Two B1 and a crossover - Page 3

AndrewT · 21st October 2009, 08:15 PM

that Pllxo article omits a few cases that need component value corrections.
Rs (the source output impedance) when feeding the High Pass and when feeding the Low Pass. The Low Pass is easy. R1+Rs = R'1

How does one correct the High Pass component values for a Rs<>0r0?

What does one do when the Low Pass has a resistance (Ramp) parallel to C1?

Melon Head · 08:39 PM

Quote:

Originally Posted by Floric

But this is an active Sallen-Key filter...

I think this is still relevant no matter what type of filter is used

"I strongly suggest that resistor values should be not lower than 2k2 and no higher than 20k - this is a reasonable compromise between opamp loading and noise. " Rod Elliott

Maybe you didn't read it carefully.

Floric · 09:15 PM

Quote:

Originally Posted by AndrewT

that Pllxo article omits a few cases that need component value corrections.
Rs (the source output impedance) when feeding the High Pass and when feeding the Low Pass. The Low Pass is easy. R1+Rs = R'1

I measured my ones after tey were built, I think you may omit it.

Quote:

Originally Posted by AndrewT

How does one correct the High Pass component values for a Rs<>0r0?

I think that is not necessary because Rs is in series with C1, so no voltage-divider is built.

Quote:

Originally Posted by AndrewT

What does one do when the Low Pass has a resistance (Ramp) parallel to C1?

It is in my opinion in series with C1. Even if there is an output impedance, there is still a voltage source.

Edit: Had overseen the questions.

Floric · 21st October 2009, 08:59 PM

Quote:

Originally Posted by thanh1973

I think this is still relevant no matter what type of filter is used

"I strongly suggest that resistor values should be not lower than 2k2 and no higher than 20k - this is a reasonable compromise between opamp loading and noise. " Rod Elliott

Maybe you didn't read it carefully.

I read the article, some years ago. If you read Linkwitz, you will find anything around 10k.

Lower values are good for lower noise. But we are talking about a (kind of) b1 and not about an Opamp that would drive 600R without any problems.

Melon Head · 22nd October 2009, 05:44 AM

That is why I suggested using 20K resistors.

Vigo · 22nd October 2009, 06:33 AM

Ok sow if i use something between 10 and 20 kohm it should be fine.
And i dont need to calculate with the input and output of the B1.

I will calculate some and see if can get any good standard values for the components.

Thanks everyone for your help.

AndrewT · 22nd October 2009, 09:14 AM

Quote:

Originally Posted by Vigo

And i dont need to calculate with the input and output of the B1.

the output impedance of the B1 is ~1k.
you must take this into account for all filters that follow it.

A theoretically correct filter can only achieve it's Q and turnover point when the source impedance is 0r0 and the load impedance is infinite.

Melon Head · 22nd October 2009, 09:31 AM

He doesn't need to use the 1k resistor though.
Does he?

AndrewT · 22nd October 2009, 09:45 AM

there is a suggestion from the designer that the 1k was chosen to ensure stability into any load.
Some have suggested trying as low as 220r, conditional on checking stability.

Eliminating the output resistor and feeding into one or a pair of filters never entered the discussion.

Harolda · 12th March 2010, 09:02 PM

I just read this topic, as i was looking for an opamp less crossover for my Hiquphon+seas W15cy001 active setup. I will be using gainclone as amps and i had the same idea, with using PLLXO's between B1 or other buffers.
So more information please, who has build something like this? Can you post some pictures & shematics.
Could i also use this setup for balanced pre amp and power amp?
thanks.

21st October 2009, 08:15 PM	#21
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	that Pllxo article omits a few cases that need component value corrections. Rs (the source output impedance) when feeding the High Pass and when feeding the Low Pass. The Low Pass is easy. R1+Rs = R'1 How does one correct the High Pass component values for a Rs<>0r0? What does one do when the Low Pass has a resistance (Ramp) parallel to C1? __________________ regards Andrew T.

22nd October 2009, 05:44 AM	#25
Melon Head Formerly Thanh1973 Join Date: Nov 2006	That is why I suggested using 20K resistors. __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."

22nd October 2009, 06:33 AM	#26
Vigo diyAudio Member Join Date: Mar 2006 Location: Helsingborg Sweden	Ok sow if i use something between 10 and 20 kohm it should be fine. And i dont need to calculate with the input and output of the B1. I will calculate some and see if can get any good standard values for the components. Thanks everyone for your help. __________________ To play with OP-amps in audio is like playing card with devil, you can never win.

22nd October 2009, 09:31 AM	#28
Melon Head Formerly Thanh1973 Join Date: Nov 2006	He doesn't need to use the 1k resistor though. Does he? __________________ "No, this sucker's electrical, but I need a nuclear reaction to generate the 1.21 gigawatts of electricity I need."

22nd October 2009, 09:45 AM	#29
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	there is a suggestion from the designer that the 1k was chosen to ensure stability into any load. Some have suggested trying as low as 220r, conditional on checking stability. Eliminating the output resistor and feeding into one or a pair of filters never entered the discussion. __________________ regards Andrew T.


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th March 2010, 09:02 PM	#30
Harolda diyAudio Member Join Date: Jul 2005 Location: Hoensbroek	I am also interested in this XO I just read this topic, as i was looking for an opamp less crossover for my Hiquphon+seas W15cy001 active setup. I will be using gainclone as amps and i had the same idea, with using PLLXO's between B1 or other buffers. So more information please, who has build something like this? Can you post some pictures & shematics. Could i also use this setup for balanced pre amp and power amp? thanks.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Crossover for vifa 2 way setup - how can I find out what this crossover is doing?	Tino	Multi-Way	11	17th May 2009 04:21 AM
Passive crossover into active crossover	hahfran	Multi-Way	16	10th February 2008 06:16 PM
3 way crossover help?	bruce ferrara	Multi-Way	6	8th February 2008 10:35 PM
Can you hear the crossover point of a speaker with a well-designed crossover?	454Casull	Multi-Way	11	2nd April 2004 05:48 AM
About crossover	billy	Multi-Way	14	25th July 2002 04:54 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read