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AA mod


CECAA850

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I'm knocking down the mids 3db on my AAs  by moving a tap on the tranformer and adding a resistor across the squawker.  The transformer is a 3670 and the squawker positive wire is currently on the tap marked 3.  I'm assuming I move it to the tap marked 6?  The taps on the back of the transformer are marked 3, 6, 9 and 12.

 

TIA

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I'm thinking the numbers are dB reduction levels, so bigger is higher reduction.  And that the impedance seen by the crossover will become higher, so a parallel resistor would be correct.  But the resistor will also consume signal, dropping the output of the driver yet more.  So you'll end up at more than -3 dB output.  ("upwards" of -6?)

 

Might be better to leave the tap alone and use a combination of series and parallel resistors after the transformer such that the impedance stays nominally the same.  Or use just a series resistor upstream of the crossover, but then you'll have to move the tweeter crossover stuff ahead of that unless you want to maintain the mid-to-high relationship.

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21 minutes ago, rockhound said:

It would be useful to those that may want to do the same to see a picture of what the final mod looked like from the original a before and after if you will.

Too late.  It's back together.  The only picture I have of the resistor installed can't be posted as I'm over my limit.

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On 3/28/2020 at 8:34 PM, glens said:

I'm thinking the numbers are dB reduction levels, so bigger is higher reduction.  And that the impedance seen by the crossover will become higher, so a parallel resistor would be correct.  But the resistor will also consume signal, dropping the output of the driver yet more.  So you'll end up at more than -3 dB output.  ("upwards" of -6?)

 

Might be better to leave the tap alone and use a combination of series and parallel resistors after the transformer such that the impedance stays nominally the same.  Or use just a series resistor upstream of the crossover, but then you'll have to move the tweeter crossover stuff ahead of that unless you want to maintain the mid-to-high relationship.

 

There are multiple threads on here about how much power a constant impedance network uses. The 'swamping' resistor across the the autoformer will work fine. Where's @Deang when we need him.

 

My DH2 crossovers use this method and you just need to go

Bruce

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4 minutes ago, CECAA850 said:

Too late.  It's back together.  The only picture I have of the resistor installed can't be posted as I'm over my limit.

 Did you end up soldering a 15 - 16 ohm resistor across the squawker and move the squawker to taps 0 - 3?  

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3 hours ago, mboxler said:

 Did you end up soldering a 15 - 16 ohm resistor across the squawker and move the squawker to taps 0 - 3?  

The resistor had long leads so I actually mounted it to the crossover at the terminal strip.

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