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Old 14th October 2009, 12:34 PM   #41
tinitus is offline tinitus  Europe
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Yeah, didnt you say speakers sounds excellent, so why bother
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Old 14th October 2009, 04:59 PM   #42
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Default be careful !

or another "nightmare" may be about to begin ...

Read what I Posted in the Celestion 66 Mid-range Thread
in #293 on Page 30, and through to the end of the Thread,
including a bit in #301 on page 31.

I have to go now, as no more time today.
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Last edited by alan-1-b; 14th October 2009 at 05:01 PM.
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Old 14th October 2009, 05:48 PM   #43
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Quote:
Originally Posted by P.T.R.D Productions View Post
Hi all,...

Example....1.5uf 50V x 4=6uf 200v.....1x6uf 400v= correct uF...but not sure about extra 200V on caps....L.L (Low Leakage)........mite put my 66's in the wheely bin.....
The example given here is quite wrong and ultimately dangerous. and I don't mean to be rude here, but if you don't understand what I am about to write, you probably shouldn't be attempting this:

If you have 4 x 1.5uF caps, used in series they can, maybe, regarded as having a 200v rating, but they will collectively only have a 0.375uF value.

The 200v rating relies on the values being exactly matched so the voltage drop across all the caps while they are working is the same, your mileage may vary. Personally I'd not do it with any speakers (or amplifiers) I cared about.

Caps in parallel 'add' their values together, but they do not achieve higher voltage rating, in fact the rating drops to the value of the lowest. So paralleling 4 x 1.5u/50v caps gives you a 6.0uF cap with a 50v rating.

Once again if you don't know the difference between serial and parallel connections of components you are out of your depth and at best will end up with something that sounds awful, or at worst bursts into flames.

HTH

Stuart
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Old 14th October 2009, 06:47 PM   #44
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Thanks for advice......not attempted yet...but just reviewing the situation....but even though you have stated that my calculatios are incorrect...could you please tell me the correct way to achieve my gold.....repairing my crossover.....hopefully i will find a new tweeter.pair

Thanks
P.T.R.D
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Old 15th October 2009, 12:04 AM   #45
speedie is offline speedie  Australia
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Default connections

I thought that lorienblack had the issues with his speakers
must be more dud speaker connections in these models than warrants
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Old 15th October 2009, 04:15 AM   #46
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The picture you posted was very clear, in terms of the components shown, but can you give me a hand with the wires?

Looks to me like the round black disk with the pair of terminals is the input cup...

Then there is a pair headed upwards, to the tweeter?

There are two pairs headed off to the left, so I assume there is a pair of woofers?

One quick test, get a small, but full-range (not tweeter) speaker, then play music at a level you can clearly hear through the FR, reconnect the wires to the ditton, and make sure you hear the music at the back of the input terminals, just as when the FR is connected directly to the amp, then move to test at the end of the wires at the entry to the crossover boards.

Obviously if you can't hear the input clearly here, there are but two options, either the crossover is not to blame, the input wires are defective, or it's a dead short...

I'm going to look around and see if I can find an' official' schematic of the crossover.

Stuart
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Old 15th October 2009, 04:34 AM   #47
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and to answer the other question you posed...

You can definitely replace the components with modern correctly rated parts. Whether the result will sound different to the original is hard or probably impossible for me, you or anyone else to judge, since even a perfectly functional ditton 44 from that era will have components whose values have become quite different over the years, and (IMHO) nobody should trust audio memory from a different decade.

Given they are presently completely non-functional, getting the correct nominal values in a working crossover will give you an infinite improvement, and likely be as good or better than original. Obviously you can tune things once you achieve functionality, since virtually none of the moving parts will be within original spec, magnets lose strength, spiders stiffen or loosen, surrounds sag a little etc.

As other posters have mentioned, it's hard to imagine the coils are defective as long as they are still connected properly. Assuming no inductance tester, you can test this with a multi-meter, simply un-solder one end and then measure the resistance of the coil. It should be some quite low number of ohms or may simply look like a short circuit. Re-solder the end when you are done testing. It may sound silly, but basic metal fatigue can make connections flaky after many years of vibrating.

Assuming you can determine the values of the resistors from looking at them, unsolder one end and measure to ensure they are within a few percent of the nominal value.

With respect to the caps: the values you need are pretty easy to figure out, simply add up the paralleled caps. But as you are aware, these may not be available in a single exact match. The easiest way to make the final value is simply to parallel caps with the correct voltage to add up to the correct value.

I'd not be spending any large amount of money getting high end caps until you'd had some audition time with the original values in place, then you will have a chance to tune a bit and then spend the money where it does you the most good, better tweeter and mid caps. I find it hard to believe it's critical in the bass, since the caps there are 'subtractive'.

HTH

Stuart

Last edited by Stuart Easson; 15th October 2009 at 04:47 AM. Reason: more info...
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Old 17th October 2009, 07:41 PM   #48
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Default Capacitors' internal circuits

Hi Stuart,

-{and P.T.R.D. - do read this }-,

No capacitor is actually a pure Capacitance only, though some types, including the modern Polypropylene types,
are very close to pure capacitance in the frequency bands they are designed and manufactured for.

Even a simplified internal circuit of a capacitor would contain :-
three capacitors + three resistors + one inductor.

All these are significantly present in Electrolytic caps,
and to somewhat lesser degree in Mylar caps.

The effects of all these internals are audible, and only two of them are useful for cross-overs' applications -
- the rated Capacitance and the Equivalent Series Resistance -{ESR}.
Thus when one changes from electrolytics to polypropylenes,
an equivalent resistance to the ESR of the electro may have to be added in electrical Series
with the polyprop cap for the cross-over to continue to work in the way the original designer intended.

Even with polypropylene caps, there are differences made to the Transient Response of the audio signal
when polyprop caps with different internal plates' widths are connected in Parallel.
To retain the original transient response one should connect only caps of the same internal plates' widths in parallel.
Usually Axial type poly caps of the same body length have the same internal plates' width, at least when from the same Manufacturer.
For Radial type caps, the plate width is usually equal to the distance between the connecting leads.
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Last edited by alan-1-b; 17th October 2009 at 07:48 PM. Reason: to add a sentance
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Old 18th October 2009, 11:38 AM   #49
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Hi Alan, Tinitus et al,

If I find out the crossover points for the 3 drivers from Celestion, would making or even buying new crossovers be a simple matter, or complex? I ask because the notion of going from electro to polyprop with ESR values to calculate seems like a compromise at best.

Would it make sense economic sense to buy new air coil inductors and polyprops to conform to the ideal crossover points? I want my speakers to sound as good as they can. These drivers are really superb. Maybe it's a bit geeky and obsessive all this, but well, that's me! I could get all the caps for about £50 I reckon What about inductors?

Thanks, Lucas
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Old 19th October 2009, 08:55 AM   #50
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Default Sounds of the caps ?

Quote:
Originally Posted by tinitus View Post

Caps only have the sellers company name written
Relabelled, noone knows where they come from

Well, the only cap I have used is 100uf, on mids highpass
Dialectric is possible the cheapest

Ofcourse there are better caps
But I guess they are ok, and cheap
How good they are, I dont know

These NOS pios I got fore free
Unfortunately all 8uf
Thanks for your reply tinitus !

What does the 100uF mystery dielectric cap sound like
in comparison to other caps you have used for mids' highpass ?

Those PIOs look good - you are fortunate -
- I hope none of them are electrically leaky !

You can use all the same uF value in parallel if you use all the same type of cap,
and as you have 2 types of PIOs you have choice of 2 types of multiples of 8uF.

My experience is that different internal widths of capacitors' plates cause the audible problem when 2 or more different internal width caps are used in parallel.
The plate width is the distance between the 2 connection terminals in most modern Axial and Radial plastic film caps, but it could be anything inside an old PIO !
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