Crossover nightmare!!!!!!!

[LucasAdamson]

Originally Posted by speedie

lucas
just rereading your post and noticed that you had already diagnoised the fault in your previous post point number two speaker connections bypassed tick!
see ya
speedie

Yeah, it's funny, because I bypassed the speaker connections to where they connect to the board, but because they were still connected, I merely eliminated the possibility of bad soldering, not a total short, which I hadn't considered as it did seem totally impossible looking from the inside of the box, as both terminals were on an insulated plate. Doh! It does seem a bit weird for Celestion to put their speaker terminals onto an aluminium id plate with only cardboard washers to protect their tiny crappy connectors from meeting the plate.

[alan-1-b]

Unfortunately after Engineers have designed working Prototypes,
those get taken to Marketing Departments where the Visual Priorities are decided, such as where to put the Company's label , etc ...
AND, the Accounting Department ALWAYS wants least possible money spent,
thus likely why the cardboard washers !

Cardboard is a good insulator, when dry and undamaged,
and it seems no-one gave much thought to the Life Expectancy of this design,
nor referred the finished selling product back to the Engineering Dept !!

Now-a-days, as result of Consumer Safety Legislation,
there are final checks done which would hopefully find the potential problem you have discovered.

It is good that you have posted this, as other Celestion 44 restorers can replace those old washers !

************************************************** ***

There are some audio crossover suitable Bi-Polar electrolytics available.
They have larger surge voltage capability than standard bi-polars which are made for solid-state electronics applications primarily now,
thus are better for handling the peaks of loud audio signals.

List the all Capacitance values that are in your cross-overs,
and I'll Post the cheapest suitable replacements.

However, as it seems you don't mind extending to ClarityCap prices for the treble circuit,
such would be audibly beneficial in the midrange circuit also,
but you decide, and state what you prefer to install ... ?

Look carefully, as those Parallel connected black caps may not all be 2uF - some may be 1u5 or other values.

Don't worry if there is no EXACT available cap value for the large Series connected cap in the mids' filter.
Post what is there, and I'll recommend further.

Are you buying via Mail Order - limited to UK only ? - or can to EU ? - or can to USA/Canada ?
or only buying what you can find at a local over-the-counter retailer -{who ?}- ?

[LucasAdamson]

Thanks once again Alan. Well, now Lorian and I each have a pair of Ditton 44s, both with replaced speaker connectors, and now working very well.

Personally speaking, I'd like to replace the caps, because I think that the cost is justified by the potential improvement.

I know that electrolytic caps, and probably other types too, have an insidious degradation, that is hard to notice, but when replaced after 40 years, should take the speakers a leap back up to original spec.



From what I read, the mids and treble caps (C1, C5 & C6 on this photo) are much more critical for quality polypropylene caps, as they are on the + side of the drivers, filtering out the bass, whereas the others are on the return from the drivers and so can be served with electrolytics without any degradation of sound whatsoever. Is that about right? I interpreted that from this quote I read:

"When it comes to high-pass filters, the best-sounding capacitors are the high-voltage Mylar and polypropylene variety. (They're also the most expensive.) With low-pass filters, however, you can use any type of capacitor – it's the type of inductor that counts."

[LucasAdamson]

[IMG][/IMG]

[tinitus]

I would NEVER use any other than film caps, anywhere
Though I admit even the cheapest ones are awfully expencive when BIG

And Im not into expencive stuff either, just use what sounds good, and dont let the price influence your judgement in any way

Fore inductors, use only wire wound air core when possible
No need to use very thick wire either, unless you have problems with lack of control
NEVER use standard iron powder core
Find some good toroid core, if you need them big ones

Fore internal wire, just use ordinary cheap close to costing zero single solid core copper
And not too thick ones either

Yeah, many will agree
But a word of caution
The sound may change a lot, and maybe not even to your liking
When changing components, other adjustments may be needed too

Best I can say, dont overdo it
Im sure very many people hear miracle effects from certain components because they change the sound in a way that compensates for a flawed design, mostly crossover related
So, in many cases when a certain component is suggested as being better, it could easily be very different when used in any other design

And the point of all this? the "best" is not always the bette choise
But dont let that scare you

[wintermute]

Good to hear it is sorted. nice to know I was on the right track when I said it could be a short, just targeting the wrong spot

If you want some polyprops that should do the job without breaking the bank you could look at jarcars polyproylene caps They also have a range of electros suitable for crossovers for the larger values

They only have polyprops up to 10uf, but that will do you for most of the values you would need. certainly in the mid + tweeter section where it is probably more critical. (A bit under 13 pouds for 2 X 10 and a 4.7 would get you pretty close to your 25uf one (tolerances aside).

The big electros in the low pass I'd personally just leave as electros... will start getting expensive to replace them with film caps! There are caps available in film up to values close to that big but they are VERY expensive

Tony.

[LucasAdamson]

Originally Posted by tinitus

I would NEVER use any other than film caps, anywhere
Though I admit even the cheapest ones are awfully expencive when BIG

And Im not into expencive stuff either, just use what sounds good, and dont let the price influence your judgement in any way

Why? The prices are just crazy...it might cost me hundreds to re-cap my speakers like that. I'm going with polypropylene unless someone can give me a really sensible reason not to.

Originally Posted by tinitus

Fore inductors, use only wire wound air core when possible
No need to use very thick wire either, unless you have problems with lack of control
NEVER use standard iron powder core
Find some good toroid core, if you need them big ones

I'm keeping the factory installed inductors as they are. There's no way I can realistically become more knowledgeable about these things than the UK's top speaker company of the 1970's crossover designer.

Originally Posted by tinitus

Fore internal wire, just use ordinary cheap close to costing zero single solid core copper
And not too thick ones either

Now that's advice that makes a lot of sense. I will make sure it's OFC though, as it is only slightly more expensive and makes sense (to me).

Originally Posted by tinitus

Yeah, many will agree
But a word of caution
The sound may change a lot, and maybe not even to your liking
When changing components, other adjustments may be needed too

Best I can say, dont overdo it
Im sure very many people hear miracle effects from certain components because they change the sound in a way that compensates for a flawed design, mostly crossover related
So, in many cases when a certain component is suggested as being better, it could easily be very different when used in any other design

And the point of all this? the "best" is not always the bette choise
But dont let that scare you

That's useful information to hear. I hadn't considered that. I did think that there would be an ideal solution and only benefits, and as you say, maybe that's naive. Having said that, they are 40 years old....probably not at their best, like me.

[tinitus]

These film caps are ok, and affordable
http://frequence-shop.dk/produkter/39-pca-caps/

I know, not all what I wrote was aimed directly at you, but just a very short summary of what I would consider sensible fore a highend design

Anyway, IF you wanted to use the much better aircore inductors, a "meter" fore measureing caps and inductors is still affordable, maybe around 100GBP
A thing I couldnt do without and use a lot

OFC copper? nah, just strip ordinary wire fore house wireing. Maybe just look in a container, and its free
Just remember, just a single wire fore each driver terminal lug. DONT be tempted to twist multiple wires, and avoid very thick ones

[LucasAdamson]

Originally Posted by tinitus

These film caps are ok, and affordable
http://frequence-shop.dk/produkter/39-pca-caps/

OFC copper? nah, just strip ordinary wire fore house wireing. Maybe just look in a container, and its free
Just remember, just a single wire fore each driver terminal lug. DONT be tempted to twist multiple wires, and avoid very thick ones

Thanks Tinitus, that's very helpful. I will do the house-wiring copper single strand. Just one question - 1.5mm sq (light circuit), 2.5mm sq (sockets) or 6mm sq (oven) cable?

Those Danish caps are quite cheap. I am still concerened that it is not necessary to use anything fancy for the stage after the driver, as with the bass speaker. 2x 72uf caps per speaker is still a lot of money.

I might consider air core inductors in the future, but for now, I just want to return the speakers close to their original sound.

Also, I have a question: Can these bass return caps really be 72uf? They are so small, physically! Is that a realistic value? I thought it might be more like 7.2 or even .72 considering the physical size.

[wintermute]

Originally Posted by LucasAdamson

Also, I have a question: Can these bass return caps really be 72uf? They are so small, physically! Is that a realistic value? I thought it might be more like 7.2 or even .72 considering the physical size.

Assuming that they are indeed nonpolar electrolytics then for 72uF 50V it is more than reasonable that they are that small IMO That is the main (only?) advantage of Electrolytics over film caps, they pack a lot more capacitance into a given unit of size!

Check out this datasheet for the specs on some random non-polar electros I found through RS-Components. the 100uf 50V has dimensions of 10mm X 16mm (they didn't have a 72uF)..

Tony.