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Old 4th July 2005, 06:18 AM   #1
piro is offline piro  Israel
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Default help with wattage rating of coponents in crossover

So, I'm building this circuit (crossover in fact), but I'm not sure what is the max poewr the components should be able to handle.

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C1- 23
L1 -0.5
R1- 1
R2 -1.6
L2 -2.3
C3 -11.6
L3 -10.8
R4 -0.6
C4 -5.1
R5 -14.7

tweeter imedance: 6 ohm
woofer impedance: 8 ohm

Here are the specifications (in pdf) of the tweeter and of the woofer. I wasn't sure which values to take as power and resistance.

TIA
- Jonathan
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Old 4th July 2005, 08:50 AM   #2
rabbitz is offline rabbitz  Australia
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Use these as a minimum.

Resistors 5W wire wound, non inductive
Caps 200V metalised polypropylene
Inductors 1mm (18AWG) or larger wire so the inductor DCR is around 5% of the driver's DCR (Re)
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Old 5th July 2005, 06:50 AM   #3
piro is offline piro  Israel
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Are you sure about the resistors?
I was told that evey resistor in parallel or in line with the drivers should have about the same power handaling capabilities as the driver itself.
And could you explain a bit about how you calculated the values for the caps? I've never dealt with them before so my knowwledge about them is purely theoretical (and not much at that).

Thanks
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Old 5th July 2005, 11:38 AM   #4
rabbitz is offline rabbitz  Australia
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Yep.... sure.

You might need to do some reading such as the Loudspeaker Design Cookbook or some research as it will pay dividends.

Go out and smack the guy in the mouth that told you the resistor has to be the same watts as the driver Remember, the resistor is burning off a small amount of the power with the bulk still going to the driver, overwise there would be no sound.

As far as caps, you don't need the 200V but that's the starting rating of decent polypropylenes. If you used Solens for example, they are rated at 400V but you don't get them for the voltage but for their sonic abililty in a crossover.
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Old 5th July 2005, 01:54 PM   #5
piro is offline piro  Israel
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Okay then, I guess that's that.
I actually did quite a bit of research about the actual design of the circuit but I have very little experience in practical electronics
I'm working on fixing that though, as soon as I finish with the speakers this crossover is for I'll start work on a Cmoy amp. I hear they are good practice.

thanks again
- Jonathan
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Old 6th July 2005, 07:13 AM   #6
rabbitz is offline rabbitz  Australia
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Cmoys are good practice and have a look through the Chipamp section as there's some good info there. What does help with those is adding by-pass caps on the power inputs to the op amp.

Like this... done right....
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Old 6th July 2005, 07:15 AM   #7
rabbitz is offline rabbitz  Australia
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.... or like this which is quite OK if space is limited. Have fun with it all.
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