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2.2uF 2.0uF and Types you use. Chorus "I"


VSAT88

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10 hours ago, dsmdylan said:

Good info. Changing the crossover point is not quite as simple as just changing the capacitance, though, right? I've seen Al K state many times that you need to redesign the whole network. On the other hand, I get the sense that Al might tend to get caught up in the minutia.


Right, but the question related to the difference between a 2.0uF and a 2.2uF. 2.2uF is a common value, 2.0uF is not. A 2.2uF is within 10%, if it’s spot on at 2.2, and they usually aren’t. Dayton Audio makes a 2.0uF 1% capacitor which is a great value part. 13uF is also not a common value, and as has been pointed out several times in the past, old Klipsch A’s are littered with 12uF. It just doesn’t seem that PK was much concerned about this on the 1st order sections of his filters. 

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16 minutes ago, VSAT88 said:

And now I am thinking about building an external crossover to play with parts........ Where my mind go's sometimes, whew.

Others have certainly done it.

Interesting hobby if you've the 

time.

Hope you are closer to deciding on recapping your networks.

Cool...

 

 

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11 hours ago, dsmdylan said:
11 hours ago, dsmdylan said:

 

I don't doubt it! I'm very interested to know the how, though.

 

 

One of the reasons this is so is because the impedance of the driver is not constant. It varies with freq so when changing a cap that has different specs or a different value or both, it has to work in conjunction with the impedance. It is especially challenging when working with horn horn loaded drivers because the impedance curve is increase and varies quite a bit more. 
 

that’s also why your network calculator is giving strange values. It is assuming a constant impedance. That doesn’t happen in the real world. 

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11 hours ago, dsmdylan said:

What am I doing wrong here (Cornwall 1)? C1 seems close enough but C2 is obviously way off from the 2uF that's actually in the network.

 

C2 is not the tweeter, C1 is.

 

Your network uses an autotransformer to attenuate the drivers in the high pass. It increases the impedance to do this. The reflected impedance back from your midrange driver to the amp is 60 ohms.

 

The 2uF isn't the right value for 6000Hz, 3.3uF is. So why 2uF? I'm not sure we ever really settled that one around here. My guess is that it was the most inexpensive way to provide tweeter protection, because it further attenuates the frequencies near and below the crossover point and/or resonant frequency.

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@Chief bonehead Said "It is especially challenging when working with horn horn loaded drivers because the impedance curve is increase and varies quite a bit more." And this is what I was concerned with and why I was asking about this cap thing. Horns are a different breed when it comes to speakers. I am just not familiar with them at all. Also the transformer/autotransformer (not sure what its actually called). I have never played with networks with that involved.

Edited by VSAT88
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What "Scala" part are you using? 🙂

 

Basically you're dinking around with a Cornwall cabinet.

 

The 811b has an Fc of 800Hz, so it's not really a good choice. the idea is to cross lower. Also, with the type of network you are most likely going to end up using, you need to be at least a half octave above the horn's Fc. You will also have to use an adapter, another unknown variable without measuring.

 

Others who have done this kind of thing will eventually show up with comments. You might want to start a new thread, or search out an existing "CornScala" thread for your questions about this.

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Another thing if you guys are still looking. Should I test the autotransformer ? If so how. Do they generally work or not work ? It seems to me that would be the case however with my limited knowledge I would rather ask. Once again just to re state my problem. When using one of the networks is down a few dB from the other one and I have swapped the horns. Same results from the same network. Muted sound from the squawker. I pulled the 7uF and used a cheap tester on it. ESR was high but uF measured at or around 7. The resistor measured just fine.

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