Speaker problem

[hikernick]

Hi, first post, and apologies for it being a problem thread, and probably a pretty dumb one at that.

I have a pair of old Wharfedale Denton 2XP speakers that recently have started having an issue. They're used in partnership with an old Eagle amplifier. They've never been driven hard, and visually are in perfect condition.

Recently (well, maybe a while ago but I'm a slow worker ) they started exhibiting a behaviour where when the music got bass-y the bass would seem to cut out intermittently, in combination with a nasty crackling sound. I experimented with cables etc. and at christmas, when I'd bought my son some speakers, we hooked those up and tried them, and they were perfect. So I'm pretty sure it's my speakers.

The woofer cones look pretty good and pushing on them gently produced no scratchy noise or feel, but I bought a pair of cheap replacements on the basis that the issue was with bass, so it must be the bass drivers, and maybe the voice coils were broken down or catching. I tried those today and they make no difference at all. The issue is still there.

So now I'm wondering where to look next. I know I could just go to a shop and buy a new set of speakers, but I like these

They are 2 way units and they have a very simple crossover unit with two coils and a capacitor. As far as I can work out it's a series crossover. The coils look mint, as do the capacitors, but I wonder if breakdown of the capacitors could be at the root of my problem? One speaker is much worse than the other, but to some extent the issue is there in both.

Is it worth replacing the caps, on the off chance? They're 5MFD 50V items and I can get something pretty similar fairly cheap, although not exactly 5MFD - 4.7 seems more common. What difference will that make?

Many thanks, and apologies again for the noob question.

Nick

[AndrewT]

Buy some cheap 4u7F 50V non polarised electrolytic.
This is just to identify the problem.

If it proves to be the caps that have gone bad then consider whether it is worth replacing the electrolytic with cheap plastic film caps.

You can add a 330nF to bring the capacitance up to ~5uF. Do this by "ear" it might not help at all, or might need to be >>330nF

[KatieandDad]

The tolerance of electrolytics is appaulling. +50 - 20% in a lot of cases.

5uF - 20% = 4uF. 5uF + 50% = 7.5uF.

As AndrewT says. 4.7uF will prove if this is the cause of your problem.

You could use 2 x 10uF Polarised Electrolytics connected in series with the + connected to + and use the two - connections for a 5uF.
Is that clear ? They need to be connected end to end with the central connection being the + of one and the + of the second. The two outside connections of the pair (the -ves) now become the two leads of your homemade 5uF Non-Polarised cap.

[hikernick]

Understood.

What is the significance of the capacitor rating? Will it affect the crossover frequency, or something else?

[KatieandDad]

I'm not sure what you are asking.

RATING usually refers to the VOLTAGE which is important otherwise you may blow components if they are underspecified.

TEMPERATURE is also a factor which is not really important in a crossover.

[hikernick]

Sorry, capacitance.

[chris661]

Capacitance values will change your crossover point.

A small deviation from the original values will probably make sod all difference, but try to keep close to the original values, as then you've a better chance of it working as intended.

I'd second what AndrewT has said - get some more electrolytics, give those a try, see if the problem persists. If its fixed, you can consider upgrading to film caps (which don't deteriorate) at a later date.

It may also be worth looking at all the solder joints on the crossover, to make sure there's no dry/loose ones. For reference, the joints should be shiny and not move when nudged with the blunt end of a pencil (one of my preferred poking-around tools).

Chris

[hikernick]

Fitted the electrolytic caps but at the same time found a loose connector on the end of one cable which reproduced the problem when wiggled. Hopefully now resolved. Thanks all.