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Multi-Way Conventional loudspeakers with crossovers

Celestion Ditton 25 Crossovers
Celestion Ditton 25 Crossovers
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Old 27th June 2013, 12:26 AM   #21
gmwhitehead is offline gmwhitehead  United Kingdom
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Join Date: Dec 2012
Update on progress with my 25s: I originally ordered PP caps as per Kei's photographs on spec, even though my speakers are some of the really early ones with tweeters mounted from the rear, but I've only actually gotten around to doing the work on them in the last few weeks.

The crossovers on these are organised very differently - there're a couple of coils and a 'big' cap attached directly to the binding posts on the back, feeding the 12" bass directly, and a pair of wires running the height of the cabinet to feed the crossover for the rest of the drivers. The capacitor values, however, are exactly the same values as in the later modles - though some of them are crazy large old things, and none of them high voltage ratings. I found that one of the bass filter caps in mine - date stamped Feb 72 :-) - whilst rated at 24uF only measures ~7uF!

The bass filter section of the crossover is a lot less comfortable to work on, and one of the two inductors in this section - which solders directly to one lead-out of the capacitor that needs replacing. I managed to snap this and had to spend quite a bit of time fixing my mistake. Another thing I didn't quite expect was that these older cabinets don't seem to be chipboard throughout. The sides at least showed a clean wood finish on the inside, suggesting that they may be plywood, and have heavy bituminous pads stapled hard against them.

I took lots of photos of the crossovers as I was working on them, and will post these later. The board for the mid-top is nice and easy to work on, and it's rather easy to bend the metal clips used to hold the original capacitors in place so that they fit the new caps - some of which I found were significantly larger than the newer 400V polyprops that replaced them.

Recapping the crossover made an immediate and noticeable improvement to the speakers. The mid filled out again (I have another pair of speakers at the rear of the room, and previously had noticed the lack of mid-range when I switched these in/out - but this no longer happens) and the tops gained quite a bit of sparkle. The bottom end regained some speed, and quite a bit of 'bop' that had been lacking from these speakers of late. Unfortunately I also found that one of my HF2000s had finally, completely and utterly given up the ghost.

I've since acquired a pair of Vifa D27TG-35 (these were recommended to me by a speaker refurbishment shop) which are sat in wooden plinths on top of the main cabinets, fed from the through-bolts of the original crossover meaning I can return them to stock if I ever want to spend the 150 it seems rear-mount HF2000s are currently selling for :-S

I think though that it's unlikely, as the results have been nothing short of stupendous. The top end has gained some airiness, clarity, and detail, and the speakers overall have gathered a touch of brightness - but without shrieking or sounding harsh so far. The new Vifa seems to be easily a match for a dying HF2000.

I've been playing a range of material through them, and for the most part really enjoying revisiting my music collation. They've already got me spending time just listening - but classical and jazz material are showing an emphasised warmth at the bottom end, and switching to pop/rock seems to highlight a bump in the response somewhere in the bass - I can't help wondering if this isn't related to the ESR of the filter cap for the bass driver.

I'm now trying to decide whether to swap the polyprops I put in the bass filter for alcaps or to add resistors in to try to compensate for the reduced ESR of the PPs. Or something else entirely. Either way, it's been an enjoyable experience and the results so far have been very entertaining indeed.

Pics from my recap to follow :-)
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Old 8th December 2013, 01:40 PM   #22
Jonbignall is offline Jonbignall  United Kingdom
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Join Date: Dec 2013
Location: Woking, Surrey
Celestion Ditton 25 Crossovers
Default Celestion Ditton 25 Crossovers

Hi all.

Jumping on the bandwagon as it were, I'd like to add my two penn'orth to endorse the comments previously made on this topic.

As a friend of the poster gmwhitehead, I put my long love affair with Epos standmount speakers on hold and bought a pair of tidy looking 25 mk2s from that well known auction site.

It was apparent that one of the HF2000s was dead, and this was duly replaced with the same Vifa tweeter Gerard used. Whilst the speakers then gave a big warm authorative sound, I never felt they had the clarity, definition and punch my Epos ES11s and M12.2s had. The midrange was rather soft and lacking detail.

Having heard the improvements to Gerard's 25s, and after some egging on, I finally ordered the same set of Solen MKP capacitors from Falcon Acoustics and got to work.

All I can say is wow, what a transformation! I'm not quite ready to ditch my Epos's, but the 25's now sound beautifully open, dynamic and natural. I'm currently running on my standby Nad 304 amplifier as my beloved Exposure XX is currently broken, but even with the old Nad, the sound is big, expansive and clear with a brilliant soundstage, I can only imagine how they'll be with the Exposure when it's fixed!

I would say to anyone considering whether to recap their crossovers in vintage Dittons of any model, go ahead and do it, the results will be well worth it.

At some point I may replace the remaining HF2000 with the other Vifa tweeter of the pair I bought as a preventive measure, but I can't hear any difference in treble output between the two speakers, so for now, I'm enjoying listening and rediscovering my music collection all over again!

Thanks to Kei for his informative post and pictures. It made my job a lot simpler!

Jon
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Old 6th December 2018, 04:43 PM   #23
sidsparks is offline sidsparks  United Kingdom
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Join Date: Jan 2008
Here are the inductor values that I measured
L1 440uH
L2 4mH
L3 345uH
L4 348uH
L5 196uH

This may be useful to someone.

Sid.
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