Speaker attenuator for impedance setting

discussion of magnetic volume control design for both line and speaker levels.

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Daniel
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Joined: Fri Jan 10, 2014 4:50 pm

Speaker attenuator for impedance setting

Post by Daniel »

Hi, Dave mentions that the choice of impedance setting via a parallel resistor is a way to crank up impedance to use smaller capacitors. How about using it to match impedances at the crossover point? Say you build a two way speaker, cross at 1k5 and the woofer is at 7 Ohm and the tweeter at 9 Ohms. Would there be a benefit of setting the impedance of the tweeter to 7 Ohm at 1k5 as well?
dave slagle
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Post by dave slagle »

I don't think have the crossovers at the same impedance is an important factor. I do think taking advantage that the autoformer steps up the apparent speaker impedance can be used to your advantage since higher crossover impedances use smaller caps and that many feel smaller caps sound better and a 1µ cap is generally cheaper than a 2µ cap so for the same $$ a higher quality cap can be used.

Of course if the filter is 2nd order, then the inductor must get bigger so the cost can be a horizontal move but making that cap smaller has always been a good move for me.

dave
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Daniel
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Post by Daniel »

Ok. Say if I needed two inductors for low pass filters at somewhere around 6.5mH @ 800Hz and 8kHz, what type of core would you suggest and is there a chance to wind these guys with a DCR below 100 mΩ?

And to get back to the topic of attenuators, if I built a bandpass filter for the mids with a 12dB high pass and some low pass after it, is there a chance to combine these two inductors into an attenuator for level setting or would the combination be too much hassle with a compromised outcome?
dave slagle
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Post by dave slagle »

80% nickel on the core and 0.1 ohm isn't a problem.

the autoformer can be used as a crossover inductor and if you are going ot go this route I strongly suggest simming it in LT spice.

dave
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Daniel
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Post by Daniel »

Cool! I'll get in touch once I'm done DSPing the drivers into submission and know my numbers.
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