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greyeyezz

How to test crossover on Advent/1

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In simplest terms how do I test the components of my crossover? These are Advent/1.  Also what characteristics do the speakers show when caps are bad? Thank you.

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The only components in the Advent/1 crossover subject to age-related degradation are the capacitors. Since you are asking the question, you obviously do not have a capacitance tester. In that case, testing is not required. Replace the capacitors. Reassemble the speakers. Play music. If you hear music and it sounds good, then the crossovers are good. For the low cost of replacement capacitors and the little amount of time to replace them, testing is not cost efficient nor a good way to spend time.

Electrolytic caps fail in two ways. They fail because the electrolytic in the capacitor dries out over time.

The first failure mode is that capacitance value changes over time. The change in capacitance value will shift the crossover point. If a tweeter crossover point is shifted high enough, there will be a hole in the frequency response between the woofer and tweeter. If the crossover frequency shifts down, there will be a peak. Generally, the change in capacitance value is not sufficient to result in audible holes or peaks.

The second failure mode is that the equivalent series resistance (ESR) will increase. The increase in ESR will attenuate the driver if the cap is in series with the driver. Tweeter attenuation, in severe cases, results in a muffled sound, much like someone placed a thick blanket over the speaker. 

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3 hours ago, RTally said:

Replace the capacitors. Reassemble the speakers. Play music.

Welcome greyeyezz

I agree. The Advent/1 was produced 1978-1983 so your capacitors are about 40 years old. Electrolytic caps have a life expectancy of 23-30 years or so. Some last longer but they are on borrowed time.

The Advent/1 has just one 13uF capacitor. I've never been inside them but here's a photo I "borrowed" from an ebay listing. 13uF is an odd value but you could use 12uF (close enough) or use 2 caps paralleled.  Film caps are preferred because unlike electrolytics they don't go bad. These are good, and they're inexpensive: https://www.madisoundspeakerstore.com/carli-capacitors/

If you've never done it before, it's easier than it looks. Plenty of help available here.

And how are the woofer surrounds? Foam surrounds deteriorate faster than capacitors. We can help with that too.

-Kent

Advent 1 xo.jpg

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Surrounds have been redone.

Reason I ask about the crossovers is these Advents seem kind of bright compared to my NLA's in the late seventies. I didn't know if that was a characteristic of bad caps or not. Could be the live room, (basement rec room with hard tile floors and little soft furniture) poorly mixed cd's or my aged hearing. I do have some cd's that sound very good with this system so the caps might be fine I might leave them. Thanks for the help. I did take a pic of the crossover for posterity.

 

32432551577_bc882fdcc8_c.jpgP1000527 by

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I would replace the capacitors regardless, as pointed out by the others.

I've had great success with Dayton Audio's poly caps being on-spec, even the cheaper 5% tolerance caps.  I would buy two of each of these connect them in parallel (for a total of 13uf), and then replace the old single capacitors in each crossover:

https://www.parts-express.com/dayton-audio-dmpc-12-12uf-250v-polypropylene-capacitor--027-430

https://www.parts-express.com/dayton-audio-dmpc-10-10uf-250v-polypropylene-capacitor--027-410

If you plan on playing these loud, replacing the inductor with an air core or p-core (as opposed to iron core) inductor might be a good idea.

 

Edit - I'm not sure this would help with brightness, though.  The hard surfaces might be part of the issue.

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That is a New Large Advent (NLA) where the stock inductor IS air core.

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I'm sure it's an Advent/1 and not an NLA. The photo I posted was an Advent/1 and the OP's sure looks the same to me. But your point, I think, is that the inductor is air core. I think this shot (also "borrowed") shows the construction of the coil better.

-Kent

Advent 1 xo.jpg

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