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Multi-Way Conventional loudspeakers with crossovers

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Old 8th October 2009, 01:20 AM   #11
Andy G is offline Andy G  Australia
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Quote:
Originally Posted by LucasAdamson View Post
The sound is like a whisper, and a distorted one at that,
sounds like the typical sound you get when you wire the tweeter where the woofer should be. (and vice-versa).... something I have never done btw
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Old 8th October 2009, 09:36 AM   #12
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Quote:
Originally Posted by Andy G View Post
sounds like the typical sound you get when you wire the tweeter where the woofer should be. (and vice-versa).... something I have never done btw
No, it's not that, but thanks.

1. Speaker wire and amp output checked with another speaker. Tick
2. Speaker connectors bypassed by taking speaker wire straight to crossover connections. Tick
3. Drive units individually tested to work. Tick
4. Solder joints wetted to ensure clean joints. Tick

It is completely befuddling. 3x crossover boards, non that work, all wired in correctly, no question. If, as has been said, caps going doesn't produce this effect, then what the hell do I look for? The coils failing? On all 3x boards?

The logical thing, for me, is to question the solder and possibly the wires, because it has the sound of a dirty negative return that lets only the faintest of a circuit, hence the tiny whisper of distorted sound.

Tell me, what is the sound of a completely failed capacitor? Are failed "metalised" caps going to sound the same as failed electrolytics? Some of these things are dated 1969 - 1971.
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Old 8th October 2009, 12:32 PM   #13
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I'd simply check the values of the electros, go to a local electronics shop, by cheap bipolars of the same value, replace in one crossover and try it out. Will only cost a few dollars at most and will rule it out. Capacitors can fail in many ways, if it has deveilped an incredibly high impedance you will get virtually no sound... I haven't heard a dead capacitor in a crossover, but If you think about it, the only logical things to be focusing on are the caps in my oppinion

It looks like some of the caps are film caps... I'd think it was far less likely that they would have failed, but anything is possible.. I think someone else already suggested getting some bipolars to replace them as well, which I think is a great idea, if it shows they are the problem, then get some good quality new film caps to replace them... bipolar electros are cheap

Tony.
edit: just realised the bit about the cap going high impedance was completly ** for the woofer, as it is in paralell in the low pass... however if it was almost a short circuit, then the amp would be having a hernia, and most of the drive would be being shunted off to ground... this could explain what you are hearing... perhaps a quick check with a multimeter is in order?
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Last edited by wintermute; 8th October 2009 at 12:55 PM.
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Old 9th October 2009, 02:21 PM   #14
elac310 is offline elac310  France
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1. If amp is OK
2. If external wiring is OK (not chewed by a cat or dog somewhere and no tiny piece of multi wire hanging between red and black on the posts of the amp or speaker)
3. If loudspeaker plug is OK (no short circuit between red and black as may happen with a speakon or other similar terminal where bolts are difficult to tighten and space between the two is limited)
4. If loudspeaker internal wiring is OK
5. If speaker units individually are OK
6. if no inciduous sabotage by 0-WAF partner or kid,

the source of the problem is clearly the crossover

AFAIK, in the 70s and 80s, it was not uncommon for british loudspeaker manufacturers to wire a capacitor in series with the woofer if not the whole loudspeaker; it offered a protection against turntable generated low frequencies and it was part of the enclosure adjustment ; I once got a pair of second hand KEF with one of them being dead silent whereas the box's speaker units were all working when connected individually directly to the amp; I made a schematic of the crossover, found out there was a serial capacitor and presumed this was the faulty bit, changed it and everything was then OK (needless to say, I changed all the 'lytics for film caps) . I have no other experience with semi-faulty electrolytics as I have banned them from any signal wiring.

Litterally, sounds strange that various crossovers all produce the same result; probability is low that the two old crossovers plus the two extra-bought NOS ones are all faulty in exactly the same manner (= same symptoms); I presume swaps have been made.

I would still reconsider item 1 to 6 of the above checklist.
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Old 9th October 2009, 02:27 PM   #15
elac310 is offline elac310  France
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I forgot to mention: I assume there is no other electric part in the speaker enclosure that could have been faulty, e.g. fuse, volume control etc...
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Old 9th October 2009, 03:52 PM   #16
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Default replace ALL the capacitors

Lorien, and Lucas ,

most, perhaps all, of the black capacitors will be now useless,
and likely also the orange capacitor,
and perhaps also the white capacitor - other than PYE as I cannot see clearly what type it is.

You will be wasting a lot of time testing these capacitors.

Disconnect them ALL from the other components, then measure the DC resistance of the Inductors to find out if they still have electrical conductivity.
If all are conductive, and fairly low DCR, then they will almost certainly be OK.

Go to the Celestion 66 Thread I listed in your other Celestion 44 Thread, and read what I Posted there about old capacitors,
and how to restore Celestion cross-overs to give similar sound with modern capacitors to the original, good, Celestion design.

Yes, there are a lot of pages and Posts to read through to find the ones relevant to only the capacitors,
but those are too many for me to have time to Post again here.

Lucas, read any parts there that Lorien does not clearly understand.

The applications I described do work for ALL types of cross-overs with these types of old capacitiors.

If you want to query something I posted in that Thread for specific reference to your case,
then please Post the Page number and the Post # of the relevant part of that Thread here.

If you can only afford to use low price, or UK available, replacement caps,
then list ALL the capacitors' marked values here and I will list some replacements for you to buy.
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Last edited by alan-1-b; 9th October 2009 at 04:12 PM. Reason: add a sentance
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Old 9th October 2009, 06:09 PM   #17
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Thanks Alan, you are a diamond for that. Now...

I feel like a complete klutz, because....

I just noticed that on the back of the speaker, on the outside of the cabinet (and we were working entirely on the inside) is an aluminium information plate on top of the plastic terminal mount, causing a perfect short circuit.

I feel like a complete moron. Problem solved. I only realised because I went out and bought another pair of these for myself this morning, and whilst replacing my terminals, I saw the plate, and instantly knew. Otherwise, we could have gone on for an age like this.

It wasn't apparent to us because on the inside, the mounting plate is plastic. So, so dumb of me! Thanks for all of your help. I will be replacing my caps soon enough, but it's no longer urgent.

Lucas
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Old 9th October 2009, 11:10 PM   #18
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Hey Alan,

For crossover upgrading on a 40 yr old Celestion 44 Mk1, I am thinking of replacing the lower value 2uf black ones with standard Claritycaps (Metalised polypropylene axials) and for costs sake, replace the larger values with non-polarised Elna or Nichicon electrolytics, to get as close to the original values as possible. Is this the way to go?

Many thanks for your help
Lucas
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Old 10th October 2009, 02:02 AM   #19
speedie is offline speedie  Australia
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Thumbs up crossovers

Lucas
It is so easy to get misled when attempting to diagnose any electrical fault, it seems like human nature takes over and clouds rational thinking
I see it like following a road map if you follow the streets (circuits) you will get to your destination just like all good map reading
I do hope that you get the speakers working to your satisfaction the bonus is that there are spare crossovers for future use and you havenít wasted any more time running around buying and changing any unnecessary parts
Good luck Speedie
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Old 10th October 2009, 02:13 AM   #20
speedie is offline speedie  Australia
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Default crossovers

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
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