Crossover Question

woody · 25th January 2006, 10:16 PM

I need a 12/db oct xover at 1900hz. Well this is simple enough
but I may be driving it from an amplifier with a 12 ohm output
impedience. Would this high output impedience change the calculations.

Thanks

AndrewT · 26th January 2006, 08:36 AM

Hi,
put simply YES, it will alter the crossover.

Is that 12ohm, the output impedance or the required load impedance for that output stage?

12ohm output impedance is extremely high for a power amplifier, even for a valve amplifier with a transformer coupled output.

Many a preamp has an output impedance down around that 12ohm level. These are specifically designed for driving long cables/high capacitance into the higher impedance load of the next amplifying stage.

To answer the question; we cannot tell because you have not specified the two load impedances on the other side of the crossover.

woody · 26th January 2006, 11:41 AM

Andrew, thanks for the reply. I was thinking about a small
OTL amp built without feedback which explains the high output
impedience. The drivers I intend to use will be 8 ohms after
the zobel circuite is added. On the other hand if I use my SOZ
the output impedience will be 4 ohms. Won`t this call for yet
different component values ?

sreten · 26th January 2006, 11:53 AM

Hi,

you've got more problems than the c/o.

Amplifier source impedances of 4R and 12R will totally change
the bass alignment of the speaker they are connected to.

/sreten.

25th January 2006, 10:16 PM	#1
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Crossover Question I need a 12/db oct xover at 1900hz. Well this is simple enough but I may be driving it from an amplifier with a 12 ohm output impedience. Would this high output impedience change the calculations. Thanks

26th January 2006, 08:36 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, put simply YES, it will alter the crossover. Is that 12ohm, the output impedance or the required load impedance for that output stage? 12ohm output impedance is extremely high for a power amplifier, even for a valve amplifier with a transformer coupled output. Many a preamp has an output impedance down around that 12ohm level. These are specifically designed for driving long cables/high capacitance into the higher impedance load of the next amplifying stage. To answer the question; we cannot tell because you have not specified the two load impedances on the other side of the crossover. __________________ regards Andrew T.

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26th January 2006, 11:41 AM	#3
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Andrew, thanks for the reply. I was thinking about a small OTL amp built without feedback which explains the high output impedience. The drivers I intend to use will be 8 ohms after the zobel circuite is added. On the other hand if I use my SOZ the output impedience will be 4 ohms. Won`t this call for yet different component values ?

26th January 2006, 11:53 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, you've got more problems than the c/o. Amplifier source impedances of 4R and 12R will totally change the bass alignment of the speaker they are connected to. /sreten.

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