Celestion Ditton 25 help needed

[landlesspesant]

Hi there. I am trying to replace the caps on a pair of wonderful celestion Ditton 25's mark 2 circa 1980. I am looking for any tips, preferably from someone who has replaced the caps in vintage speakers before.

I'm looking for the schematic of the cross over, I've found only one online and would like to get the values confirmed before proceeding with the replacement.
All help greatly appreciated.

[RojDW48]

Non polarised electrolytics - as close as you can get - I have bought from these people before - they seem to know their stuff - https://www.hificollective.co.uk/com...apacitors.html

[Diabolical Artificer]

Welcome t' forum.

The lads at hifi collective know their stuff as Roj says, as long as you stay away from the boutique caps.

Modern film caps can replace the electrolytics if you can get the right value, you might have to put two caps in series to get the right value ( half the value for two caps the same).

Re the schematic, when I overhauled my Mission speakers, I drew out the schematic, it's not hard. you could always check using Spice if so inclined. If not, keep searching online, pics/images are a good source of info.

Andy.

[RojDW48]

Good point Andy - you can buy caps that are so expensive you are bound to hear the difference!!!

[Herald1360]

That's the squealing noise from your wallet!

[landlesspesant]

Originally Posted by RojDW48

Non polarised electrolytics - as close as you can get - I have bought from these people before - they seem to know their stuff

A big thanks for the link, they certainly have a wide range. Can you narrow down the field, I'm trying to get the original sound not up graded from the shop floor.
Here is a pic with the board not removed yet.

I see you're in Bristol too

[landlesspesant]

Originally Posted by Diabolical Artificer

Re the schematic, when I overhauled my Mission speakers, I drew out the schematic, it's not hard. you could always check using Spice if so inclined. If not, keep searching online, pics/images are a good source of info.

Thanks for the welcome
So far I've only found one Schematic ... and that's not for the lack of looking.
It would be stretching my abilities to lay it out on the Spice ..but I might try and learn as I go.

[Goldie99]

I assume you've already seen this thread ?

http://www.diyaudio.com/forums/multi...rossovers.html

[landlesspesant]

Thanks Goldie .. I have seen that one .. Its got a lot in it ... Almost every thing I need to know
I lifted this from it :

So I've managed to lift this from the web from some one said they used these per speaker.
1x 1.5uF 50v Low Loss + 2.2uF 100v Mylar Film cap
1x 3.3uF 50v Low Loss
2x 12uF 100v

Can any one rewrite these out with there C numbers as per schematic. That would help my confidence loads. And why the mylar film mix ? and the 2x 12uF are not a specified type ?
And any opinions on using this mix of caps would be a help ... I'm trying to get back to the original sound from the factory door
Here is a pic of one of the boards in situ ... Its looking good so far as reading the values might be poss
T.I.A .... Dom

[Diabolical Artificer]

Right someone's been in your speakers and have altered things. Those yellow caps are new. Perhaps they tried to tweak the frequency response.

Essentially you only have four caps (stick with me) going from the pic, top left, top middle and top right. Celestion used groups of caps to get the right value. The first two are three caps in parallel, (there should be two going from DIY thread). Caps in parallel get multiplied, see here - https://www.allaboutcircuits.com/tex...el-capacitors/. Therefore the actual values are 3u (1.5+1.5) and 3.5u (2u+1.5u) . You can use a calculator - http://www.learningaboutelectronics....calculator.php

So if you can find a 3u and 3.5u cap you don't need to get four caps. You could use one of these for the 3u - http://uk.farnell.com/c/passive-comp...apacitance=3uf or one on these for the 3.5u - http://uk.farnell.com/epcos/b32776t1...ilm-capacitors Doing it this way with film caps should mean it will be better than factory.

top right cap = 24u - http://uk.farnell.com/c/passive-comp...pacitance=25uf There are no 24u but 25u is near enough. the caps used in your Xover unless specially selected would have been 24u ish anyway due to the tolerance of the cap.

Bottom cap = 2u - http://uk.farnell.com/c/passive-comp...apacitance=2uf

I went with Farnell as they have a search engine. Hifi collective have a bloke at the other end of the blower who knows a bit about audio and has more time to help than the technical desk at Farnell though.

Hope that helps, Andy.

[Techman]

Comparing it with the picture in the link in post #8, it looks like the whole lot has already been replaced, so other than checking out what's there and how it's been done, leave it as it is. Why undo another repair persons work just for the sake of it if the job's already been done and done properly?

[Edward Huggins]

It's highly unlikley that you will ever get the original "factory door" sound. All the cone suspensions will have changed over time and even like-for-like crossver component replacements will have subtle variances.

[ajgriff]

By the way, how do the speakers sound to you as they are now?

Alan

[landlesspesant]

Originally Posted by Diabolical Artificer

Hope that helps, Andy.

Thanks Andy, this is a GREAT HELP
I'm wondering if I should return them all to the NP electrolytic type ... As this is what Celestion used for many a year in the 25's
Is this a stupid Idea
I have also a slightly older pair with a warmer sound. My end goal is to learn how to recap these ... After learning what to do on the newer pair.
here is a pic I just took from the older pair !

[landlesspesant]

Originally Posted by Techman

Comparing it with the picture in the link in post #8, it looks like the whole lot has already been replaced, so other than checking out what's there and how it's been done, leave it as it is. Why undo another repair persons work just for the sake of it if the job's already been done and done properly?

I'm wondering if going back to Electrolytic would improve the sound ?

Originally Posted by ajgriff

By the way, how do the speakers sound to you as they are now?

I am comparing them to my older 25's .. ( I got the newer ones cheap last month )
the newer ones maybe be lack a bit volume at the top end on one speaker ... And the very bottom .. doesn't quite ASTOUND you like the older ones can ... I think there is a bit of room for improvement in the mid on both ... I think
But when they sing .... WOW
I brought the newer ones last month for £100 ... I couldn't resist it ..

[Ted Kendall]

When the Cambridge R50 was first reviewed in HiFi News, Ralph West was so concerned by the shrieking treble response, Knowing that the designer, Bert Webb, knew better than that, he asked for another pair, which performed really well, as expected. On investigation, the errant pair was found to have been fitted with crossover capacitors of different type but the correct value, sourced when the correct type could not be obtained.

[Edward Huggins]

I think you may be expecting far too much audio excitement by re-capping the crossover. Whether you are using Electrolytics or Non-Polarised, Alcaps, Solons or even more exotic types, close tolerance or whatever - there are sonic limits as to what "improvements" can be made to older, well run in speakers such as these.....

[landlesspesant]

Originally Posted by Ted Kendall

When the Cambridge R50 was first reviewed in HiFi News, Ralph West was so concerned by the shrieking treble response, Knowing that the designer, Bert Webb, knew better than that, he asked for another pair, which performed really well, as expected. On investigation, the errant pair was found to have been fitted with crossover capacitors of different type but the correct value, sourced when the correct type could not be obtained.

Thanks Ted..
This is confirms my thoughts/worries ...
After looking closely at the 2 pairs .. I can see the later pair were not constructed with the same love as the older pair ..And a few other minor parts are more modern ,screws etc.. And i wonder if the choice of pp caps was also a compromise .. As the XO was made with electrolytic in the early days ..
Someone said that ALCAP or MKP would be a good replacement ...
I don't know the pros or cons of either !

Originally Posted by Edward Huggins

I think you may be expecting far too much audio excitement by re-capping the crossover. Whether you are using Electrolytics or Non-Polarised, Alcaps, Solons or even more exotic types, close tolerance or whatever - there are sonic limits as to what "improvements" can be made to older, well run in speakers such as these.....

This maybe the case ...
But nothing ventured .. etc

[RojDW48]

I have (so far) re-capped one of my Radford Studio 60 T-lines and the difference is just about discernible. Don't expect miracles - maybe we could compare these 'upgrades'? Whereabouts in Bristol are you? I'm in Whitchurch Village.

[Diabolical Artificer]

Those caps in yours, apart from the yellow ones are in a lot of Xovers of the time and like any electrolytic will have a tolerance, which for "normal" electrolytics it's -10/+50%.

In any passive Xover the caps form a filter with any resistors or inductors, would a few pico farads or nanofarads either way or the dialetric make a difference? You wouldn't think so, but who knows.

As other's have said re capping might make no or little difference, bi amping might or adding /taking away stuffing is likely to make more difference. I wouldn't bother unless there was a fault, check em with an ESR meter; caps for this application won't be cheap.

You could try just recapping the tweeter bit of the Xover though or as you have two pairs swap Xovers.

Whichever, have fun, Andy.