Change in ohms of bookshelf speakers

[Kamranbits]

I have pair of bookshelf speakers 6ohms 3 way

Both when measured shows 6ohms

But one of the speakers suddenly shoes 20-40 ohms

Is it a problem of concern?



After few days it automatically goes to 6ohms but again changes in few days.



So I decided to look into it if it had some crossover issue but found nothing.



Attaching pic of crossover

 

[AllenB]

Try shorting the leads for a moment, then try again.

 

[Kamranbits]

When the ohms changes if i sort them too there is no effect but after some days it goes back to normal
(During those days i keep them in use)

And if the same speaker the other one shows same result without sorting why do we need to short this one and try checking?

 

[AllenB]

It's a long shot, but shorting the leads ensures there's no charge on the capacitor if there is no longer another discharge path. It's a good habit in general when testing, as an ohm meter will give false readings in that case.

In addition to that, make sure your environment is reasonably quiet when you measure.

 

[krevilplays]

Reflow xovers all solder joints. Might be also that, your woofers voice coil might be failing.

 

[Kamranbits]

Yes I have sorted and check still it shows 20-30ohms but leaving it for some days changes it back to normal.

When I disassembled them i checked woofer and tweeter individual they are fine.
Is it something to do with crossover?
The capasitor is bad or?

Checked this speakers with other one it there is any change in sound but it sounds same like it's other pair

 

[oscroft]

My first thought was exactly the same as AllenB's. In use, the capacitors will hold charge and that will upset the ohms measurement. Always make sure the capacitors are discharged by shorting the leads first. I'd suggest short them, then wait a few minutes, and then short them again. A discharged capacitor can build charge back up a little due to an effect of the dielectric, and that might be enough to make measurements of such low ohms inaccurate.

 

[krevilplays]

>> During those days i keep them in use.

This implied your sound is not fine when reading is 20ohms?

 

[Kamranbits]

Sound doesn't change it is same as other speaker. Normally if ohms change there should be a drastic change but in my case no change in sound

 

[Kamranbits]

And the sorting of legs yes I get it too but why it doesn't apply to other speakers,
It's the same speaker same crossover, the capasitor is not holding charge?

 

[Kamranbits]

Ok so now when I check the ohms are back to normal and to verify the sorting I just played them for some time then directly removed from amplifier and checked it, normal as said it should hold charge and should show wrong result but it shows exact result 6ohms how much I try it is accurate now but after some days again they will be 20-30

What is the issue? 😨

 

[AllenB]

Perhaps your meter leads are beginning to fail.

 

[Kamranbits]

I have tested on multiple meters
They all show the other speakers ohms accurate but this one keep on changing bad then good then again after some times bad
Is something bad with crossover capasitor?
Inspecting visually it doesn't seems to have any issue.

The suprise, sound stays same as the other speaker no difference in sound not a minor diffrence

 

[AllenB]

Disconnect all connectors to make them clean. Test the drivers on their own. Attend to solder joints as already advised. Measure crossover components when disconnected. Wiggle joints while you measure them.

 

[Kamranbits]

Tried testing drives individually
They measure normal
6ohms woofer
7ohms tweeter
There is nothing on crossover to measure the resistor is shorted with jumper you can check the pic, it was done from manufacturer only
So that resistor is null(should i remove that resistor ?) i think it doesn't contribute to the sound or crossover

And that capasitor looks good

 

[oscroft]

Ok so now when I check the ohms are back to normal and to verify the sorting I just played them for some time then directly removed from amplifier and checked it, normal as said it should hold charge and should show wrong result but it shows exact result 6ohms how much I try it is accurate now but after some days again they will be 20-30

What is the issue? 😨

Might the charge on the capacitor depend on the last part of the signal it's just seen? It's getting an AC signal, and its charge will be going up and down very fast. But, it might also be starting to fail and perhaps developing an intermittently high series resistance?

I'd be tempted to remove and check each component (it looks like only two in each crossover). Capacitors can be hard to test without the proper equipment, but I'd probably change them anyway - electrolytics do degrade and fail with age.

 

[Kamranbits]

Crossover I can see just two components one is resistor and other is capasitor.

Resistor is disabled in that circuit, it has jumper connected on both ends

Maybe a falling capasitor but will it have this effect?
And if it is failing I should see some sound changes but I don't hear any.

 

[baldrick]

Maybe a falling capasitor but will it have this effect?
And if it is failing I should see some sound changes but I don't hear any.

How old is that capacitor?
Maybe you should replace it as a matter of course.
If it is in your budget replace the electrolytic with a film type, and if the value is high (thereby necessitating that the equivalent film cap will be expensive) replace it with an equal value high quality non-polarized electrolytic and bypass it with a 0.1 uF film type capacitor in parallel.

 

[Kamranbits]

The old capasitor is may be nearly 10y old
I can get same capasitor film one
2.2uf 100v
Old too had same specs
So should I reply this on both speakers or just one ?

 

[Galu]

Replace both capacitors and, when you have done so, report back with your findings.