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Old 29th April 2013, 05:57 AM   #31
Tomos is offline Tomos  Croatia
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Quote:
Originally Posted by PeteMcK View Post
Tomos, use the L Pad calculator I linked in post#6 to work out your resistor values, for a Ztotal of 4 ohms
I understand L-pad.
The point of my issue is -I don't want to keep nominal impendance of driver, but cut it in half + attenuate for about 5 db.
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Old 29th April 2013, 11:53 PM   #32
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For the crossover to work as designed, it needs to see the same impedance with the new tweeter as with the old, so the L pad needs to do two things - maintain the total impedance, and incorporate the attenuation you require. (It may be simpler to use a variable resistor & replace with two fixed resistors once you've found the level required)
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 30th April 2013, 05:24 AM   #33
AllenB is offline AllenB  Australia
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The beauty of an L-pad is that it will partially flatten out the impedance, bringing it closer to the L-pad design impedance. The more you attenuate, the more it will do this. For example, if you pretend the tweeter is a four ohm tweeter and calculate the L-pad for 4 ohms and attenuate by a fraction of a dB, it will still look like an 8 ohm tweeter with all its peaks and curves....but if you attenuate by several dB then it all begins to look just like a 4 ohm resistor without the peaks and curves.
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Old 30th April 2013, 05:42 AM   #34
Tomos is offline Tomos  Croatia
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Thanks for comments, but I still didn't get practical solution for problem I have. I want to attenuate by 5db and cut impendance in half in same time.
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Old 1st May 2013, 06:59 PM   #35
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Tomos View Post
Thanks for comments, but I still didn't get practical solution for problem I
have. I want to attenuate by 5db and cut impedance in half in same time.
Hi, About 2R in series and about 3R in parallel will do it, rgds, sreten.

(1.8R series and 3R parallel gives 4 ohms and -5dB.)
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Last edited by sreten; 1st May 2013 at 07:05 PM.
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Old 1st May 2013, 07:23 PM   #36
Tomos is offline Tomos  Croatia
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Sounds good. Thanks. Still curious what would I get wit only 8 ohm in paralel. In case I'm affraid of messing up the signal line to spraker ;-)


?
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Old 1st May 2013, 07:38 PM   #37
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Tomos View Post
Sounds good. Thanks. Still curious what would I get wit only 8 ohm in
paralel. In case I'm affraid of messing up the signal line to spraker ;-)


?

Hi, 4 ohms with no attenuation, rgds, sreten.
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Old 3rd May 2013, 11:00 AM   #38
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Tomos View Post
In case I'm affraid of messing up the signal line to spraker ;-)
Not sure I understand what your concern is here?
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Old 3rd May 2013, 05:22 PM   #39
Tomos is offline Tomos  Croatia
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Well, I would't like to put many elements to signal path. I wouldnt like to spoil it. However, resistors are passive elements. Maybe it's just my imagination.... :-p
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Old 3rd May 2013, 07:43 PM   #40
AllenB is offline AllenB  Australia
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There is a difference but it's not easy to notice. It's probably best to put in everything you need.
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