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Small Advent X-overs


Guest 1080i

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Sorry if this has been covered before, but I did a search and can't find a good answer. I have opened up 3 small Advents (out of 4 I have)to rebuild them, caps and surrounds. So far, all three crossovers are different.

Ignoring the parts that are the same in them:

#1 from 1975 has a 5uF cap in parallel with a 3 ohm resistor.

#2 from 1975 has an 8uF cap in parallel with a 2 ohm resistor.

#3 from (I forgot when) has a 4uF cap in parallel with a 3 ohm resistor.

I suspect #4 will be still different.

All four have orange tweeters.

What's going on? What is the "correct" value of these parts? What do you think I should do? Pick one and make them all the same, or leave them different as they are?

Thank you.

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>Sorry if this has been covered before, but I did a search and

>can't find a good answer. I have opened up 3 small Advents

>(out of 4 I have)to rebuild them, caps and surrounds. So far,

>all three crossovers are different.

>

>Ignoring the parts that are the same in them:

>

>#1 from 1975 has a 5uF cap in parallel with a 3 ohm resistor.

>

>#2 from 1975 has an 8uF cap in parallel with a 2 ohm

>resistor.

>

>#3 from (I forgot when) has a 4uF cap in parallel with a 3 ohm

>resistor.

>

>I suspect #4 will be still different.

>

>All four have orange tweeters.

>

>What's going on? What is the "correct" value of

>these parts? What do you think I should do? Pick one and make

>them all the same, or leave them different as they are?

>

>Thank you.

The 'correct' parts are the ones that make each speaker sound great. Listen to all 4 and let your ears decide what's right.

It's all about the music

Carl

Carl's Custom Loudspeakers

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Guest sbalfour

Assuming all the parts are original, you might check the tweeters

(DCR, impedance and resonance). If there are any differences, the

crossovers would correspond to those. I think the Advent tweeter

(same as in the Large Advent) underwent a revision which took it

from 4 ohms to 3.1, though I think the revision was in 1971. For

comparision, the Advent Large crossover underwent 4 revisions, not

including that for the New Advent, which was entirely different.

One was a manufacturing economy, one was to protect the fragile

tweeter, and two were apparently design concept driven.

The parallel cap/resistor is a high frequency boost, equivalent

to the "extend" position of the contour switch on the Larger

Advent. The differences you note appear to me to be fiddle-

faddling. The larger cap (8uf) and smaller resistor (2ohm) will

give a slightly smaller boost cutting in at a little lower frequency.

The smaller Advent was known for having a lifeless lower treble,

so maybe they were attempting to remedy that. However, the Smaller

Advent loudspeaker was discontinued after 1975, so the change would

have been short lived.

Stuart

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Actually, the smaller Advent tweeter was not originally the same as the large Advent. The magnet structure was smaller to match the efficiency to the smaller Advent woofer. The magnet is 2.5 inches square rather than 3 inches square as in the large Advents.

I think that they may have changed this in later production units, however, making them the same as the large Advents.

Doug

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