they were ever overheated they may have shorted a turn. You wouldn't necessarily detect this by measuring resistance. In that case they would lose their inductance and may effectively act as a short. The consequence depends on the circuit position.

Should I replace like for like or 'upgrade' to foam or rubber?

'Hifi' drivers have foam or rubber surrounds, but that doesn't mean that there's anything wrong with the traditional pleated cloth. It's just a different approach and it has it's merits.

 

[Dr Smith]

Since you haven't commented on my findings, I should like to assure you that I have verified by calculation that the component values of 2.5 mH, 12 uF and 2 uF (or equally 2.2 uF) are correct for this crossover.

If you can't find the 2 uF paper in oil capacitor, it may be that someone has removed it for another purpose believing it to have special musical qualities.

Morning Galu,
I had a very close look over the corssovers and found a small cap taped tp the inductor core covered with black tape. It's a 2uf and looks like an electrolytic bipolar. Before I found it I'd already ordered two 4uF polyporp given what it stated on the scematic I have. Should I reorder?
The cloth and glue have rrived so I'll get on with the support restore when I get a minute.

 

[Dr Smith]

Normally it's a lower risk assumption to keep them as is. Measuring resistance isn't a bad thing to do, not only to see that they have continuity, but also the requisite resistance.

That said, if they were ever overheated they may have shorted a turn. You wouldn't necessarily detect this by measuring resistance. In that case they would lose their inductance and may effectively act as a short. The consequence depends on the circuit position.


'Hifi' drivers have foam or rubber surrounds, but that doesn't mean that there's anything wrong with the traditional pleated cloth. It's just a different approach and it has it's merits.

Thanks Allen, i've opted for cloth to try to replicte the original construction.

 

[Galu]

Should I reorder?

Yes, 2.2 uF is the one you want. Wharfedale did not fit a 4 uF on this speaker.

 

[Galu]

P.S. The crossover circuit you have shown in post #10 is extracted from Gilbert Briggs' book 'Loudspeakers'. The circuit is the same as that in the W3, but the 4 uF capacitor is the wrong value for crossing at 5,000 Hz.

The actual crossover point using a 4 uF capacitor is, in fact, closer to 3,000 Hz, an error that was corrected in his follow-up book 'More About Loudspeakers'.