D9 Crossover Redo...

jbeckva

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I like 'em, but I think after 30 years it's time to replace the caps...

100uf 100V
15uf 100V
5uf
2.5uf

(noting em down while I have the xover opened up... )

Here's the before pic. Note the labels on the two yellow "mexico" caps... they say 2.5K and 5K.. which I am assuming is in picofarads, hence the 2.5uf and 5uf values I will need. Does that look right to you guys?

IMG_1685.jpg
 

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Gibsonian

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I went nearly all out on mine before they departed me. Braced the speaker boxes considerably and coated the inside with rubber roofing coating for increased dampening before putting the factory dampening back in. Re-capped as well. The x-over is not the greatest, and it prolly would not hurt to upsize the inductors with higher wire gage of same values. Ended up using 5 amp fast blow fuses in the end rather than the factory 2.5 amp slow blow. PL700 could still blow em no problem, and I never took out any drivers while doing so. It was amazing to me the power handling of the speakers, as none of the drivers seem that well built, but they can sure crank out the jams.
 
laatsch55

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Scott, to see how ridiculously loud we could be one night, I had tri-amped the K's to get a taste of it and after a few crown and cokes, put a WOPL1000 on my D-9's which sat right in front of the K's. The put a WOPL 500 on each pair of Heresies (there were 2 side by side on top of the K's) . Fired up each set of speaks by themselves to get a hint of where they would clip, then turned em all on. For some reason it DID NOT sound like a clusterf^%$!! We were amazed. I did not own an SPL meter at the time which was a good thing, probably would have scarit me...
 
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laatsch55 said:
Scott, to see how ridiculously loud we could be one night, I had tri-amped the K's to get a taste of it and after a few crown and cokes, put a WOPL1000 on my D-9's which sat right in front of the K's. The put a WOPL 500 on each pair of Heresies (there were 2 side by side on top of the K's) . Fired up each set of speaks by themselves to get a hint of where they would clip, then turned em all on. For some reason it DID NOT sound like a clusterf^%$!! We were amazed. I did not own an SPL meter at the time which was a good thing, probably would have scarit me...
Click to expand...
You trying to crack your foundation, Lee???!!! Geezus that must have been about as loud as the David Lee Roth concert I remember going to back in '85'ish.. It was at the Hampton Coliseum (back when concerts USED to be smoke fests.. ahh.. PC bassids taking over the world... ahem.. where was I... ), and it was the first in his tour after leaving VH. He played a tune or two, then in the middle said "hold it.... I can't hear the music... TURN IT UP... TURN IT UP MAAAAN!! I just remember having to go to work the next day and not regaining ANY of my hearing until lunchtime...

But it was... COOL.. heheh
 
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Anywhoo... so back to the matter at hand.

The tweeters aint too shabby... I took a peek at them tonight. I also studied the layout and you know... that crossover is pretty "odd", but I guess they knew what they were doing. The woofer section is a 2nd order, the tweeter section a 3rd order, and the midrange is a 1st order. Strange mix, I dunno.. maybe? But... note that with the tweeter being a 3rd order, that BOTH of those old looking paper/film whatever caps are in the circuit.. and in series with each other with a coil splitting them in the middle.

So yeah.. time to get that parts express order going. I figured it might make a diff with decent, new caps. But wow.. the 100uF's are going to be HUGE... like twice the size of a tylenol bottle!
 
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laatsch55

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I don't know if the word "overkill" should be applied to a crossover, "extended reliability" maybe.....
 
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laatsch55 said:
Good guess huh??
Click to expand...
Well like I said, just thinking a bit (and the 30 bucks apiece price tag is part of my "thinking" hehe)... Why spend 30 for these to replace a bipolar electro when due to their place in the circuit, they are just shunting signal instead of passing it through to the driver? Why not just go for a 100uf bipolar electro HERE, but of course use the metal polys for mid and tweeter circuits because over there, they most certainly have the signal passing through... from input to drivers.
 
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So, you are saying shunting doesn't add to the signal in some way?? If it manipulates the signal in any way I would think the chances for it putting it's signature there also is pretty good.
 
Gepetto

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laatsch55 said:
So, you are saying shunting doesn't add to the signal in some way?? If it manipulates the signal in any way I would think the chances for it putting it's signature there also is pretty good.
Click to expand...
I think you are describing the woofer zoebel network in the preceding text. The woofer zoebel is quite critical to proper performance of the mid and tweet that also share the speaker wire pair from your amp to the speaker box.
 
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Gepetto said:
I think you are describing the woofer zoebel network in the preceding text. The woofer zoebel is quite critical to proper performance of the mid and tweet that also share the speaker wire pair from your amp to the speaker box.
Click to expand...
I'm talking about the (very typical) 2nd order low pass filter for the woofer. You know - The one with an inductor in series and a cap in parallel with the driver?

calc_cr_12db.gif

The first order 6db slope of L2 is enhanced by the SHUNT action of C2, which combined creates a 12db slope. The main signal is passed through L2, however. This entire circuit is in parallel with the THIRD order high pass filter for the tweeter, and a FIRST order bandpass filter for the midrange - Aside from the final interaction between the drivers on the "sound producing" end (phase relationships, slope overlap, etc), I don't see where it matters too much. I am also not too concerned about a bipolar electrolytic because C2's particular function is NOT PASSING the signal through, and hell... that's what is in there NOW.

However.... moving on here....

3rd order, high pass filter (tweeter). Signal is PASSED through C1 and C2... you're damn skippy I am going to use metal polys here...

calc_cr_18db.gif

1st order, bandpass filter (midrange.. the two midranges in the D9 are paralleled on the output). Also going to use metal polys here... because the signal is passed through. I could perhaps replace the inductor too, but honestly... really???

bpass.jpg
 
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Putting a poly in for the woofer shunt cap. Inductor is "ok" - I would replace it, but not sure what value it is. Hmmm... maybe Joe would know... given the following parameters...

Xover frequency - 500hz
Woofer impedance - 8 ohms
Value of C - 100uF

(what's the value of L in the woofer circuit above??)

Which leads me to this point too, so MAYBE I might end up with a poly in there... Seems to me that 100uF is pretty high, given all the calculators I have used to calculate based on just the woofer impedance, xover freq, and desired slope.. They come up with a 20uF cap and 5mH inductor.

So yeah, that's another way of going about it too - junk the inductor, and go with one that doesn't require such a big cap.
 
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