Celestion Ditton 25 help needed

[planet10]

Maybe a bit late, but i found another map on my HD.

dave

 

[Galu]

Maybe a bit late, but i found another map.

Your new crossover circuit certainly appears to correlate with the physical arrangement of the circuit board.

5 inductors and 4 capacitors - that's all there is in essence.

Looking at the two sets of paralleled capacitors, I suspect that this crossover board may have been modified in the past.

Will be interesting to find out what the values of the capacitors on the board actually are.

 

[system7]

I just ran a rough sim of this speaker.

That 12" bass section is a bit strange. Wharfedale used to just run a 2mH coil on the bass in the Melton II. Which looks much better. As it is, the bass is running almost full range.

Phase was all over the place in my effort. This speaker would work a lot better with an 8" bass IMO. Then it all falls into place. I'd know what to do with that idea.

 

[phivates]

Maybe a mistake with the component values on the bass? Transposed? Strange indeed

 

[landlesspeasant]

In the picture of your crossover board, the yellow capacitors are film types and it looks like the brown capacitors are also film types.

If that is the case, then there is no urgent need to replace those capacitors.

The only capacitor that is in definite need of replacement is the black one at top right as this is an NP electrolytic and will have changed in value by now. This one must be C1 (24uF).

Hey Galu and Steve..... A really big thanks for your help ...
. This begs the question .... Would the speakers sound better if I replaced the film types with NP electrolytic ???
if some one has messed with these before .. Maybe they didn't make the best choice of cap .. What do you think ?? I'm thinking it probably won't make them worse ... But What do I know !!!
So this pair of 25's is actually my 2nd pair ..... I was half heartedly searching/ dreaming for a pair of 66's when I came across these going cheap last month £100 June 2018... and I couldn't resist . ...
When listening to them .. I noticed that on at least one of them the HF2000 wasn't really singing compared to my others and wondered what they would sound like with a revamp ... With a mind to do the same to my original ones if it didn't end in disaster, as I think the mid on those could be improved
I have just taken a pic of the board in one of the older pair ..

 

[landlesspeasant]

Yes, I agree there. Only one NP to replace!

BTW, that schematic I dug up is clearly wrong. We had a thread a while back on this speaker, and the guy adding the new capacitors got quite confused IIRC.

Thanks ... I'm tempted to replace them all with the NP electrolytic ..See if it would help . ( but thats probably because I have no knowledge or sense )

 

[landlesspeasant]

Maybe a bit late, but i found another map on my HD.

dave

Thanks Dave ? ... or Planet 10

 

[landlesspeasant]

At the moment I'm running a single pair off a Quad 405 with a quad 34 pre ....
Its a beautiful thing
I briefly had them both running off a horrible pioneer amp .... while giving off a wall of sound rarely heard in a terraced house .. I have great neighbours .. It just lacked the quality needed to justify using the 4 x 25's

 

[landlesspeasant]

I just ran a rough sim of this speaker.

That 12" bass section is a bit strange. Wharfedale used to just run a 2mH coil on the bass in the Melton II. Which looks much better. As it is, the bass is running almost full range.

Phase was all over the place in my effort. This speaker would work a lot better with an 8" bass IMO. Then it all falls into place. I'd know what to do with that idea.

This is above my pay grade unfortunately .... Does it take account of the ABR or is that a stupid question ?
The bass on these is so delightful .. ... I'd love to hear//own.. the 66's

 

[planet10]

. This begs the question .... Would the speakers sound better if I replaced the film types with NP electrolytic ???

Very unlikely. I won’t use NPs in a passive XO. Multiple 240 uF film caps means a biggish box for the XO.

dave

 

[Galu]

Would the speakers sound better if I replaced the film types with NP electrolytic ???

Looking at the pic of the board in the older speaker, I can see a mixture of electrolytic and film capacitors.

My advice would be to change all the capacitors to film types, with the exception of the 24/25uF, for which I would choose an NP electrolytic because of its high value.

Note that the blocks of paralleled capacitors can each be replaced by single capacitors of the required value.

 

[Galu]

There are two blocks of parallel capacitors.

I don't know the extent of your electrical knowledge so:

Just add the values of the capacitors in a block together to find the value of the single capacitor needed to replace the block.

You may have to use the nearest modern equivalent value for that single capacitor.

 

[system7]

Apparently all the caps can be replaced with new MKPs.

I found the old project thread:
Celestion Ditton 25 Crossovers

The crossover looks a bit unconventional here, but we seem to have got there. Everybody says it was worth doing. C5 is 2uF as Galu points out.

 

[Galu]

I found the old project thread:
Celestion Ditton 25 Crossovers

Well found Steve!

Just to avoid possible confusion, the OP in that old thread stated that C5 should be 2uF, not 3uF.

 

[system7]

I've corrected it Galu. Good pickup, as they used to say in ER.

We were being a bit dim with the 24uF Non Polar. In series with 8 ohms it might as well be an MKP.

 

[Galu]

Yes Steve!

The only advantage of using a 24/25uF NP electrolytic in this case would be that it's cheaper than the film equivalent.

 

[phivates]

Inductor values? Not 1H...

 

[Galu]

The inductor values are unknown.

The OP in the old thread did not have an inductance meter.

Ignore the 1H markings.

 

[system7]

The reason I spend time on threads is usually that there is something I like about a speaker, and some details I'd like to know so I can do something along similar lines.

Doubtless thunderous bass here. But it's always a problem finding a tweeter that can keep up with almost any big bass on loudness.

People who know me, know I have got this 8" one working very well.

Where should I go from there? The HF1300 is not really obtainable anymore. Double the cone tweeters and lower distortion, and add a supertweeter for better dispersion maybe. The Celestion 25 is an interesting design.

 

[Galu]

The Celestion 25 is an interesting design.

For me, the most interesting aspect of the Ditton 25 is its Auxiliary Bass Radiator (ABR).

Celestion described the ABR on the Ditton 15 as having a plastic foam diaphragm of high rigidity and low mass with a free air resonance of only 8Hz. The double roll suspension allowed excursions up to 0.75" with virtual absence of distortion.

The construction of the rear of the ABR mirrors its front.

A modern take on the ABR is the Klipsch Forte III which has a 12" woofer at the front and a 15" ABR or 'radiator woofer' at the rear.