Bad capacitors in crossover?

[ratbuddy]

What do these sound like? One of my floorstanders recently started sounding very muffled in the midrange on one side, almost with a kazoo-like quality to it. Or maybe like humming with your mouth open and a piece of plastic wrap stretched over it. Something like that.

The drivers look fine, no rotted surrounds or anything, but the speakers were made quite a long time ago, so I was thinking maybe the caps dried out? The speakers were never abused in any way, volume levels always kept sensible etc.. The problem may have come on gradually, but it only became annoying lately.

Ideas?

[gearhead1972]

I have not really ever heard of caps in a crossover going, especially on higher quality speakers. I have however blown up a few on some home made crossovers that I overloaded. The sounds you are describing sound like a bad driver, try substituting another driver to rule out crossover or driver.
If its either here (http://www.parts-express.com/home.cfm?CFID=5988103&CFTOKEN=49000708) is a good source for such stuff.

[ratbuddy]

I have not really ever heard of caps in a crossover going, especially on higher quality speakers. I have however blown up a few on some home made crossovers that I overloaded. The sounds you are describing sound like a bad driver, try substituting another driver to rule out crossover or driver.
If its either here (http://www.parts-express.com/home.cfm?CFID=5988103&CFTOKEN=49000708) is a good source for such stuff.

Capacitors do go bad with time, no matter what type of device they are in :) These were made in 1980, so I'm sure they (the crossover caps) are well past their prime.. But they were certainly 'higher quality' when they were new. http://www.kef.com/history/1980/carlton3.asp has a bit about them.

[Sir Barton]

You can usually expect to get ~15 to 20 years out of a well built crossover. I replaced the crossovers on my Klipsch Fortes (built in '85) last year with some Bob Crites crossovers...the difference in sound was dramatic. If youre going to replace one cap, might as well do all the caps in both speakers so as to not have any sound issues. BTW, nice speakers Ratbuddy! I doubt its a driver going bad, sounds like a crossover cap to me. Parts Express sells good caps. My recommendation on caps would be either Auricaps, Sonicaps, or Janzen Silver Caps...all are relatively affordable. If you wanna spend the big bucks, go for Mundorfs.

[ratbuddy]

You can usually expect to get ~15 to 20 years out of a well built crossover. I replaced the crossovers on my Klipsch Fortes (built in '85) last year with some Bob Crites crossovers...the difference in sound was dramatic. If youre going to replace one cap, might as well do all the caps in both speakers so as to not have any sound issues. BTW, nice speakers Ratbuddy! I doubt its a driver going bad, sounds like a crossover cap to me. Parts Express sells good caps. My recommendation on caps would be either Auricaps, Sonicaps, or Janzen Silver Caps...all are relatively affordable. If you wanna spend the big bucks, go for Mundorfs.

Yeah, if this sounds remotely like something that could be caused by caps, I'm just going to replace them all. I need to peek inside the boxes and see if the crossovers are mounted on boards or just wired inline, or what. If on boards, I think Super Nade will be getting a little soldering work.

Do you suggest replacing the other components as well? Again, I don't know what else is in the circuit, I assume coils don't go bad with time, what about resistors or whatever else might be in there?

edit: Well, KEF says it's fourth order, Wikipedia says it's very sensitive to part selection :-/

Fourth order crossovers
Fourth-order filters have an 80 dB/decade (or 24 dB/octave) slope. These filters are complex to design in passive form, as the components interact with each other. Steep-slope passive networks are less tolerant of parts value deviations or tolerances, and more sensitive to mis-termination with reactive driver loads. A 4th order crossover with -6 dB crossover point and flat summing is also known as a Linkwitz-Riley crossover (named after its inventors), and can be constructed in active form by cascading two 2nd order Butterworth filter sections. The output signals of this crossover order are in phase, thus avoiding partial phase inversion if the crossover bandpasses are electrically summed, as they would be within the output stage of a multiband compressor. Crossovers used in loudspeaker design do not require the filter sections to be in phase: smooth output characteristics are often achieved using non-ideal, asymmetric crossover filter characteristics.[1] Bessel, Butterworth and Chebyshev are among the possible crossover topologies.

Such steep-slope filters have greater problems with overshoot and ringing[2] but there are several key advantages, even in their passive form, such as a the potential for a lower crossover point and increased power handling for tweeters, together with less overlap between drivers, dramatically reducing lobing, or other unwelcome off-axis effects. With less overlap between adjacent drivers, their location relative to each other, becomes less critical and allows more latitude in speaker system cosmetics or (in car audio) practical installation constraints.

[Sir Barton]

My rule of thumb is to replace everything with parts rated for the same specs. Most of the caps should have their ratings printed on them.

[BobbyBubblehead]

Would it not be cheaper just to test said crossovers and stave off replacing everything. I would have thought any component on the one crossovers that was duff should be replaced on the other side just for performance sake.
He could of heat damaged the coil or anything possibly could at a push even be a loose component subject to vibration (encounted this in celestion and mission`s of old. the glue simply gives up and off they come)
And foam composition surrounds on cones can look fine but actually have a tear or hole that takes pressure to reveal itself as a fault.
just look at fault finding on computers its not always where you assume.

#Fingers crossed dont pick me apart you swines nobody love`s me or my oppinions LOL#
#not even the moderators im a sinner#

[Theocnoob]

What do these sound like? One of my floorstanders recently started sounding very muffled in the midrange on one side, almost with a kazoo-like quality to it. Or maybe like humming with your mouth open and a piece of plastic wrap stretched over it. Something like that.

The drivers look fine, no rotted surrounds or anything, but the speakers were made quite a long time ago, so I was thinking maybe the caps dried out? The speakers were never abused in any way, volume levels always kept sensible etc.. The problem may have come on gradually, but it only became annoying lately.

Ideas?


That sounds like an internally blown rather than externally blown speaker, like the voice coil became slightly seperated from its mount under higher than spec'd vibrations.

I've heard this happen before and it sounds exactly like you describe.

Do you have anything with really powerful percussion decays on it? It'd have to be a piece you're used to listening to. Something like Sing Sing Sing (the big band tune) would be perfect. When the entire band cuts out to a drum solo and there's a noticeable decaying echo, that's where you're going to notice the damage most. If the decays are no longer clearly audible, you've got a problem.

[ratbuddy]

That sounds like an internally blown rather than externally blown speaker, like the voice coil became slightly seperated from its mount under higher than spec'd vibrations.

I've heard this happen before and it sounds exactly like you describe.

Do you have anything with really powerful percussion decays on it? It'd have to be a piece you're used to listening to. Something like Sing Sing Sing (the big band tune) would be perfect. When the entire band cuts out to a drum solo and there's a noticeable decaying echo, that's where you're going to notice the damage most. If the decays are no longer clearly audible, you've got a problem.

I'm not sure. I really only notice the problem when someone is talking, and don't listen to much music on the thing. My cable box and DVD player run through this stereo.

I'm quite sure I've never overdriven the speakers (the amp is 37.5 or 50 wpc, I forget which) or clipped the amp driving them, volume dial never above 1/3 or so. Is voice coil seperation always a case of damage, or is it a part that just wears out eventually? Have you heard a bad crossover as well? Do they sound different?

Thanks

[Old Thrashbarg]

That sounds like an internally blown rather than externally blown speaker, like the voice coil became slightly seperated from its mount under higher than spec'd vibrations.

I've heard this happen before and it sounds exactly like you describe.

Oh, bad caps in a crossover can definitely do that. I've got a growing collection of vintage speakers, stuff dating back as far as the '50s, and the first thing I do now before I even bother seriously listening to a newly acquired pair of speakers is to replace all the electrolytics/oil caps in the crossovers. I've had speakers with supposedly dead tweeters that now work great after working on the crossovers.

The replacements I use depend kinda on the crossover design, but, space permitting, I usually try to replace the electrolytics with polypropylene film types... the Dayton Precision 1% off PartsExpress work well for the task. (Warning, they're a little pricey compared to electrolytics, but it's worth the extra few bucks IMO.) When space doesn't permit, a high quality non-polar electrolytic will do. Again, I get them off PartsExpress, they've got a section on their site under electronics components, specifically with a selection of crossover capacitors. I will say, don't bother with the super-expensive Auricaps or any of that, they're not really anything special, even the generic yellow tubular polyprops will do fine if you can find them, but I've never seen 'em cheaper than the Daytons anyhow.

[ratbuddy]

Oh, bad caps in a crossover can definitely do that. I've got a growing collection of vintage speakers, stuff dating back as far as the '50s, and the first thing I do now before I even bother seriously listening to a newly acquired pair of speakers is to replace all the electrolytics/oil caps in the crossovers. I've had speakers with supposedly dead tweeters that now work great after working on the crossovers.

The replacements I use depend kinda on the crossover design, but, space permitting, I usually try to replace the electrolytics with polypropylene film types... the Dayton Precision 1% off PartsExpress work well for the task. (Warning, they're a little pricey compared to electrolytics, but it's worth the extra few bucks IMO.) When space doesn't permit, a high quality non-polar electrolytic will do. Again, I get them off PartsExpress, they've got a section on their site under electronics components, specifically with a selection of crossover capacitors. I will say, don't bother with the super-expensive Auricaps or any of that, they're not really anything special, even the generic yellow tubular polyprops will do fine if you can find them, but I've never seen 'em cheaper than the Daytons anyhow.

I do order from PE somewhat often, like every time someone asks me to build them a subwoofer. I'm not going to go looking for NOS Black Gates or something but it's no biggie to spend a little extra for quality :)

[Old Thrashbarg]

like every time someone asks me to build them a subwoofer.

Ah, I hear ya on that, done a few of the Dayton kits myself. Yeah, as long as you get caps of the right kind with decently tight tolerances, you'll be good, doesn't really matter the brand. (Although, I wouldn't use the orange blob-looking ones, those don't seem to do so well with audio for some reason.) I just know the Daytons are good quality, since I've used quite a few of 'em.

[Theocnoob]

Oh, bad caps in a crossover can definitely do that. I've got a growing collection of vintage speakers, stuff dating back as far as the '50s, and the first thing I do now before I even bother seriously listening to a newly acquired pair of speakers is to replace all the electrolytics/oil caps in the crossovers. I've had speakers with supposedly dead tweeters that now work great after working on the crossovers.

The replacements I use depend kinda on the crossover design, but, space permitting, I usually try to replace the electrolytics with polypropylene film types... the Dayton Precision 1% off PartsExpress work well for the task. (Warning, they're a little pricey compared to electrolytics, but it's worth the extra few bucks IMO.) When space doesn't permit, a high quality non-polar electrolytic will do. Again, I get them off PartsExpress, they've got a section on their site under electronics components, specifically with a selection of crossover capacitors. I will say, don't bother with the super-expensive Auricaps or any of that, they're not really anything special, even the generic yellow tubular polyprops will do fine if you can find them, but I've never seen 'em cheaper than the Daytons anyhow.

Would you mind posting a how to for this? I might change mine just for the experience. This is very interesting information :thup::clap:

[Old Thrashbarg]

Would you mind posting a how to for this?

Well, there's not really a whole lot to it... Some speakers have crossovers that consist simply of a single capacitor connected in series with the positive line going to the tweeter, connected either by solder or, more often, spade terminals. Replacing those is simply a case of looking at the value of the cap and finding a similar replacement, and either attaching new terminals or soldering it directly in.

As for the ones mounted on a PCB with other components, it's not entirely unlike replacing the caps on a motherboard or anything else, so rather than re-write all that info, I'll just defer you to one of those how-to's. (I think there's even one somewhere on the main site here.) If you're replacing small electrolytics with the physically larger polypropylene film types, there's an extra step of determining how to fit it on there, but that's just a judgment call...

Here's a picture of a relatively simple crossover in an old set of Pioneer CS-33 speakers I have. You can see the old silver-colored capacitor glued to the backing board and soldered into the terminals. What I would do there is just clip the leads and pull the old cap (may even leave it in place and disconnected, depending on how strong the glue is), and hot-glue a new polypropylene film cap to the wood above the crossover board, behind the green/white wires. Bend the leads around and solder 'em in.

That's all there is to it, really.

[ratbuddy]

Are those new wires? Do you generally suggest running new internal wire on older speakers like this?

[Old Thrashbarg]

Are those new wires?

I don't know, they could be, it appears somebody had messed with the internals before me, but they were like that when I got the speakers. As long as the original wires are intact, I see no reason to replace them, with possible exception being if the originals seem grossly undersized (i.e., 28ga on a high wattage subwoofer, or something like that). Even with the latter, it's more a matter of preference, as the voice coils on speakers are pretty tiny gauge anyway.

[Theocnoob]

I don't know, they could be, it appears somebody had messed with the internals before me, but they were like that when I got the speakers. As long as the original wires are intact, I see no reason to replace them, with possible exception being if the originals seem grossly undersized (i.e., 28ga on a high wattage subwoofer, or something like that). Even with the latter, it's more a matter of preference, as the voice coils on speakers are pretty tiny gauge anyway.

So what specifically have you done here?

http://www.ocforums.com/attachment.php?attachmentid=71421&stc=1&d=1235052090

Also, I imagine something in a newer speaker would be much more 'solid state'? No wire bundles or anything?

Is a sauldering gun required for this?

Also for fun I ripped an old router apart and removed some of the larger film-style non solid state capacitors. I notice the small ones break but the big ones can be slid off and expose these two sort of metallic plates. I don't see how those could be slid into a new cap without breaking them though since they are very fragile.

This is all neat new info

[Old Thrashbarg]

So what specifically have you done here?

Nothing, yet. I just took the picture to illustrate one possible thing you might encounter.

Also, I imagine something in a newer speaker would be much more 'solid state'? No wire bundles or anything?

No, that's just one of the kinds of crossovers, and a fairly simple one at that. Most newer, higher-end speakers will have something similar. The basic technology of speakers hasn't really changed in fifty years or so.

Yes, you'd need some sort of soldering tool.

I don't see how those could be slid into a new cap without breaking them though since they are very fragile.

I'm not sure what you mean here.

Honestly, it sounds to me like you might want to do a little reading about crossover design and perhaps soldering in general before trying to undertake any repair work. It's not that it's really complicated, but a basic understanding of how the equipment works would go a long way, since not every speaker is designed the same way.