Series Resistor for attenuation in Passive Crossover

Eddie Wolve · 13th November 2010, 04:45 AM

Hi all.

Can someone varify my maths here...(it's been a while)

I wish to provide about 7dB attenuation for a horn tweeter. (8 ohms) using a non-inductive series resistor. (not L pad)

My intention is to increase the overall impedance of the tweeter / attenuation, so as to allow me to use lower value capacitors (therefore cheaper) in the passive crossover which will be 18dB/ Octave.

My calculations are a resistor of about 10 ohms will be required..

Any comments appreciated...

Ed.

godfrey · 13th November 2010, 07:11 AM

Your calculation would be correct if the tweeter's impedance was really 8 ohms. To get the crossover design right, you need to get a graph of your tweeter's impedance vs frequency.

Eddie Wolve · 13th November 2010, 09:16 AM

Thanks Godfrey..

The problem you mention is a problem with ALL passive crossovers is it not..?

Usually adressed by impedance EQ circuits etc..?

I guess off the top of my head, an L pad 'might' be less susceptible, as it has a purely resistive load in parallel to the driver..?

godfrey · 13th November 2010, 10:22 AM

Yes, sometimes and yes.

A transformer could be useful too, with it's inductance forming part of the filter.

13th November 2010, 04:45 AM	#1
Eddie Wolve diyAudio Member Join Date: Dec 2005 Location: South Hedland	Series Resistor for attenuation in Passive Crossover Hi all. Can someone varify my maths here...(it's been a while) I wish to provide about 7dB attenuation for a horn tweeter. (8 ohms) using a non-inductive series resistor. (not L pad) My intention is to increase the overall impedance of the tweeter / attenuation, so as to allow me to use lower value capacitors (therefore cheaper) in the passive crossover which will be 18dB/ Octave. My calculations are a resistor of about 10 ohms will be required.. Any comments appreciated... Ed.

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13th November 2010, 07:11 AM	#2
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	Your calculation would be correct if the tweeter's impedance was really 8 ohms. To get the crossover design right, you need to get a graph of your tweeter's impedance vs frequency.

13th November 2010, 09:16 AM	#3
Eddie Wolve diyAudio Member Join Date: Dec 2005 Location: South Hedland	Thanks Godfrey.. The problem you mention is a problem with ALL passive crossovers is it not..? Usually adressed by impedance EQ circuits etc..? I guess off the top of my head, an L pad 'might' be less susceptible, as it has a purely resistive load in parallel to the driver..?

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