Help a poor noob pls!

[jw2k_fr]

Hi.

My first pair of loudspeakers were purchased when I lived in England and are about ten years old (lordy!). Two years ago, I used them as part of the entertainment system at our wedding reception and due to the temporary nature of the wiring, a short occurred across the speaker terminals.

Surprisingly the amp (a little Denon UD-M31) didn't bat an eyelid and is still doing sterling service as we speak. The loudspeaker in question, on the other hand didn't like it and instantly expired. I am just now getting time to investigate what blew.

When connecting to an amp, the other speaker works fine, but this one gives absolutely no output. The drivers show no visible damage and there was no audible sign that one channel had gone so I am assuming the problem lies with the crossover.

I have a basic knowledge of electronics and am the proud owner of a soldering iron, screwdrivers and enough enthusiasm to be dangerous! I am hoping that someone here may be able to help guide me through the process of troubleshooting and repairing what are a sentimentally valuable pair of speakers.

Here is a review of the speakers to give you a very basic idea of what they are:
http://www.audioreview.com/mfr/castl...2_1594crx.aspx

Here is a photo of the crossover (I hope I have identified the components correctly)



Components are labelled as follows:

Inductor A no label
Resistor A Expotus 7W 6.8ohms J
Capacitor A Expotus 4.7J 250V MPP

Inductor B no label
Resistor B Expotus 5W 6ohms J
Capacitor B Expotus 10.0J 250V MPP


Using my multimeter, the resistors appear to measure correctly, but I don't know how to test the caps or the inductors. I would expect to get continuity for the inductors, but don't - is that my meter or something else?

Any and all assistance with working out what's dead would be very much appreciated.

Thanks
James

[dark_avenger]

one thing to try is to wire each speaker one by one just directly to the amp to see if you get output (without the crossover) that way you can be certain if it's the crossover or not.

[Curmudgeon]

Yes, the inductors should have a resistance of less than perhaps 10 Ohms.

I assume you know that the inductor wire has an enamel insulation, so you can only easily measure from the board foil at the input and output of the inductors. That said, a blown inductor would usually show signs of a lot of heat, and I don't see that.

Caps need a special instrument, but when you connect the ohmmeter you should see a small "kick" of the needle (?) or flicker of the digits as the cap charges very briefly when connecting the meter.

Could there be a fuse tucked away somewhere? If you connect the ohmmeter or a 1.5 Volt battery directly across each driver, do you hear a small click? (Ohms X 1 Scale.)

[Hezz]

Originally posted by dark_avenger
one thing to try is to wire each speaker one by one just directly to the amp to see if you get output (without the crossover) that way you can be certain if it's the crossover or not.

Yes try this approach first but at very low volume level with the tweeter. If the speakers don't work they are bad.

A super easy way to see if the speakers are working is to brush the leads to the speakers across the terminals of a 9 volt battery. You should hear a click as was described above. But don't try this with the tweeter, it may damage it.

[sreten]

Originally posted by jw2k_fr


...... a short occurred across the speaker terminals.

Surprisingly the amp (a little Denon UD-M31) didn't bat an eyelid and is still doing sterling service as we speak.
The loudspeaker in question, on the other hand didn't like it and instantly expired.
I am just now getting time to investigate what blew.

Thanks
James

Hi,

A short across a speakers terminals cannot damage a speaker.
Whatever the problem is there seems to be some misunderstanding.
Swapping the crossover boards between the speakers will help.

/sreten.

[rabbitz]

Use a 1.5V battery to be safe.

To check the drivers, check the VC resistance using a DMM on the +ve and -ve terminals. That will give a good indication if it's an open (no reading) or closed circuit (0R). Look for a reading between 3R & 8R if OK (assuming they are a 4R-8R driver).

[jw2k_fr]

Originally posted by dark_avenger
one thing to try is to wire each speaker one by one just directly to the amp to see if you get output (without the crossover) that way you can be certain if it's the crossover or not.

Hmmm, I may wait a bit on this one - don't want to risk any un-necessary damage (I'm so new to this I am a little paranoid)

Originally posted by Curmudgeon
I assume you know that the inductor wire has an enamel insulation, so you can only easily measure from the board foil at the input and output of the inductors. That said, a blown inductor would usually show signs of a lot of heat, and I don't see that.

Could there be a fuse tucked away somewhere? If you connect the ohmmeter or a 1.5 Volt battery directly across each driver, do you hear a small click? (Ohms X 1 Scale.) [/B]

Oooh - yeah enamelled wires That made a difference. Am seeing a resistance of about 0.6ohms for one inductor and 0.8ohms for the other.

No sign of any fuses - you can see all the components from the photo - nothing under the circuit board other than the speaker terms.

Originally posted by Hezz
A super easy way to see if the speakers are working is to brush the leads to the speakers across the terminals of a 9 volt battery. You should hear a click as was described above. But don't try this with the tweeter, it may damage it. [/B]

Hmmm don't have a 9v at the mo, will wait a bit for that one

Originally posted by sreten
Hi,

A short across a speakers terminals cannot damage a speaker.
Whatever the problem is there seems to be some misunderstanding.
Swapping the crossover boards between the speakers will help.

/sreten.

The short occurred across the speaker terms of the amp whilst connected to the speakers - arcing was seen so I assume that the current flow went way up....

I will indeed swap the crossover boards - the simplest ideas are always the best!

Originally posted by rabbitz
Use a 1.5V battery to be safe.

To check the drivers, check the VC resistance using a DMM on the +ve and -ve terminals. That will give a good indication if it's an open (no reading) or closed circuit (0R). Look for a reading between 3R & 8R if OK (assuming they are a 4R-8R driver).

They should be 8ohm, but I get no reading - let's see what the crossover swap reveals. (I really hope the drivers are okay)


Thanks again!

[jw2k_fr]

Dag-nammit !

It appears that the crossover is fine and both drivers may be dead. I was really hoping to avoid that given how they are an unusual shape surround for the woofer.

*sigh* Guess I'll have to contact the factory regarding replacements.

However, on a similar note... I also have a pair of Castle Harlech S2 speakers which I upgraded to, from the Avons. The Harlechs are a measure less veiled than the Avons although both are very musically engaging. I wondered about upgrading the internal wire and perhaps the caps in the crossover. I've read a number of articles about replacing standard caps with Black Gates etc and wondered whether this might open up the sound to a degree?

Are there other components worth replacing? I don't feel confident to do the inductors as they are affixed to the circuit board, but what about the resistors?

I suppose I could consider replacing the drivers too, but given that the speaker was voiced with this cabinet in mind, I would be concerned about totally mucking up what the speaker does well.

Any thoughts?

[jw2k_fr]

Okay, I've extracted the tweeter from the cabinet:

Front:




Rear:




Nothing really to see - no signs of scorching etc. I get an open circuit across the terms. I am assuming that the delicate wires in the voice coil have probably fried?

What likelihood is there of getting these drivers repaired as opposed to replaced?

[spock]

If the manufacturer still has voice coils for the drivers, your in luck. If they have complete driver replacements in stock, your even luckier. If no to both of the above, time to write an obituary.