HIGHLY unlikely. I suppose if some component is REALLY low quality, its value might change slightly over time, but otherwise, no.
The dialectric material (plastic film, usually) in capacitors will change sound quality slightly as it 'takes a set' due to electical voltage passing thru it (generally called breaking in), but that's all.
BTW, the entire issue of 'passive'-component values in crossovers is highly overrated IMO. Understand that most caps, resistors, and inductors in crossovers are of a + or -10% tolerance from the beginning, and some are + or - 20%! Also understand that it takes doubling or having of a component's value to change its effect by one octave.
However, if you're after highest quality, it makes sense to upgrade the passive parts in a highly loved speaker. Doesn't matter is it's a month or 2 decades old, it's HIGHLY unlikely the manufacturer installed the best-quality parts when he built it. Increasing the quality of parts in a complex crossover could easily change the retail price by $100 - $500 each. For instance, the crossover in my Aerial CC3B contains 6 film caps (plus a 150uF electolytic), 3 of which are rather large at 33uF. All the midrange- and tweeter-series caps were Axon 'propylenes without any bypasses. There are several better-sounding but still affordable caps than Axons, and my the sound from my CC3B benefits from some of them.
So replace because they're old? No. Replace with higher-quality parts for better sound? YES!
Coupling capacitors in tube amps are famous for degradation, but this is attributed to the high temperature environment and the high dc voltage they see. Film capacitors in a crossover network will probably last forever.
"'passive'-component values in crossovers is highly overrated IMO"
Disagree. Small changes here can make huge changes in sound.
"caps, resistors, and inductors in crossovers are of a + or -10% tolerance from the beginning, and some are + or - 20%"
You don't think the person building the crossover tests them all? Come on.
"Also understand that it takes doubling or having of a component's value to change its effect by one octave."
that depends on the crossover topology, not true in all cases, AFAIk.
"Replace with higher-quality parts for better sound? "
Maybe, maybe not. doing so presumes you know more about the parts/sound/speaker/crossover than the designer, which I find is not often the case. Parts usually were chosen for a reason, and that is not always price.
"Axon 'propylenes without any bypasses" - which is not a bad thing. Axon (aka Solen) is basically about the best film cap that can be had in larger values (say, over 10uf.) in the .1-1uf range there are lots of choices however.
Regarding caps degrading - its' mostly electrolytic types that have this problem, and then usually in stuff that runs higher voltage than speakers. (e.g. amps, power supply bypass, etc.) IN that case, replacing elytics is a good idea. Even better is getting rid of them entirely and replacing with oil or film caps.
"You don't think the person building the crossover tests them all? Come on."
Ed, YOU and I might measure them, but do you really think manufacturers of even expensive speakers measure and select every cap, resistor, and inductor that goes into their crossovers? "Come on" yourself. Maybe SOME of them might measure to see if they're close, but in anything less than the most-expensive speakers, that stuff gets installed exactly as it comes from the supplier, without selection. That happens because it makes virtually NO difference to the performance of the crossover whether, for instance, that hi-pass cap's -3dB point is 2.8KHz or 2.9KHz or 3KHz or 3.1KHz or... Plus or minus 10% is less than an eighth of an octave, and only the most-skilled listener could hear the difference, and only God knows what's correct.
I agree that Axon/Solen/SCR 'propylenes are quite-decent-sounding caps and probably the best dollar values in caps over maybe 10uFs, but even this tinned-eared audiofool can hear the improvement even in the midrange when they're bypassed with, for instance, a North Creek Harmony 0.22/625, and then more improvement when they're replaced with bypassed large-value NC 'propylenes.
Aerial's VP of marketing actually had the nerve to tell me that they built their crossovers with the best-sounding parts available. I almost laughed in his face.
And you're right about changing values depending on the filter topology--I was generalizing about a 1st-order filter. In higher-order filters, changing a value by double or half makes LESS than an octave difference.
I'm firmly in the camp that believes that manufacturers pick the best parts they can find FOR THE PRICE and that it's easy for us audiofools to find better-sounding parts.
"You don't think the person building the crossover tests them all? This reflects the old fashoned way of thinking about quality control tests.
The modern approach is that the output of a production process is monitored by testing a sample of what is being produced. The test results are used, not to verify that the tested items are good, but to detect if the production process is correct. If tested samples fail, the production process is fixed. After doing this for a while all the output is good, and does not require testing. Quality of the product depends on the production process, not on testing. A small percentage of the output continues to be tested, but only to detect if something goes wrong with the process.
From personal experience, I recommend that drivers need new suspensions after 6 or 7 years. Despite their looking fine, I was shocked to find mine COMPLETELY deteriorated. The improvement in sonics via slam, immediacy, bass, and naturalness was astonishing. This is far more critical than capacitor aging.
The premise that
more expensive = better sound
more botiquey = better sound
is what I find to be a fallacy. Sometimes it's true, sometimes its' not. Unless you try every reasonable value of every type cap in a particular application, there can be no conclusions drawn one way or another. IMHO, the manufacturer is a lot more likely to have done experiments like that than any end user is likely to do.
most expensive parts do not equal necessarily better sound. Case in point re: caps - I'd take a vintage (read: cheap-ass $2 or so) paper-in-oil cap over ANYTHING made by Blackgate, for values where it's appropriate (mostly power supply stuff). there couldnt' be a greater difference in price vs. hype vs. quality of sound. The cheap ugly oil cap sounds and performs way better than the overrated Elytic.
What do you think of this statement by Rod Elliott of Elliott Sound Products:
"Non-polarised electrolytics are a different matter, especially when used in crossover networks. These have a tendency to lose capacitance as they age, shifting the crossover frequency with disasterous results (sonically speaking). Because the loss is gradual, you may possibly not even hear it until the tweeter has almost stopped working, as you get used to the sound over a period of time. Unless all bi-polars age at the same rate (unlikely), you will start to notice a difference between the two speakers. This is your cue to head off to the electronics shop and buy some replacements (non electrolytic, preferably)."
Because of this I started the thread.
Gee, Ed, I'm glad I never said any of those things and never recommended Blackgate.
I'll say it another way:
1. Speaker manufacturers use the best-sounding parts they can WITHIN SEVERE PRICE CONSTRAINTS.
2. There are LOTS of better-sounding caps out there that lots of us know about and have heard in our own systems that sound better than the generally inexpensive stuff most manufacturers use in their crossovers.
Stop accusing me of saying what I didn't.
Process control bsed manufacturing produces parts that are within a spec range. If the spec range for a cap is 10%, and sampling indicates they are within that range, they don't tweek the process further - it is in control. If (and this is a big if) - a speaker works better with more tightly controlled values, the manufacturer will have to test or buy selected value parts. If a copmpany is selling selected value parts, that means the stuff they sell everyone else is by design farther off nominal. I know that Spica used to measure their caps, and match caps individually to balance out their differences. That is why there are so many caps in a Spica crossover.
Dazzdax, if your crossover uses electrolytic caps, do indeed replace them, and as Mr. Elliott indicates, with better-quality caps. If the 'lytics are in the midrange or tweeter sections, replace them with the best film caps you can afford. As indicated above, the SCR/Solen/Axon 'propylene caps are good-sounding caps that are highly affordable; they're available here http://www.percyaudio.com/Catalog.pdf , and Michael has low prices and great service. If these caps are in series with the midrange or hi-frequency drivers, probably you should also bypass the SCRs with a small, higher-quality cap. To keep costs down and stay with the same supplier, I suggest you use a Reliable MultiCap RTX in 0.01 or 0.22uF value, at $3.50 to $5.95.
Another source of good-sounding, affordable film caps is North Creek, here http://www.northcreekmusic.com/CrossoverComponents.html . I used a combination of Zen and Harmony 'propylenes in my last 3 crossover projects and am VERY pleased with the results.
I've used TRT DynamiCaps for couplers in my vacuumtubed amps, but they're only 0.22s so they're still affordable. In larger values, the TRT-Ds are quite expensive IMO.
Honest1...NO. NO. NO. Exactly the opposite of what you said. Process control manufacturing produces product that is dead nuts on nominal, even if it doesn't need to be perfect. The process is tweeked until this happens. The old fashoned way was to 100 percent test the product and accept those which are in spec and junk or rework the others. Not only is this more expensive, but it results in an inferior product.
Go to Google, and research Taguchi. His engineering approach also involves design concepts. For example: if a circuit requires a 1 percent or a selected value resistor, the best approach is to go back to the drawing board and redesign the circuit so that it only needs 2 or 5 percent resistors. The brute force (stupid) approach is to spend a lot of time and money on precision resistors.