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Celestion Ditton 25 - Another eBay purchase..

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originalracingsnake

Member
I won the 25's by using a sniper plug-in, and I wasn't even on line when my bid went in, and won... Oh. Let me give you a little history before you all roll your eyes and declare the 25's terrible reputation for lack of midrange.. Yes, I have read all of the 25 related threads here, before posting, and the reason I came here will be apparent as you read on.

It is the late70's, I am a small boy with a Hi-Fi obsessed and upwardly mobile Dad. One day, he drives home in a car that is not his, an estate Hillman Hunter! What! Why? As soon as I ran out to see the reason became apparent, two HUGE boxes in the back of the car. Ditton 66's. Wow. Then more boxes... TD125 Mk2. Quad 303. Quad 33. Quad FM3. This was his system until way into the late 90's when he went all Naim. The 66's were sent top the naughty step, probably by my Mum, and in their place was something I can't recall from Monitor Audio. I bought a 34/405-2 at some point whilst living at home in my late teens, and paired them up with Tannoy Oxfords. Zip forwards..

66's were the goal, but the cost! My word. I ended up with these incredibly tatty 25's via the eBay bid. Veneer is shot. Covers are not too terrible. However they sound, well, underwhelming. I still own the Quads, and despite trying all combinations the 25's remain uninspiring. So I cruised the forums for others experiences and as a start, want to now rebuild the crossovers. This is my first time in a crossover, and I am not the type who will use boutique caps in things. £100 for a cap is way beyond my wallet.

Removing the board from the first speaker revealed some loose solder terminations for 2 out of the 3 I looked at.... So all of the cables were unsoldered and the board removed. Caps out. So as not to break protocol here, I am looking for some practical recommendations on what to recap with. I've got myself in a right state with Farnell, Mouser, RS, HiFiCollective, etc... and as a result no longer trust my selections! The values for the caps are as follows, as removed from the board:

24uf, 25v
A pair of 1uf, 250v caps in parallel
A pair of 1.5uf 250v caps in parallel
A 2uf and 1.5uf 250v caps in parallel

I have read and digested the forum advice elsewhere, and understand that you don't have to be spot on with the values when replacing, but it'd be nice to have it the way the ears at Celestion intended. Or perhaps there are better ways, ideas to be doing this?

Once rebuilt, I'll look at the cosmetics of the speakers. I don't mind them being patinated. Not bothered really as my music room is also my workplace, and I prioritise things working right over looking right...

Thank you for reading this far. Blame my Dad, that Hillman, and those 66's for this post.
 
If you want retain the original voicing then the simplest approach is to replace like for like otherwise you can end up in a real mess like that mammoth Ditton 66 thread over on DIYAudio demonstrates!

When I recapped my 66s, I used ALCAPs in the bass and midrange shunt positions, Mundorf ECAP Plains in the midrange series positions, and Ansars in the tweeter series positions.
I've never re-capped a 25 crossover, however, so cannot comment on how authentic these caps will sound in that application but I don't imagine it being drastically different to the 66.

Equally important as re-capping the crossovers is confirming that all of the drivers are working correctly, especially the HF2000s which are notorious for either being burned out or drifting off spec. In the one and only pair of 25's I briefly owned (a very early pair that looked like they'd been built in someone's shed!) one HF2000 was dead and the other was operating a good few dBs down in level from the HF1300 units and thus was contributing very little to the listening experience!

Would you mind posting a photo of your speakers and crossovers? My pair looked like this:

celestion-ditton-25.jpg
 
originalracingsnake said:
The single 24uf cap
https://flic.kr/p/2pFZLY3

Crossover out of the enclosure:
https://flic.kr/p/2pG6jXQ

More stacked caps:
https://flic.kr/p/2pFZLXg

All in pieces!
https://flic.kr/p/2pG5gNP

My paper based back up of the board:
https://flic.kr/p/2pG6jWC
Click to expand...
Excellent, you have a late model so, assuming they haven't been abused, chances are the crossover components and drive units will be in better shape than mine were. Still worthwhile replacing the caps though, especially if you found bad solder joints on the crossover, but worth putting them in a bag in a safe place in the event that you want to revert back to them. I'll post links to my cap recommendations shortly.
 
I'd replace the 24uF PYE electrolytic with a 24uF Mundorf ECAP Plain:

ECAP70-24: 24uF 50Vac / 70Vdc Mundorf ECap AC PLAIN electrolytic bipolar capacitor | HIFICollective

ECAP70-24: 24uF 50Vac / 70Vdc Mundorf ECap AC PLAIN electrolytic bipolar capacitor
www.hificollective.co.uk www.hificollective.co.uk

However if you don't mind wasting a few extra quid you could also try a Low-Loss ALCAP in this position and see which you prefer. There's no 24uF ALCAP so you'd need to make up the value by paralleling a 20uF 50V and 4.7uF 50V, a 20uF 50V and 4.2uF 100V, or three 7.5uF 50V. (IME electrolytic capacitors tend to measure a little higher than their printed value and slowly drift higher as they age so three 7.5uF caps will probably be closer to measuring 24uF than 22.5uF anyway!):

Alcap capacitors, Solen Capacitors, ClarityCap capacitors, for all loudspeaker crossovers.

Alcap capacitors, ideal for loudspeaker crossovers and networks. full range of 50V, 100V and Low Loss types, tolerances available .
www.falconacoustics.co.uk www.falconacoustics.co.uk

You have lots of choices when replacing the stacked green caps but the only type I have experience with is Ansar SuperSound and I found these very satisfactory when I installed them in my 66's. These caps tend to measure pretty much bang on spec so try to get as close to the required value as you can. If you can't achieve the required value with a single cap in each position then paralleling multiple caps is fine. I bought mine from Cricklewood Electronics but I just checked and they no longer stock them. They're selling Monacors instead. I have no idea how close in sound these are to the Ansars but chances are they'll be fine as they are also polypropylene:

Capacitors | Cricklewood Electronics

Visit Cricklewood Electronics for Professional CCTV Systems that give full security to the homeowner. We offer high quality Home Security CCTV Systems.
www.cricklewoodelectronics.com www.cricklewoodelectronics.com
 
originalracingsnake said:
This is superb, thanks very much!

I just walked into the study and found the HF2000 mesh on the carpet... It looks as if the dome is dented. :-(
Click to expand...
The mesh grille is dented or the tweeter dome is dented? The mesh grille is vital to obtaining the correct output level from the HF2000. Without it in place the tweeter output level will be approx -3dB quieter than it should be.

However, if the tweeter dome itself is dented then this will also affect its output level. After recapping the crossovers I suggest placing the speakers side by side, temporarily reattach the metal grille, and play 5kHz-20kHz band-limited noise* on the left speaker and then on the right speaker to see if you hear an objectionable difference in sound level and/or quality. If you do then you'll need to try to somehow 'suck' the dented dome back into its correct shape. If that fixes the issue then job done, if not then a replacement HF2000 will be needed. I have a small stock of HF2000s so may be able to help you out, but your wallet won't be happy I'm afraid!

* If you don't have access to such a noise signal then I can email you one. Or, if you'd feel more comfortable assessing the speakers with music, I can send you a mono music track that pans between the left and right speakers every few seconds. This makes it very easy to hear if something is amiss.
 
originalracingsnake said:
Grilles off:
https://flic.kr/p/2pG6k1v
Click to expand...
That's a bit of nostalgia. I have a pair of those that went into the spare room in 2004.

As for re-capping, the bipolar electrolytics for sure. I would not (at least initially) replace the green Erie type M312 ones. I suspect they are mylar or polyester and probably will be close to "as new". However I see you have already unsoldered them so that's a moot point.

I don't recall the Ditton 25 as being the most dynamic of 'speakers. Unlike others, my memory is that I didn't think it was a mid-range issue. However maybe I will sortie the pair and my Quad 909, replace the bipolar electrolytic capacitors and see if that opinion changes.
 
There's a quite informative thread on DIYaudio https://www.diyaudio.com/community/threads/celestion-ditton-25-crossovers.214488/
Post #12 shows the crossover diagram. Ignore the inductor values - they are all wrong as they were never measured!

I recapped my 44's a few years ago and they sound much better than I ever remember. I used film caps throughout but had to add ESR compensating resistors in series to get the sound balanced. Took much experimenting. (I bought them new 50 years ago and still love them).

That 24uF electrolytic cap is critical to the sound. The other ones look like film caps and they should last for ever. Earlier versions of the 25 used polar electrolytics in those positions.
 
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