Zaph's BAMTM Crossover Overhaul?

[Hawkifan]

Hello Everyone. I have had my BAMTM's for close to 13 years now and I still love listening to them but I have a question. I remember reading on his ZaphAudio.com site that he states the electrolytic caps he uses in the crossover degrade over time(range 10-20 years). If that is the case should I consider replacing them? If so should I consider upgrading/replacing them with something else if that is possible?

Just curious if they do degrade, how does that affect the sound quality. Is it something my ears would notice?

I appreciate everyone's input....

Thanks!

[djg]

It looks like just the 31 mfd cap was specified as a NPE. You can get those for $1.70 ea at another well known Madison, WI based supplier. The freight will be more than the merchandise. So for like ten bucks you can be good for another 10-15 years. Replacing them with poly caps would be about 30-40 dollars. 31 mfd would need two in parallel to hit that exact value.

If it weighs heavy on your psyche, I say go for it. BAMTM is a nice speaker, I had one as a center HT unit for years.

[fpitas]

Electrolytics do degrade over time. High temperatures are one of the biggest contributing factors. However, modern brand name electrolytics used at room temperature will last almost indefinitely, unless there was a manufacturing defect. Some people do replace them with polypropylene film caps as an upgrade, if the capacitance isn't real big (say, 47uF and below). Whether you would hear a difference is debatable, but some people say they do.

I agree with djg, the cost of direct replacement is almost nil, so do that if you'll feel better. Note that capacitance in parallel adds, so if you can't find 31uF, you could combine smaller caps to get there. Be sure to get NPE.

[Chris Roemer]

Well, that design only lists 2 caps, a large one (31uF), and a medium-size one (10uF).
Poly caps don't go bad (from age), only electrolytics. The big cap is in shunt (to gnd.), and I'd use an npe there, even if those were $100 woofers.
I'd probably have used a poly for the 10uF in series with the tweeter (even if it was a $10 tweeter), but I wouldn't have been opposed to an npe there (to save $ome).

I'd bet you $1 that your npe caps haven't gone bad, and probably won't for another 10-20 yrs.

If you ran a Z-sweep (impedance, like w/a DATS/WooferTester) 13 yrs ago, you could compare it to now. It would show you if anything had changed. A DATS/WT could also test the value of your caps. A "10uF" npe MIGHT fall in the 9-11uF range, even when new. Everything's PROBably okay though.

[fpitas]

Well, that design only lists 2 caps, a large one (31uF), and a medium-size one (10uF).
Poly caps don't go bad (from age), only electrolytics. The big cap is in shunt (to gnd.), and I'd use an npe there, even if those were $100 woofers.
I'd probably have used a poly for the 10uF in series with the tweeter (even if it was a $10 tweeter), but I wouldn't have been opposed to an npe there (to save $ome).

I'd bet you $1 that your npe caps haven't gone bad, and probably won't for another 10-20 yrs.

If you ran a Z-sweep (impedance, like w/a DATS/WooferTester) 13 yrs ago, you could compare it to now. It would show you if anything had changed. A DATS/WT could also test the value of your caps. A "10uF" npe MIGHT fall in the 9-11uF range, even when new. Everything's PROBably okay though.

To your point, the 10uF is already poly:

C7 - 10 uF Bennic Metallized Poly $3.75

[davidroberts]

From what I have read the electrolytic caps do degrade over time but it is also dependent on how much they are used. Unless you are listening daily for hours and hours at a time I doubt they are going to degrade in your lifetime to a measurable difference.