Speaker repair

[patknk939]

Hi All

I have a pair of small Mission bookshelf speakers with one DEAD. Absolutely no sound when connected to amp. Tried switching with the other one that works, same result - nothing came out.

Is this problem common? I have a feeling that both the tweeter and woofer dead at the same time is quite seldom. Is the cross-over the culprit or something else?

I'd like to fix it myself. Any solutions or ideas would be welcome.

Thanks.

[John L]

Check your wiring first, then the crossover. Incidentially, does the speaker have a fuse or circuit breaker?

[sauuuuuce]

Originally posted by patknk939
Hi All

Tried switching with the other one that works, same result - nothing came out.

Thanks.

So when you switched how did you switch? Did you put the "dead" cabinet on the live cabinet amp channel or the live cabinet on the "dead" amp channel? Or to put it another way.....does the problem move with the speaker or does it stay with the amp channel?

[patknk939]

Originally posted by John L
Check your wiring first, then the crossover. Incidentially, does the speaker have a fuse or circuit breaker?

Originally posted by sauuuuuce


So when you switched how did you switch? Did you put the "dead" cabinet on the live cabinet amp channel or the live cabinet on the "dead" amp channel? Or to put it another way.....does the problem move with the speaker or does it stay with the amp channel?

I don't think wiring (I assume this refers to speaker cabling) is the problem because the problem speakers were tested by connecting to a pair of working speakers. The problem moves with the speaker when switched between channels. I did take out the tweeter/woofer and saw the crossover at the back of the cabinet but hadn't taken it out and not sure there's a circuit breaker or fuse.

[John L]

Ok, if you know for certain that the problem is definately related to the speaker, not the cable or the amp, then you will need to pop the lid to the speaker, or remove the main driver so you can look in at the inner wiring.

You need to see if the wiring to the terminal, is sound. I find it highly unlikely that both the tweet and woofer would be gone all at the same time, and not have the other channel do same to the other speaker.

I still think that the odds are a loose connection. I could be wrong though.

[Bobken]

Hi,

A quick and cheap way of establishing if internal wiring and component continuity exists, is to briefly connect a single cell battery across the input terminals of the speaker. Just touch the terminals of the speaker with a battery using a piece of suitable wire to make the connection, for a second or so at a time, on and off.

So long as it is a single cell giving merely 1.5 or maybe 1.6V DC, there will be no harm to anything (except an active speaker, of course), and on making the connection briefly, there should be an obvious 'click' or 'pop' heard each time. Also, you should be able to see most diaphragms move briefly inwards or outwards when the battery is connected, and this is a good way of checking the 'polarity' of the driver wiring, although with the very limited movement of most tweeter diaphragms, this is not always easy to see.

If nothing at all visually or aurally happens when you try this out, either both voice coils have burned out or similar (which is less likely), or something has become open circuit within the enclosure which prevents the signals from reaching the drivers.

Regards,

[patknk939]

Hi Bob

As suggested, I've just tested both the tweeter and the woofer with a battery. Both have "click" when connected to the battery. This proves that both in fact work. Therefore, the problem seems to come from the cross-over. I've also checked the wiring and the connection to the x-over, they are not loose. At the same time, I've taken the x-over out from the enclosure. The x-over just made up of 2 coils, two 5W 3.3ohm JF resistors, two 12uF 50V capacitors and one 4.7uF 50V capacitor. So, how am I going to test where the problem is? Thanks for your advice.

Pat

[John L]

If both speakers are working, and you think it is the crossover, you are faced with either a completely fried crossover, where both circuits are fried, or the wiring leading to, or from, the crossover is shorted.

If the crossover is not fried, then the fact that both speakers do not work strongly suggests that only wiring that is used by Both drivers has a short. Just check the circuit up to the point where the line branches out to the high and low frequency drivers. If not that, then I would suggest a complete breakdown.

[Bobken]

Hi Pat,

That is a good start but are you saying that you don't get any clicks/pops if you connect the same battery across the input terminals to the speaker?

Even though the DC battery voltage will probably be 'blocked' by some intervening capacitors (at least in the tweeter circuit, anyway), you should still hear a similar or at least some noise when you touch the battery on and off the entire speaker unit's input terminals.

If doing this test, it is absolutely quiet, then you have isolated the problem to somewhere between the input terminals and the drive-units, which basically means in the x'over itself, or any connecting wiring between x'over and input (most likely), or possibly between the x'over and the drivers. As John L suggests, this latter situation is much less likely as there will be separate wiring from the x'over to each driver, and it would be rather unlikely that both sets of wires would have failed at the same time.

If it doesn't seem like there is an obvious problem with the 'shared' wiring from input to the x'over, then it will take a bit of work to identify which x'over component(s) is/ are the culprits here. In my experience, something going completely 'dead' as you suggest, is more likely to be a failed solder-joint or similar, as although individual components will sometimes fail, often (mostly?) they will still pass some sounds, albeit distorted or reduced in amplitude.

Do you have access to any test gear like maybe even a cheap multimeter, and are you able to solder and unsolder various parts in the crossover? If not, and you do establish that the problem is within the x'over itself, then I think you will need some help with this from a local technician, unfortunately.

Regards,

[patknk939]

Hi Bob. I've done the test of touching the battery on and off the input terminals of the speaker. It's absolutely quiet. No click nor pop from both drivers. I have both needle and digital multimeters. I'm quite comfortable with soldering and de-soldering. I appreciate your further advice. Thanks.

Regards

Pat