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redpackman

Small Advent Crossover Variation and questions

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I am in the process of restoring a pair of Small Advents. I opened them up today and found the crossover has a 12uf and an 8 uf cap along with a 1ohm 5w resistor.

As near as I can tell the diagram of the crossover is like the attached diagram EXCEPT that the cap between the 4 ohm (+) terminal and the place where the other 8 uf cap and resistor join is a 12 uf cap and not an 8 uf cap as diagrammed and the resistor is a 1 ohm and not a 3 ohm as listed. Put another way working from the 4 ohm terminal the first capacitor one would reach in the chain would be a 12 uf cap, [ then an 8 uf and 1 ohm 5 watt resistor in parallel.]

Some report 5 uf caps, others report 2 8uf caps. Then others say they have........ :wacko:

I have read elsewhere that the best cross over is the one that "sounds the best." I haven't the time or the sonic memory to try out all the variations. Is there one that Advent seemed to "settle on" or do they simply have about a dozen variations for the crossover for their Small Advent speaker and we're to just guess at which is "best" and hope it works out.

Suggestions from the experts?

Smaller_Advent_Crossover.pdf

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Which tweeters do your Smaller Advents have? The green ones or the orange ones?

The original green ones had a smaller magnet than the full sized Advents had to match the efficiency of the woofer. Later, Advent put tweeters in that had the large magnets in them and the cones are orange (although there may be some with green cones). The thing to do is actually look at the magnets. The smaller ones are 2.5 inches square and the larger ones are 3 inches square.

I believe Advent changed the crossover when they made the change sometime in 1975. It makes sense that the crossover you have would have been used in the smaller magnet units and the crossover with the 3 ohm resistor in the later, large magnet units.

Doug

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Red,

The last pair of Smaller Advents I opened up had original green tweeters and your crossover, which would be consistent with Doug's comments.

Roy

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Thank you. That is a help. BTW the caps tested out at 8.1 uf for the 8 uf cap and 12.45 uf for the 12 uf cap. I assume they are therefore still serviceable?

I also checked the tweets. They had September 1973 stamped on them and they were the smaller 2.xx size. Thanks again for the info.

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BTW the caps tested out at 8.1 uf for the 8 uf cap and 12.45 uf for the 12 uf cap. I assume they are therefore still serviceable?

I do not see any reason to replace the caps. "If it ain't broke..."

Roy

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I agree with Roy. These days, there seems to be almost a religion about automatically replacing capacitors in the belief they are automatically bad after x number of years.

Although there are perfectly valid reasons for that (the electrolyte drying out, etc.), I just think it's better to leave them alone if they still are in spec. Of course, ideally, you would want to check the series resistance also but every time I have, they seem to be OK in that regard too.

And, even more of a religion seems to be to replace the original style of capacitors with some other types, even exotic types, in the belief that these different types of capacitors will automatically improve the sound of the speakers. This all without considering the speakers were possibly voiced with the types originally included and using others may affect the sound of the speakers but maybe not in a positive way.

I say all the above in spite of my belief, through experimentation over the years, that there really isn't that much difference in sound between different capacitor types.

I just think it's better to leave them alone if they are working and the speakers sound good. All five pairs of my original Advents have their original capacitors and they all sound alike and all sound wonderful.

Doug

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I agree with Roy. These days, there seems to be almost a religion about automatically replacing capacitors in the belief they are automatically bad after x number of years...

Doug

I agree wholeheartedly. Recap fever is epidemic. Like the tech at McIntosh told me when I asked if they recap older units that come in for repair, "We don't replace parts that aren't broken." I refoamed a pair of Smaller Advents this morning and the caps tested and sound perfect after 40 years.

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On 8/18/2013 at 7:14 PM, RoyC said:

Red,

The last pair of Smaller Advents I opened up had original green tweeters and your crossover, which would be consistent with Doug's comments.

Roy

I finally have a pair with green tweeters and also have 12uF to 1 ohm/5W resistor with 8uF across it,

 a light blue dot type inductor to ground (across the tweeter) is  .36 mH/1.1ohm DCR.

The green 2.5" square (small) magnet tweeter is 3.2 ohms DCR.

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Something odd, I finally opened the second Small Advent in this pair and the 

inductor has a yellow dot and measures .056 mH .30 R.  I'd guess that they dot

color is a code for value but not sure, so it was either fabricated incorrectly or

the coil overheated and has shorted windings.

I might just unwind both of these since I have no use for them.

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