Tuesday, 7 May 2013

Celestion Ditton 15 XR refurbishment

For 15 XR tweeter repairs please see this post: Celestion Ditton 33 Tweeter Repair

I have always been a fan of Celestion loudspeakers ever since hearing a pair of 662s as a young teenager. It took me about 20 years before I fulfilled my dream and managed to find a pair in London on ebay. In the meantime I had all but given up and had added a pair of A3s to the collection. My eldest son also got bitten by the Ditton bug so I started searching for a bedroom sized pair, namely the Ditton 15 XR. After months of saved searches on ebay I finally found a one-owner pair locally. They were untouched having been purchased in 1980, complete with the original retro chrome stands and the seller even claimed that the grilles had never been removed.


The cabinet tops were a bit tired after supporting numerous plant posts but the overall condition was very good.  We got them home and having never heard a pair, were very pleased with the sound they produced, especially in the lower registers. Now, I am a tinkerer, so purists look away now.

First thing was to strip them to component form. Next up was ordering new parts: A pair of Supersound polypropylene capacitors were ordered along new gasket seals from Wilmslow Audio. New acoustically transparent grille cloth & QED cabling were also purchased.

The bare cabinets were wire wooled & treated to numerous coasts of Tung oil to feed the veneer. A coat of bees-wax finished them off. The bass drivers were carefully masked off & the metal surrounds sprayed in matt black. The capacitors on the crossover boards were replaced & the boards drilled to accept the new QED wire directly.


Next up was a copy of a modification done by Bruce at Briarsfield HiFi whose 15 XR rebuild I came across on the internet. It involved adding a logo to the passive radiator to replace the original funny looking white & black circle affair. The passives are tuned by mass so I had to be careful to replace all the mass that I needed to remove. I carefully cut out the black mastic centre which to me is what Celestion used as the tuning mass. They looked to me like they found them on the drill press.


Next thing was to use the laser machine to form new plastic centres which would be bonded to the passives. I built these up using three plys of white plastic, 3M double sided tape & black plastic. To regain the correct mass I also siliconed three steel washers into the recess I cut whilst removing the original centres.

I wasn't happy at all with the method that Celestion used to bolt the drivers to the boxes. The serrated washers had a tendency to twist the rubber suspension around the fixing holes so I machined up a set of sixteen washers from 4mm aluminium that fitted perfectly inside the pressed steel driver basket. The woofers were rotated through 180 degrees to counter act any suspension sag.


Next up was a set of badges to set them apart slightly from the norm. I copied the original badge design and added 'Limited Edition' to the base of the. These I machined from 3mm aluminium & finished with etch primer & matt black paint.

All the connections were cleaned & the speakers were reassembled. The grilles were recovered & new speaker stands machined from MDF, 4" soil pipe, floor spiked & sand filled. The results are very pleasing, producing a full, sweet sound. Played along side the similarly rebuilt 662s or even A3s, they can hold their own.



5 comments:

  1. Hi there,

    I am absolutely floored by what you have done with these speakers. Limited Edition is correct. I myself am a big fan of Celestion Ditton speakers and most British speakers of this flavor. I own a pair of Ditton 25s, as well as Kef 107s, IMF RSPM Mk IVs, Kef 104/2s, the list goes on..

    I am actually going to be embarking on a custom Celestion Ditton speaker, rebuilding cabinets for a pair of Ditton 44s with a modern tweeter but using the same midrange and bass driver. I am hoping to have some custom badges/plates made for them and after seeing what you've done with these beautiful 15 XRs, I am wondering if you would laser cut something for me? I would happily pay you for your time.

    Excellent work on these, what a great restoration and custom job!

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  2. Thanks Jeff, much appreciated. I would be very interested in seeing what you do to the 44s. When you are ready, let me know what you need & I will see what I can do for you.

    I picked up another set of 15XRs with perfect drivers but bad cabinets. I will also be building new boxes for these, building them up using CNC cut curved profiles from MDF in a sandwich effect. I just need to learn how to apply veneer.

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  3. Fascinating (and intimidating!). I've just bought a pair of Ditton 15s in excellent condition for £5 from the local charity shop...cleaned them up (removed the disintegrating foam, etc) and replaced the speaker terminals with gold-plated banana connections. They sound wonderful as they are...how much further do I want to go bearing in mind the fact that they're ancient speakers and components must be ending the end of their useful life? All best, John

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    Replies
    1. Hi John, you picked up a real bargain there! I think you will be fine to enjoy them the way they are. Celestions with their rubber suspension surrounds stand the test of time and should have plenty of life left in them. The only part that you may want to update would be the tweeter capacitor as these do decay over time. Other than that, feed them with a good clean source to prevent damaging the tweeters and they will serve you well. Enjoy, Gavin

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  4. great post, helped me a lot.
    thank you.

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