Crossover impedances

grendal · 30th December 2011, 10:09 PM

Hi there, I have purchased a Dayton crossover (2000Hz) which is designed for an 8Ohm tweeter. I didn't realise the tweeter I purchased is only 4 ohms. What are the implications of hooking these up? I currently have it running and it sounds fine.

Does it change the crossover point? I'm assuming the fix is to wire a 4 ohm resister before the tweeter?

AllenB · 30th December 2011, 10:20 PM

Depending on the crossover itself, it is likely to run the tweeter a little quiet near the crossover point, but otherwise it should behave similarly to an 8 ohm tweeter.

grendal · 30th December 2011, 10:35 PM

Thanks for the reply Allen. It's a second order Linkwitz-Riley arrangement if that helps. Would you suggest running a resistor in series with the tweeter to bring it to 8Ohms?

Also, I've heard that if you use a 4ohm woofer on a crossover designed for 8 ohm woofer this affects the crossover frequency? Is this true?

AllenB · 31st December 2011, 04:20 AM

The effect of a second order type of crossover will be the same way above and below the crossover point, with just a change in level near the crossover point when the impedance is not as designed for.

A first order filter will cause the rolloff to happen at a different frequency, an actual shift. In the case of a pair of 4 ohm drivers with a generic 8 ohm style crossover, the responses will cut off away from the crossover point encouraging a hole in the response.

You asked about using a resistor, if you do it will make the tweeter more quiet. If this is needed then go ahead. It will also alter the response a little. If you don't need your tweeter reduced in level, then I wouldn't do this.

If you do notice a problem with a lack of lower treble, you could play with increasing the tweeter capacitance by clipping another capacitor in parallel with the one you have. This will partially compensate for the problem, but a lot depends on a lot of things.

grendal · 1st January 2012, 06:12 AM

Thanks for the help Allen. I am pretty happy with the current result so feel no need to alter it. Hard to know exactly what is going on without proper measurements, but when I do a frequency sweep it sounds natural to my ears.

30th December 2011, 10:09 PM	#1
grendal diyAudio Member Join Date: Jul 2011	Crossover impedances Hi there, I have purchased a Dayton crossover (2000Hz) which is designed for an 8Ohm tweeter. I didn't realise the tweeter I purchased is only 4 ohms. What are the implications of hooking these up? I currently have it running and it sounds fine. Does it change the crossover point? I'm assuming the fix is to wire a 4 ohm resister before the tweeter?

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30th December 2011, 10:20 PM	#2
AllenB diyAudio Member Join Date: Oct 2008	Depending on the crossover itself, it is likely to run the tweeter a little quiet near the crossover point, but otherwise it should behave similarly to an 8 ohm tweeter.

30th December 2011, 10:35 PM	#3
grendal diyAudio Member Join Date: Jul 2011	Thanks for the reply Allen. It's a second order Linkwitz-Riley arrangement if that helps. Would you suggest running a resistor in series with the tweeter to bring it to 8Ohms? Also, I've heard that if you use a 4ohm woofer on a crossover designed for 8 ohm woofer this affects the crossover frequency? Is this true?

31st December 2011, 04:20 AM	#4
AllenB diyAudio Member Join Date: Oct 2008	The effect of a second order type of crossover will be the same way above and below the crossover point, with just a change in level near the crossover point when the impedance is not as designed for. A first order filter will cause the rolloff to happen at a different frequency, an actual shift. In the case of a pair of 4 ohm drivers with a generic 8 ohm style crossover, the responses will cut off away from the crossover point encouraging a hole in the response. You asked about using a resistor, if you do it will make the tweeter more quiet. If this is needed then go ahead. It will also alter the response a little. If you don't need your tweeter reduced in level, then I wouldn't do this. If you do notice a problem with a lack of lower treble, you could play with increasing the tweeter capacitance by clipping another capacitor in parallel with the one you have. This will partially compensate for the problem, but a lot depends on a lot of things.

1st January 2012, 06:12 AM	#5
grendal diyAudio Member Join Date: Jul 2011	Thanks for the help Allen. I am pretty happy with the current result so feel no need to alter it. Hard to know exactly what is going on without proper measurements, but when I do a frequency sweep it sounds natural to my ears.

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