Castle Acoustics Pembroke Speakers Restoration Project

These are of the same model as the speakers I own and use. Got a great deal on eBay.

With a minimum of efforts, these should be looking gorgeous on top of being great sounding!

I may keep them (excuse for a second system, anyone? ) or put them back on eBay (but parting with them will be hard after giving them all that attention, and they are such lovely sounding speakers to have. But I need the money these days...). In the meantime, they are providing a very nice way of keeping cleverly busy!

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Step 0 - Initial state

Left speaker

Right speaker

Miscellaneous

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Step 1 - Fixing the left bass driver

After checking that the electronics were not in a worrying shape, I plugged the speakers into the amplifiers... The spider on the left bass unit was detached from the basket, which generated vibrations; nothing dramatic. Nothing that Superglue Gel wouldn't solve!

And indeed, after 12h, I plugged the speaker back, and did some testing. A few clean sine waves (40 Hz and a few others in the low range, generated using Audacity), then music, starting with Limit To Your Love by James Blake, as it proposes a great mix of electronically generated deep bass along with a generous helping of the rest of the audible bandwidth.

Back to sounding as good as new, properly gorgeous: very clean sound, articulate medium, tight bass (amazing for the size).

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Step 2 - Wood restoration, right speaker

Steps:

1. Clean with a damp cloth
2. Dry with a dry cloth
3. Use 000 steel wool
4. Get rid of the dust with a dry cloth
5. Apply Restor-A-Finish with 0000 steel wool
6. Wipe dry
7. Wait for 30mn
8. Apply Feed-N-Wax
9. Wait for 30mn
10. Wipe with a clean cloth
11. Buff with a soft cloth

Let's compare directly...

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Step 3 - Wood restoration, left speaker

Plinth progression

Right side, before and after

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Final result

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Step 4 - Fixing the right tweeter

So, either the tweeter broke since the first test, or I wasn't too careful and too focused on the vibrating bass/medium driver! In any case, zero treble from the right tweeter...

After testing the components of the crossover network (all good) and applying a 10 kHz sine directly to the twitter (no sound), I unsoldered it and measured an open loop.

Finding an original component might prove difficult, and I am not too keen on using a pair of new but non-original tweeters. So I performed open driver surgery. What did I have to lose?

The small wire between the voice coil and the connection post is broken.

Four positive factors:

1. The cut is close to the connection post, far away from the voice coil, in a place where it is completely static
2. There is a possible overlap of the two broken ends
3. The enamel used for isolation appears to be pretty easy to get rid of
4. I have measured the voice coil between the loose wire and the other connecting post at 5.3 Ohm. The voice coil is in a good shape!

I need to find someone better equipped and more experienced than me to solder this, especially as it may be aluminium wire and thus need special solder (Alusol).

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Step 5 (much, much later) - Finally fixing the right tweeter

Many attempts later, a trip to France and multiple phone calls and visits to specialists, all with no positive result, that voice coil wire is decidedly too thin...

Last hope attempt, as it was more or less a make or break forever: I used a short length of copper tube (from a models/hobbies store) filled with a bit of solder wire and speaker cable elements, then inserted my two pieces of voice coil wire on each end. I applied heat from the soldering iron to melt the solder, and voilà! Contact, continuity and correct direct impedance! A few drops of super glue made sure that it will never, ever move around.

I soldered the tweeter back to the filters, put it all back together and started playing with HF sine waves. Sounds perfect! The test tracks provided a lot of pleasure too!

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Step 6 - Castle logo badges

Well know problem with Castle speakers: the logo badges break and drop off the cabinets. It is also quite difficult to source new or old badges due to the complicated history of the brand.

Of course that pair is missing its logos.

I used an online-sourced image of the logo, tweaked it in The Gimp, made is a vector-based SVG drawing in Inkscape, then transformed it into a 3D model using Tinkercad. Here is the STL file for 3D printing.

There is an online community of owners of 3D printers selling printing services, a bit like Uber for 3D printing. It's all on 3D Hubs, and, most importantly, there is a guy offering his services literally up my street. I was delivered the following in less than three hours, for the grand sum of £1.98!

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Text and specs

Our smallest floor standing system, the Castle Pembroke combines high performance with great flexibility. That is because it uses our acclaimed downward firing reflex port technique. This gives the twin advantages of dispersing the ‘chuffing’ effect common to all forward firing reflex designs and allows greater freedom of room placement. The Pembroke can be positioned very close to a rear wall without impairing sound quality.

A 130mm carbon fibre coned bass unit with a shaped 30mm pole, oversized magnet and long throw voice coil gives the Pembroke performance which belies its compact size with bass extension down to 52Hz. High frequencies are handled by Castle’s own low modulus polyamide dome tweeter used in many of our Classic Range models for its smooth extension, clarity and accuracy. Overall smooth, dynamic response is assured by the Pembroke’s audiophile grade crossover which also offers the option of bi-wiring.

Frequency Response 45Hz-20kHz
Nominal Impedance 8 ohms
Sensitivity 87dB for 1W at 1m
Amplifier Requirements 15-75 Watts
System Type Downward firing reflex
Bass Unit 130mm (5 in.) woven carbon fibre coned, cast chassis
Treble Unit 19mm (.75 inch) low modulus polyamide
Height 710mm (28 in.)
Width 190mm (8.4 in)
Depth 220mm (8.7 in.)
Weight Each 9.7kg (21.3 lbs)
Weight Packed 22kg (48.4 lbs)

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