View Full Version : When good crossovers go bad.


cubdog
04-14-2009, 05:46 PM
Someone, please give us a primer on what happens when crossovers, due to age, fail to perform as intended. How is the sound of a speaker degraded and what can be expected by a rebuild. Thanks.

cubdog

dc270
04-14-2009, 06:15 PM
Typically I find old capacitors that have exploded and failed causing the whole driver circuit to go down! A fair amount of time the old caps drift way out of spec and can endanger the tweeter by allowing to much low feq. to enter into the signal path.
DC

dshoaf
04-14-2009, 08:38 PM
Typically I find old capacitors that have exploded and failed causing the whole driver circuit to go down! A fair amount of time the old caps drift way out of spec and can endanger the tweeter by allowing to much low feq. to enter into the signal path.
DC

I've seen this failure mode in speakers that have been consistently overdriven - think disco-use every night with your favorite speaker. Ditto for burned out level controls.

Other failure modes I've seen:

- Tweeter and/or midrange completely out or very little sound coming out.
- Poor mid-bass response with 12 or 18 db crossover designs. This implies more sophisticated speaker designs.
- Poor response from tweeter or midrange level controls.

Hope that helps.

Cheers,

David

lissjw
04-14-2009, 10:26 PM
Would you ever hear noise that sounds like a lose connection or dirty switch?

dc270
04-14-2009, 10:50 PM
More often than not the L-Pads always need lubing and if let to sit for to long un-touched will corrode and become defective. Then you always have the blown fuses and occasional cold solder joint in other cases. As if all these things mentioned and more you can always have a magnet come unglued on a frame and bind up the voice coils, or the spider suspenstion come un-glued from the former or basket and even a bent frame from being dropped. I have experienced all this and even some I have forgotten. All this makes me now wonder why the hell I been at this for 35+ years now- guess I like the challenge...there is plenty of it to go around.....
DC

Knet70
04-15-2009, 03:37 AM
Capacitors within crossovers or any electronic device function similar to batteries. They store and release energy. Think of them like water towers holding a reserve of water to be released when needed and filled back up constantly. Capacitors provide a steady stream of power to the speaker in order to level out peaks and dips in the signal. As well capacitors suppress certain frequencies to specific drivers thus creating the "crossover frequency" range i.e 3000 Hz. What I've noticed in older capacitors and cheap eloctrolytic caps is that high frequencies in the tweeter can sound grainy, too much edge, too crisp and fatiguing on the ears or oppositely some people notice that the speaker sounds flatter, less fidelity than it used to, highs are no longer bright and revealing. It really depends on individual equipment and circumstances. You may not notice it consciously or you may if you are paying attention and know the speakers really well. Unless of course the crossover is just completely crapped out.

the better the quality of the speaker the better it will respond to upgrading the crossover.

what can be expected by a rebuild?

Balance to the crossover settings restored
Smoother sounding highs and mid range, bright in a revealing way, not harsh.
subjective: perceived warmth to the overall sound of the speaker if you upgrade the capacitors to poly caps
sound will hopefully be clearer and easier to focus on and hear detail within music
instruments should sound more realistic and full.
integration between the woofer and the tweeter should be as seemless as possible so that the sound appears to be coming from only one source, not two or three seperate drivers.

Most often it is only the capacitors within a simple crossover design that need to be replaced. This can greatly improve the performance of a speaker especially if it is over 20 years old.

cdfac
04-15-2009, 07:59 AM
What I've noticed in older capacitors and cheap eloctrolytic caps is that high frequencies in the tweeter can sound grainy, too much edge, too crisp and fatiguing on the ears or oppositely some people notice that the speaker sounds flatter, less fidelity than it used to, highs are no longer bright and revealing. It really depends on individual equipment and circumstances. You may not notice it consciously or you may if you are paying attention and know the speakers really well.

the better the quality of the speaker the better it will respond to upgrading the crossover.

what can be expected by a rebuild?

Balance to the crossover settings restored
Smoother sounding highs and mid range, bright in a revealing way, not harsh.
subjective: perceived warmth to the overall sound of the speaker if you upgrade the capacitors to poly caps
sound will hopefully be clearer and easier to focus on and hear detail within music
instruments should sound more realistic and full.
integration between the woofer and the tweeter should be as seemless as possible so that the sound appears to be coming from only one source, not two or three seperate drivers.

Most often it is only the capacitors within a simple crossover design that need to be replaced. This can greatly improve the performance of a speaker especially if it is over 20 years old.

+1 for all the above, IME.

as far as balance goes, the capacitors in one speaker may age differently than in the other (or if the speaker is quite old, they might never have been that close in the first place), creating slightly different crossover points for the same drivers. this can potentially muddy up the soundstage and create wavering images. put new 5% or 1% poly's in there and you'll notice that imaging locks in place and becomes much more obvious (if your speaker is good enough to ever image well). again, though, you'll notice a bigger difference the better and/or more complex the speaker is.

and in reference to another post above, capacitors only lose capacitance with age, so a tweeter XO point will only get higher...right?

cubdog
04-15-2009, 10:20 PM
Thanks to all for the feedback. Very enlightening Knet.

cubdog