Aging of capacitors within crossover networks

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!
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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.

"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.
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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.
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